Segment Reporting - Financial Information for Operating Segments (Details) - USD ($) $ in Thousands	3 Months Ended						9 Months Ended
	Sep. 30, 2025	Jun. 30, 2025	Mar. 31, 2025	Sep. 30, 2024	Jun. 30, 2024	Mar. 31, 2024	Sep. 30, 2025	Sep. 30, 2024	Dec. 31, 2024	Dec. 31, 2023
Financial information for the Company's operating segments
Total interest income	$ 351,098			$ 229,043			$ 915,326	$ 662,433
Total interest expense	127,578			98,045			338,750	283,119
Net interest income (loss)	223,520			130,998			576,576	379,314
Provision for credit losses	10,450			935			96,522	6,673
Noninterest income (loss)	46,026			89,299			130,755	169,442
Salaries and employee benefits	98,982			71,307			270,481	213,508
Net occupancy and equipment	18,415			11,415			47,528	34,648
Other segment expenses	66,433			39,261			162,901	98,715
Income (loss) before income taxes	75,266			97,379			129,899	195,212
Income tax expense (benefit)	15,478			24,924			27,575	44,502
Net income (loss)	59,788	$ 1,018	$ 41,518	72,455	$ 38,846	$ 39,409	102,324	150,710
Total assets (liabilities)	26,726,165			17,958,840			26,726,165	17,958,840	$ 18,034,868
Total assets (liabilities)	(22,900,387)						(22,900,387)		(15,356,550)
Goodwill	1,411,711			988,898			1,411,711	988,898	988,898	$ 991,665
Community Banks
Financial information for the Company's operating segments
Goodwill	1,411,711			988,898			1,411,711	988,898	$ 988,898	988,898
Insurance
Financial information for the Company's operating segments
Goodwill				0				0		$ 2,767
Operating segments | Community Banks
Financial information for the Company's operating segments
Total interest income	351,075			229,028			915,257	661,444
Total interest expense	119,100			91,168			314,976	262,474
Net interest income (loss)	231,975			137,860			600,281	398,970
Provision for credit losses	10,450			935			96,522	6,673
Noninterest income (loss)	35,656			83,244			106,441	145,179
Salaries and employee benefits	94,288			67,852			258,427	199,969
Net occupancy and equipment	18,132			11,227			46,794	33,875
Other segment expenses	62,834			37,956			156,796	93,697
Income (loss) before income taxes	81,927			103,134			148,183	209,935
Income tax expense (benefit)	17,698			26,867			33,818	49,507
Net income (loss)	64,229			76,267			114,365	160,428
Total assets (liabilities)	26,715,563			17,959,839			26,715,563	17,959,839
Goodwill	1,411,711			988,898			1,411,711	988,898
Operating segments | Insurance
Financial information for the Company's operating segments
Total interest income								942
Total interest expense								0
Net interest income (loss)								942
Provision for credit losses								0
Noninterest income (loss)								6,473
Salaries and employee benefits								3,626
Net occupancy and equipment								189
Other segment expenses								577
Income (loss) before income taxes								3,023
Income tax expense (benefit)								785
Net income (loss)								2,238
Total assets (liabilities)				0				0
Goodwill				0				0
Operating segments | Wealth Management
Financial information for the Company's operating segments
Total interest income	0			15			0	47
Total interest expense	0			0			0	0
Net interest income (loss)	0			15			0	47
Provision for credit losses	0			0			0	0
Noninterest income (loss)	10,861			6,447			25,742	18,933
Salaries and employee benefits	4,694			3,455			12,054	9,913
Net occupancy and equipment	249			188			667	584
Other segment expenses	3,144			868			5,248	3,228
Income (loss) before income taxes	2,774			1,951			7,773	5,255
Income tax expense (benefit)	198			47			435	147
Net income (loss)	2,576			1,904			7,338	5,108
Total assets (liabilities)	7,031			1,163			7,031	1,163
Goodwill	0			0			0	0
Other
Financial information for the Company's operating segments
Total interest income	23			0			69	0
Total interest expense	8,478			6,877			23,774	20,645
Net interest income (loss)	(8,455)			(6,877)			(23,705)	(20,645)
Provision for credit losses	0			0			0	0
Noninterest income (loss)	(491)			(392)			(1,428)	(1,143)
Salaries and employee benefits	0			0			0	0
Net occupancy and equipment	34			0			67	0
Other segment expenses	455			437			857	1,213
Income (loss) before income taxes	(9,435)			(7,706)			(26,057)	(23,001)
Income tax expense (benefit)	(2,418)			(1,990)			(6,678)	(5,937)
Net income (loss)	(7,017)			(5,716)			(19,379)	(17,064)
Total assets (liabilities)	3,571			(2,162)			3,571	(2,162)
Total assets (liabilities)				(2,162)				(2,162)
Goodwill	$ 0			$ 0			$ 0	$ 0