Segment Reporting - Financial Information for Operating Segments (Details) - USD ($) $ in Thousands	3 Months Ended				6 Months Ended
	Jun. 30, 2023	Mar. 31, 2023	Jun. 30, 2022	Mar. 31, 2022	Jun. 30, 2023	Jun. 30, 2022	Dec. 31, 2022
Financial information for the Company's operating segments
Net interest income (loss)	$ 130,216		$ 113,515		$ 265,991	$ 213,144
Provision for credit losses	3,000		2,000		10,960	3,500
Noninterest income (loss)	17,226		37,214		54,519	74,672
Noninterest expense	109,165		98,194		216,873	192,299
Income (loss) before income taxes	35,277		50,535		92,677	92,017
Income tax expense (benefit)	6,634		10,857		17,956	18,792
Net income (loss)	28,643	$ 46,078	39,678	$ 33,547	74,721	73,225
Total assets	17,224,342		16,618,101		17,224,342	16,618,101	$ 16,988,176
Goodwill	991,665		946,291		991,665	946,291	991,708
Community Banks
Financial information for the Company's operating segments
Goodwill	988,898				988,898		988,941
Insurance
Financial information for the Company's operating segments
Goodwill	2,767				2,767		$ 2,767
Operating segments | Community Banks
Financial information for the Company's operating segments
Net interest income (loss)	136,370		117,580		278,153	221,512
Provision for credit losses	3,000		2,000		10,960	3,500
Noninterest income (loss)	8,931		28,729		37,652	57,035
Noninterest expense	102,044		91,249		202,663	178,120
Income (loss) before income taxes	40,257		53,060		102,182	96,927
Income tax expense (benefit)	8,258		12,093		20,980	21,224
Net income (loss)	31,999		40,967		81,202	75,703
Total assets	17,181,988		16,520,685		17,181,988	16,520,685
Goodwill	988,898		943,524		988,898	943,524
Operating segments | Insurance
Financial information for the Company's operating segments
Net interest income (loss)	428		95		714	188
Provision for credit losses	0		0		0	0
Noninterest income (loss)	2,859		2,611		6,221	5,708
Noninterest expense	2,070		2,005		4,109	4,121
Income (loss) before income taxes	1,217		701		2,826	1,775
Income tax expense (benefit)	316		185		732	466
Net income (loss)	901		516		2,094	1,309
Total assets	37,867		34,264		37,867	34,264
Goodwill	2,767		2,767		2,767	2,767
Operating segments | Wealth Management
Financial information for the Company's operating segments
Net interest income (loss)	28		529		52	1,019
Provision for credit losses	0		0		0	0
Noninterest income (loss)	5,866		6,315		11,450	12,820
Noninterest expense	4,645		4,591		9,335	9,346
Income (loss) before income taxes	1,249		2,253		2,167	4,493
Income tax expense (benefit)	(18)		0		(14)	0
Net income (loss)	1,267		2,253		2,181	4,493
Total assets	4,757		65,709		4,757	65,709
Goodwill	0		0		0	0
Other
Financial information for the Company's operating segments
Net interest income (loss)	(6,610)		(4,689)		(12,928)	(9,575)
Provision for credit losses	0		0		0	0
Noninterest income (loss)	(430)		(441)		(804)	(891)
Noninterest expense	406		349		766	712
Income (loss) before income taxes	(7,446)		(5,479)		(14,498)	(11,178)
Income tax expense (benefit)	(1,922)		(1,421)		(3,742)	(2,898)
Net income (loss)	(5,524)		(4,058)		(10,756)	(8,280)
Total assets	(270)		(2,557)		(270)	(2,557)
Goodwill	$ 0		$ 0		$ 0	$ 0