Condensed Financial Information - Parent Company - Condensed Balance Sheets (Details) - USD ($) $ in Thousands		Dec. 31, 2021	Dec. 31, 2020	Mar. 27, 2020	Dec. 31, 2019	Dec. 31, 2018
ASSETS
Interest-bearing deposits in subsidiary bank		$ 323,535	$ 517,971
Total cash and cash equivalents		528,588	729,084		$ 282,604	$ 248,647
Securities available-for-sale, at fair value		6,573,179	4,393,029
Other assets		170,834	133,258
Total assets		13,102,461	10,904,500
LIABILITIES AND SHAREHOLDERS’ EQUITY
Total liabilities		11,343,237	9,226,310
SHAREHOLDERS’ EQUITY:
Common stock		1,425	1,422
Capital surplus		676,871	669,644
Retained earnings		981,675	836,729	$ 466,000
Accumulated other comprehensive earnings		99,253	170,395
Total shareholders’ equity		1,759,224	1,678,190		1,227,197	1,053,295
Total liabilities and shareholders’ equity		13,102,461	10,904,500
Subsidiary Bank [Member]
ASSETS
Cash in banks	[1]	83,547	67,904
Interest-bearing deposits in subsidiary bank	[1]	68,814	68,760
Unaffiliated Banks [Member]
ASSETS
Cash in banks	[1]	2	2
Parent Company [Member]
ASSETS
Total cash and cash equivalents		152,363	136,666		$ 125,076	$ 101,262
Securities available-for-sale, at fair value		2,489	2,610
Investment in and advances to subsidiaries, at equity	[1]	1,629,387	1,558,851
Intangible assets		723	723
Other assets		3,610	2,982
Total assets		1,788,572	1,701,832
LIABILITIES AND SHAREHOLDERS’ EQUITY
Total liabilities		29,348	23,642
SHAREHOLDERS’ EQUITY:
Common stock		1,425	1,422
Capital surplus		676,871	669,644
Retained earnings		981,675	836,729
Treasury stock		(10,090)	(9,126)
Deferred compensation		10,090	9,126
Accumulated other comprehensive earnings		99,253	170,395
Total shareholders’ equity		1,759,224	1,678,190
Total liabilities and shareholders’ equity		$ 1,788,572	$ 1,701,832

[1] Eliminates in consolidation.