Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019
Cash Flows From Operating Activities: [Abstract]
Net income	$ 280,362	$ 389,903
Adjustments to reconcile net income to net cash used in operating activities: [Abstract]
Provision for credit losses	229,092	25,000
Change in fair value of mortgage servicing rights due to market assumption changes	85,800	62,814
Change in the fair value of mortgage servicing rights due to principal payments	28,971	27,600
Net unrealized (gains) losses from derivative contracts	(51,323)	(25,306)
Share-based compensation	14,879	11,620
Depreciation and amortization	74,330	69,762
Net amortization of discounts and premiums	1,921	(16,648)
Net losses (gains) on financial instruments and other losses (gains), net	(4,216)	(2,656)
Net gain on mortgage loans held for sale	(77,039)	(25,803)
Mortgage loans originated for sale	(2,773,686)	(2,170,287)
Proceeds from sale of mortgage loans held for sale	2,757,412	2,070,572
Capitalized mortgage servicing rights	(21,330)	(24,821)
Change in trading and fair value option securities	338,992	(1,251,759)
Change in receivables	(936,428)	(613,872)
Change in other assets	(8,574)	12,981
Change in accrued interest, taxes and expense	8,678	(15,600)
Change in other liabilities	412,686	419,982
Net cash provided by (used in) operating activities	360,527	(1,056,518)
Cash Flows From Investing Activities: [Abstract]
Proceeds from maturities or redemptions of investment securities	35,967	49,621
Proceeds from maturities or redemptions of available for sale securities	1,813,057	1,267,190
Purchases of available for sale securities	(3,238,556)	(3,802,635)
Proceeds from sales of available for sale securities	206,979	628,385
Change in amount receivable on unsettled available for sale securities transactions	3,988	29,010
Loans originated, net of principal collected	(1,894,663)	(590,196)
Net payments on derivative asset contracts	(96,109)	40,922
Proceeds from disposition of assets	1,302,013	127,476
Purchases of assets	(1,007,240)	(308,630)
Net cash used in investing activities	(2,874,564)	(2,558,857)
Cash Flows From Financing Activities: [Abstract]
Net change in demand deposits, transaction deposits and savings accounts	7,561,708	773,152
Net change in time deposits	(209,876)	129,980
Net change in other borrowed funds	(4,839,524)	3,027,298
Net proceeds on derivative liability contracts	102,064	(43,932)
Net change in derivative margin accounts	(260,949)	(85,468)
Change in amount due on unsettled available for sale securities transactions	54,408	111,828
Issuance of common and treasury stock, net	(5,022)	(348)
Repurchase of common stock	(33,380)	(106,639)
Dividends paid	(107,842)	(107,332)
Net cash provided by financing activities	2,261,587	3,698,539
Net increase (decrease) in cash and cash equivalents	(252,450)	83,164
Cash and cash equivalents at beginning of period	1,258,821	1,143,424
Cash and cash equivalents at end of period	1,006,371	1,226,588
Supplemental Cash Flow Information: [Abstract]
Cash paid for interest	138,877	316,481
Cash paid for taxes	91,977	77,912
Net loans and bank premises transferred to repossessed real estate and other assets	42,099	8,489
Residential mortgage loans guaranteed by U.S. government agencies that became eligible for repurchase during the period	239,200	65,286
Conveyance of other real estate owned guaranteed by U.S. government agencies	9,165	22,449
Right-of-use assets obtained in exchange for operating lease liabilities	$ 9,481	$ 58,766