Parent Company Condensed Financial Statements (Condensed Statement of Cash Flows) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Statement of cash flows
Net income	$ 872,981	$ 567,797	$ 674,035
Adjustments to reconcile net income to net cash provided by operating activities:
Deferred income tax expense (benefit)	4,762	(41,515)	(21,604)
Net change in other assets	124,496	(340,566)	(172,506)
Net change in other liabilities	(29,412)	170,420	6,015
Net cash provided by operating activities	1,168,422	692,644	733,145
CASH FLOWS FROM INVESTING ACTIVITIES
Net increase in investments in tax credit investments	(189,836)	(154,887)	(146,902)
Distributions received from equity method investees	14,440	15,901	9,502
Other investing activities	(925)	6,858	2,560
Net cash (used in) provided by investing activities	(9,117,204)	(6,873,736)	(2,592,926)
Common stock:
Proceeds from issuance pursuant to various stock compensation plans and agreements	2,573	2,326	3,383
Stocks tendered for payment of withholding taxes	(15,702)	(8,253)	(14,635)
Repurchase of common stocks pursuant to the Stock Repurchase Program	0	(145,966)	0
Cash dividends paid	(188,762)	(158,222)	(155,107)
Net cash provided by financing activities	7,835,045	6,908,908	2,125,938
Net (decrease) increase in cash and cash equivalents	(105,036)	756,822	259,772
CASH AND CASH EQUIVALENTS, BEGINNING OF YEAR	4,017,971	3,261,149	3,001,377
CASH AND CASH EQUIVALENTS, END OF YEAR	3,912,935	4,017,971	3,261,149
Parent Company
Statement of cash flows
Net income	872,981	567,797	674,035
Adjustments to reconcile net income to net cash provided by operating activities:
Undistributed earnings of subsidiaries, principally bank	(680,958)	(65,046)	(498,569)
Amortization expense	1,877	1,523	8,703
Deferred income tax expense (benefit)	2,721	491	(10,132)
Net change in other assets	(5,685)	40	10,246
Net change in other liabilities	(81,706)	77,052	(18)
Net cash provided by operating activities	109,230	581,857	184,265
CASH FLOWS FROM INVESTING ACTIVITIES
Net increase in investments in tax credit investments	(346)	(172)	(292)
Distributions received from equity method investees	436	4,096	2,577
Net increase in investments in and advances to nonbank subsidiaries	(1,476)	(2,732)	(3,314)
Other investing activities	0	0	(157)
Net cash (used in) provided by investing activities	(1,386)	1,192	(1,186)
Common stock:
Proceeds from issuance pursuant to various stock compensation plans and agreements	2,573	2,326	3,383
Stocks tendered for payment of withholding taxes	(15,702)	(8,253)	(14,635)
Repurchase of common stocks pursuant to the Stock Repurchase Program	0	(145,966)	0
Cash dividends paid	(188,762)	(158,222)	(155,107)
Net cash provided by financing activities	(201,891)	(310,115)	(166,359)
Net (decrease) increase in cash and cash equivalents	(94,047)	272,934	16,720
CASH AND CASH EQUIVALENTS, BEGINNING OF YEAR	439,065	166,131	149,411
CASH AND CASH EQUIVALENTS, END OF YEAR	$ 345,018	$ 439,065	$ 166,131