Condensed Financial Information - Parent Company - Condensed Balance Sheets (Details) - USD ($) $ in Thousands		Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
ASSETS
Interest-bearing deposits in subsidiary bank		$ 255,237	$ 37,392
Total cash and cash equivalents		536,591	330,678
Securities available-for-sale, at fair value		4,732,762	5,474,359
Other assets		295,521	322,523
Total assets		13,105,594	12,974,066
LIABILITIES AND SHAREHOLDERS’ EQUITY
Total liabilities		11,606,694	11,708,329
Shareholders' equity:
Common stock		1,427	1,427
CAPITAL SURPLUS		681,246	677,593
RETAINED EARNINGS		1,219,525	1,121,945
Accumulated other comprehensive earnings		(403,298)	(535,228)
Total shareholders’ equity		1,498,900	1,265,737	$ 1,759,224	$ 1,678,190
Total liabilities and shareholders’ equity		13,105,594	12,974,066
Subsidiary Bank [Member]
ASSETS
Cash in banks	[1]	92,905	50,204
Interest-bearing deposits in subsidiary bank	[1]	50,412	69,053
Unaffiliated Banks [Member]
ASSETS
Cash in banks	[1]	2	2
Parent Company [Member]
ASSETS
Total cash and cash equivalents		143,319	119,259	$ 152,363	$ 136,666
Securities available-for-sale, at fair value		2,200	2,235
Investment in and advances to subsidiaries, at equity	[1]	1,376,986	1,171,095
Intangible assets		723	723
Other assets		7,044	5,355
Total assets		1,530,272	1,298,667
LIABILITIES AND SHAREHOLDERS’ EQUITY
Total liabilities		31,372	32,930
Shareholders' equity:
Common stock		1,427	1,427
CAPITAL SURPLUS		681,246	677,593
RETAINED EARNINGS		1,219,525	1,121,945
Treasury stock		(11,855)	(11,035)
Deferred compensation		11,855	11,035
Accumulated other comprehensive earnings		(403,298)	(535,228)
Total shareholders’ equity		1,498,900	1,265,737
Total liabilities and shareholders’ equity		$ 1,530,272	$ 1,298,667

[1] Eliminates in consolidation.