Segment Reporting - Financial Information for Operating Segments (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2021
Financial information for the Company's operating segments
Net interest income (loss)	$ 99,629	$ 109,648
Provision for credit losses	1,500	0	$ 0
Noninterest income (loss)	37,458	81,037
Noninterest expense	94,105	115,935
Income (loss) before income taxes	41,482	74,750
Income tax expense (benefit)	7,935	16,842
Net income (loss)	33,547	57,908
Total assets	16,863,757	15,622,571		$ 16,810,311
Goodwill	946,291	939,683		939,683
Community Banks
Financial information for the Company's operating segments
Goodwill	943,524			936,916
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)	103,932	112,948
Provision for credit losses	1,500	0
Noninterest income (loss)	28,306	73,070
Noninterest expense	86,871	109,586
Income (loss) before income taxes	43,867	76,432
Income tax expense (benefit)	9,131	17,656
Net income (loss)	34,736	58,776
Total assets	16,757,670	15,525,500
Goodwill	943,524	936,916
Operating segments | Insurance
Financial information for the Company's operating segments
Net interest income (loss)	93	107
Provision for credit losses	0	0
Noninterest income (loss)	3,097	3,248
Noninterest expense	2,116	1,923
Income (loss) before income taxes	1,074	1,432
Income tax expense (benefit)	281	367
Net income (loss)	793	1,065
Total assets	33,794	31,004
Goodwill	2,767	2,767
Operating segments | Wealth Management
Financial information for the Company's operating segments
Net interest income (loss)	490	384
Provision for credit losses	0	0
Noninterest income (loss)	6,505	5,171
Noninterest expense	4,755	4,101
Income (loss) before income taxes	2,240	1,454
Income tax expense (benefit)	0	0
Net income (loss)	2,240	1,454
Total assets	64,761	64,320
Goodwill	0	0
Other
Financial information for the Company's operating segments
Net interest income (loss)	(4,886)	(3,791)
Provision for credit losses	0	0
Noninterest income (loss)	(450)	(452)
Noninterest expense	363	325
Income (loss) before income taxes	(5,699)	(4,568)
Income tax expense (benefit)	(1,477)	(1,181)
Net income (loss)	(4,222)	(3,387)
Total assets	7,532	1,747
Goodwill	$ 0	$ 0