Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019
Cash Flows From Operating Activities: [Abstract]
Net income	$ 126,270	$ 248,045
Adjustments to reconcile net income to net cash used in operating activities: [Abstract]
Provision for credit losses	229,092	13,000
Change in fair value of mortgage servicing rights due to market assumption changes	89,241	50,221
Change in the fair value of mortgage servicing rights due to principal payments	17,779	15,664
Net unrealized (gains) losses from derivative contracts	(56,678)	(17,095)
Share-based compensation	6,125	8,149
Depreciation and amortization	47,016	45,926
Net amortization of discounts and premiums	7,199	(10,913)
Net losses (gains) on financial instruments and other losses (gains), net	(2,186)	564
Net gain on mortgage loans held for sale	(42,411)	(16,735)
Mortgage loans originated for sale	(1,733,205)	(1,240,368)
Proceeds from sale of mortgage loans held for sale	1,654,433	1,215,756
Capitalized mortgage servicing rights	(13,906)	(14,939)
Change in trading and fair value option securities	801,215	(799,241)
Change in receivables	(724,486)	(228,973)
Change in other assets	(29,352)	(4,965)
Change in accrued interest, taxes and expense	36,773	(41,866)
Change in other liabilities	373,541	100,731
Net cash provided by (used in) operating activities	786,460	(677,039)
Cash Flows From Investing Activities: [Abstract]
Proceeds from maturities or redemptions of investment securities	23,296	26,513
Proceeds from maturities or redemptions of available for sale securities	1,070,585	704,542
Purchases of available for sale securities	(2,139,775)	(2,510,271)
Proceeds from sales of available for sale securities	205,945	367,357
Change in amount receivable on unsettled available for sale securities transactions	(118,744)	(28,580)
Loans originated, net of principal collected	(2,294,658)	(569,075)
Net payments on derivative asset contracts	(67,105)	(10,838)
Proceeds from disposition of assets	710,269	116,163
Purchases of assets	(416,815)	(250,911)
Net cash used in investing activities	(3,027,002)	(2,155,100)
Cash Flows From Financing Activities: [Abstract]
Net change in demand deposits, transaction deposits and savings accounts	6,136,235	(73,200)
Net change in time deposits	134,911	114,377
Net change in other borrowed funds	(3,971,540)	2,968,697
Net proceeds on derivative liability contracts	60,851	6,140
Net change in derivative margin accounts	(96,114)	(152,533)
Change in amount due on unsettled available for sale securities transactions	75,544	313,736
Issuance of common and treasury stock, net	(5,022)	(525)
Repurchase of common stock	(33,380)	(80,702)
Dividends paid	(71,992)	(71,784)
Net cash provided by financing activities	2,229,493	3,024,206
Net increase (decrease) in cash and cash equivalents	(11,049)	192,067
Cash and cash equivalents at beginning of period	1,258,821	1,143,424
Cash and cash equivalents at end of period	1,247,772	1,335,491
Supplemental Cash Flow Information: [Abstract]
Cash paid for interest	117,471	203,513
Cash paid for taxes	5,470	54,722
Net loans and bank premises transferred to repossessed real estate and other assets	19,556	2,606
Residential mortgage loans guaranteed by U.S. government agencies that became eligible for repurchase during the period	157,300	44,258
Conveyance of other real estate owned guaranteed by U.S. government agencies	6,255	15,484
Right-of-use assets obtained in exchange for operating lease liabilities	$ 9,151	$ 12,754