Loans and Loans Held for Sale - Summary of Restructured Loans (Details) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020
Financing Receivable, Troubled Debt Restructuring [Line Items]
Restructured loans	$ 6,865	$ 1,897
Commercial real estate | Commercial
Financing Receivable, Troubled Debt Restructuring [Line Items]
Restructured loans	0	0
Commercial and industrial | Commercial
Financing Receivable, Troubled Debt Restructuring [Line Items]
Restructured loans	6,296	0
Commercial construction | Commercial
Financing Receivable, Troubled Debt Restructuring [Line Items]
Restructured loans	0	1,806
Business banking | Commercial
Financing Receivable, Troubled Debt Restructuring [Line Items]
Restructured loans	0	0
Consumer real estate | Consumer
Financing Receivable, Troubled Debt Restructuring [Line Items]
Restructured loans	568	91
Other consumer | Consumer
Financing Receivable, Troubled Debt Restructuring [Line Items]
Restructured loans	1	$ 0
Total TDRs
Financing Receivable, Troubled Debt Restructuring [Line Items]
Restructured loans	47,899		$ 46,748
Total TDRs | Commercial real estate | Commercial
Financing Receivable, Troubled Debt Restructuring [Line Items]
Restructured loans	15,762		16,668
Total TDRs | Commercial and industrial | Commercial
Financing Receivable, Troubled Debt Restructuring [Line Items]
Restructured loans	19,001		16,975
Total TDRs | Commercial construction | Commercial
Financing Receivable, Troubled Debt Restructuring [Line Items]
Restructured loans	3,245		3,267
Total TDRs | Business banking | Commercial
Financing Receivable, Troubled Debt Restructuring [Line Items]
Restructured loans	1,868		1,933
Total TDRs | Consumer real estate | Consumer
Financing Receivable, Troubled Debt Restructuring [Line Items]
Restructured loans	8,018		7,900
Total TDRs | Other consumer | Consumer
Financing Receivable, Troubled Debt Restructuring [Line Items]
Restructured loans	5		5
Performing TDRs
Financing Receivable, Troubled Debt Restructuring [Line Items]
Restructured loans	17,916		17,460
Performing TDRs | Commercial real estate | Commercial
Financing Receivable, Troubled Debt Restructuring [Line Items]
Restructured loans	9		14
Performing TDRs | Commercial and industrial | Commercial
Financing Receivable, Troubled Debt Restructuring [Line Items]
Restructured loans	7,576		7,090
Performing TDRs | Commercial construction | Commercial
Financing Receivable, Troubled Debt Restructuring [Line Items]
Restructured loans	3,245		3,267
Performing TDRs | Business banking | Commercial
Financing Receivable, Troubled Debt Restructuring [Line Items]
Restructured loans	1,471		1,503
Performing TDRs | Consumer real estate | Consumer
Financing Receivable, Troubled Debt Restructuring [Line Items]
Restructured loans	5,611		5,581
Performing TDRs | Other consumer | Consumer
Financing Receivable, Troubled Debt Restructuring [Line Items]
Restructured loans	5		5
Nonperforming TDRs
Financing Receivable, Troubled Debt Restructuring [Line Items]
Restructured loans	29,983		29,288
Nonperforming TDRs | Commercial real estate | Commercial
Financing Receivable, Troubled Debt Restructuring [Line Items]
Restructured loans	15,754		16,654
Nonperforming TDRs | Commercial and industrial | Commercial
Financing Receivable, Troubled Debt Restructuring [Line Items]
Restructured loans	11,425		9,885
Nonperforming TDRs | Commercial construction | Commercial
Financing Receivable, Troubled Debt Restructuring [Line Items]
Restructured loans	0		0
Nonperforming TDRs | Business banking | Commercial
Financing Receivable, Troubled Debt Restructuring [Line Items]
Restructured loans	397		430
Nonperforming TDRs | Consumer real estate | Consumer
Financing Receivable, Troubled Debt Restructuring [Line Items]
Restructured loans	2,407		2,319
Nonperforming TDRs | Other consumer | Consumer
Financing Receivable, Troubled Debt Restructuring [Line Items]
Restructured loans	$ 0		$ 0