Loans and Allowance for Credit Losses Past Due Loan Status and Non-Accrual Loans by Portfolio Segment (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Financing Receivable, Past Due [Line Items]
≥ 90 Days Past Due and Accruing	$ 9,929	$ 16,057
Non- accrual	137,198	125,098
Current	18,673,373	16,620,575
Net Loans	18,900,820	16,837,526
Financial Asset, 30 to 59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due and Non-accrual	59,999	56,326
Financial Asset, 60 to 89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due and Non-accrual	20,321	19,470
Real estate - commercial mortgage
Financing Receivable, Past Due [Line Items]
≥ 90 Days Past Due and Accruing	1,177	4,113
Non- accrual	51,470	33,166
Current	7,028,173	6,651,042
Net Loans	7,105,092	6,700,776
Real estate - commercial mortgage | Financial Asset, 30 to 59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due and Non-accrual	14,999	10,912
Real estate - commercial mortgage | Financial Asset, 60 to 89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due and Non-accrual	9,273	1,543
Commercial and industrial (1)
Financing Receivable, Past Due [Line Items]
≥ 90 Days Past Due and Accruing	616	1,385
Non- accrual	31,993	48,106
Current	5,625,866	4,392,278
Net Loans	5,670,828	4,446,701
Commercial and industrial (1) | Financial Asset, 30 to 59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due and Non-accrual	11,285	2,302
Commercial and industrial (1) | Financial Asset, 60 to 89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due and Non-accrual	1,068	2,630
Real estate - home equity
Financing Receivable, Past Due [Line Items]
≥ 90 Days Past Due and Accruing	2,753	3,564
Non- accrual	9,588	7,004
Current	1,183,296	1,292,035
Net Loans	1,202,913	1,314,944
Real estate - home equity | Financial Asset, 30 to 59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due and Non-accrual	5,622	9,635
Real estate - home equity | Financial Asset, 60 to 89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due and Non-accrual	1,654	2,706
Real estate - residential mortgage
Financing Receivable, Past Due [Line Items]
≥ 90 Days Past Due and Accruing	4,687	5,735
Non- accrual	26,107	16,676
Current	3,081,165	2,584,763
Net Loans	3,141,915	2,641,465
Real estate - residential mortgage | Financial Asset, 30 to 59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due and Non-accrual	22,281	26,982
Real estate - residential mortgage | Financial Asset, 60 to 89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due and Non-accrual	7,675	7,309
Real-estate - construction
Financing Receivable, Past Due [Line Items]
≥ 90 Days Past Due and Accruing	155	688
Non- accrual	1,395	3,618
Current	1,043,730	964,158
Net Loans	1,047,218	971,079
Real-estate - construction | Financial Asset, 30 to 59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due and Non-accrual	1,938	1,715
Real-estate - construction | Financial Asset, 60 to 89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due and Non-accrual	0	900
Consumer
Financing Receivable, Past Due [Line Items]
≥ 90 Days Past Due and Accruing	417	458
Non- accrual	332	0
Current	462,486	457,556
Net Loans	466,772	463,164
Consumer | Financial Asset, 30 to 59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due and Non-accrual	3,036	4,228
Consumer | Financial Asset, 60 to 89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due and Non-accrual	501	922
Leasing and other and overdrafts
Financing Receivable, Past Due [Line Items]
≥ 90 Days Past Due and Accruing	124	114
Non- accrual	16,313	16,528
Current	248,657	278,743
Net Loans	266,082	299,397
Leasing and other and overdrafts | Financial Asset, 30 to 59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due and Non-accrual	838	552
Leasing and other and overdrafts | Financial Asset, 60 to 89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due and Non-accrual	$ 150	$ 3,460