Consolidated Statements of Cash Flows (Unaudited) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Cash Flows From Operating Activities:
Net income	$ 354,124	$ 289,824	$ 248,294
Adjustments to reconcile net income to net cash provided by operating activities:
Provision for credit losses	(22,000)	(6,050)	105,139
Change in fair value of mortgage servicing rights	9,210	40,447	(3,661)
Unrealized gains from derivatives	(984)	(9,651)	(18,882)
Tax benefit on exercise of stock options	(120)	(659)	(425)
Change in bank-owned life insurance	(11,089)	(11,280)	(12,066)
Stock-based compensation	8,030	9,396	8,160
Depreciation and amortization	54,935	49,967	58,987
Net amortization of securities discounts and premiums	87,769	112,227	105,680
Net realized losses (gains) on financial instruments and other assets	(135,696)	(3,589)	1,420
Mortgage loans originated for resale	(3,708,350)	(2,293,436)	(2,256,943)
Proceeds from sale of mortgage loans held for resale	3,731,830	2,369,895	2,246,228
Capitalized mortgage servicing rights	(42,191)	(26,251)	(27,603)
Change in trading and fair value option securities	226,144	(247,386)	(139,319)
Change in receivables	9,244	24,236	(40,118)
Change in other assets	10,999	16,469	9,023
Change in accrued interest, taxes and expense	23,424	63,827	22,227
Change in other liabilities	(3,429)	(50,198)	59,037
Net cash provided by operating activities	591,850	327,788	365,178
Cash Flows From Investing Activities:
Proceeds from maturities or redemptions of investment securities	111,511	68,020	111,976
Proceeds from maturities or redemptions of available for sale securities	4,456,363	3,650,900	3,185,131
Purchases of investment securities	(172,327)	(37,085)	(211,312)
Purchases of available for sale securities	(7,334,843)	(7,504,261)	(5,565,931)
Proceeds from sales of available for sale securities	1,744,662	2,725,760	2,013,620
Change in amount receivable on unsettled securities transactions	(135,901)	59,908	(135,059)
Loans originated net of principal collected	(1,077,075)	(598,499)	469,223
Net proceeds from (payments on) derivative asset contracts	(13,273)	4,994	201,289
Acquisitions, net of cash acquired	(23,615)	0	0
Proceeds from disposition of assets	170,907	122,314	38,640
Purchases of assets	(94,756)	(56,195)	(64,916)
Net cash provided by (used in) investing activities	(2,368,347)	(1,564,144)	42,661
Net Cash Provided by (Used in) Financing Activities [Abstract]
Net change in demand deposits, transaction deposits and savings accounts	2,830,470	1,710,705	1,919,658
Net change in time deposits	(413,990)	(127,026)	(257,586)
Net payments or proceeds on derivative liability contracts	(7,560)	15,674	(194,831)
Net change in derivative margin accounts	39,237	(102,262)	70,340
Change in amount due on unsettled security transactions	(355,918)	492,946	(51,910)
Issuance of common and treasury stock, net	14,650	14,541	8,552
Sale of non-controlling interest	300	0	0
Tax benefit on exercise of stock options	120	659	425
Repurchase of common stock	(20,558)	(26,446)	0
Dividends paid	(166,982)	(76,423)	(66,557)
Net cash provided by (used in) financing activities	2,076,671	953,317	(59,651)
Net decrease in cash and cash equivalents	299,874	(283,039)	348,188
Cash and cash equivalents at beginning of period	986,365	1,269,404	921,216
Cash and cash equivalents at end of period	1,286,239	986,365	1,269,404
Cash paid for interest	90,137	122,166	144,095
Cash paid for taxes	158,703	156,465	133,551
Net loans transferred to real estate and other repossessed assets	133,502	87,476	72,845
Residential mortgage loans guaranteed by U.S. government agencies that became elgible fo repurchase during the year	121,432	154,134	0
Conveyance of other real estate owned guaranteed by U.S. government agencies	89,223	14,501	0
Parent Company and other non-bank subsidiaries [Member]
Net Cash Provided by (Used in) Financing Activities [Abstract]
Net change in other borrowings	10,500	(7,217)	0
Subsidiary Bank [Member]
Net Cash Provided by (Used in) Financing Activities [Abstract]
Net change in other borrowings	200,107	(941,834)	(1,487,742)
Repayment of subordinated debt	$ (53,705)	$ 0	$ 0