Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
CASH FLOWS FROM OPERATING ACTIVITIES
Net income	$ 188,301	$ 190,509	$ 188,692
Adjustments to reconcile net income to net cash provided by operating activities:
Provision for credit losses	37,500	16,000	10,100
Depreciation and amortization	47,168	50,281	49,711
(Recovery of) addition to valuation allowance on mortgage servicing rights, net	(425)	321	(14,563)
Amortization of mortgage servicing rights	11,601	11,067	15,488
Amortization of other intangible assets	3,094	3,747	4,043
Amortization and accretion on earning assets, funding, and other, net	39,806	28,145	44,965
Deferred income taxes	(3,522)	9,890	25,920
Tax impact of stock based compensation	(1,518)	1,288	(25)
Gain on sales of investment securities, net	(8,133)	(494)	(564)
Gain on sales of assets and impairment write-downs, net	(1,592)	(10,288)	(5,413)
Gain on mortgage banking activities, net	(20,258)	(13,765)	(34,268)
Mortgage loans originated and acquired for sale	(1,228,106)	(1,069,852)	(2,304,006)
Proceeds from sales of mortgage loans held for sale	1,241,012	1,010,167	2,516,690
Pension contributions	0	(21,000)	(28,000)
(Increase) decrease in interest receivable	395	(1,264)	2,078
Increase (decrease) in interest payable	3,898	1,536	(2,214)
Other, net	(10,513)	(4,203)	9,274
Net cash provided by operating activities	301,744	199,509	477,958
CASH FLOWS FROM INVESTING ACTIVITIES
Net increase in loans	(1,136,793)	(1,736,571)	(593,591)
Purchases of:
Available for sale securities	(2,859,793)	(1,096,410)	(1,954,936)
Held to maturity securities	(250,767)	(229,795)	(135,785)
Federal Home Loan Bank and Federal Reserve Bank stocks	(35,647)	(7,857)	(28,399)
Premises, equipment, and software, net of disposals	(54,636)	(50,396)	(67,723)
Other assets	(15,187)	(4,496)	(2,098)
Proceeds from:
Sales of available for sale securities	1,601,947	102,011	136,152
Sale of Federal Home Loan Bank and Federal Reserve Bank stocks	77,514	0	14,399
Prepayments, calls, and maturities of available for sale securities	1,099,625	862,037	1,298,077
Prepayments, calls, and maturities of held to maturity securities	17,013	6,420	0
Prepayments, calls and maturities of other assets	21,236	36,452	41,668
Sales of loans originated for investment	0	0	39,002
Net cash received in acquisition	1,132	0	0
Net cash used in investing activities	(1,534,356)	(2,118,605)	(1,253,234)
CASH FLOWS FROM FINANCING ACTIVITIES
Net increase in deposits	2,244,161	1,496,337	394,340
Net decrease in deposits due to branch sales	0	0	(65,430)
Net increase (decrease) in short-term funding	(233,872)	327,362	(1,586,013)
Repayment of long-term funding	(1,500,035)	(155,066)	(427,430)
Proceeds from issuance of long-term funding	250,000	996,030	2,500,000
Proceeds from issuance of preferred shares	62,966	0	0
Proceeds from issuance of common stock for stock-based compensation plans	20,054	13,228	9,305
Purchase of preferred stock	(1,335)	(2,451)	(1,626)
Purchase of common stock returned to authorized but unissued	(93,000)	(150,498)	0
Purchase of treasury stock	(5,154)	(112,312)	(123,349)
Cash dividends on common stock	(62,400)	(58,710)	(54,991)
Cash dividends on preferred stock	(7,155)	(5,002)	(5,158)
Net cash provided by financing activities	674,230	2,348,918	639,648
Net increase (decrease) in cash and cash equivalents	(558,382)	429,822	(135,628)
Cash and cash equivalents at beginning of period	1,032,067	602,245	737,873
Cash and cash equivalents at end of period	473,685	1,032,067	602,245
Supplemental disclosures of cash flow information:
Cash paid for interest	73,054	54,330	65,552
Cash paid for income taxes	84,407	72,431	49,200
Loans and bank premises transferred to other real estate owned	10,988	21,413	26,151
Capitalized mortgage servicing rights	12,372	8,253	18,256
Fair value of assets acquired, including cash and cash equivalents	4,590	0	0
Fair value ascribed to goodwill and intangible assets	51,791	0	0
Fair value of liabilities assumed	12,851	0	0
Common stock issued in acquisition	$ 43,530	$ 0	$ 0