Allowance for Credit Losses - Schedule of Loan Portfolio by Credit Quality Indicator (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022	Dec. 31, 2022
Financing Receivable, Credit Quality Indicator [Line Items]
2023	$ 10,722,343		$ 10,722,343
2022	6,539,701		6,539,701
2021	5,384,844		5,384,844
2020	3,298,044		3,298,044
2019	2,528,296		2,528,296
Prior	8,341,065		8,341,065
Revolving	4,619,809		4,619,809
Revolving to term	11,930		11,930
Total Loans	41,446,032	$ 38,167,613	41,446,032	$ 38,167,613	$ 39,196,485
Three months ended September 30, 2023
2023	6,285		11,726
2022	2,889		8,351
2021	525		2,774
2020	35		5,531
2019	350		5,682
Prior	393		2,280
Revolving	0		0
Revolving to term	0		0
Total loans	10,477	7,524	36,344	24,565
Commercial, industrial and other
Financing Receivable, Credit Quality Indicator [Line Items]
2023	2,190,915		2,190,915
2022	2,273,907		2,273,907
2021	1,813,036		1,813,036
2020	796,529		796,529
2019	524,107		524,107
Prior	1,056,029		1,056,029
Revolving	4,062,959		4,062,959
Revolving to term	7,991		7,991
Total Loans	12,725,473		12,725,473
Construction and development
Financing Receivable, Credit Quality Indicator [Line Items]
2023	231,587		231,587
2022	763,430		763,430
2021	438,554		438,554
2020	183,955		183,955
2019	134,733		134,733
Prior	122,308		122,308
Revolving	18,842		18,842
Revolving to term	364		364
Total Loans	1,893,773		1,893,773
Non-construction
Financing Receivable, Credit Quality Indicator [Line Items]
2023	1,115,648		1,115,648
2022	1,869,325		1,869,325
2021	1,435,250		1,435,250
2020	1,034,216		1,034,216
2019	810,044		810,044
Prior	2,615,381		2,615,381
Revolving	169,654		169,654
Revolving to term	2,889		2,889
Total Loans	9,052,407		9,052,407
Home equity
Financing Receivable, Credit Quality Indicator [Line Items]
2023	0		0
2022	228		228
2021	141		141
2020	157		157
2019	177		177
Prior	14,916		14,916
Revolving	326,953		326,953
Revolving to term	686		686
Total Loans	343,258	328,822	343,258	328,822	332,698
Three months ended September 30, 2023
Total loans	227	43	227	432
Residential real estate
Financing Receivable, Credit Quality Indicator [Line Items]
2023	361,605		361,605
2022	845,709		845,709
2021	808,227		808,227
2020	231,196		231,196
2019	133,792		133,792
Prior	327,074		327,074
Revolving	0		0
Revolving to term	0		0
Total Loans	2,707,603	2,235,459	2,707,603	2,235,459	2,372,383
Three months ended September 30, 2023
Total loans	78	5	78	471
Premium finance receivables - property and casualty
Financing Receivable, Credit Quality Indicator [Line Items]
2023	6,551,482		6,551,482
2022	147,858		147,858
2021	20,098		20,098
2020	3,174		3,174
2019	135		135
Prior	0		0
Revolving	0		0
Revolving to term	0		0
Total Loans	6,722,747		6,722,747
Premium finance receivables - life
Financing Receivable, Credit Quality Indicator [Line Items]
2023	268,027		268,027
2022	637,571		637,571
2021	868,576		868,576
2020	1,048,697		1,048,697
2019	924,944		924,944
Prior	4,183,993		4,183,993
Revolving	0		0
Revolving to term	0		0
Total Loans	7,931,808		7,931,808
Consumer and other
Financing Receivable, Credit Quality Indicator [Line Items]
2023	3,079		3,079
2022	1,673		1,673
2021	962		962
2020	120		120
2019	364		364
Prior	21,364		21,364
Revolving	41,401		41,401
Revolving to term	0		0
Total Loans	68,963	47,702	68,963	47,702	$ 50,836
Three months ended September 30, 2023
Total loans	184	$ 635	447	$ 1,081
Pass
Financing Receivable, Credit Quality Indicator [Line Items]
2023	10,551,479		10,551,479
2022	6,407,567		6,407,567
2021	5,241,014		5,241,014
2020	3,216,387		3,216,387
2019	2,377,985		2,377,985
Prior	7,977,092		7,977,092
Revolving	4,402,588		4,402,588
Revolving to term	7,916		7,916
Total Loans	40,182,028		40,182,028
Pass | Commercial, industrial and other
Financing Receivable, Credit Quality Indicator [Line Items]
2023	2,148,269		2,148,269
2022	2,182,012		2,182,012
2021	1,717,737		1,717,737
2020	772,160		772,160
2019	492,465		492,465
Prior	1,011,144		1,011,144
Revolving	3,854,978		3,854,978
Revolving to term	5,633		5,633
Total Loans	12,184,398		12,184,398
Pass | Construction and development
Financing Receivable, Credit Quality Indicator [Line Items]
2023	231,587		231,587
2022	760,955		760,955
2021	434,667		434,667
2020	174,574		174,574
2019	85,436		85,436
Prior	94,739		94,739
Revolving	18,842		18,842
Revolving to term	364		364
Total Loans	1,801,164		1,801,164
Pass | Non-construction
Financing Receivable, Credit Quality Indicator [Line Items]
2023	1,108,119		1,108,119
2022	1,856,346		1,856,346
2021	1,402,456		1,402,456
2020	999,191		999,191
2019	762,188		762,188
Prior	2,482,011		2,482,011
Revolving	164,654		164,654
Revolving to term	1,452		1,452
Total Loans	8,776,417		8,776,417
Pass | Home equity
Financing Receivable, Credit Quality Indicator [Line Items]
2023	0		0
2022	0		0
2021	0		0
2020	45		45
2019	93		93
Prior	6,438		6,438
Revolving	322,726		322,726
Revolving to term	467		467
Total Loans	329,769		329,769
Pass | Residential real estate
Financing Receivable, Credit Quality Indicator [Line Items]
2023	359,397		359,397
2022	835,153		835,153
2021	796,743		796,743
2020	218,433		218,433
2019	112,360		112,360
Prior	177,538		177,538
Revolving	0		0
Revolving to term	0		0
Total Loans	2,499,624		2,499,624
Pass | Premium finance receivables - property and casualty
Financing Receivable, Credit Quality Indicator [Line Items]
2023	6,433,013		6,433,013
2022	133,881		133,881
2021	19,877		19,877
2020	3,167		3,167
2019	135		135
Prior	0		0
Revolving	0		0
Revolving to term	0		0
Total Loans	6,590,073		6,590,073
Pass | Premium finance receivables - life
Financing Receivable, Credit Quality Indicator [Line Items]
2023	268,027		268,027
2022	637,571		637,571
2021	868,576		868,576
2020	1,048,697		1,048,697
2019	924,944		924,944
Prior	4,183,993		4,183,993
Revolving	0		0
Revolving to term	0		0
Total Loans	7,931,808		7,931,808
Pass | Consumer and other
Financing Receivable, Credit Quality Indicator [Line Items]
2023	3,067		3,067
2022	1,649		1,649
2021	958		958
2020	120		120
2019	364		364
Prior	21,229		21,229
Revolving	41,388		41,388
Revolving to term	0		0
Total Loans	68,775		68,775
Special mention
Financing Receivable, Credit Quality Indicator [Line Items]
2023	124,533		124,533
2022	65,053		65,053
2021	102,912		102,912
2020	33,473		33,473
2019	60,355		60,355
Prior	74,795		74,795
Revolving	120,476		120,476
Revolving to term	2,692		2,692
Total Loans	584,289		584,289
Special mention | Commercial, industrial and other
Financing Receivable, Credit Quality Indicator [Line Items]
2023	18,043		18,043
2022	47,296		47,296
2021	69,910		69,910
2020	18,805		18,805
2019	16,248		16,248
Prior	5,140		5,140
Revolving	112,580		112,580
Revolving to term	1,255		1,255
Total Loans	289,277		289,277
Special mention | Construction and development
Financing Receivable, Credit Quality Indicator [Line Items]
2023	0		0
2022	0		0
2021	3,887		3,887
2020	0		0
2019	19,937		19,937
Prior	14,302		14,302
Revolving	0		0
Revolving to term	0		0
Total Loans	38,126		38,126
Special mention | Non-construction
Financing Receivable, Credit Quality Indicator [Line Items]
2023	6,621		6,621
2022	11,567		11,567
2021	27,250		27,250
2020	13,324		13,324
2019	23,755		23,755
Prior	48,640		48,640
Revolving	5,000		5,000
Revolving to term	1,437		1,437
Total Loans	137,594		137,594
Special mention | Home equity
Financing Receivable, Credit Quality Indicator [Line Items]
2023	0		0
2022	228		228
2021	64		64
2020	0		0
2019	67		67
Prior	1,622		1,622
Revolving	2,893		2,893
Revolving to term	0		0
Total Loans	4,874		4,874
Special mention | Residential real estate
Financing Receivable, Credit Quality Indicator [Line Items]
2023	1,186		1,186
2022	3,373		3,373
2021	1,673		1,673
2020	1,343		1,343
2019	348		348
Prior	4,991		4,991
Revolving	0		0
Revolving to term	0		0
Total Loans	12,914		12,914
Special mention | Premium finance receivables - property and casualty
Financing Receivable, Credit Quality Indicator [Line Items]
2023	98,681		98,681
2022	2,574		2,574
2021	128		128
2020	1		1
2019	0		0
Prior	0		0
Revolving	0		0
Revolving to term	0		0
Total Loans	101,384		101,384
Special mention | Premium finance receivables - life
Financing Receivable, Credit Quality Indicator [Line Items]
2023	0		0
2022	0		0
2021	0		0
2020	0		0
2019	0		0
Prior	0		0
Revolving	0		0
Revolving to term	0		0
Total Loans	0		0
Special mention | Consumer and other
Financing Receivable, Credit Quality Indicator [Line Items]
2023	2		2
2022	15		15
2021	0		0
2020	0		0
2019	0		0
Prior	100		100
Revolving	3		3
Revolving to term	0		0
Total Loans	120		120
Substandard accrual
Financing Receivable, Credit Quality Indicator [Line Items]
2023	7,031		7,031
2022	48,856		48,856
2021	25,648		25,648
2020	24,516		24,516
2019	63,130		63,130
Prior	138,900		138,900
Revolving	96,580		96,580
Revolving to term	1,231		1,231
Total Loans	405,892		405,892
Substandard accrual | Commercial, industrial and other
Financing Receivable, Credit Quality Indicator [Line Items]
2023	3,683		3,683
2022	40,284		40,284
2021	19,105		19,105
2020	1,409		1,409
2019	9,179		9,179
Prior	38,135		38,135
Revolving	95,331		95,331
Revolving to term	1,103		1,103
Total Loans	208,229		208,229
Substandard accrual | Construction and development
Financing Receivable, Credit Quality Indicator [Line Items]
2023	0		0
2022	2,475		2,475
2021	0		0
2020	1,132		1,132
2019	29,360		29,360
Prior	13,132		13,132
Revolving	0		0
Revolving to term	0		0
Total Loans	46,099		46,099
Substandard accrual | Non-construction
Financing Receivable, Credit Quality Indicator [Line Items]
2023	0		0
2022	1,412		1,412
2021	5,519		5,519
2020	20,916		20,916
2019	24,101		24,101
Prior	77,789		77,789
Revolving	0		0
Revolving to term	0		0
Total Loans	129,737		129,737
Substandard accrual | Home equity
Financing Receivable, Credit Quality Indicator [Line Items]
2023	0		0
2022	0		0
2021	0		0
2020	0		0
2019	0		0
Prior	5,885		5,885
Revolving	1,239		1,239
Revolving to term	128		128
Total Loans	7,252		7,252
Substandard accrual | Residential real estate
Financing Receivable, Credit Quality Indicator [Line Items]
2023	919		919
2022	2,575		2,575
2021	1,022		1,022
2020	1,059		1,059
2019	490		490
Prior	3,924		3,924
Revolving	0		0
Revolving to term	0		0
Total Loans	9,989		9,989
Substandard accrual | Premium finance receivables - property and casualty
Financing Receivable, Credit Quality Indicator [Line Items]
2023	2,429		2,429
2022	2,103		2,103
2021	2		2
2020	0		0
2019	0		0
Prior	0		0
Revolving	0		0
Revolving to term	0		0
Total Loans	4,534		4,534
Substandard accrual | Premium finance receivables - life
Financing Receivable, Credit Quality Indicator [Line Items]
2023	0		0
2022	0		0
2021	0		0
2020	0		0
2019	0		0
Prior	0		0
Revolving	0		0
Revolving to term	0		0
Total Loans	0		0
Substandard accrual | Consumer and other
Financing Receivable, Credit Quality Indicator [Line Items]
2023	0		0
2022	7		7
2021	0		0
2020	0		0
2019	0		0
Prior	35		35
Revolving	10		10
Revolving to term	0		0
Total Loans	52		52
Substandard nonaccrual/doubtful
Financing Receivable, Credit Quality Indicator [Line Items]
2023	39,300		39,300
2022	15,701		15,701
2021	9,769		9,769
2020	14,118		14,118
2019	8,703		8,703
Prior	17,003		17,003
Revolving	165		165
Revolving to term	91		91
Total Loans	104,850		104,850
Substandard nonaccrual/doubtful | Commercial, industrial and other
Financing Receivable, Credit Quality Indicator [Line Items]
2023	20,920		20,920
2022	4,315		4,315
2021	6,284		6,284
2020	4,155		4,155
2019	6,215		6,215
Prior	1,610		1,610
Revolving	70		70
Revolving to term	0		0
Total Loans	43,569		43,569
Substandard nonaccrual/doubtful | Construction and development
Financing Receivable, Credit Quality Indicator [Line Items]
2023	0		0
2022	0		0
2021	0		0
2020	8,249		8,249
2019	0		0
Prior	135		135
Revolving	0		0
Revolving to term	0		0
Total Loans	8,384		8,384
Substandard nonaccrual/doubtful | Non-construction
Financing Receivable, Credit Quality Indicator [Line Items]
2023	908		908
2022	0		0
2021	25		25
2020	785		785
2019	0		0
Prior	6,941		6,941
Revolving	0		0
Revolving to term	0		0
Total Loans	8,659		8,659
Substandard nonaccrual/doubtful | Home equity
Financing Receivable, Credit Quality Indicator [Line Items]
2023	0		0
2022	0		0
2021	77		77
2020	112		112
2019	17		17
Prior	971		971
Revolving	95		95
Revolving to term	91		91
Total Loans	1,363		1,363
Substandard nonaccrual/doubtful | Residential real estate
Financing Receivable, Credit Quality Indicator [Line Items]
2023	103		103
2022	2,084		2,084
2021	3,288		3,288
2020	811		811
2019	2,471		2,471
Prior	7,346		7,346
Revolving	0		0
Revolving to term	0		0
Total Loans	16,103		16,103
Substandard nonaccrual/doubtful | Premium finance receivables - property and casualty
Financing Receivable, Credit Quality Indicator [Line Items]
2023	17,359		17,359
2022	9,300		9,300
2021	91		91
2020	6		6
2019	0		0
Prior	0		0
Revolving	0		0
Revolving to term	0		0
Total Loans	26,756		26,756
Substandard nonaccrual/doubtful | Premium finance receivables - life
Financing Receivable, Credit Quality Indicator [Line Items]
2023	0		0
2022	0		0
2021	0		0
2020	0		0
2019	0		0
Prior	0		0
Revolving	0		0
Revolving to term	0		0
Total Loans	0		0
Substandard nonaccrual/doubtful | Consumer and other
Financing Receivable, Credit Quality Indicator [Line Items]
2023	10		10
2022	2		2
2021	4		4
2020	0		0
2019	0		0
Prior	0		0
Revolving	0		0
Revolving to term	0		0
Total Loans	16		16
Early buy-out loans guaranteed by U.S. government agencies
Financing Receivable, Credit Quality Indicator [Line Items]
2023	0		0
2022	2,524		2,524
2021	5,501		5,501
2020	9,550		9,550
2019	18,123		18,123
Prior	133,275		133,275
Revolving	0		0
Revolving to term	0		0
Total Loans	168,973		168,973
Early buy-out loans guaranteed by U.S. government agencies | Residential real estate
Financing Receivable, Credit Quality Indicator [Line Items]
2023	0		0
2022	2,524		2,524
2021	5,501		5,501
2020	9,550		9,550
2019	18,123		18,123
Prior	133,275		133,275
Revolving	0		0
Revolving to term	0		0
Total Loans	$ 168,973		$ 168,973