Allowance for Credit Losses (Loan Portfolio by Credit Quality Indicator) (Details) - USD ($) $ in Thousands	Jun. 30, 2022	Dec. 31, 2021	Jun. 30, 2021
Financing Receivable, Credit Quality Indicator [Line Items]
2022	$ 7,679,289
2021	7,127,310
2020	4,141,666
2019	2,988,822
2018	2,255,110
Prior	8,140,075
Revolving	4,671,106
Revolving to Term	49,725
Total Loans	37,053,103	$ 34,789,104	$ 32,911,187
Commercial, industrial and other
Financing Receivable, Credit Quality Indicator [Line Items]
2022	1,267,452
2021	2,649,694
2020	1,347,658
2019	843,782
2018	632,378
Prior	1,017,319
Revolving	4,161,422
Revolving to Term	45,311
Total Loans	11,965,016
Commercial PPP loans
Financing Receivable, Credit Quality Indicator [Line Items]
2022	0
2021	63,542
2020	18,547
2019	0
2018	0
Prior	0
Revolving	0
Revolving to Term	0
Total Loans	82,089
Construction and development
Financing Receivable, Credit Quality Indicator [Line Items]
2022	177,013
2021	453,495
2020	456,141
2019	205,876
2018	70,993
Prior	122,958
Revolving	19,842
Revolving to Term	0
Total Loans	1,506,318
Non-construction
Financing Receivable, Credit Quality Indicator [Line Items]
2022	958,792
2021	1,538,694
2020	1,069,291
2019	927,383
2018	743,438
Prior	2,505,961
Revolving	153,903
Revolving to Term	3,425
Total Loans	7,900,887
Home equity
Financing Receivable, Credit Quality Indicator [Line Items]
2022	0
2021	0
2020	0
2019	56
2018	281
Prior	15,301
Revolving	309,199
Revolving to Term	989
Total Loans	325,826	335,155	369,806
Residential real estate
Financing Receivable, Credit Quality Indicator [Line Items]
2022	503,562
2021	841,961
2020	253,794
2019	151,973
2018	74,528
Prior	253,089
Revolving	0
Revolving to Term	0
Total Loans	2,078,907	1,637,099	1,530,285
Premium finance receivables - property and casualty
Financing Receivable, Credit Quality Indicator [Line Items]
2022	4,600,514
2021	922,284
2020	13,512
2019	4,835
2018	302
Prior	0
Revolving	0
Revolving to Term	0
Total Loans	5,541,447
Premium finance receivables - life
Financing Receivable, Credit Quality Indicator [Line Items]
2022	170,609
2021	655,484
2020	982,199
2019	854,124
2018	732,262
Prior	4,213,755
Revolving	0
Revolving to Term	0
Total Loans	7,608,433
Consumer and other
Financing Receivable, Credit Quality Indicator [Line Items]
2022	1,347
2021	2,156
2020	524
2019	793
2018	928
Prior	11,692
Revolving	26,740
Revolving to Term	0
Total Loans	44,180	$ 24,199	$ 9,024
Early buy-out loans guaranteed by U.S. government agencies
Financing Receivable, Credit Quality Indicator [Line Items]
2022	0
2021	1,021
2020	5,575
2019	19,486
2018	18,474
Prior	69,300
Revolving	0
Revolving to Term	0
Total Loans	113,856
Early buy-out loans guaranteed by U.S. government agencies | Residential real estate
Financing Receivable, Credit Quality Indicator [Line Items]
2022	0
2021	1,021
2020	5,575
2019	19,486
2018	18,474
Prior	69,300
Revolving	0
Revolving to Term	0
Total Loans	113,856
Pass
Financing Receivable, Credit Quality Indicator [Line Items]
2022	7,585,957
2021	7,011,737
2020	4,047,492
2019	2,821,345
2018	2,054,174
Prior	7,825,801
Revolving	4,513,029
Revolving to Term	48,430
Total Loans	35,907,965
Pass | Commercial, industrial and other
Financing Receivable, Credit Quality Indicator [Line Items]
2022	1,260,184
2021	2,565,443
2020	1,279,656
2019	758,679
2018	558,129
Prior	963,346
Revolving	4,008,344
Revolving to Term	45,005
Total Loans	11,438,786
Pass | Commercial PPP loans
Financing Receivable, Credit Quality Indicator [Line Items]
2022	0
2021	63,524
2020	17,374
2019	0
2018	0
Prior	0
Revolving	0
Revolving to Term	0
Total Loans	80,898
Pass | Construction and development
Financing Receivable, Credit Quality Indicator [Line Items]
2022	177,013
2021	452,444
2020	447,683
2019	201,983
2018	41,299
Prior	107,465
Revolving	19,842
Revolving to Term	0
Total Loans	1,447,729
Pass | Non-construction
Financing Receivable, Credit Quality Indicator [Line Items]
2022	954,387
2021	1,534,813
2020	1,061,773
2019	871,589
2018	667,917
Prior	2,356,129
Revolving	153,903
Revolving to Term	3,425
Total Loans	7,603,936
Pass | Home equity
Financing Receivable, Credit Quality Indicator [Line Items]
2022	0
2021	0
2020	0
2019	56
2018	0
Prior	5,352
Revolving	304,216
Revolving to Term	0
Total Loans	309,624
Pass | Residential real estate
Financing Receivable, Credit Quality Indicator [Line Items]
2022	502,728
2021	839,183
2020	244,861
2019	129,292
2018	53,337
Prior	168,254
Revolving	0
Revolving to Term	0
Total Loans	1,937,655
Pass | Premium finance receivables - property and casualty
Financing Receivable, Credit Quality Indicator [Line Items]
2022	4,519,689
2021	899,305
2020	13,424
2019	4,835
2018	302
Prior	0
Revolving	0
Revolving to Term	0
Total Loans	5,437,555
Pass | Premium finance receivables - life
Financing Receivable, Credit Quality Indicator [Line Items]
2022	170,609
2021	654,884
2020	982,199
2019	854,124
2018	732,262
Prior	4,213,755
Revolving	0
Revolving to Term	0
Total Loans	7,607,833
Pass | Consumer and other
Financing Receivable, Credit Quality Indicator [Line Items]
2022	1,347
2021	2,141
2020	522
2019	787
2018	928
Prior	11,500
Revolving	26,724
Revolving to Term	0
Total Loans	43,949
Special mention
Financing Receivable, Credit Quality Indicator [Line Items]
2022	87,294
2021	57,798
2020	46,680
2019	104,133
2018	123,299
Prior	141,606
Revolving	86,706
Revolving to Term	235
Total Loans	647,751
Special mention | Commercial, industrial and other
Financing Receivable, Credit Quality Indicator [Line Items]
2022	5,275
2021	40,753
2020	38,258
2019	62,110
2018	54,302
Prior	42,247
Revolving	82,418
Revolving to Term	235
Total Loans	325,598
Special mention | Commercial PPP loans
Financing Receivable, Credit Quality Indicator [Line Items]
2022	0
2021	18
2020	680
2019	0
2018	0
Prior	0
Revolving	0
Revolving to Term	0
Total Loans	698
Special mention | Construction and development
Financing Receivable, Credit Quality Indicator [Line Items]
2022	0
2021	1,051
2020	0
2019	3,583
2018	17,951
Prior	2,001
Revolving	0
Revolving to Term	0
Total Loans	24,586
Special mention | Non-construction
Financing Receivable, Credit Quality Indicator [Line Items]
2022	4,405
2021	3,881
2020	7,518
2019	37,670
2018	48,762
Prior	93,106
Revolving	0
Revolving to Term	0
Total Loans	195,342
Special mention | Home equity
Financing Receivable, Credit Quality Indicator [Line Items]
2022	0
2021	0
2020	0
2019	0
2018	238
Prior	61
Revolving	4,281
Revolving to Term	0
Total Loans	4,580
Special mention | Residential real estate
Financing Receivable, Credit Quality Indicator [Line Items]
2022	280
2021	576
2020	169
2019	765
2018	2,046
Prior	4,071
Revolving	0
Revolving to Term	0
Total Loans	7,907
Special mention | Premium finance receivables - property and casualty
Financing Receivable, Credit Quality Indicator [Line Items]
2022	77,334
2021	10,917
2020	54
2019	0
2018	0
Prior	0
Revolving	0
Revolving to Term	0
Total Loans	88,305
Special mention | Premium finance receivables - life
Financing Receivable, Credit Quality Indicator [Line Items]
2022	0
2021	600
2020	0
2019	0
2018	0
Prior	0
Revolving	0
Revolving to Term	0
Total Loans	600
Special mention | Consumer and other
Financing Receivable, Credit Quality Indicator [Line Items]
2022	0
2021	2
2020	1
2019	5
2018	0
Prior	120
Revolving	7
Revolving to Term	0
Total Loans	135
Substandard accrual
Financing Receivable, Credit Quality Indicator [Line Items]
2022	3,498
2021	45,831
2020	38,038
2019	37,270
2018	46,203
Prior	82,352
Revolving	63,400
Revolving to Term	1,060
Total Loans	317,652
Substandard accrual | Commercial, industrial and other
Financing Receivable, Credit Quality Indicator [Line Items]
2022	1,993
2021	43,404
2020	26,150
2019	18,264
2018	7,454
Prior	8,171
Revolving	62,689
Revolving to Term	71
Total Loans	168,196
Substandard accrual | Commercial PPP loans
Financing Receivable, Credit Quality Indicator [Line Items]
2022	0
2021	0
2020	493
2019	0
2018	0
Prior	0
Revolving	0
Revolving to Term	0
Total Loans	493
Substandard accrual | Construction and development
Financing Receivable, Credit Quality Indicator [Line Items]
2022	0
2021	0
2020	8,458
2019	310
2018	11,743
Prior	12,603
Revolving	0
Revolving to Term	0
Total Loans	33,114
Substandard accrual | Non-construction
Financing Receivable, Credit Quality Indicator [Line Items]
2022	0
2021	0
2020	0
2019	18,124
2018	26,759
Prior	46,897
Revolving	0
Revolving to Term	0
Total Loans	91,780
Substandard accrual | Home equity
Financing Receivable, Credit Quality Indicator [Line Items]
2022	0
2021	0
2020	0
2019	0
2018	0
Prior	8,847
Revolving	702
Revolving to Term	989
Total Loans	10,538
Substandard accrual | Residential real estate
Financing Receivable, Credit Quality Indicator [Line Items]
2022	554
2021	1,088
2020	2,936
2019	572
2018	247
Prior	5,762
Revolving	0
Revolving to Term	0
Total Loans	11,159
Substandard accrual | Premium finance receivables - property and casualty
Financing Receivable, Credit Quality Indicator [Line Items]
2022	951
2021	1,333
2020	0
2019	0
2018	0
Prior	0
Revolving	0
Revolving to Term	0
Total Loans	2,284
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	6
2020	1
2019	0
2018	0
Prior	72
Revolving	9
Revolving to Term	0
Total Loans	88
Substandard nonaccrual/doubtful
Financing Receivable, Credit Quality Indicator [Line Items]
2022	2,540
2021	10,923
2020	3,881
2019	6,588
2018	12,960
Prior	21,016
Revolving	7,971
Revolving to Term	0
Total Loans	65,879
Substandard nonaccrual/doubtful | Commercial, industrial and other
Financing Receivable, Credit Quality Indicator [Line Items]
2022	0
2021	94
2020	3,594
2019	4,729
2018	12,493
Prior	3,555
Revolving	7,971
Revolving to Term	0
Total Loans	32,436
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	889
Revolving	0
Revolving to Term	0
Total Loans	889
Substandard nonaccrual/doubtful | Non-construction
Financing Receivable, Credit Quality Indicator [Line Items]
2022	0
2021	0
2020	0
2019	0
2018	0
Prior	9,829
Revolving	0
Revolving to Term	0
Total Loans	9,829
Substandard nonaccrual/doubtful | Home equity
Financing Receivable, Credit Quality Indicator [Line Items]
2022	0
2021	0
2020	0
2019	0
2018	43
Prior	1,041
Revolving	0
Revolving to Term	0
Total Loans	1,084
Substandard nonaccrual/doubtful | Residential real estate
Financing Receivable, Credit Quality Indicator [Line Items]
2022	0
2021	93
2020	253
2019	1,858
2018	424
Prior	5,702
Revolving	0
Revolving to Term	0
Total Loans	8,330
Substandard nonaccrual/doubtful | Premium finance receivables - property and casualty
Financing Receivable, Credit Quality Indicator [Line Items]
2022	2,540
2021	10,729
2020	34
2019	0
2018	0
Prior	0
Revolving	0
Revolving to Term	0
Total Loans	13,303
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	7
2020	0
2019	1
2018	0
Prior	0
Revolving	0
Revolving to Term	0
Total Loans	$ 8