Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Cash Flows From Operating Activities: [Abstract]
Net income	$ 61,984	$ 110,265
Adjustments to reconcile net income to net cash used in operating activities:
Provision for credit losses	93,771	8,000
Change in fair value of mortgage servicing rights due to market changes	88,480	20,666
Change in the fair value of mortgage servicing rights due to principal payments	8,019	6,583
Net unrealized losses from derivative contracts	15,369	695
Share-based compensation	3,245	5,414
Depreciation and amortization	23,198	19,412
Net amortization of discounts and premiums	2,013	4,339
Net losses (gains) on financial instruments and other losses (gains), net	10,742	1,872
Net gain on mortgage loans held for sale	(13,278)	(5,640)
Mortgage loans originated for sale	(548,956)	(510,527)
Proceeds from sale of mortgage loans held for sale	548,077	507,459
Capitalized mortgage servicing rights	(5,441)	(6,188)
Change in trading and fair value option securities	(1,092,249)	(608,232)
Change in receivables	(1,107,130)	(682,957)
Change in other assets	(17,198)	(5,074)
Change in accrued interest, taxes and expense	(7,305)	(18,220)
Change in other liabilities	193,857	46,147
Net cash used in operating activities	(1,742,802)	(1,105,986)
Cash Flows From Investing Activities: [Abstract]
Proceeds from maturities or redemptions of investment securities	19,079	23,227
Proceeds from maturities or redemptions of available for sale securities	394,205	337,822
Purchases of available for sale securities	(1,552,914)	(663,193)
Proceeds from sales of available for sale securities	26,894	245,259
Change in amount receivable on unsettled available for sale securities transactions	(22,113)	31,618
Loans originated, net of principal collected	(729,881)	(97,656)
Net payments on derivative asset contracts	(98,215)	(33,781)
Proceeds from disposition of assets	165,282	70,379
Purchases of assets	(119,785)	(116,692)
Net cash used in investing activities	(1,917,448)	(203,017)
Cash Flows From Financing Activities: [Abstract]
Net change in demand deposits, transaction deposits and savings accounts	1,608,360	(16,970)
Net change in time deposits	14,624	84,828
Net change in other borrowed funds	1,747,640	1,614,995
Net proceeds on derivative liability contracts	82,126	36,250
Net change in derivative margin accounts	(163,911)	(150,722)
Change in amount due on unsettled available for sale securities transactions	160,211	(22,923)
Issuance of common and treasury stock, net	(5,022)	(549)
Repurchase of common stock	(33,380)	(60,577)
Dividends paid	(36,142)	(36,052)
Net cash provided by financing activities	3,374,506	1,448,280
Net increase (decrease) in cash and cash equivalents	(285,744)	139,277
Cash and cash equivalents at beginning of period	1,258,821	1,143,424
Cash and cash equivalents at end of period	973,077	1,282,701
Supplemental Cash Flow Information: [Abstract]
Cash paid for interest	87,468	94,660
Cash paid for taxes	853	898
Net loans and bank premises transferred to repossessed real estate and other assets	18,474	1,032
Residential mortgage loans guaranteed by U.S. government agencies that became eligible for repurchase during the period	20,277	22,970
Conveyance of other real estate owned guaranteed by U.S. government agencies	5,694	8,404
Right-of-use assets obtained in exchange for operating lease liabilities	$ 7,108	$ 4,209