Borrowed Funds - Debt Disclosure by Year (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Debt Disclosure [Abstract]
Securities sold under repurchase agreements, maximum balance	$ 346,361	$ 255,633
FHLB line of credit, maximum balance	160,000	180,000
FHLB advances, maximum balance	1,363,122	1,190,280
Securities sold under repurchase agreements, average balance	273,934	245,260
FHLB line of credit, average balance	80,847	104,121
FHLB advances, average balance	$ 1,249,193	$ 989,245
Securities sold under repurchase agreements, weighted average interest rate	1.49%	1.72%
FHLB line of credit, weighted average interest rate	0.40%	0.37%
FHLB advances, weighted average interest rate	1.84%	2.08%