Quarterly report pursuant to Section 13 or 15(d)

Fair Value Measurements - Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail)

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Fair Value Measurements - Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail) - USD ($)
$ in Thousands
Sep. 30, 2015
Dec. 31, 2014
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Total securities available for sale $ 669,340 $ 1,060,717
U.S. government agency securities [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Total securities available for sale 57,674 128,207
Other securities [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Total securities available for sale 23,007 22,893
Equity security [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Total securities available for sale   414
Municipal bonds-tax exempt [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Total securities available for sale 48,001 4,390
Municipal bonds-taxable [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Total securities available for sale 14,372 16,922
Collateralized mortgage obligations [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Total securities available for sale 116,314 188,047
Recurring Basis [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Total securities available for sale 669,340 1,060,717
Recurring Basis [Member] | Mortgage-backed securities [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Total securities available for sale 324,504 573,286
Recurring Basis [Member] | U.S. government agency securities [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Total securities available for sale 57,674 128,207
Recurring Basis [Member] | Corporate bonds [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Total securities available for sale 17,005 16,948
Recurring Basis [Member] | U.S treasury securities [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Total securities available for sale 162 163
Recurring Basis [Member] | Other securities [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Total securities available for sale 23,007 22,893
Recurring Basis [Member] | Equity security [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Total securities available for sale   414
Recurring Basis [Member] | SBA loan pools securities [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Total securities available for sale 68,301 109,447
Recurring Basis [Member] | Municipal bonds-tax exempt [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Total securities available for sale 48,001 4,390
Recurring Basis [Member] | Municipal bonds-taxable [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Total securities available for sale 14,372 16,922
Recurring Basis [Member] | Collateralized mortgage obligations [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Total securities available for sale 116,314 188,047
Recurring Basis [Member] | Fair Value, Inputs, Level 1 [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Total securities available for sale 23,169 23,056
Recurring Basis [Member] | Fair Value, Inputs, Level 1 [Member] | Mortgage-backed securities [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Total securities available for sale 0 0
Recurring Basis [Member] | Fair Value, Inputs, Level 1 [Member] | U.S. government agency securities [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Total securities available for sale 0 0
Recurring Basis [Member] | Fair Value, Inputs, Level 1 [Member] | Corporate bonds [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Total securities available for sale 0 0
Recurring Basis [Member] | Fair Value, Inputs, Level 1 [Member] | U.S treasury securities [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Total securities available for sale 162 163
Recurring Basis [Member] | Fair Value, Inputs, Level 1 [Member] | Other securities [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Total securities available for sale 23,007 22,893
Recurring Basis [Member] | Fair Value, Inputs, Level 1 [Member] | Equity security [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Total securities available for sale   0
Recurring Basis [Member] | Fair Value, Inputs, Level 1 [Member] | SBA loan pools securities [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Total securities available for sale 0 0
Recurring Basis [Member] | Fair Value, Inputs, Level 1 [Member] | Municipal bonds-tax exempt [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Total securities available for sale 0 0
Recurring Basis [Member] | Fair Value, Inputs, Level 1 [Member] | Municipal bonds-taxable [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Total securities available for sale 0 0
Recurring Basis [Member] | Fair Value, Inputs, Level 1 [Member] | Collateralized mortgage obligations [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Total securities available for sale 0 0
Recurring Basis [Member] | Fair Value, Inputs, Level 2 [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Total securities available for sale 646,171 1,036,538
Recurring Basis [Member] | Fair Value, Inputs, Level 2 [Member] | Mortgage-backed securities [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Total securities available for sale 324,504 573,286
Recurring Basis [Member] | Fair Value, Inputs, Level 2 [Member] | U.S. government agency securities [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Total securities available for sale 57,674 128,207
Recurring Basis [Member] | Fair Value, Inputs, Level 2 [Member] | Corporate bonds [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Total securities available for sale 17,005 16,948
Recurring Basis [Member] | Fair Value, Inputs, Level 2 [Member] | U.S treasury securities [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Total securities available for sale 0 0
Recurring Basis [Member] | Fair Value, Inputs, Level 2 [Member] | Other securities [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Total securities available for sale 0 0
Recurring Basis [Member] | Fair Value, Inputs, Level 2 [Member] | Equity security [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Total securities available for sale   0
Recurring Basis [Member] | Fair Value, Inputs, Level 2 [Member] | SBA loan pools securities [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Total securities available for sale 68,301 109,447
Recurring Basis [Member] | Fair Value, Inputs, Level 2 [Member] | Municipal bonds-tax exempt [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Total securities available for sale 48,001 3,681
Recurring Basis [Member] | Fair Value, Inputs, Level 2 [Member] | Municipal bonds-taxable [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Total securities available for sale 14,372 16,922
Recurring Basis [Member] | Fair Value, Inputs, Level 2 [Member] | Collateralized mortgage obligations [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Total securities available for sale 116,314 188,047
Recurring Basis [Member] | Fair Value, Inputs, Level 3 [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Total securities available for sale 0 1,123
Recurring Basis [Member] | Fair Value, Inputs, Level 3 [Member] | Mortgage-backed securities [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Total securities available for sale 0 0
Recurring Basis [Member] | Fair Value, Inputs, Level 3 [Member] | U.S. government agency securities [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Total securities available for sale 0 0
Recurring Basis [Member] | Fair Value, Inputs, Level 3 [Member] | Corporate bonds [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Total securities available for sale 0 0
Recurring Basis [Member] | Fair Value, Inputs, Level 3 [Member] | U.S treasury securities [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Total securities available for sale 0 0
Recurring Basis [Member] | Fair Value, Inputs, Level 3 [Member] | Other securities [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Total securities available for sale 0 0
Recurring Basis [Member] | Fair Value, Inputs, Level 3 [Member] | Equity security [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Total securities available for sale   414
Recurring Basis [Member] | Fair Value, Inputs, Level 3 [Member] | SBA loan pools securities [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Total securities available for sale 0 0
Recurring Basis [Member] | Fair Value, Inputs, Level 3 [Member] | Municipal bonds-tax exempt [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Total securities available for sale 0 709
Recurring Basis [Member] | Fair Value, Inputs, Level 3 [Member] | Municipal bonds-taxable [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Total securities available for sale 0 0
Recurring Basis [Member] | Fair Value, Inputs, Level 3 [Member] | Collateralized mortgage obligations [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Total securities available for sale $ 0 $ 0