SEGMENT INFORMATION (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023	Dec. 31, 2023
SEGMENT INFORMATION
Net interest income	$ 106,990	$ 111,030
Provision for credit losses	6,148	3,500
Operating noninterest revenues	70,285	13,495
Operating noninterest expenses	118,084	114,052
Operating income before income taxes	53,043	6,973
Assets	15,858,670	15,255,953	$ 15,555,753
Goodwill	849,790	842,936	$ 845,396
Core deposit intangibles & Other intangibles, net	54,649	57,978
Operating Segment
SEGMENT INFORMATION
Operating noninterest revenues	71,518	66,817
Operating noninterest expenses	115,603	111,563
Operating income before income taxes	56,757	62,784
Assets	15,987,073	15,365,360
Inter segment elimination
SEGMENT INFORMATION
Operating noninterest revenues	(1,249)	(1,235)
Operating noninterest expenses	(1,249)	(1,235)
Assets	(128,403)	(109,407)
Banking and Corporate | Operating Segment
SEGMENT INFORMATION
Net interest income	106,214	110,682
Provision for credit losses	6,148	3,500
Operating noninterest revenues	18,185	16,445
Operating noninterest expenses	78,227	78,413
Operating income before income taxes	40,024	45,214
Assets	15,632,930	15,045,902
Goodwill	732,598	733,064
Core deposit intangibles & Other intangibles, net	8,143	11,629
Employee Benefit Services | Operating Segment
SEGMENT INFORMATION
Net interest income	623	254
Provision for credit losses	0	0
Operating noninterest revenues	32,570	30,187
Operating noninterest expenses	20,333	18,274
Operating income before income taxes	12,860	12,167
Assets	254,668	229,091
Goodwill	89,778	85,384
Core deposit intangibles & Other intangibles, net	30,792	31,778
Insurance | Operating Segment
SEGMENT INFORMATION
Net interest income	27	35
Provision for credit losses	0	0
Operating noninterest revenues	11,127	11,548
Operating noninterest expenses	10,123	8,781
Operating income before income taxes	1,031	2,802
Assets	64,337	61,244
Goodwill	23,979	21,990
Core deposit intangibles & Other intangibles, net	13,757	13,040
Wealth Management | Operating Segment
SEGMENT INFORMATION
Net interest income	126	59
Provision for credit losses	0	0
Operating noninterest revenues	9,636	8,637
Operating noninterest expenses	6,920	6,095
Operating income before income taxes	2,842	2,601
Assets	35,138	29,123
Goodwill	3,435	2,498
Core deposit intangibles & Other intangibles, net	$ 1,957	$ 1,531