Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Cash Flows From Operating Activities: [Abstract]
Net income	$ 144,308	$ 61,984
Adjustments to reconcile net income to net cash used in operating activities: [Abstract]
Provision for credit losses	(25,000)	93,771
Change in fair value of mortgage servicing rights due to market assumption changes	(33,874)	88,480
Change in the fair value of mortgage servicing rights due to principal payments	11,961	8,019
Net unrealized (gains) losses from derivative contracts	92,502	15,369
Share-based compensation	2,724	3,245
Depreciation and amortization	24,918	23,198
Net amortization of discounts and premiums	4,853	2,013
Net losses (gains) on financial instruments and other losses (gains), net	(10,587)	10,742
Net gain on mortgage loans held for sale	(19,045)	(13,278)
Mortgage loans originated for sale	(843,053)	(548,956)
Proceeds from sale of mortgage loans held for sale	836,209	548,077
Capitalized mortgage servicing rights	(9,830)	(5,441)
Change in trading and fair value option securities	(335,624)	(1,092,249)
Change in receivables	15,650	(1,107,130)
Change in other assets	(24,991)	(24,503)
Change in other liabilities	(49,998)	193,857
Net cash used in operating activities	(218,877)	(1,742,802)
Cash Flows From Investing Activities: [Abstract]
Proceeds from maturities or redemptions of investment securities	18,624	19,079
Proceeds from maturities or redemptions of available for sale securities	877,257	394,205
Purchases of available for sale securities	(1,451,909)	(1,552,914)
Proceeds from sales of available for sale securities	56,037	26,894
Change in amount receivable on unsettled available for sale securities transactions	(26,130)	(22,113)
Loans originated, net of principal collected	498,667	(729,881)
Net payments on derivative asset contracts	(7,016)	(98,215)
Net change in restricted equity securities	31,777	70,510
Proceeds from disposition of assets	43,739	15,282
Purchases of assets	(63,110)	(40,295)
Net cash used in investing activities	(22,064)	(1,917,448)
Cash Flows From Financing Activities: [Abstract]
Net change in demand deposits, transaction deposits and savings accounts	1,671,518	1,608,360
Net change in time deposits	37,228	14,624
Net change in other borrowed funds	(1,078,174)	1,747,640
Net proceeds on derivative liability contracts	8,437	82,126
Net change in derivative margin accounts	2,995	(163,911)
Change in amount due on unsettled available for sale securities transactions	(101,311)	160,211
Issuance of common and treasury stock, net	(4,866)	(5,022)
Repurchase of common stock	(20,071)	(33,380)
Dividends paid	(36,192)	(36,142)
Net cash provided by financing activities	479,564	3,374,506
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Period Increase (Decrease), Including Exchange Rate Effect, Total	238,623	(285,744)
Cash and cash equivalents at beginning of period	1,180,573	1,258,821
Cash and cash equivalents at end of period	1,419,196	973,077
Supplemental Cash Flow Information: [Abstract]
Cash paid for interest	16,743	87,468
Cash paid for taxes	852	853
Net loans and bank premises transferred to repossessed real estate and other assets	147	18,474
Residential mortgage loans guaranteed by U.S. government agencies that became eligible for repurchase during the period	36,496	20,277
Conveyance of other real estate owned guaranteed by U.S. government agencies	1,448	5,694
Right-of-use assets obtained in exchange for operating lease liabilities	$ 1,191	$ 7,108