Quarterly report pursuant to Section 13 or 15(d)

Investment Securities - Summary of Investment Securities Available for Sale (Detail)

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Investment Securities - Summary of Investment Securities Available for Sale (Detail) (USD $)
In Thousands, unless otherwise specified
Sep. 30, 2014
Dec. 31, 2013
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost $ 1,139,173 $ 549,113
Gross Unrealized Gain 686 782
Gross Unrealized Loss 11,235 18,969
Estimated Fair Value 1,128,624 530,926
Collateralized mortgage obligations [Member]
    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 197,784 130,636
Gross Unrealized Gain 146 274
Gross Unrealized Loss 1,719 3,217
Estimated Fair Value 196,211 127,693
Municipal bonds-tax exempt [Member]
    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 4,335 13,857
Gross Unrealized Gain 94 110
Gross Unrealized Loss   30
Estimated Fair Value 4,429 13,937
Municipal bonds-taxable [Member]
    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 16,666 33,361
Gross Unrealized Gain 141 73
Gross Unrealized Loss 147 1,080
Estimated Fair Value 16,660 32,354
Corporate bonds [Member]
    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 17,018 21,013
Gross Unrealized Gain 11 8
Gross Unrealized Loss 89 186
Estimated Fair Value 16,940 20,835
Mortgage-backed securities [Member]
    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 588,638 222,768
Gross Unrealized Gain 230 317
Gross Unrealized Loss 4,711 6,026
Estimated Fair Value 584,157 217,059
U.S. government agency securities [Member]
    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 176,449 90,852
Gross Unrealized Loss 3,656 7,316
Estimated Fair Value 172,793 83,536
SBA loan pool securities [Member]
    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 114,753 13,598
Gross Unrealized Gain 64  
Gross Unrealized Loss 700 969
Estimated Fair Value 114,117 12,629
U.S. treasury securities [Member]
    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 164 19,998
Gross Unrealized Loss 1 1
Estimated Fair Value 163 19,997
Other securities [Member]
    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 22,916 3,030
Gross Unrealized Loss 212 144
Estimated Fair Value 22,704 2,886
Equity security [Member]
    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 450  
Estimated Fair Value $ 450