Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015
Cash Flows From Operating Activities: [Abstract]
Net income	$ 107,260	$ 155,367
Adjustments to reconcile net income to net cash provided by (used in) operating activities:
Provision for credit losses	55,000	4,000
Change in fair value of mortgage servicing rights	44,271	512
Net unrealized gains from derivative contracts	(15,459)	(982)
Tax effect from equity compensation, net	(351)	(744)
Change in bank-owned life insurance	(4,515)	(4,596)
Share-based compensation	5,730	4,922
Depreciation and amortization	41,474	33,753
Net amortization of securities discounts and premiums	21,814	29,341
Net realized gains on financial instruments and other net gains	(9,787)	(12,483)
Net gain on mortgage loans held for sale	(37,151)	(39,192)
Mortgage loans originated for sale	(3,062,859)	(3,393,246)
Proceeds from sale of mortgage loans held for sale	2,981,973	3,244,010
Capitalized mortgage servicing rights	(34,355)	(42,382)
Change in trading and fair value option securities	90,484	(95,757)
Change in receivables	(9,698)	11,610
Change in other assets	(225)	(7,749)
Change in accrued interest, taxes and expense	20,299	2,644
Change in other liabilities	(8,854)	21,943
Net cash provided by (used in) operating activities	185,051	(89,029)
Cash Flows From Investing Activities: [Abstract]
Proceeds from maturities or redemptions of investment securities	52,463	32,786
Proceeds from maturities or redemptions of available for sale securities	721,432	954,893
Purchases of investment securities	(18,599)	(9,584)
Purchases of available for sale securities	(1,155,261)	(1,711,619)
Proceeds from sales of available for sale securities	795,140	713,660
Change in amount receivable on unsettled securities transactions	(102,627)	65,566
Loans originated, net of principal collected	(481,085)	(890,180)
Net payments on derivative asset contracts	(204,041)	(174,475)
Acquisitions, net of cash acquired	(7,700)	(18,064)
Proceeds from disposition of assets	78,629	102,736
Purchases of assets	(107,241)	(144,454)
Net cash used in investing activities	(428,890)	(1,078,735)
Cash Flows From Financing Activities: [Abstract]
Net change in demand deposits, transaction deposits and savings accounts	(169,354)	(96,793)
Net change in time deposits	(159,003)	15,663
Net change in other borrowed funds	259,359	1,675,859
Repayment of subordinated debentures	0	(121,810)
Issuance of subordinated debentures	145,390	0
Net proceeds on derivative liability contracts	196,225	157,498
Net change in derivative margin accounts	(188,823)	(47,716)
Change in amount due on unsettled security transactions	(5,140)	(252,969)
Issuance of common and treasury stock, net	2,276	5,739
Tax effect from equity compensation, net	351	744
Sale of non-controlling interests	0	5,500
Repurchase of common stock	(17,770)	(29,484)
Dividends paid	(56,720)	(57,660)
Net cash provided by financing activities	6,791	1,254,571
Net increase (decrease) in cash and cash equivalents	(237,048)	86,807
Cash and cash equivalents at beginning of period	2,643,599	2,475,842
Cash and cash equivalents at end of period	2,406,551	2,562,649
Supplemental Cash Flow Information: [Abstract]
Cash paid for interest	40,213	34,116
Cash paid for taxes	14,671	51,699
Net loans and bank premises transferred to repossessed real estate and other assets	5,372	4,262
Residential mortgage loans guaranteed by U.S. government agencies that became eligible for repurchase during the period	49,325	52,569
Conveyance of other real estate owned guaranteed by U.S. government agencies	$ 29,512	$ 80,048