Segment Reporting - Financial Information for Operating Segments (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023	Dec. 31, 2023
Financial information for the Company's operating segments
Net interest income (loss)	$ 123,290	$ 135,775
Provision for credit losses	2,438	6,460
Noninterest income (loss)	41,381	37,293
Noninterest expense	112,912	109,208
Income (loss) before income taxes	49,321	57,400
Income tax expense (benefit)	9,912	11,322
Net income (loss)	39,409	46,078
Total assets	17,345,741	17,474,083	$ 17,360,535
Goodwill	991,665	991,665	991,665
Community Banks
Financial information for the Company's operating segments
Goodwill	988,898		988,898
Insurance
Financial information for the Company's operating segments
Goodwill	2,767		$ 2,767
Operating segments | Community Banks
Financial information for the Company's operating segments
Net interest income (loss)	129,691	141,796
Provision for credit losses	2,438	6,460
Noninterest income (loss)	31,491	28,493
Noninterest expense	105,167	101,881
Income (loss) before income taxes	53,577	61,948
Income tax expense (benefit)	11,364	12,722
Net income (loss)	42,213	49,226
Total assets	17,303,709	17,362,799
Goodwill	988,898	988,898
Operating segments | Insurance
Financial information for the Company's operating segments
Net interest income (loss)	481	286
Provision for credit losses	0	0
Noninterest income (loss)	3,596	3,362
Noninterest expense	2,147	2,039
Income (loss) before income taxes	1,930	1,609
Income tax expense (benefit)	501	416
Net income (loss)	1,429	1,193
Total assets	41,905	37,168
Goodwill	2,767	2,767
Operating segments | Wealth Management
Financial information for the Company's operating segments
Net interest income (loss)	11	11
Provision for credit losses	0	0
Noninterest income (loss)	6,633	5,812
Noninterest expense	5,185	4,928
Income (loss) before income taxes	1,459	895
Income tax expense (benefit)	20	4
Net income (loss)	1,439	891
Total assets	5,409	79,452
Goodwill	0	0
Other
Financial information for the Company's operating segments
Net interest income (loss)	(6,893)	(6,318)
Provision for credit losses	0	0
Noninterest income (loss)	(339)	(374)
Noninterest expense	413	360
Income (loss) before income taxes	(7,645)	(7,052)
Income tax expense (benefit)	(1,973)	(1,820)
Net income (loss)	(5,672)	(5,232)
Total assets	(5,282)	(5,336)
Goodwill	$ 0	$ 0