Loans and Loans Held for Sale - Summary of Restructured Loans (Details) - USD ($) $ in Thousands		3 Months Ended			12 Months Ended
		Mar. 31, 2020		Mar. 31, 2019	Dec. 31, 2019
Financing Receivable, Troubled Debt Restructuring [Line Items]
Restructured loans	[1]	$ 8,297	[2]	$ 5,499
Commercial real estate
Financing Receivable, Troubled Debt Restructuring [Line Items]
Restructured loans	[1]	2,210
Commercial and industrial
Financing Receivable, Troubled Debt Restructuring [Line Items]
Restructured loans	[1]	3,780		5,201
Commercial construction
Financing Receivable, Troubled Debt Restructuring [Line Items]
Restructured loans	[1]	1,891
Consumer real estate
Financing Receivable, Troubled Debt Restructuring [Line Items]
Restructured loans	[1]	415
Residential Mortgage
Financing Receivable, Troubled Debt Restructuring [Line Items]
Restructured loans	[1]			49
Home equity
Financing Receivable, Troubled Debt Restructuring [Line Items]
Restructured loans	[1]			$ 249
Performing TDRs
Financing Receivable, Troubled Debt Restructuring [Line Items]
Restructured loans		15,189	[3]		$ 36,960
Performing TDRs | Commercial real estate
Financing Receivable, Troubled Debt Restructuring [Line Items]
Restructured loans		30			22,233
Performing TDRs | Commercial and industrial
Financing Receivable, Troubled Debt Restructuring [Line Items]
Restructured loans		4,566			6,909
Performing TDRs | Commercial construction
Financing Receivable, Troubled Debt Restructuring [Line Items]
Restructured loans		3,316			1,425
Performing TDRs | Business banking
Financing Receivable, Troubled Debt Restructuring [Line Items]
Restructured loans		1,524
Performing TDRs | Consumer real estate
Financing Receivable, Troubled Debt Restructuring [Line Items]
Restructured loans		5,749
Performing TDRs | Residential Mortgage
Financing Receivable, Troubled Debt Restructuring [Line Items]
Restructured loans					2,013
Performing TDRs | Home equity
Financing Receivable, Troubled Debt Restructuring [Line Items]
Restructured loans					4,371
Performing TDRs | Other consumer
Financing Receivable, Troubled Debt Restructuring [Line Items]
Restructured loans		4
Performing TDRs | Installment and other consumer
Financing Receivable, Troubled Debt Restructuring [Line Items]
Restructured loans					9
Nonperforming TDRs
Financing Receivable, Troubled Debt Restructuring [Line Items]
Restructured loans		36,055	[3]		8,912
Nonperforming TDRs | Commercial real estate
Financing Receivable, Troubled Debt Restructuring [Line Items]
Restructured loans		28,973			6,713
Nonperforming TDRs | Commercial and industrial
Financing Receivable, Troubled Debt Restructuring [Line Items]
Restructured loans		4,665			695
Nonperforming TDRs | Commercial construction
Financing Receivable, Troubled Debt Restructuring [Line Items]
Restructured loans		0			0
Nonperforming TDRs | Business banking
Financing Receivable, Troubled Debt Restructuring [Line Items]
Restructured loans		352
Nonperforming TDRs | Consumer real estate
Financing Receivable, Troubled Debt Restructuring [Line Items]
Restructured loans		2,064
Nonperforming TDRs | Residential Mortgage
Financing Receivable, Troubled Debt Restructuring [Line Items]
Restructured loans					822
Nonperforming TDRs | Home equity
Financing Receivable, Troubled Debt Restructuring [Line Items]
Restructured loans					678
Nonperforming TDRs | Other consumer
Financing Receivable, Troubled Debt Restructuring [Line Items]
Restructured loans		0
Nonperforming TDRs | Installment and other consumer
Financing Receivable, Troubled Debt Restructuring [Line Items]
Restructured loans					4
Total TDRs
Financing Receivable, Troubled Debt Restructuring [Line Items]
Restructured loans		51,243	[3]		45,872
Total TDRs | Commercial real estate
Financing Receivable, Troubled Debt Restructuring [Line Items]
Restructured loans		29,003			28,946
Total TDRs | Commercial and industrial
Financing Receivable, Troubled Debt Restructuring [Line Items]
Restructured loans		9,231			7,604
Total TDRs | Commercial construction
Financing Receivable, Troubled Debt Restructuring [Line Items]
Restructured loans		3,316			1,425
Total TDRs | Business banking
Financing Receivable, Troubled Debt Restructuring [Line Items]
Restructured loans		1,876
Total TDRs | Consumer real estate
Financing Receivable, Troubled Debt Restructuring [Line Items]
Restructured loans		7,813
Total TDRs | Residential Mortgage
Financing Receivable, Troubled Debt Restructuring [Line Items]
Restructured loans					2,835
Total TDRs | Home equity
Financing Receivable, Troubled Debt Restructuring [Line Items]
Restructured loans					5,049
Total TDRs | Other consumer
Financing Receivable, Troubled Debt Restructuring [Line Items]
Restructured loans		$ 4
Total TDRs | Installment and other consumer
Financing Receivable, Troubled Debt Restructuring [Line Items]
Restructured loans					$ 13

[1] Excludes loans that were fully paid off or fully charged-off by period end. The pre-modification balance represents the balance outstanding prior to modification. The post-modification balance represents the outstanding balance at period end.

[2] Refer to Note 1, Basis of Presentation for details of reclassification of our portfolio segments related to the adoption of ASU 2016-13 Financial Instruments - Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instrument.

[3] Refer to Note 1, Basis of Presentation for details of reclassification of our portfolio segments related to the adoption of ASU 2016-13 Financial Instruments - Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments.