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Interest-Bearing Deposits - Additional Information (Detail) - USD ($)
$ in Millions
12 Months Ended
Dec. 31, 2015
Dec. 31, 2014
Dec. 31, 2013
Deposits [Abstract]      
Interest-bearing demand deposit, money market $ 580.8 $ 427.7  
Certificates of deposit in denominations of $100 thousand or more 157.7 334.0  
Interest expense related to certificates of deposit $100 thousand or greater $ 1.8 $ 3.7 $ 4.7