Parent Company Condensed Financial Statements - Condensed Statement of Cash Flows (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Statement of cash flows
Net income	$ 1,161,161	$ 1,128,083	$ 872,981
Adjustments to reconcile net income to net cash provided by operating activities:
Deferred income tax expense (benefit)	(49,139)	(43,988)	4,762
Net change in other assets	(146,270)	187,512	124,496
Net change in other liabilities	105,304	461,385	(63,360)
Other operating activities, net	3,860	1,673	558
Net cash provided by operating activities	1,424,909	2,066,022	1,168,422
CASH FLOWS FROM INVESTING ACTIVITIES
Net increase in investments in tax credit investments	(228,550)	(167,303)	(189,836)
Distributions received from equity method investees	23,774	18,221	14,440
Other investing activities, net	(112,036)	(7,720)	(4,763)
Net cash used in investing activities	(4,247,161)	(4,582,892)	(9,117,204)
Common stock:
Proceeds from issuance pursuant to various stock compensation plans and agreements	3,208	3,178	2,573
Stocks tendered for payment of withholding taxes	(23,751)	(19,087)	(15,702)
Repurchase of common stocks pursuant to the Stock Repurchase Program	(82,174)	(99,990)	0
Cash dividends paid	(274,554)	(228,381)	(188,762)
Net cash provided by financing activities	3,962,454	2,114,210	7,835,045
Net increase (decrease) in cash and cash equivalents	1,133,200	(431,151)	(105,036)
CASH AND CASH EQUIVALENTS, BEGINNING OF YEAR	3,481,784	3,912,935	4,017,971
CASH AND CASH EQUIVALENTS, END OF YEAR	4,614,984	3,481,784	3,912,935
Parent Company
Statement of cash flows
Net income	1,161,161	1,128,083	872,981
Adjustments to reconcile net income to net cash provided by operating activities:
Undistributed earnings of subsidiaries, principally bank	(470,740)	(897,069)	(680,958)
Deferred income tax expense (benefit)	948	(2,193)	2,721
Net change in other assets	(4,160)	4,250	(5,685)
Net change in other liabilities	(47)	779	(81,706)
Other operating activities, net	2,443	1,333	1,877
Net cash provided by operating activities	689,605	235,183	109,230
CASH FLOWS FROM INVESTING ACTIVITIES
Net increase in investments in tax credit investments	0	(1,612)	(346)
Distributions received from equity method investees	1,594	410	436
Other investing activities, net	(96,689)	(6,188)	(1,476)
Net cash used in investing activities	(95,095)	(7,390)	(1,386)
Common stock:
Proceeds from issuance pursuant to various stock compensation plans and agreements	3,208	3,178	2,573
Stocks tendered for payment of withholding taxes	(23,751)	(19,087)	(15,702)
Repurchase of common stocks pursuant to the Stock Repurchase Program	(82,174)	(99,990)	0
Cash dividends paid	(274,554)	(228,381)	(188,762)
Net cash provided by financing activities	(377,271)	(344,280)	(201,891)
Net increase (decrease) in cash and cash equivalents	217,239	(116,487)	(94,047)
CASH AND CASH EQUIVALENTS, BEGINNING OF YEAR	228,531	345,018	439,065
CASH AND CASH EQUIVALENTS, END OF YEAR	$ 445,770	$ 228,531	$ 345,018