Loan Portfolio and Credit Quality - Credit Quality Indicators (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans	$ 7,216,325	$ 7,104,309
Commercial and industrial
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans	668,217	558,343
Paycheck Protection Program
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans	351,170	312,356
Commercial tax-exempt
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans	488,507	442,159
Commercial real estate
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans	2,697,677	2,757,375
Construction and land
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans	181,482	159,204
Residential
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans	2,632,554	2,677,464
Home equity
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans	71,752	77,364
Consumer and other
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans	124,966	120,044
Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans	6,901,959	6,786,338
Pass | Commercial and industrial
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans	623,253	519,680
Pass | Paycheck Protection Program
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans	351,170	312,356
Pass | Commercial tax-exempt
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans	485,720	434,850
Pass | Commercial real estate
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans	2,452,482	2,505,424
Pass | Construction and land
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans	178,501	156,908
Pass | Residential
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans	2,615,079	2,660,684
Pass | Home equity
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans	71,101	76,693
Pass | Consumer and other
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans	124,653	119,743
Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans	152,472	187,237
Special Mention | Commercial and industrial
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans	12,795	11,314
Special Mention | Commercial tax-exempt
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans	2,787	2,806
Special Mention | Commercial real estate
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans	133,609	170,521
Special Mention | Construction and land
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans	2,981	2,296
Special Mention | Consumer and other
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans	300	300
Accruing Classified
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans	136,130	106,883
Accruing Classified | Commercial and industrial
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans	27,403	22,955
Accruing Classified | Commercial tax-exempt
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans		4,503
Accruing Classified | Commercial real estate
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans	105,727	76,169
Accruing Classified | Residential
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans	3,000	3,000
Accruing Classified | Home equity
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans		256
Nonaccrual Loans
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans	25,764	23,851
Nonaccrual Loans | Commercial and industrial
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans	4,766	4,394
Nonaccrual Loans | Commercial real estate
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans	5,859	5,261
Nonaccrual Loans | Residential
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans	14,475	13,780
Nonaccrual Loans | Home equity
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans	651	415
Nonaccrual Loans | Consumer and other
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans	13	1
Nonaccrual Loans | Accruing Classified
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans	25,764	23,851
Nonaccrual Loans | Accruing Classified | Commercial and industrial
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans	4,766	4,394
Nonaccrual Loans | Accruing Classified | Paycheck Protection Program
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans	0	0
Nonaccrual Loans | Accruing Classified | Commercial tax-exempt
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans	0	0
Nonaccrual Loans | Accruing Classified | Commercial real estate
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans	5,859	5,261
Nonaccrual Loans | Accruing Classified | Construction and land
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans	0	0
Nonaccrual Loans | Accruing Classified | Residential
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans	14,475	13,780
Nonaccrual Loans | Accruing Classified | Home equity
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans	651	415
Nonaccrual Loans | Accruing Classified | Consumer and other
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans	13	1
Performing Financial Instruments | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans	6,901,959	6,786,338
Performing Financial Instruments | Pass | Commercial and industrial
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans	623,253	519,680
Performing Financial Instruments | Pass | Paycheck Protection Program
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans	351,170	312,356
Performing Financial Instruments | Pass | Commercial tax-exempt
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans	485,720	434,850
Performing Financial Instruments | Pass | Commercial real estate
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans	2,452,482	2,505,424
Performing Financial Instruments | Pass | Construction and land
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans	178,501	156,908
Performing Financial Instruments | Pass | Residential
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans	2,615,079	2,660,684
Performing Financial Instruments | Pass | Home equity
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans	71,101	76,693
Performing Financial Instruments | Pass | Consumer and other
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans	124,653	119,743
Performing Financial Instruments | Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans	152,472	187,237
Performing Financial Instruments | Special Mention | Commercial and industrial
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans	12,795	11,314
Performing Financial Instruments | Special Mention | Paycheck Protection Program
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans	0	0
Performing Financial Instruments | Special Mention | Commercial tax-exempt
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans	2,787	2,806
Performing Financial Instruments | Special Mention | Commercial real estate
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans	133,609	170,521
Performing Financial Instruments | Special Mention | Construction and land
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans	2,981	2,296
Performing Financial Instruments | Special Mention | Residential
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans	0	0
Performing Financial Instruments | Special Mention | Home equity
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans	0	0
Performing Financial Instruments | Special Mention | Consumer and other
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans	300	300
Performing Financial Instruments | Accruing Classified
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans	136,130	106,883
Performing Financial Instruments | Accruing Classified | Commercial and industrial
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans	27,403	22,955
Performing Financial Instruments | Accruing Classified | Paycheck Protection Program
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans	0	0
Performing Financial Instruments | Accruing Classified | Commercial tax-exempt
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans	0	4,503
Performing Financial Instruments | Accruing Classified | Commercial real estate
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans	105,727	76,169
Performing Financial Instruments | Accruing Classified | Construction and land
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans	0	0
Performing Financial Instruments | Accruing Classified | Residential
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans	3,000	3,000
Performing Financial Instruments | Accruing Classified | Home equity
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans	0	256
Performing Financial Instruments | Accruing Classified | Consumer and other
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans	$ 0	$ 0