Quarterly report pursuant to Section 13 or 15(d)

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

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Fair Value Measurements - Assets and Liabilities Measured at Fair Value on Non-Recurring Basis (Detail) - Non-recurring Basis [Member] - USD ($)
$ in Thousands
3 Months Ended 12 Months Ended
Mar. 31, 2016
Dec. 31, 2015
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Unrealized losses impaired loans $ 646 $ 2,756
Unrealized losses other real estate owned 0 0
Impaired loans [Member] | Real estate loans [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Impaired loans 21,800 27,900
Impaired loans [Member] | Commercial and industrial loans [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Impaired loans 337 1,000
Impaired loans [Member] | Consumer loans [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Impaired loans 700 1,700
OREO [Member] | Commercial property loan [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Impaired loans 6,700 6,600
OREO [Member] | Residential property loan [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Impaired loans 2,700 1,900
Fair Value, Inputs, Level 1 [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Impaired loans 0 0
Other real estate owned 0 0
Fair Value, Inputs, Level 2 [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Impaired loans 21,619 29,595
Other real estate owned 9,411 8,511
Fair Value, Inputs, Level 3 [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Impaired loans 1,209 1,044
Other real estate owned $ 0 $ 0