Deposits - Additional Information (Detail) (USD $)
12 Months Ended
Dec. 31, 2014
Customer
Dec. 31, 2013
Customer
Dec. 31, 2012
Schedule Of Deposits [Line Items]      
Time deposits greater than or equal to $100,000 $ 85,302,000 $ 86,491,000  
Aggregate deposits 206,207,000 138,063,000  
Brokered certificates of deposits 48,935,000   0
Average weighted rate 0.81%    
Customer [Member]      
Schedule Of Deposits [Line Items]      
Number of customers 1 2  
Aggregate deposits $ 66,411,000,000 $ 72,250,000,000  
Percentage of bank deposits 7.00% 11.00%