Income Taxes (Details) - USD ($) $ in Thousands		12 Months Ended
	Dec. 22, 2017	Dec. 31, 2017	Dec. 31, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Deferred Tax Assets, Operating Loss Carryforwards		$ 12,800	$ 12,800	$ 12,800
Unrecognized Tax Benefits, Income Tax Penalties and Interest Expense			450		$ 357	$ 298
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Beginning balance of unrecognized tax benefits			28,879		5,975	3,865
Unrecognized Tax Benefits, Decrease Resulting from Prior Period Tax Positions			0		(327)	(79)
Unrecognized Tax Benefits, Increase Resulting from Current Period Tax Positions			125		23,231	2,189
Ending balance of unrecognized tax benefits			29,004		28,879	5,975
Current tax expense
Federal			87,992		84,946	105,367
State			6,116		7,493	16,111
Total current tax expense			94,108		92,439	121,478
Deferred Income Tax Expense (Benefit)
Federal			115,392		23,144	(2,758)
State			10,446		10,002	3,308
Total deferred tax expense			125,838		33,146	550
Total income tax expense			219,946		125,585	122,028
Effective Income Tax Rate Reconciliation, Amount [Abstract]
Federal statutory rate	21.00%	35.00%		35.00%
Income taxes at federal statutory rates			190,294		122,874	116,345
Nontaxable income on loans, leases and investments, net of nondeductible expenses			(2,525)		(2,901)	(3,020)
State and local income taxes, including change in valuation allowance, net of federal income tax benefit			10,765		11,372	12,622
Effect of federal rate change			25,762		0	0
Acquisition Stock Settlement			0		(98)	0
Tax credits net of amortization			(4,840)		(4,138)	(3,060)
Other, net			490		(1,524)	(859)
Total income tax expense			219,946		125,585	$ 122,028
Deferred Tax Assets, Net [Abstract]
Allowance for loan and lease losses		$ 50,853	50,853	$ 50,853	80,939
Pension liability		704	704	704	15,679
Executive separation from service agreements		8,548	8,548	8,548	14,278
Federal net operating loss carryforward		2,685	2,685	2,685	5,019
Net unrealized loss on securities included in accumulated other comprehensive loss		10,849	10,849	10,849	26,832
Deferred Tax Assets, accelerated depreciation		0	0	0	133
Deferred Tax Assets, FDIC-Assisted Transaction Timing Differences		0	0	0	52,579
Deferred Tax Assets, Other reserves		5,570	5,570	5,570	10,504
Other		10,116	10,116	10,116	26,663
Deferred tax asset		89,325	89,325	89,325	232,626
Deferred Tax Liabilities, accelerated depreciation		7,562	7,562	7,562	0
Lease financing activities		9,131	9,131	9,131	11,651
Net deferred loan fees and costs		8,708	8,708	8,708	10,867
Intangible assets		12,252	12,252	12,252	6,335
Deferred Tax Liability, Security, loan and debt valuations		7,018	7,018	7,018	22,656
FDIC-assisted transactions timing differences		1,113	1,113	1,113	0
Other		4,565	4,565	4,565	8,501
Deferred tax liability		50,349	50,349	50,349	60,010
Net deferred tax assets		$ 38,976	$ 38,976	$ 38,976	$ 172,616