Allowance for Credit Losses (Loan Portfolio by Credit Quality Indicator) (Details) $ in Thousands	Jun. 30, 2020 USD ($)
Financing Receivable, Credit Quality Indicator [Line Items]
2020	$ 8,884,430
2019	4,699,039
2018	3,417,530
2017	2,753,167
2016	2,261,808
Prior	6,073,037
Revolving	3,305,341
Revolving to Term	8,551
Total Loans	31,402,903
Loans with COVID-19 related modifications	702,700
Commercial, industrial and other
Financing Receivable, Credit Quality Indicator [Line Items]
2020	1,124,108
2019	1,578,693
2018	1,220,579
2017	857,228
2016	457,080
Prior	620,742
Revolving	2,657,954
Revolving to Term	7,480
Total Loans	8,523,864
Commercial PPP Loans
Financing Receivable, Credit Quality Indicator [Line Items]
2020	3,335,368
2019	0
2018	0
2017	0
2016	0
Prior	0
Revolving	0
Revolving to Term	0
Total Loans	3,335,368
Construction and development
Financing Receivable, Credit Quality Indicator [Line Items]
2020	97,379
2019	465,701
2018	390,547
2017	186,991
2016	91,527
Prior	85,801
Revolving	22,102
Revolving to Term	0
Total Loans	1,340,048
Non-construction
Financing Receivable, Credit Quality Indicator [Line Items]
2020	581,447
2019	1,149,184
2018	1,051,513
2017	936,788
2016	830,208
Prior	2,139,736
Revolving	171,442
Revolving to Term	379
Total Loans	6,860,697
Home equity
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	57
2018	182
2017	511
2016	605
Prior	28,930
Revolving	435,619
Revolving to Term	692
Total Loans	466,596
Residential real estate
Financing Receivable, Credit Quality Indicator [Line Items]
2020	108,314
2019	407,658
2018	169,366
2017	177,864
2016	148,114
Prior	416,113
Revolving	0
Revolving to Term	0
Total Loans	1,427,429
Premium finance receivables - commercial
Financing Receivable, Credit Quality Indicator [Line Items]
2020	3,382,635
2019	606,087
2018	10,644
2017	408
2016	0
Prior	0
Revolving	0
Revolving to Term	0
Total Loans	3,999,774
Premium finance receivables - life
Financing Receivable, Credit Quality Indicator [Line Items]
2020	253,869
2019	488,256
2018	572,343
2017	592,444
2016	733,692
Prior	2,760,198
Revolving	0
Revolving to Term	0
Total Loans	5,400,802
Consumer and other
Financing Receivable, Credit Quality Indicator [Line Items]
2020	1,310
2019	3,403
2018	2,356
2017	933
2016	582
Prior	21,517
Revolving	18,224
Revolving to Term	0
Total Loans	48,325
Pass
Financing Receivable, Credit Quality Indicator [Line Items]
2020	8,794,036
2019	4,301,609
2018	3,117,115
2017	2,527,336
2016	2,009,059
Prior	5,611,541
Revolving	3,066,382
Revolving to Term	7,859
Total Loans	29,434,937
Pass \| Commercial, industrial and other
Financing Receivable, Credit Quality Indicator [Line Items]
2020	1,072,045
2019	1,333,365
2018	1,070,718
2017	749,203
2016	349,600
Prior	549,941
Revolving	2,434,548
Revolving to Term	7,480
Total Loans	7,566,900
Pass \| Commercial PPP Loans
Financing Receivable, Credit Quality Indicator [Line Items]
2020	3,335,368
2019	0
2018	0
2017	0
2016	0
Prior	0
Revolving	0
Revolving to Term	0
Total Loans	3,335,368
Pass \| Construction and development
Financing Receivable, Credit Quality Indicator [Line Items]
2020	97,379
2019	445,363
2018	352,613
2017	180,506
2016	86,444
Prior	65,689
Revolving	22,102
Revolving to Term	0
Total Loans	1,250,096
Pass \| Non-construction
Financing Receivable, Credit Quality Indicator [Line Items]
2020	578,157
2019	1,047,153
2018	945,334
2017	835,676
2016	701,769
Prior	1,818,599
Revolving	169,035
Revolving to Term	379
Total Loans	6,096,102
Pass \| Home equity
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	0
2018	47
2017	28
2016	43
Prior	7,701
Revolving	422,478
Revolving to Term	0
Total Loans	430,297
Pass \| Residential real estate
Financing Receivable, Credit Quality Indicator [Line Items]
2020	108,260
2019	404,584
2018	165,085
2017	168,879
2016	136,930
Prior	388,898
Revolving	0
Revolving to Term	0
Total Loans	1,372,636
Pass \| Premium finance receivables - commercial
Financing Receivable, Credit Quality Indicator [Line Items]
2020	3,347,679
2019	579,537
2018	8,624
2017	404
2016	0
Prior	0
Revolving	0
Revolving to Term	0
Total Loans	3,936,244
Pass \| Premium finance receivables - life
Financing Receivable, Credit Quality Indicator [Line Items]
2020	253,869
2019	488,256
2018	572,343
2017	591,854
2016	733,692
Prior	2,760,183
Revolving	0
Revolving to Term	0
Total Loans	5,400,197
Pass \| Consumer and other
Financing Receivable, Credit Quality Indicator [Line Items]
2020	1,279
2019	3,351
2018	2,351
2017	786
2016	581
Prior	20,530
Revolving	18,219
Revolving to Term	0
Total Loans	47,097
Special mention
Financing Receivable, Credit Quality Indicator [Line Items]
2020	76,216
2019	241,351
2018	175,678
2017	117,788
2016	174,399
Prior	214,548
Revolving	132,686
Revolving to Term	0
Total Loans	1,132,666
Special mention \| Commercial, industrial and other
Financing Receivable, Credit Quality Indicator [Line Items]
2020	42,463
2019	132,621
2018	64,833
2017	46,902
2016	73,195
Prior	22,074
Revolving	122,136
Revolving to Term	0
Total Loans	504,224
Special mention \| Commercial PPP Loans
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	0
2018	0
2017	0
2016	0
Prior	0
Revolving	0
Revolving to Term	0
Total Loans	0
Special mention \| Construction and development
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	19,198
2018	25,776
2017	0
2016	0
Prior	13,214
Revolving	0
Revolving to Term	0
Total Loans	58,188
Special mention \| Non-construction
Financing Receivable, Credit Quality Indicator [Line Items]
2020	1,914
2019	75,935
2018	82,827
2017	66,962
2016	98,309
Prior	164,795
Revolving	1,573
Revolving to Term	0
Total Loans	492,315
Special mention \| Home equity
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	0
2018	0
2017	393
2016	83
Prior	5,007
Revolving	8,975
Revolving to Term	0
Total Loans	14,458
Special mention \| Residential real estate
Financing Receivable, Credit Quality Indicator [Line Items]
2020	54
2019	2,217
2018	2,238
2017	2,811
2016	2,811
Prior	9,105
Revolving	0
Revolving to Term	0
Total Loans	19,236
Special mention \| Premium finance receivables - commercial
Financing Receivable, Credit Quality Indicator [Line Items]
2020	31,769
2019	11,350
2018	3
2017	0
2016	0
Prior	0
Revolving	0
Revolving to Term	0
Total Loans	43,122
Special mention \| Premium finance receivables - life
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	0
2018	0
2017	590
2016	0
Prior	0
Revolving	0
Revolving to Term	0
Total Loans	590
Special mention \| Consumer and other
Financing Receivable, Credit Quality Indicator [Line Items]
2020	16
2019	30
2018	1
2017	130
2016	1
Prior	353
Revolving	2
Revolving to Term	0
Total Loans	533
Substandard accrual
Financing Receivable, Credit Quality Indicator [Line Items]
2020	10,156
2019	139,601
2018	104,925
2017	91,615
2016	58,060
Prior	178,590
Revolving	100,545
Revolving to Term	692
Total Loans	684,184
Substandard accrual \| Commercial, industrial and other
Financing Receivable, Credit Quality Indicator [Line Items]
2020	8,334
2019	109,572
2018	76,045
2017	54,875
2016	26,689
Prior	37,065
Revolving	97,278
Revolving to Term	0
Total Loans	409,858
Substandard accrual \| Commercial PPP Loans
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	0
2018	0
2017	0
2016	0
Prior	0
Revolving	0
Revolving to Term	0
Total Loans	0
Substandard accrual \| Construction and development
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	1,140
2018	10,161
2017	3,403
2016	4,011
Prior	3,220
Revolving	0
Revolving to Term	0
Total Loans	21,935
Substandard accrual \| Non-construction
Financing Receivable, Credit Quality Indicator [Line Items]
2020	1,376
2019	24,969
2018	17,159
2017	30,774
2016	21,377
Prior	121,063
Revolving	834
Revolving to Term	0
Total Loans	217,552
Substandard accrual \| Home equity
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	0
2018	135
2017	0
2016	239
Prior	11,084
Revolving	2,430
Revolving to Term	692
Total Loans	14,580
Substandard accrual \| Residential real estate
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	519
2018	1,286
2017	2,563
2016	5,744
Prior	5,916
Revolving	0
Revolving to Term	0
Total Loans	16,028
Substandard accrual \| Premium finance receivables - commercial
Financing Receivable, Credit Quality Indicator [Line Items]
2020	431
2019	3,393
2018	139
2017	0
2016	0
Prior	0
Revolving	0
Revolving to Term	0
Total Loans	3,963
Substandard accrual \| Premium finance receivables - life
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	0
2018	0
2017	0
2016	0
Prior	0
Revolving	0
Revolving to Term	0
Total Loans	0
Substandard accrual \| Consumer and other
Financing Receivable, Credit Quality Indicator [Line Items]
2020	15
2019	8
2018	0
2017	0
2016	0
Prior	242
Revolving	3
Revolving to Term	0
Total Loans	268
Substandard nonaccrual/doubtful
Financing Receivable, Credit Quality Indicator [Line Items]
2020	4,022
2019	16,478
2018	19,812
2017	16,428
2016	20,290
Prior	68,358
Revolving	5,728
Revolving to Term	0
Total Loans	151,116
Substandard nonaccrual/doubtful \| Commercial, industrial and other
Financing Receivable, Credit Quality Indicator [Line Items]
2020	1,266
2019	3,135
2018	8,983
2017	6,248
2016	7,596
Prior	11,662
Revolving	3,992
Revolving to Term	0
Total Loans	42,882
Substandard nonaccrual/doubtful \| Commercial PPP Loans
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	0
2018	0
2017	0
2016	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]
2020	0
2019	0
2018	1,997
2017	3,082
2016	1,072
Prior	3,678
Revolving	0
Revolving to Term	0
Total Loans	9,829
Substandard nonaccrual/doubtful \| Non-construction
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	1,127
2018	6,193
2017	3,376
2016	8,753
Prior	35,279
Revolving	0
Revolving to Term	0
Total Loans	54,728
Substandard nonaccrual/doubtful \| Home equity
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	57
2018	0

Allowance for Credit Losses (Loan Portfolio by Credit Quality Indicator) (Details)
$ in Thousands

Jun. 30, 2020

USD ($)

Financing Receivable, Credit Quality Indicator [Line Items]

$ 8,884,430

4,699,039

3,417,530

2,753,167