Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018
Cash Flows From Operating Activities: [Abstract]
Net income	$ 389,903	$ 338,047
Adjustments to reconcile net income to net cash used in operating activities:
Provision for credit losses	25,000	(1,000)
Change in fair value of mortgage servicing rights due to market changes	62,814	(28,901)
Change in the fair value of mortgage servicing rights due to principal payments	27,600	25,783
Net unrealized losses (gains) from derivative contracts	(25,306)	3,309
Share-based compensation	11,620	5,975
Depreciation and amortization	69,762	41,999
Net amortization of discounts and premiums	(16,648)	19,001
Net losses (gains) on financial instruments and other losses (gains), net	(2,656)	5,581
Net gain on mortgage loans held for sale	(25,803)	(26,242)
Mortgage loans originated for sale	(2,170,287)	(2,093,860)
Proceeds from sale of mortgage loans held for sale	2,070,572	2,165,989
Capitalized mortgage servicing rights	(24,821)	(28,688)
Change in trading and fair value option securities	(1,251,759)	(848,409)
Change in receivables	(613,872)	(249,347)
Change in other assets	12,981	(15,157)
Change in accrued interest, taxes and expense	(15,600)	66,697
Change in other liabilities	419,982	229,815
Net cash used in operating activities	(1,056,518)	(389,408)
Cash Flows From Investing Activities: [Abstract]
Proceeds from maturities or redemptions of investment securities	49,621	89,099
Proceeds from maturities or redemptions of available for sale securities	1,267,190	1,208,373
Purchases of investment securities	0	(4,218)
Purchases of available for sale securities	(3,802,635)	(1,404,291)
Proceeds from sales of available for sale securities	628,385	232,826
Change in amount receivable on unsettled available for sale securities transactions	29,010	67,775
Loans originated, net of principal collected	(590,196)	(1,187,762)
Net payments on derivative asset contracts	40,922	(39,485)
Acquisitions, net of cash acquired	0	(13,870)
Proceeds from disposition of assets	127,476	265,786
Purchases of assets	(308,630)	(250,447)
Net cash used in investing activities	(2,558,857)	(1,036,214)
Cash Flows From Financing Activities: [Abstract]
Net change in demand deposits, transaction deposits and savings accounts	773,152	(406,446)
Net change in time deposits	129,980	(22,570)
Net change in other borrowed funds	3,027,298	1,035,549
Net proceeds on derivative liability contracts	(43,932)	42,883
Net change in derivative margin accounts	(85,468)	(46,390)
Change in amount due on unsettled available for sale securities transactions	111,828	(148,190)
Issuance of common and treasury stock, net	(348)	(310)
Repurchase of common stock	(106,639)	(8,408)
Dividends paid	(107,332)	(91,303)
Net cash provided by financing activities	3,698,539	354,815
Net increase (decrease) in cash and cash equivalents	83,164	(1,070,807)
Cash and cash equivalents at beginning of period	1,143,424	2,317,054
Cash and cash equivalents at end of period	1,226,588	1,246,247
Supplemental Cash Flow Information: [Abstract]
Cash paid for interest	316,481	163,381
Cash paid for taxes	77,912	77,373
Net loans and bank premises transferred to repossessed real estate and other assets	8,489	9,513
Residential mortgage loans guaranteed by U.S. government agencies that became eligible for repurchase during the period	65,286	70,814
Conveyance of other real estate owned guaranteed by U.S. government agencies	22,449	32,206
Right-of-use assets obtained in exchange for operating lease liabilities	$ 58,766	$ 0