Premises and Equipment, Net and Other Assets - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Property Plant And Equipment [Abstract]
Noncash construction in progress for retainage payable	$ 2,400,000
Other assets in equity interest	$ 11,100,000
Percentage of equity investment	50.00%
Low income housing tax credit investments	$ 18,100,000	$ 20,400,000
Tax credits and other tax benefits recognized from LIHTC investments	5,600,000	5,400,000	$ 5,400,000
Amortization expense resulting from LIHTC investments	4,600,000	4,500,000	4,400,000
Unfunded commitment on investments	$ 19,400,000
Percentage of qualified investment	39.00%
Period of qualified investments taken	7 years
New market tax credit investments	$ 18,500,000	21,800,000
Tax credits and other tax benefits recognized from NMTC investments	4,000,000.0	4,500,000	1,800,000
Amortization expense resulting from NMTC investments	3,300,000	$ 3,700,000	$ 1,400,000
Unfunded commitment on NMTC investments	$ 0