Premises and Equipment - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Property, Plant and Equipment [Line Items]
Operating Lease, Right-of-Use Asset	$ 42,617	$ 48,642
Operating Lease, Liability	46,819	52,894
Premises and equipment, available-for-sale	2,600
Operating Leases, Rent Expense, Contingent Rentals	6,700	4,900	$ 4,100
Gain (Loss) on Termination of Lease	700
Assets
Property, Plant and Equipment [Line Items]
Gain (Loss) on Contract Termination	3,800
Liability
Property, Plant and Equipment [Line Items]
Gain (Loss) on Contract Termination	3,600
Premises and Equipment [Member]
Property, Plant and Equipment [Line Items]
Depreciation included in noninterest expense	10,900	10,500	$ 9,500
Property Subject to Operating Lease [Member]
Property, Plant and Equipment [Line Items]
Depreciation included in noninterest expense	2,600	$ 3,500
Accounting Standards Update 2016-02 [Member]
Property, Plant and Equipment [Line Items]
Operating Lease, Right-of-Use Asset	38,500
Operating Lease, Liability	$ 41,800