Income Taxes (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Current tax expense
Federal	$ 105,367	$ 84,430	$ 46,848
State	16,111	13,941	7,080
Total current tax expense	121,478	98,371	53,928
Deferred Income Tax Expense (Benefit)
Federal	(2,758)	(30,658)	38,731
State	3,308	(2,681)	8,915
Total deferred tax expense (benefit)	550	(33,339)	47,646
Total income tax expense	$ 122,028	65,032	101,574
Effective Income Tax Rate Reconciliation, Amount [Abstract]
Federal statutory rate	35.00%
Income taxes at statutory rates	$ 116,345	71,258	93,956
Nontaxable income on loans, leases and investments, net of nondeductible expenses	(3,020)	(1,832)	(1,185)
State and local income taxes, including change in valuation allowance, net of federal income tax benefit	12,622	7,319	10,397
Effective Income Tax Rate Reconciliation, Acquisition Stock Settlement, Amount	0	(10,185)	0
Tax credits	(3,060)	(2,896)	(960)
Other, net	(859)	1,368	(634)
Total income tax expense	122,028	65,032	$ 101,574
Deferred Tax Assets, Net [Abstract]
Allowance for loan and lease losses	78,878	79,537
Pension liability	7,206	17,147
Executive separation from service agreements	9,856	13,753
State operating loss carryforwards	21	29
Unrealized loss on cash flow hedge	537	1,673
Net unrealized loss on securities included in accumulated other comprehensive loss	9,379	0
Deferred Tax Assets, Property, Plant and Equipment	13,195	3,495
Deferred Tax Assets, FDIC-Assisted Transaction Timing Differences, Amount	66,456	77,388
Deferred Tax Assets, Tax Deferred Expense, Reserves and Accruals, Reserves	10,772	12,770
Other	29,279	26,788
Gross deferred tax asset	225,579	232,580
Lease financing activities	15,492	12,706
Net unrealized gain on securities included in accumulated other comprehensive loss	0	3,245
Net deferred loan fees and costs	6,051	4,532
Intangible assets	2,040	7,789
Deferred Tax Liability, Mark to Market Section 475, Amount	31,486	40,910
Other	12,026	13,287
Deferred tax liability	67,095	82,469
Net deferred tax assets	$ 158,484	$ 150,111