Allowance for Credit Losses (Loan Portfolio by Credit Quality Indicator) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022	Dec. 31, 2022
Financing Receivable, Credit Quality Indicator [Line Items]
2023	$ 4,283,318
2022	9,223,672
2021	5,892,389
2020	3,520,606
2019	2,743,658
Prior	9,288,586
Revolving	4,607,959
Revolving to term	5,283
Total Loans	39,565,471	$ 35,280,547	$ 39,196,485
Current period gross write offs
2023	478
2022	4,893
2021	1,194
2020	337
2019	318
Prior	131
Revolving	0
Revolving to term	0
Total loans	7,351	4,725
Commercial, industrial and other
Financing Receivable, Credit Quality Indicator [Line Items]
2023	752,521
2022	2,645,352
2021	2,219,819
2020	963,189
2019	667,396
Prior	1,266,790
Revolving	4,057,697
Revolving to term	4,221
Total Loans	12,576,985
Construction and development
Financing Receivable, Credit Quality Indicator [Line Items]
2023	42,635
2022	513,241
2021	515,074
2020	228,894
2019	134,991
Prior	149,223
Revolving	12,626
Revolving to term	369
Total Loans	1,597,053
Non-construction
Financing Receivable, Credit Quality Indicator [Line Items]
2023	472,528
2022	1,866,721
2021	1,456,089
2020	1,026,578
2019	861,605
Prior	2,772,170
Revolving	185,685
Revolving to term	649
Total Loans	8,642,025
Home equity
Financing Receivable, Credit Quality Indicator [Line Items]
2023	0
2022	0
2021	77
2020	116
2019	74
Prior	16,157
Revolving	320,548
Revolving to term	44
Total Loans	337,016	321,435	332,698
Current period gross write offs
Total loans	0	197
Residential real estate
Financing Receivable, Credit Quality Indicator [Line Items]
2023	95,766
2022	820,307
2021	830,293
2020	238,480
2019	141,577
Prior	379,122
Revolving	0
Revolving to term	0
Total Loans	2,505,545	1,799,985	2,372,383
Current period gross write offs
Total loans	0	466
Premium finance receivables - property and casualty
Financing Receivable, Credit Quality Indicator [Line Items]
2023	2,869,954
2022	2,825,178
2021	37,543
2020	5,299
2019	906
Prior	0
Revolving	0
Revolving to term	0
Total Loans	5,738,880
Premium finance receivables - life
Financing Receivable, Credit Quality Indicator [Line Items]
2023	49,164
2022	550,396
2021	832,073
2020	1,057,850
2019	936,674
Prior	4,699,645
Revolving	0
Revolving to term	0
Total Loans	8,125,802
Consumer and other
Financing Receivable, Credit Quality Indicator [Line Items]
2023	750
2022	2,477
2021	1,421
2020	200
2019	435
Prior	5,479
Revolving	31,403
Revolving to term	0
Total Loans	42,165	48,519	$ 50,836
Current period gross write offs
Total loans	153	$ 193
Pass
Financing Receivable, Credit Quality Indicator [Line Items]
2023	4,239,546
2022	9,070,338
2021	5,729,342
2020	3,434,032
2019	2,586,332
Prior	8,876,620
Revolving	4,418,070
Revolving to term	4,515
Total Loans	38,358,795
Pass | Commercial, industrial and other
Financing Receivable, Credit Quality Indicator [Line Items]
2023	752,119
2022	2,576,073
2021	2,081,628
2020	940,341
2019	603,016
Prior	1,213,066
Revolving	3,872,419
Revolving to term	3,497
Total Loans	12,042,159
Pass | Construction and development
Financing Receivable, Credit Quality Indicator [Line Items]
2023	42,635
2022	506,714
2021	512,801
2020	204,113
2019	111,497
Prior	119,478
Revolving	12,626
Revolving to term	369
Total Loans	1,510,233
Pass | Non-construction
Financing Receivable, Credit Quality Indicator [Line Items]
2023	472,528
2022	1,862,370
2021	1,441,054
2020	1,002,397
2019	814,910
Prior	2,637,342
Revolving	184,246
Revolving to term	649
Total Loans	8,415,496
Pass | Home equity
Financing Receivable, Credit Quality Indicator [Line Items]
2023	0
2022	0
2021	0
2020	0
2019	56
Prior	5,633
Revolving	317,387
Revolving to term	0
Total Loans	323,076
Pass | Residential real estate
Financing Receivable, Credit Quality Indicator [Line Items]
2023	95,403
2022	815,003
2021	825,881
2020	225,297
2019	118,840
Prior	196,150
Revolving	0
Revolving to term	0
Total Loans	2,276,574
Pass | Premium finance receivables - property and casualty
Financing Receivable, Credit Quality Indicator [Line Items]
2023	2,826,947
2022	2,757,313
2021	35,647
2020	5,270
2019	906
Prior	0
Revolving	0
Revolving to term	0
Total Loans	5,626,083
Pass | Premium finance receivables - life
Financing Receivable, Credit Quality Indicator [Line Items]
2023	49,164
2022	550,396
2021	830,917
2020	1,056,414
2019	936,674
Prior	4,699,645
Revolving	0
Revolving to term	0
Total Loans	8,123,210
Pass | Consumer and other
Financing Receivable, Credit Quality Indicator [Line Items]
2023	750
2022	2,469
2021	1,414
2020	200
2019	433
Prior	5,306
Revolving	31,392
Revolving to term	0
Total Loans	41,964
Special mention
Financing Receivable, Credit Quality Indicator [Line Items]
2023	42,467
2022	112,677
2021	108,506
2020	31,527
2019	77,126
Prior	105,280
Revolving	152,647
Revolving to term	268
Total Loans	630,498
Special mention | Commercial, industrial and other
Financing Receivable, Credit Quality Indicator [Line Items]
2023	402
2022	55,314
2021	92,315
2020	9,462
2019	23,220
Prior	10,695
Revolving	149,012
Revolving to term	268
Total Loans	340,688
Special mention | Construction and development
Financing Receivable, Credit Quality Indicator [Line Items]
2023	0
2022	0
2021	1,475
2020	16,480
2019	23,494
Prior	14,360
Revolving	0
Revolving to term	0
Total Loans	55,809
Special mention | Non-construction
Financing Receivable, Credit Quality Indicator [Line Items]
2023	0
2022	4,351
2021	11,872
2020	2,140
2019	29,868
Prior	74,174
Revolving	1,439
Revolving to term	0
Total Loans	123,844
Special mention | Home equity
Financing Receivable, Credit Quality Indicator [Line Items]
2023	0
2022	0
2021	0
2020	0
2019	0
Prior	1,430
Revolving	2,193
Revolving to term	0
Total Loans	3,623
Special mention | Residential real estate
Financing Receivable, Credit Quality Indicator [Line Items]
2023	40
2022	3,816
2021	718
2020	1,992
2019	542
Prior	4,488
Revolving	0
Revolving to term	0
Total Loans	11,596
Special mention | Premium finance receivables - property and casualty
Financing Receivable, Credit Quality Indicator [Line Items]
2023	42,025
2022	49,190
2021	969
2020	17
2019	0
Prior	0
Revolving	0
Revolving to term	0
Total Loans	92,201
Special mention | Premium finance receivables - life
Financing Receivable, Credit Quality Indicator [Line Items]
2023	0
2022	0
2021	1,156
2020	1,436
2019	0
Prior	0
Revolving	0
Revolving to term	0
Total Loans	2,592
Special mention | Consumer and other
Financing Receivable, Credit Quality Indicator [Line Items]
2023	0
2022	6
2021	1
2020	0
2019	2
Prior	133
Revolving	3
Revolving to term	0
Total Loans	145
Substandard accrual
Financing Receivable, Credit Quality Indicator [Line Items]
2023	528
2022	18,658
2021	45,533
2020	33,925
2019	30,597
Prior	123,155
Revolving	36,912
Revolving to term	500
Total Loans	289,808
Substandard accrual | Commercial, industrial and other
Financing Receivable, Credit Quality Indicator [Line Items]
2023	0
2022	13,415
2021	40,397
2020	2,401
2019	12,670
Prior	40,814
Revolving	36,035
Revolving to term	456
Total Loans	146,188
Substandard accrual | Construction and development
Financing Receivable, Credit Quality Indicator [Line Items]
2023	0
2022	2,337
2021	0
2020	8,301
2019	0
Prior	14,969
Revolving	0
Revolving to term	0
Total Loans	25,607
Substandard accrual | Non-construction
Financing Receivable, Credit Quality Indicator [Line Items]
2023	0
2022	0
2021	3,163
2020	22,041
2019	16,827
Prior	54,862
Revolving	0
Revolving to term	0
Total Loans	96,893
Substandard accrual | Home equity
Financing Receivable, Credit Quality Indicator [Line Items]
2023	0
2022	0
2021	0
2020	0
2019	0
Prior	8,214
Revolving	869
Revolving to term	44
Total Loans	9,127
Substandard accrual | Residential real estate
Financing Receivable, Credit Quality Indicator [Line Items]
2023	323
2022	1,204
2021	1,825
2020	1,182
2019	1,100
Prior	4,256
Revolving	0
Revolving to term	0
Total Loans	9,890
Substandard accrual | Premium finance receivables - property and casualty
Financing Receivable, Credit Quality Indicator [Line Items]
2023	205
2022	1,700
2021	148
2020	0
2019	0
Prior	0
Revolving	0
Revolving to term	0
Total Loans	2,053
Substandard accrual | Premium finance receivables - life
Financing Receivable, Credit Quality Indicator [Line Items]
2023	0
2022	0
2021	0
2020	0
2019	0
Prior	0
Revolving	0
Revolving to term	0
Total Loans	0
Substandard accrual | Consumer and other
Financing Receivable, Credit Quality Indicator [Line Items]
2023	0
2022	2
2021	0
2020	0
2019	0
Prior	40
Revolving	8
Revolving to term	0
Total Loans	50
Substandard nonaccrual/doubtful
Financing Receivable, Credit Quality Indicator [Line Items]
2023	777
2022	21,999
2021	8,239
2020	11,872
2019	30,173
Prior	16,828
Revolving	330
Revolving to term	0
Total Loans	90,218
Substandard nonaccrual/doubtful | Commercial, industrial and other
Financing Receivable, Credit Quality Indicator [Line Items]
2023	0
2022	550
2021	5,479
2020	10,985
2019	28,490
Prior	2,215
Revolving	231
Revolving to term	0
Total Loans	47,950
Substandard nonaccrual/doubtful | Construction and development
Financing Receivable, Credit Quality Indicator [Line Items]
2023	0
2022	4,190
2021	798
2020	0
2019	0
Prior	416
Revolving	0
Revolving to term	0
Total Loans	5,404
Substandard nonaccrual/doubtful | Non-construction
Financing Receivable, Credit Quality Indicator [Line Items]
2023	0
2022	0
2021	0
2020	0
2019	0
Prior	5,792
Revolving	0
Revolving to term	0
Total Loans	5,792
Substandard nonaccrual/doubtful | Home equity
Financing Receivable, Credit Quality Indicator [Line Items]
2023	0
2022	0
2021	77
2020	116
2019	18
Prior	880
Revolving	99
Revolving to term	0
Total Loans	1,190
Substandard nonaccrual/doubtful | Residential real estate
Financing Receivable, Credit Quality Indicator [Line Items]
2023	0
2022	284
2021	1,100
2020	759
2019	1,665
Prior	7,525
Revolving	0
Revolving to term	0
Total Loans	11,333
Substandard nonaccrual/doubtful | Premium finance receivables - property and casualty
Financing Receivable, Credit Quality Indicator [Line Items]
2023	777
2022	16,975
2021	779
2020	12
2019	0
Prior	0
Revolving	0
Revolving to term	0
Total Loans	18,543
Substandard nonaccrual/doubtful | Premium finance receivables - life
Financing Receivable, Credit Quality Indicator [Line Items]
2023	0
2022	0
2021	0
2020	0
2019	0
Prior	0
Revolving	0
Revolving to term	0
Total Loans	0
Substandard nonaccrual/doubtful | Consumer and other
Financing Receivable, Credit Quality Indicator [Line Items]
2023	0
2022	0
2021	6
2020	0
2019	0
Prior	0
Revolving	0
Revolving to term	0
Total Loans	6
Early buy-out loans guaranteed by U.S. government agencies
Financing Receivable, Credit Quality Indicator [Line Items]
2023	0
2022	0
2021	769
2020	9,250
2019	19,430
Prior	166,703
Revolving	0
Revolving to term	0
Total Loans	196,152
Early buy-out loans guaranteed by U.S. government agencies | Residential real estate
Financing Receivable, Credit Quality Indicator [Line Items]
2023	0
2022	0
2021	769
2020	9,250
2019	19,430
Prior	166,703
Revolving	0
Revolving to term	0
Total Loans	$ 196,152