Income Taxes (Schedule of Deferred Tax Assets and Liabilities) (Detail) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Income Tax Disclosure [Abstract]
Lease liabilities under operating leases	$ 67,839	$ 67,975
Allowance for credit losses	64,573	27,860
Net actuarial loss on defined benefit post-retirement benefit plans	13,512	12,210
Stock-based compensation	10,033	11,211
Bonus accrual	3,961	5,055
Deferred loan and lease origination fees	10,252	2,254
Other	3,834	2,058
Total gross deferred tax assets	174,004	128,623
Net unrealized gain on securities available for sale and transferred securities	(149,870)	(83,281)
Right-of-use assets under operating leases	(61,963)	(63,463)
Premises and equipment	(49,602)	(29,730)
Intangible assets	(14,596)	(12,642)
Defined benefit post-retirement benefit plans	(10,081)	(9,419)
Partnership interests	(2,913)	(2,894)
Leases	(1,090)	(1,572)
Other	(1,387)	(1,440)
Total gross deferred tax liabilities	(291,502)	(204,441)
Deferred Tax Liabilities, Net	$ (117,498)	$ (75,818)