Allowance for Credit Losses (Loan Portfolio by Credit Quality Indicator) (Details) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021	Mar. 31, 2021
Financing Receivable, Credit Quality Indicator [Line Items]
2022	$ 3,888,002
2021	8,840,780
2020	4,257,987
2019	3,229,287
2018	2,346,275
Prior	8,442,094
Revolving	4,266,869
Revolving to Term	9,253
Total Loans	35,280,547	$ 34,789,104	$ 33,171,233
Commercial, industrial and other
Financing Receivable, Credit Quality Indicator [Line Items]
2022	524,897
2021	2,797,844
2020	1,473,338
2019	980,153
2018	694,389
Prior	1,102,645
Revolving	3,748,163
Revolving to Term	8,570
Total Loans	11,329,999
Commercial PPP loans
Financing Receivable, Credit Quality Indicator [Line Items]
2022	0
2021	213,948
2020	40,016
2019	0
2018	0
Prior	0
Revolving	0
Revolving to Term	0
Total Loans	253,964
Construction and development
Financing Receivable, Credit Quality Indicator [Line Items]
2022	99,285
2021	391,570
2020	439,253
2019	235,541
2018	78,595
Prior	129,758
Revolving	22,404
Revolving to Term	0
Total Loans	1,396,406
Non-construction
Financing Receivable, Credit Quality Indicator [Line Items]
2022	468,125
2021	1,565,795
2020	1,113,854
2019	1,026,461
2018	778,923
Prior	2,714,490
Revolving	170,873
Revolving to Term	147
Total Loans	7,838,668
Home equity
Financing Receivable, Credit Quality Indicator [Line Items]
2022	0
2021	0
2020	0
2019	107
2018	283
Prior	16,535
Revolving	303,974
Revolving to Term	536
Total Loans	321,435	335,155	390,253
Residential real estate
Financing Receivable, Credit Quality Indicator [Line Items]
2022	236,906
2021	838,278
2020	262,959
2019	152,228
2018	69,567
Prior	240,047
Revolving	0
Revolving to Term	0
Total Loans	1,799,985	1,637,099	1,421,973
Premium finance receivables - property and casualty
Financing Receivable, Credit Quality Indicator [Line Items]
2022	2,466,892
2021	2,442,973
2020	19,663
2019	7,203
2018	677
Prior	0
Revolving	0
Revolving to Term	0
Total Loans	4,937,408
Premium finance receivables - life
Financing Receivable, Credit Quality Indicator [Line Items]
2022	91,374
2021	587,895
2020	908,193
2019	826,596
2018	722,851
Prior	4,217,254
Revolving	0
Revolving to Term	0
Total Loans	7,354,163
Consumer and other
Financing Receivable, Credit Quality Indicator [Line Items]
2022	523
2021	2,477
2020	711
2019	998
2018	990
Prior	21,365
Revolving	21,455
Revolving to Term	0
Total Loans	48,519	$ 24,199	$ 35,983
Early buy-out loans guaranteed by U.S. government agencies
Financing Receivable, Credit Quality Indicator [Line Items]
2022	0
2021	241
2020	621
2019	5,920
2018	8,808
Prior	34,506
Revolving	0
Revolving to Term	0
Total Loans	50,096
Early buy-out loans guaranteed by U.S. government agencies | Residential real estate
Financing Receivable, Credit Quality Indicator [Line Items]
2022	0
2021	241
2020	621
2019	5,920
2018	8,808
Prior	34,506
Revolving	0
Revolving to Term	0
Total Loans	50,096
Pass
Financing Receivable, Credit Quality Indicator [Line Items]
2022	3,872,738
2021	8,713,279
2020	4,163,278
2019	3,062,306
2018	2,196,571
Prior	8,077,175
Revolving	4,129,622
Revolving to Term	8,489
Total Loans	34,223,458
Pass | Commercial, industrial and other
Financing Receivable, Credit Quality Indicator [Line Items]
2022	524,863
2021	2,714,254
2020	1,407,819
2019	889,866
2018	647,127
Prior	1,037,167
Revolving	3,616,144
Revolving to Term	8,342
Total Loans	10,845,582
Pass | Commercial PPP loans
Financing Receivable, Credit Quality Indicator [Line Items]
2022	0
2021	213,790
2020	33,830
2019	0
2018	0
Prior	0
Revolving	0
Revolving to Term	0
Total Loans	247,620
Pass | Construction and development
Financing Receivable, Credit Quality Indicator [Line Items]
2022	99,285
2021	391,288
2020	430,778
2019	231,618
2018	51,795
Prior	114,022
Revolving	22,404
Revolving to Term	0
Total Loans	1,341,190
Pass | Non-construction
Financing Receivable, Credit Quality Indicator [Line Items]
2022	468,125
2021	1,563,953
2020	1,103,776
2019	962,675
2018	715,014
Prior	2,500,006
Revolving	170,873
Revolving to Term	147
Total Loans	7,484,569
Pass | Home equity
Financing Receivable, Credit Quality Indicator [Line Items]
2022	0
2021	0
2020	0
2019	0
2018	0
Prior	5,502
Revolving	298,765
Revolving to Term	0
Total Loans	304,267
Pass | Residential real estate
Financing Receivable, Credit Quality Indicator [Line Items]
2022	236,643
2021	835,324
2020	259,100
2019	143,358
2018	58,132
Prior	189,137
Revolving	0
Revolving to Term	0
Total Loans	1,721,694
Pass | Premium finance receivables - property and casualty
Financing Receivable, Credit Quality Indicator [Line Items]
2022	2,451,925
2021	2,404,905
2020	19,074
2019	7,203
2018	662
Prior	0
Revolving	0
Revolving to Term	0
Total Loans	4,883,769
Pass | Premium finance receivables - life
Financing Receivable, Credit Quality Indicator [Line Items]
2022	91,374
2021	587,300
2020	908,193
2019	826,596
2018	722,851
Prior	4,210,182
Revolving	0
Revolving to Term	0
Total Loans	7,346,496
Pass | Consumer and other
Financing Receivable, Credit Quality Indicator [Line Items]
2022	523
2021	2,465
2020	708
2019	990
2018	990
Prior	21,159
Revolving	21,436
Revolving to Term	0
Total Loans	48,271
Special mention
Financing Receivable, Credit Quality Indicator [Line Items]
2022	14,891
2021	106,049
2020	75,929
2019	114,763
2018	84,161
Prior	190,738
Revolving	109,483
Revolving to Term	228
Total Loans	696,242
Special mention | Commercial, industrial and other
Financing Receivable, Credit Quality Indicator [Line Items]
2022	34
2021	77,940
2020	51,807
2019	61,656
2018	21,183
Prior	48,902
Revolving	105,022
Revolving to Term	228
Total Loans	366,772
Special mention | Commercial PPP loans
Financing Receivable, Credit Quality Indicator [Line Items]
2022	0
2021	158
2020	5,621
2019	0
2018	0
Prior	0
Revolving	0
Revolving to Term	0
Total Loans	5,779
Special mention | Construction and development
Financing Receivable, Credit Quality Indicator [Line Items]
2022	0
2021	282
2020	8,475
2019	3,611
2018	24,748
Prior	110
Revolving	0
Revolving to Term	0
Total Loans	37,226
Special mention | Non-construction
Financing Receivable, Credit Quality Indicator [Line Items]
2022	0
2021	1,842
2020	9,792
2019	49,110
2018	36,694
Prior	129,238
Revolving	0
Revolving to Term	0
Total Loans	226,676
Special mention | Home equity
Financing Receivable, Credit Quality Indicator [Line Items]
2022	0
2021	0
2020	0
2019	0
2018	240
Prior	391
Revolving	4,452
Revolving to Term	0
Total Loans	5,083
Special mention | Residential real estate
Financing Receivable, Credit Quality Indicator [Line Items]
2022	0
2021	1,612
2020	173
2019	378
2018	1,296
Prior	4,899
Revolving	0
Revolving to Term	0
Total Loans	8,358
Special mention | Premium finance receivables - property and casualty
Financing Receivable, Credit Quality Indicator [Line Items]
2022	14,857
2021	23,617
2020	59
2019	0
2018	0
Prior	0
Revolving	0
Revolving to Term	0
Total Loans	38,533
Special mention | Premium finance receivables - life
Financing Receivable, Credit Quality Indicator [Line Items]
2022	0
2021	595
2020	0
2019	0
2018	0
Prior	7,072
Revolving	0
Revolving to Term	0
Total Loans	7,667
Special mention | Consumer and other
Financing Receivable, Credit Quality Indicator [Line Items]
2022	0
2021	3
2020	2
2019	8
2018	0
Prior	126
Revolving	9
Revolving to Term	0
Total Loans	148
Substandard accrual
Financing Receivable, Credit Quality Indicator [Line Items]
2022	284
2021	15,042
2020	13,348
2019	37,861
2018	54,236
Prior	116,853
Revolving	27,692
Revolving to Term	536
Total Loans	265,852
Substandard accrual | Commercial, industrial and other
Financing Receivable, Credit Quality Indicator [Line Items]
2022	0
2021	5,596
2020	10,285
2019	22,157
2018	24,320
Prior	11,484
Revolving	26,925
Revolving to Term	0
Total Loans	100,767
Substandard accrual | Commercial PPP loans
Financing Receivable, Credit Quality Indicator [Line Items]
2022	0
2021	0
2020	565
2019	0
2018	0
Prior	0
Revolving	0
Revolving to Term	0
Total Loans	565
Substandard accrual | Construction and development
Financing Receivable, Credit Quality Indicator [Line Items]
2022	0
2021	0
2020	0
2019	312
2018	2,052
Prior	14,572
Revolving	0
Revolving to Term	0
Total Loans	16,936
Substandard accrual | Non-construction
Financing Receivable, Credit Quality Indicator [Line Items]
2022	0
2021	0
2020	286
2019	14,676
2018	26,945
Prior	74,269
Revolving	0
Revolving to Term	0
Total Loans	116,176
Substandard accrual | Home equity
Financing Receivable, Credit Quality Indicator [Line Items]
2022	0
2021	0
2020	0
2019	0
2018	0
Prior	9,045
Revolving	757
Revolving to Term	536
Total Loans	10,338
Substandard accrual | Residential real estate
Financing Receivable, Credit Quality Indicator [Line Items]
2022	263
2021	1,101
2020	2,184
2019	716
2018	904
Prior	7,407
Revolving	0
Revolving to Term	0
Total Loans	12,575
Substandard accrual | Premium finance receivables - property and casualty
Financing Receivable, Credit Quality Indicator [Line Items]
2022	21
2021	8,336
2020	27
2019	0
2018	15
Prior	0
Revolving	0
Revolving to Term	0
Total Loans	8,399
Substandard accrual | Premium finance receivables - life
Financing Receivable, Credit Quality Indicator [Line Items]
2022	0
2021	0
2020	0
2019	0
2018	0
Prior	0
Revolving	0
Revolving to Term	0
Total Loans	0
Substandard accrual | Consumer and other
Financing Receivable, Credit Quality Indicator [Line Items]
2022	0
2021	9
2020	1
2019	0
2018	0
Prior	76
Revolving	10
Revolving to Term	0
Total Loans	96
Substandard nonaccrual/doubtful
Financing Receivable, Credit Quality Indicator [Line Items]
2022	89
2021	6,169
2020	4,811
2019	8,437
2018	2,499
Prior	22,822
Revolving	72
Revolving to Term	0
Total Loans	44,899
Substandard nonaccrual/doubtful | Commercial, industrial and other
Financing Receivable, Credit Quality Indicator [Line Items]
2022	0
2021	54
2020	3,427
2019	6,474
2018	1,759
Prior	5,092
Revolving	72
Revolving to Term	0
Total Loans	16,878
Substandard nonaccrual/doubtful | Commercial PPP loans
Financing Receivable, Credit Quality Indicator [Line Items]
2022	0
2021	0
2020	0
2019	0
2018	0
Prior	0
Revolving	0
Revolving to Term	0
Total Loans	0
Substandard nonaccrual/doubtful | Construction and development
Financing Receivable, Credit Quality Indicator [Line Items]
2022	0
2021	0
2020	0
2019	0
2018	0
Prior	1,054
Revolving	0
Revolving to Term	0
Total Loans	1,054
Substandard nonaccrual/doubtful | Non-construction
Financing Receivable, Credit Quality Indicator [Line Items]
2022	0
2021	0
2020	0
2019	0
2018	270
Prior	10,977
Revolving	0
Revolving to Term	0
Total Loans	11,247
Substandard nonaccrual/doubtful | Home equity
Financing Receivable, Credit Quality Indicator [Line Items]
2022	0
2021	0
2020	0
2019	107
2018	43
Prior	1,597
Revolving	0
Revolving to Term	0
Total Loans	1,747
Substandard nonaccrual/doubtful | Residential real estate
Financing Receivable, Credit Quality Indicator [Line Items]
2022	0
2021	0
2020	881
2019	1,856
2018	427
Prior	4,098
Revolving	0
Revolving to Term	0
Total Loans	7,262
Substandard nonaccrual/doubtful | Premium finance receivables - property and casualty
Financing Receivable, Credit Quality Indicator [Line Items]
2022	89
2021	6,115
2020	503
2019	0
2018	0
Prior	0
Revolving	0
Revolving to Term	0
Total Loans	6,707
Substandard nonaccrual/doubtful | Premium finance receivables - life
Financing Receivable, Credit Quality Indicator [Line Items]
2022	0
2021	0
2020	0
2019	0
2018	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]
2022	0
2021	0
2020	0
2019	0
2018	0
Prior	4
Revolving	0
Revolving to Term	0
Total Loans	$ 4