Income Taxes (Schedule of Deferred Tax Assets and Liabilities) (Detail) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Allowance for loan losses	$ 53,566	$ 47,551
Alternative minimum tax carryforward	30,384	10,934
Net actuarial loss on defined benefit post-retirement benefit plans	21,956	25,172
Stock-based compensation	18,140	21,246
Bonus accrual	7,035	5,832
Gain on sale of assets	2,485	2,044
Transaction costs	1,587	1,716
Other	4,449	5,718
Total gross deferred tax assets	139,602	120,213
Premises and equipment	(33,777)	(23,038)
Defined benefit post-retirement benefit plans	(14,828)	(14,089)
Intangible assets	(11,697)	(8,940)
Net unrealized gain on securities available for sale and transferred securities	(8,699)	(86,484)
Leases	(3,042)	(4,491)
Section 481(a) change in accounting method (tangible property)	(1,694)	(3,387)
Prepaid expenses	(1,743)	(1,702)
Other	(436)	(563)
Total gross deferred tax liabilities	(75,916)	(142,694)
Deferred Tax Assets, Net	$ 63,686
Deferred Tax Liabilities, Net		$ (22,481)