Consolidated Statement of Cash Flows (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	$ 1,066,246	$ 1,138,480	$ 1,029,498
Adjustments to reconcile net income to net cash provided by operating activities
Provision for credit losses	124,000	185,000	204,000
Depreciation and amortization of premises and equipment	96,496	91,469	84,375
Amortization of capitalized servicing rights	68,410	65,354	59,555
Amortization of core deposit and other intangible assets	33,824	46,912	60,631
Provision for deferred income taxes	92,848	139,785	131,858
Asset write-downs	6,593	17,918	63,790
Net gain on sales of assets	(6,859)	(127,890)	(6,868)
Net change in accrued interest receivable, payable	15,163	(10,523)	(13,898)
Net change in other accrued income and expense	(68,722)	71,523	(200,704)
Net change in loans originated for sale	(350,581)	(674,062)	(924,839)
Net change in trading account assets and liabilities	21,623	(11,642)	12,583
Net cash provided by operating activities	1,099,041	932,324	499,981
Cash flows from investing activities
Proceeds from sales of investment securities Available for sale	16	1,081,802	49,528
Proceeds from sales of investment securities Other	23,445	13,172	78,071
Proceeds from maturities of investment securities Available for sale	998,413	1,034,564	1,585,260
Proceeds from maturities of investment securities Held to maturity	468,999	287,837	329,279
Purchases of investment securities Available for sale	(5,347,145)	(197,931)	(28,161)
Purchases of investment securities Held to maturity	(21,283)	(1,977,064)	(285,125)
Purchases of investment securities Other	(53,606)	(9,105)	(13,833)
Net (increase) decrease in loans and leases	(2,421,162)	123,120	(5,672,747)
Net (increase) decrease in interest-bearing deposits at banks	(4,819,729)	(1,521,193)	25,015
Capital expenditures, net	(73,161)	(129,563)	(91,519)
Net increase in loan servicing advances	(484,689)	(1,004,923)	(69,084)
Other, net	19,531	95,706	32,458
Net cash provided (used) by investing activities	(11,710,371)	(2,203,578)	(4,060,858)
Cash flows from financing activities
Net increase in deposits	6,466,697	1,513,884	6,230,391
Net increase (decrease) in short-term borrowings	(67,779)	(814,027)	292,422
Proceeds from long-term borrowings	4,345,478	799,760
Payments on long-term borrowings	(426,275)	(261,212)	(2,080,167)
Dividends paid - common	(371,199)	(365,349)	(357,717)
Dividends paid - preferred	(70,234)	(53,450)	(53,450)
Proceeds from issuance of preferred stock	346,500
Other, net	88,565	137,967	63,616
Net cash provided by financing activities	10,311,753	957,573	4,095,095
Net increase (decrease) in cash and cash equivalents	(299,577)	(313,681)	534,218
Cash and cash equivalents at beginning of year	1,672,934	1,986,615	1,452,397
Cash and cash equivalents at end of year	1,373,357	1,672,934	1,986,615
Supplemental disclosure of cash flow information
Interest received during the year	2,893,153	2,894,699	2,931,409
Interest paid during the year	257,553	301,734	371,887
Income taxes paid during the year	411,912	389,008	405,598
Supplemental schedule of noncash investing and financing activities
Securitization of residential mortgage loans allocated to Available-for-sale investment securities	134,698	1,690,490
Securitization of residential mortgage loans allocated to Held to maturity investment securities		1,245,444
Securitization of residential mortgage loans allocated to capitalized servicing rights	1,760	30,879
Real estate acquired in settlement of loans	$ 43,821	$ 44,804	$ 48,932