Allowance for Credit Losses - Age Analysis of Past Due Loans Segregated by Class of Loans (Details) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2022 USD ($) loan	Dec. 31, 2021 USD ($) loan	Dec. 31, 2020 USD ($)
Financing Receivable, Past Due [Line Items]
Total	$ 6,963,911	$ 6,999,990
Non - performing	$ 52,524	$ 66,291	$ 146,774
Number of modified loans | loan	3	8
Modified loans	$ 12,500	$ 28,800
Current
Financing Receivable, Past Due [Line Items]
Total	6,905,239	6,927,943
Total Past Due Loans
Financing Receivable, Past Due [Line Items]
Total	58,672	72,047
30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total	4,281	3,085
60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total	751	2,671
Past Due 90+ Days Still Accruing
Financing Receivable, Past Due [Line Items]
Total	$ 1,116	0
Number of modified loans | loan	5
Modified loans	$ 1,100
Commercial
Financing Receivable, Past Due [Line Items]
Total	5,331,863	5,406,584
Commercial | Commercial real estate
Financing Receivable, Past Due [Line Items]
Total	2,705,799	2,690,528
Non - performing	25,790	31,488	101,070
Commercial | Commercial and industrial
Financing Receivable, Past Due [Line Items]
Total	1,458,506	1,513,523
Non - performing	10,570	15,239	16,985
Commercial | Commercial construction
Financing Receivable, Past Due [Line Items]
Total	383,237	424,755
Non - performing	864	2,471	384
Commercial | Business banking
Financing Receivable, Past Due [Line Items]
Total	1,141,236	1,135,693
Non - performing	7,997	9,641	17,122
Commercial | Current | Commercial real estate
Financing Receivable, Past Due [Line Items]
Total	2,680,009	2,659,040
Commercial | Current | Commercial and industrial
Financing Receivable, Past Due [Line Items]
Total	1,447,404	1,497,755
Commercial | Current | Commercial construction
Financing Receivable, Past Due [Line Items]
Total	382,373	421,834
Commercial | Current | Business banking
Financing Receivable, Past Due [Line Items]
Total	1,130,830	1,124,748
Commercial | Total Past Due Loans | Commercial real estate
Financing Receivable, Past Due [Line Items]
Total	25,790	31,488
Commercial | Total Past Due Loans | Commercial and industrial
Financing Receivable, Past Due [Line Items]
Total	11,102	15,768
Commercial | Total Past Due Loans | Commercial construction
Financing Receivable, Past Due [Line Items]
Total	864	2,921
Commercial | Total Past Due Loans | Business banking
Financing Receivable, Past Due [Line Items]
Total	10,406	10,945
Commercial | 30-59 Days Past Due | Commercial real estate
Financing Receivable, Past Due [Line Items]
Total	0	0
Commercial | 30-59 Days Past Due | Commercial and industrial
Financing Receivable, Past Due [Line Items]
Total	3	529
Commercial | 30-59 Days Past Due | Commercial construction
Financing Receivable, Past Due [Line Items]
Total	0	450
Commercial | 30-59 Days Past Due | Business banking
Financing Receivable, Past Due [Line Items]
Total	1,409	813
Commercial | 60-89 Days Past Due | Commercial real estate
Financing Receivable, Past Due [Line Items]
Total	0	0
Commercial | 60-89 Days Past Due | Commercial and industrial
Financing Receivable, Past Due [Line Items]
Total	0	0
Commercial | 60-89 Days Past Due | Commercial construction
Financing Receivable, Past Due [Line Items]
Total	0	0
Commercial | 60-89 Days Past Due | Business banking
Financing Receivable, Past Due [Line Items]
Total	413	491
Commercial | Past Due 90+ Days Still Accruing | Commercial real estate
Financing Receivable, Past Due [Line Items]
Total	0	0
Commercial | Past Due 90+ Days Still Accruing | Commercial and industrial
Financing Receivable, Past Due [Line Items]
Total	529	0
Commercial | Past Due 90+ Days Still Accruing | Commercial construction
Financing Receivable, Past Due [Line Items]
Total	0	0
Commercial | Past Due 90+ Days Still Accruing | Business banking
Financing Receivable, Past Due [Line Items]
Total	587	0
Consumer
Financing Receivable, Past Due [Line Items]
Total	1,632,048	1,593,406
Consumer | Business banking
Financing Receivable, Past Due [Line Items]
Total		357,900
Consumer | Consumer real estate
Financing Receivable, Past Due [Line Items]
Total	1,162,857	1,127,585
Non - performing	7,178	7,294	11,117
Consumer | Other consumer
Financing Receivable, Past Due [Line Items]
Total	112,276	107,906
Non - performing	125	158	$ 96
Consumer | Current | Consumer real estate
Financing Receivable, Past Due [Line Items]
Total	1,152,858	1,117,074
Consumer | Current | Other consumer
Financing Receivable, Past Due [Line Items]
Total	111,765	107,492
Consumer | Total Past Due Loans | Consumer real estate
Financing Receivable, Past Due [Line Items]
Total	9,999	10,511
Consumer | Total Past Due Loans | Other consumer
Financing Receivable, Past Due [Line Items]
Total	511	414
Consumer | 30-59 Days Past Due | Consumer real estate
Financing Receivable, Past Due [Line Items]
Total	2,693	1,087
Consumer | 30-59 Days Past Due | Other consumer
Financing Receivable, Past Due [Line Items]
Total	176	206
Consumer | 60-89 Days Past Due | Consumer real estate
Financing Receivable, Past Due [Line Items]
Total	128	2,130
Consumer | 60-89 Days Past Due | Other consumer
Financing Receivable, Past Due [Line Items]
Total	210	50
Consumer | Past Due 90+ Days Still Accruing | Consumer real estate
Financing Receivable, Past Due [Line Items]
Total	0	0
Consumer | Past Due 90+ Days Still Accruing | Other consumer
Financing Receivable, Past Due [Line Items]
Total	$ 0	$ 0