Allowance for Credit Losses - Collateral Dependent Loans by Class of Loan (Details) - USD ($) $ in Thousands	Jun. 30, 2020		Jan. 01, 2020	Dec. 31, 2019
Financing Receivable, Credit Quality Indicator [Line Items]
Portfolio loans, net of unearned income	$ 7,548,558	[1]		$ 7,137,152
Real Estate
Financing Receivable, Credit Quality Indicator [Line Items]
Portfolio loans, net of unearned income	66,728
Blanket Lien
Financing Receivable, Credit Quality Indicator [Line Items]
Portfolio loans, net of unearned income	4,630
Investment/Cash
Financing Receivable, Credit Quality Indicator [Line Items]
Portfolio loans, net of unearned income	0
Other
Financing Receivable, Credit Quality Indicator [Line Items]
Portfolio loans, net of unearned income	689
Commercial | Commercial real estate
Financing Receivable, Credit Quality Indicator [Line Items]
Portfolio loans, net of unearned income	2,862,103	[1]	$ 3,416,518	3,059,592
Commercial | Commercial real estate | Real Estate
Financing Receivable, Credit Quality Indicator [Line Items]
Portfolio loans, net of unearned income	55,447
Commercial | Commercial real estate | Blanket Lien
Financing Receivable, Credit Quality Indicator [Line Items]
Portfolio loans, net of unearned income	40
Commercial | Commercial real estate | Investment/Cash
Financing Receivable, Credit Quality Indicator [Line Items]
Portfolio loans, net of unearned income	0
Commercial | Commercial real estate | Other
Financing Receivable, Credit Quality Indicator [Line Items]
Portfolio loans, net of unearned income	0
Commercial | Commercial and industrial
Financing Receivable, Credit Quality Indicator [Line Items]
Portfolio loans, net of unearned income	1,682,676	[1]	1,720,833	1,480,529
Commercial | Commercial and industrial | Real Estate
Financing Receivable, Credit Quality Indicator [Line Items]
Portfolio loans, net of unearned income	2,762
Commercial | Commercial and industrial | Blanket Lien
Financing Receivable, Credit Quality Indicator [Line Items]
Portfolio loans, net of unearned income	3,694
Commercial | Commercial and industrial | Investment/Cash
Financing Receivable, Credit Quality Indicator [Line Items]
Portfolio loans, net of unearned income	0
Commercial | Commercial and industrial | Other
Financing Receivable, Credit Quality Indicator [Line Items]
Portfolio loans, net of unearned income	0
Commercial | Commercial construction
Financing Receivable, Credit Quality Indicator [Line Items]
Portfolio loans, net of unearned income	453,098	[1]	375,445	370,060
Commercial | Commercial construction | Real Estate
Financing Receivable, Credit Quality Indicator [Line Items]
Portfolio loans, net of unearned income	5,215
Commercial | Commercial construction | Blanket Lien
Financing Receivable, Credit Quality Indicator [Line Items]
Portfolio loans, net of unearned income	0
Commercial | Commercial construction | Investment/Cash
Financing Receivable, Credit Quality Indicator [Line Items]
Portfolio loans, net of unearned income	0
Commercial | Commercial construction | Other
Financing Receivable, Credit Quality Indicator [Line Items]
Portfolio loans, net of unearned income	0
Commercial | Business banking
Financing Receivable, Credit Quality Indicator [Line Items]
Portfolio loans, net of unearned income	1,268,835	[1]	$ 0	$ 846,790
Commercial | Business banking | Real Estate
Financing Receivable, Credit Quality Indicator [Line Items]
Portfolio loans, net of unearned income	2,906
Commercial | Business banking | Blanket Lien
Financing Receivable, Credit Quality Indicator [Line Items]
Portfolio loans, net of unearned income	896
Commercial | Business banking | Investment/Cash
Financing Receivable, Credit Quality Indicator [Line Items]
Portfolio loans, net of unearned income	0
Commercial | Business banking | Other
Financing Receivable, Credit Quality Indicator [Line Items]
Portfolio loans, net of unearned income	689
Commercial | Consumer real estate | Real Estate
Financing Receivable, Credit Quality Indicator [Line Items]
Portfolio loans, net of unearned income	398
Commercial | Consumer real estate | Blanket Lien
Financing Receivable, Credit Quality Indicator [Line Items]
Portfolio loans, net of unearned income	0
Commercial | Consumer real estate | Investment/Cash
Financing Receivable, Credit Quality Indicator [Line Items]
Portfolio loans, net of unearned income	0
Commercial | Consumer real estate | Other
Financing Receivable, Credit Quality Indicator [Line Items]
Portfolio loans, net of unearned income	$ 0

[1] We had 2,360 loans that were modified totaling $1.4 billion under the CARES Act at June 30, 2020. These customers were not considered past due as a result of their delayed payments. Upon exiting the loan modification deferral program, the measurement of loan delinquency will resume where it left off upon entry into the program. Due to the modification program, this delinquency table may not accurately reflect the credit risk associated with these loans.