Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
CASH FLOWS FROM OPERATING ACTIVITIES
Net income	$ 65,001	$ 53,816	$ 179,254	$ 145,441
Adjustments to reconcile net income to net cash provided by operating activities:
Provision for credit losses	5,000	21,000	26,000	55,000
Depreciation and amortization			35,054	34,121
Addition to valuation allowance on mortgage servicing rights, net			286	2,486
Amortization of mortgage servicing rights			7,635	9,142
Amortization of other intangible assets	450	525	1,459	1,568
Amortization and accretion on earning assets, funding, and other, net			27,230	34,077
Other Depreciation and Amortization			14,685	4,437
Gain on sales of investment securities, net			(359)	(6,201)
Asset (gains) losses, net	16	1,034	716	853
(Gain) loss on mortgage banking activities, net			(3,762)	(21,741)
Mortgage loans originated and acquired for sale			(466,135)	(983,930)
Proceeds from sales of mortgage loans held for sale			551,697	1,147,278
Payment for Pension Benefits			(6,242)	0
(Increase) decrease in interest receivable			(9,765)	(5,809)
Increase (decrease) in interest payable			3,410	(5,994)
Other, net			(44,882)	5,451
Net cash provided by operating activities			316,281	416,179
CASH FLOWS FROM INVESTING ACTIVITIES
Net increase in loans			(991,334)	(1,461,884)
Purchases of:
Available for sale securities			(701,080)	(849,466)
Held to maturity securities			(121,596)	(151,556)
Federal Home Loan Bank and Federal Reserve Bank stocks			(195,356)	(72,975)
Premises, equipment, and software, net of disposals			(32,925)	(90,691)
Proceeds from:
Sales of available for sale securities			0	359,591
Sales of held to maturity securities			16,059	0
Proceeds from Sale of Federal Home Loan Bank Stock			162,911	80,000
Prepayments, calls, and maturities of available for sale investment securities			551,962	651,403
Prepayments, calls, and maturities of held to maturity investment securities			151,565	55,579
Sales, prepayments, calls, and maturities of other assets			10,833	19,351
Net Change in Tax Credit Investments [Line Items]			(35,027)	(13,138)
Net cash paid in acquisition			(217)	(685)
Net cash used in investing activities			(1,184,205)	(1,474,471)
CASH FLOWS FROM FINANCING ACTIVITIES
Net increase (decrease) in deposits			445,003	740,047
Proceeds from (Repayments of) Short-term Debt			(27,418)	405,677
Proceeds from (Repayments of) Long-term Debt and Capital Securities			(115,017)	(1,180,027)
Proceeds from issuance of long-term funding			500,000	1,265,000
Proceeds from Issuance of Preferred Stock and Preference Stock			0	97,066
Proceeds from issuance of common stock for stock-based compensation plans			22,460	7,749
Payments for Repurchase of Redeemable Preferred Stock			0	(58,903)
Purchase of preferred stock			0	(1,248)
Purchase of common stock returned to authorized but unissued			(37,031)	(20,007)
Purchase of treasury stock for tax withholding			(8,613)	(4,243)
Cash dividends on common stock			(55,058)	(49,642)
Cash dividends on preferred stock			(7,008)	(6,555)
Net cash provided by financing activities			717,318	1,194,914
Net increase (decrease) in cash and cash equivalents			(150,606)	136,622
Cash and cash equivalents at beginning of period			642,233	473,685	$ 473,685
Cash and cash equivalents at end of period	491,627	610,307	491,627	610,307	$ 642,233
Supplemental disclosures of cash flow information:
Cash paid for interest			98,151	68,371
Cash paid for income taxes			61,959	53,126
Loans and bank premises transferred to other real estate owned			5,872	8,834
Capitalized mortgage servicing rights			4,822	8,701
Loans transferred into held for sale from portfolio, net			75,289	256,188
Fair value of assets acquired, including cash and cash equivalents	0	522	0	522
Fair value ascribed to goodwill and intangible assets	217	4,119	217	4,119
Fair value of liabilities assumed	$ 0	$ 1,423	$ 0	$ 1,423