Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
CASH FLOWS FROM OPERATING ACTIVITIES
Net income	$ 200,274	$ 188,301	$ 190,509
Adjustments to reconcile net income to net cash provided by operating activities:
Provision for credit losses	70,000	37,500	16,000
Depreciation and amortization	45,434	47,168	50,281
Addition to (recovery of) valuation allowance on mortgage servicing rights, net	(200)	(425)	321
Amortization of mortgage servicing rights	12,327	11,601	11,067
Amortization of other intangible assets	2,093	3,094	3,747
Amortization and accretion on earning assets, funding, and other, net	46,615	39,806	28,145
Deferred income taxes	10,656	(3,522)	9,890
Tax impact of stock based compensation	(2,940)	1,518	(1,288)
Gain on sales of investment securities, net	(9,316)	(8,133)	(494)
Asset (gains) losses, net	86	(2,540)	(10,830)
Gain on mortgage banking activities, net	(27,060)	(20,258)	(13,765)
Mortgage loans originated and acquired for sale	(1,271,124)	(1,228,106)	(1,069,852)
Proceeds from sales of mortgage loans held for sale	1,542,660	1,241,012	1,010,167
Pension contributions	0	0	(21,000)
(Increase) decrease in interest receivable	(7,836)	395	(1,264)
Increase (decrease) in interest payable	(4,642)	3,898	1,536
Net change in other assets and other liabilities	21,915	(9,565)	(3,661)
Net cash provided by operating activities	628,942	301,744	199,509
CASH FLOWS FROM INVESTING ACTIVITIES
Net increase in loans	(1,682,579)	(1,136,793)	(1,736,571)
Purchases of:
Available for sale securities	(1,304,921)	(2,859,793)	(1,096,410)
Held to maturity securities	(195,442)	(250,767)	(229,795)
Federal Home Loan Bank and Federal Reserve Bank stocks	(92,761)	(35,647)	(7,857)
Premises, equipment, and software, net of disposals	(103,881)	(54,636)	(50,396)
Other assets	(11,057)	(15,187)	(4,496)
Proceeds from:
Sales of available for sale securities	549,555	1,601,947	102,011
Sale of Federal Home Loan Bank and Federal Reserve Bank stocks	100,000	77,514	0
Prepayments, calls, and maturities of available for sale securities	997,701	1,099,625	862,037
Prepayments, calls, and maturities of held to maturity securities	75,796	17,013	6,420
Prepayments, calls and maturities of other assets	27,692	21,236	36,452
Net cash (paid) received in acquisition	(685)	1,132	0
Net cash used in investing activities	(1,640,582)	(1,534,356)	(2,118,605)
CASH FLOWS FROM FINANCING ACTIVITIES
Net increase in deposits	880,783	2,244,161	1,496,337
Net increase (decrease) in short-term funding	257,619	(233,872)	327,362
Repayment of long-term funding	(1,180,038)	(1,500,035)	(155,066)
Proceeds from issuance of long-term funding	1,265,000	250,000	996,030
Proceeds from issuance of common stock for stock-based compensation plans	21,748	20,054	13,228
Proceeds from issuance of preferred stock	97,066	62,966	0
Redemption of preferred stock	(58,903)	0	0
Purchase of preferred stock	(1,248)	(1,335)	(2,451)
Purchase of common stock returned to authorized but unissued	(20,007)	(93,000)	(150,498)
Purchase of treasury stock	0	0	(108,600)
Purchase of treasury stock for tax withholding	(5,074)	(5,154)	(3,712)
Cash dividends on common stock	(67,855)	(62,400)	(58,710)
Cash dividends on preferred stock	(8,903)	(7,155)	(5,002)
Net cash provided by financing activities	1,180,188	674,230	2,348,918
Net increase (decrease) in cash and cash equivalents	168,548	(558,382)	429,822
Cash and cash equivalents at beginning of period	473,685	1,032,067	602,245
Cash and cash equivalents at end of period	642,233	473,685	1,032,067
Supplemental disclosures of cash flow information:
Cash paid for interest	88,269	73,054	54,330
Cash paid for income and franchise taxes	75,558	84,407	72,431
Loans and bank premises transferred to other real estate owned	9,752	10,988	21,413
Capitalized mortgage servicing rights	12,262	12,372	8,253
Loans transferred into held for sale from portfolio, net	256,194	0	0
Fair value of assets acquired, including cash and cash equivalents	522	4,590	0
Fair value ascribed to goodwill and intangible assets	4,119	51,791	0
Fair value of liabilities assumed	1,423	12,851	0
Common stock issued in acquisition	$ 0	$ 43,530	$ 0