Condensed Financial Information (Parent Company Only) - Condensed Statements of Cash Flows (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
OPERATING ACTIVITIES
Net income	$ 271,156	$ 254,904	$ 238,167
Items not requiring (providing) cash
Stock-based compensation expense	15,868	13,197	12,921
Deferred income taxes	10,937	(122)	34,911
Changes in:
Other assets	(33,495)	(7,480)	31,920
Net cash provided by operating activities	277,780	202,543	256,078
INVESTING ACTIVITIES
Net collections (originations) of loans	2,333,893	1,327,248	23,806
Proceeds from maturities of available-for-sale securities	1,001,669	2,346,930	793,270
Purchases of available-for-sale securities	(5,266,148)	(4,140,963)	(1,708,948)
Net cash provided by (used in) investing activities	(2,537,736)	1,189,869	604,477
FINANCING ACTIVITIES
Proceeds from issuance of other borrowings	0	0	25,500
Stock repurchases	132,459	113,327	10,128
Dividends paid on preferred stock	(47)	(52)	(339)
Dividends paid on common stock	(78,845)	(74,593)	(63,921)
Retirement of preferred stock	(767)	0	(42,000)
Net cash provided by (used in) financing activities	438,457	1,083,117	(697,390)
INCREASE (DECREASE) IN CASH EQUIVALENTS	(1,821,499)	2,475,529	163,165
CASH AND CASH EQUIVALENTS, BEGINNING OF YEAR	3,472,152	996,623	833,458
CASH AND CASH EQUIVALENTS, END OF YEAR	1,650,653	3,472,152	996,623
Parent Company
OPERATING ACTIVITIES
Net income	271,156	254,904	238,167
Items not requiring (providing) cash
Stock-based compensation expense	15,868	13,197	12,921
Depreciation and amortization	1,805	1,796	1,637
Deferred income taxes	3,347	1,583	(3,632)
Equity in undistributed net income of bank subsidiaries	(76,299)	29,345	(191,530)
Changes in:
Other assets	(2,099)	(27,056)	3,299
Other liabilities	11,109	7,790	(2,648)
Net cash provided by operating activities	224,887	281,559	58,214
INVESTING ACTIVITIES
Net collections (originations) of loans	(2,139)	186	117
Net (purchases of) proceeds from premises and equipment	(83)	(7)	(23,184)
(Advances to) repayment for subsidiaries	0	(15,363)	0
Proceeds from maturities of available-for-sale securities	0	0	2,544
Purchases of available-for-sale securities	0	0	(439)
Cash paid in business combinations	(6,818)	0	(36,811)
Other, net	2	185	29
Net cash provided by (used in) investing activities	(9,038)	(14,999)	(57,744)
FINANCING ACTIVITIES
(Repayment) issuance of long-term debt, net	(1,563)	(7,442)	2,000
(Cancellation) issuance of common stock, net	1,460	(3,131)	(1,077)
Stock repurchases	132,459	113,327	10,128
Dividends paid on preferred stock	(47)	(52)	(339)
Dividends paid on common stock	(78,845)	(74,593)	(63,921)
Retirement of preferred stock	(767)	0	(42,000)
Net cash provided by (used in) financing activities	(212,221)	(198,545)	(115,465)
INCREASE (DECREASE) IN CASH EQUIVALENTS	3,628	68,015	(114,995)
CASH AND CASH EQUIVALENTS, BEGINNING OF YEAR	172,083	104,068	219,063
CASH AND CASH EQUIVALENTS, END OF YEAR	$ 175,711	$ 172,083	$ 104,068