Consolidated Statements of Cash Flows (Unaudited) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
CASH FLOWS FROM OPERATING ACTIVITIES
Net income	$ 190,509	$ 188,692	$ 178,973
Adjustments to reconcile net income to net cash provided by operating activities:
Provision for credit losses	16,000	10,100	10,100
Depreciation and amortization	50,281	49,711	43,611
(Recovery of) Addition to valuation allowance on mortgage servicing rights, net	321	(14,563)	2,383
Amortization of mortgage servicing rights	11,067	15,488	23,348
Amortization of other intangible assets	3,747	4,043	4,195
Amortization and accretion on earning assets, funding, and other, net	28,145	44,965	55,101
Deferred income taxes	9,890	25,920	54,294
Tax impact of stock based compensation	(1,288)	25	(785)
(Gain) loss on sales of investment securities, net of impairment write-downs	(494)	(564)	(4,261)
(Gain) loss on sales of assets and impairment write-downs, net	(10,288)	(5,413)	12,096
Gain on mortgage banking activities, net	(13,765)	(34,268)	(60,312)
Mortgage loans originated and acquired for sale	(1,069,852)	(2,304,006)	(2,797,431)
Proceeds from sales of mortgage loans held for sale	1,010,167	2,516,690	2,822,000
Pension contributions	(21,000)	(28,000)	(40,000)
Increase (decrease) in interest receivable	(1,264)	2,078	534
Increase (decrease) in interest payable	1,536	(2,214)	(5,723)
Net change in other assets and other liabilities	9,025	18,579	52,361
Net cash provided by (used in) operating activities	212,737	487,263	350,484
CASH FLOWS FROM INVESTING ACTIVITIES
Net (increase) decrease in loans	(1,736,571)	(593,591)	(1,637,901)
Purchases of:
Available for sale securities	(1,096,410)	(1,954,936)	(2,084,500)
Premises, equipment, and software, net of disposals	(50,396)	(67,723)	(83,973)
FHLB Stock	(7,857)	(28,399)	(6,601)
Held to maturity securities	(229,795)	(135,785)	(39,925)
Other assets	(4,496)	(2,098)	(5,968)
Proceeds from:
Sales of available for sale securities	102,011	136,152	299,782
Sale of FHLB stock	0	14,399	31,428
Prepayments, calls, and maturities of available for sale securities	862,037	1,298,077	1,692,076
Prepayments, calls and maturities of held to maturity securities	6,420	0	0
Prepayments, calls, and maturities of other assets	36,452	41,668	70,920
Sales of loans originated for investment	0	39,002	130,940
Net cash provided by (used in) investing activities	(2,118,605)	(1,253,234)	(1,633,722)
CASH FLOWS FROM FINANCING ACTIVITIES
Net increase (decrease) in deposits	1,496,337	394,340	1,969,055
Net increase (decrease) in deposits due to branch sales	0	(65,430)	(113,622)
Net increase (decrease) in short-term funding	327,362	(1,586,013)	(187,546)
Repayment of long-term funding	(155,066)	(427,430)	(311,621)
Proceeds from issuance of long-term funding	996,030	2,500,000	154,738
Purchase of common stock returned to authorized but unissued	(150,498)	0	0
Purchase of treasury stock	(112,312)	(123,349)	(61,654)
Purchase of preferred stock	(2,451)	(1,626)	0
Cash dividends on common stock	(58,710)	(54,991)	(39,634)
Cash dividends on preferred stock	(5,002)	(5,158)	(5,200)
Net cash provided by (used in) financing activities	2,335,690	630,343	1,404,516
Net increase (decrease) in cash and cash equivalents	429,822	(135,628)	121,278
Cash and cash equivalents at beginning of year	602,245	737,873	616,595
Cash and cash equivalents at end of year	1,032,067	602,245	737,873
Supplemental disclosures of cash flow information:
Cash paid for interest	54,330	65,552	97,938
Cash paid (received) for income taxes	72,431	49,200	(9,722)
Loans and bank premises transferred to other real estate owned	21,413	26,151	39,511
Capitalized mortgage servicing rights	$ 8,253	$ 18,256	$ 23,528