Borrowed Funds - Debt Disclosure by Year (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Debt Disclosure [Abstract]
Securities sold under repurchase agreements, maximum balance	$ 96,914,000	$ 153,715,000
FHLB line of credit, maximum balance	451,000,000	487,000,000
FHLB advances, maximum balance	1,190,006,000	1,256,525,000
Securities sold under repurchase agreements, average balance	71,234,000	139,729,000
FHLB line of credit, average balance	325,481,000	259,189,000
FHLB advances, average balance	$ 939,916,000	$ 1,136,988,000
Securities sold under repurchase agreements, weighted average interest rate	0.49%	1.04%
FHLB line of credit, weighted average interest rate	2.40%	2.09%
FHLB advances, weighted average interest rate	2.11%	1.90%