Allowance for Credit Losses - Summary of Allowance for Credit Losses (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Receivables [Abstract]
Allowance for loan losses	$ 106,178	$ 102,353	$ 113,617
Allowance for unfunded letters of credit	2,189	1,934
Total allowance for credit losses	$ 108,367	$ 104,287