Allowance for Credit Losses - Age Analysis of Past Due Loans Segregated by Class of Loans (Details) $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2021 USD ($) loan	Dec. 31, 2020 USD ($) loan	Dec. 31, 2019 USD ($)
Financing Receivable, Past Due [Line Items]
Total	$ 7,007,351	$ 7,225,860
Non - performing	112,619	146,774	$ 54,057
Financial Asset, Not Past Due
Financing Receivable, Past Due [Line Items]
Total	6,878,389	7,069,730
Financial Asset, Past Due
Financing Receivable, Past Due [Line Items]
Total	128,962	156,130
30 to 59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total	15,063	2,888
60 to 89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total	1,281	5,965
90 Days Past Due
Financing Receivable, Past Due [Line Items]
Total		503
Commercial
Financing Receivable, Past Due [Line Items]
Total	$ 5,499,044	$ 5,673,707
Commercial | CARES Act, Paycheck Protection Program Loans
Financing Receivable, Past Due [Line Items]
Number of modified loans | loan	42	52
Modified loans	$ 68,700	$ 195,600
Commercial | Commercial real estate
Financing Receivable, Past Due [Line Items]
Total	2,740,296	2,791,947
Non - performing	80,067	101,070	25,356
Commercial | Commercial and industrial
Financing Receivable, Past Due [Line Items]
Total	1,546,247	1,559,552
Non - performing	12,198	16,985	10,911
Commercial | Commercial construction
Financing Receivable, Past Due [Line Items]
Total	467,871	466,077
Non - performing	385	384	737
Commercial | Business banking
Financing Receivable, Past Due [Line Items]
Total	1,070,875	1,160,067
Non - performing	11,064	17,122	9,863
Commercial | Financial Asset, Not Past Due | Commercial real estate
Financing Receivable, Past Due [Line Items]
Total	2,648,221	2,690,877
Commercial | Financial Asset, Not Past Due | Commercial and industrial
Financing Receivable, Past Due [Line Items]
Total	1,534,049	1,542,567
Commercial | Financial Asset, Not Past Due | Commercial construction
Financing Receivable, Past Due [Line Items]
Total	466,987	462,094
Commercial | Financial Asset, Not Past Due | Business banking
Financing Receivable, Past Due [Line Items]
Total	1,057,279	1,140,581
Commercial | Financial Asset, Past Due | Commercial real estate
Financing Receivable, Past Due [Line Items]
Total	92,075	101,070
Commercial | Financial Asset, Past Due | Commercial and industrial
Financing Receivable, Past Due [Line Items]
Total	12,198	16,985
Commercial | Financial Asset, Past Due | Commercial construction
Financing Receivable, Past Due [Line Items]
Total	885	3,983
Commercial | Financial Asset, Past Due | Business banking
Financing Receivable, Past Due [Line Items]
Total	13,597	19,486
Commercial | 30 to 59 Days Past Due | Commercial real estate
Financing Receivable, Past Due [Line Items]
Total	0	0
Commercial | 30 to 59 Days Past Due | Commercial and industrial
Financing Receivable, Past Due [Line Items]
Total	12,007	0
Commercial | 30 to 59 Days Past Due | Commercial construction
Financing Receivable, Past Due [Line Items]
Total	0	19
Commercial | 30 to 59 Days Past Due | Business banking
Financing Receivable, Past Due [Line Items]
Total	2,311	1,614
Commercial | 60 to 89 Days Past Due | Commercial real estate
Financing Receivable, Past Due [Line Items]
Total	500	0
Commercial | 60 to 89 Days Past Due | Commercial and industrial
Financing Receivable, Past Due [Line Items]
Total	0	0
Commercial | 60 to 89 Days Past Due | Commercial construction
Financing Receivable, Past Due [Line Items]
Total	0	3,580
Commercial | 60 to 89 Days Past Due | Business banking
Financing Receivable, Past Due [Line Items]
Total	222	379
Commercial | 90 Days Past Due | Commercial real estate
Financing Receivable, Past Due [Line Items]
Total		0
Commercial | 90 Days Past Due | Commercial and industrial
Financing Receivable, Past Due [Line Items]
Total		0
Commercial | 90 Days Past Due | Commercial construction
Financing Receivable, Past Due [Line Items]
Total		0
Commercial | 90 Days Past Due | Business banking
Financing Receivable, Past Due [Line Items]
Total		371
Consumer
Financing Receivable, Past Due [Line Items]
Total	1,508,307	1,552,153
Consumer | Business banking
Financing Receivable, Past Due [Line Items]
Total		303,900
Consumer | Consumer real estate
Financing Receivable, Past Due [Line Items]
Total	1,093,878	1,167,332
Non - performing	8,783	11,117	6,063
Consumer | Other consumer
Financing Receivable, Past Due [Line Items]
Total	88,184	80,885
Non - performing	121	96	$ 1,127
Consumer | Financial Asset, Not Past Due | Consumer real estate
Financing Receivable, Past Due [Line Items]
Total	1,083,947	1,153,028
Consumer | Financial Asset, Not Past Due | Other consumer
Financing Receivable, Past Due [Line Items]
Total	87,905	80,583
Consumer | Financial Asset, Past Due | Consumer real estate
Financing Receivable, Past Due [Line Items]
Total	9,930	14,304
Consumer | Financial Asset, Past Due | Other consumer
Financing Receivable, Past Due [Line Items]
Total	278	302
Consumer | 30 to 59 Days Past Due | Consumer real estate
Financing Receivable, Past Due [Line Items]
Total	640	1,087
Consumer | 30 to 59 Days Past Due | Other consumer
Financing Receivable, Past Due [Line Items]
Total	105	168
Consumer | 60 to 89 Days Past Due | Consumer real estate
Financing Receivable, Past Due [Line Items]
Total	507	1,968
Consumer | 60 to 89 Days Past Due | Other consumer
Financing Receivable, Past Due [Line Items]
Total	$ 52	37
Consumer | 90 Days Past Due | Consumer real estate
Financing Receivable, Past Due [Line Items]
Total		132
Consumer | 90 Days Past Due | Other consumer
Financing Receivable, Past Due [Line Items]
Total		$ 0