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Goodwill and Other Intangible Assets - Additional Information (Detail) - USD ($)
12 Months Ended
Dec. 31, 2015
Dec. 31, 2014
Dec. 31, 2013
Goodwill And Other Intangible Assets [Line Items]      
Useful lives of core deposit and other intangible assets 8 years    
Remaining weighted-average amortization period 6 years    
Amortization of core deposit and other intangible assets $ 26,424,000 $ 33,824,000 $ 46,912,000
Core Deposit and Other Intangible Assets [Member]      
Goodwill And Other Intangible Assets [Line Items]      
Amortization of core deposit and other intangible assets $ 26,424,000 $ 33,824,000 $ 46,912,000
Minimum [Member]      
Goodwill And Other Intangible Assets [Line Items]      
Useful lives of core deposit and other intangible assets 5 years    
Maximum [Member]      
Goodwill And Other Intangible Assets [Line Items]      
Useful lives of core deposit and other intangible assets 10 years