Allowance for Credit Losses - Summary of Provision for Credit Losses (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Receivables [Abstract]
Provision for loans									$ 7,846	$ 3,445	$ 14,895
Provision for unfunded letters of credit									255	(1,561)	1,200
Total provision for credit losses	$ 3,507	$ 94	$ 4,500	$ 0	$ 3,980	$ (423)	$ (5,671)	$ 3,998	$ 8,101	$ 1,884	$ 16,095