Allowance for Credit Losses - Loan Balances by Year of Origination and Internally Assigned Risk Rating (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Financing Receivable, Credit Quality Indicator [Line Items]
2021	$ 435,060	$ 1,360,684
2020	1,184,593	1,214,746
2019	1,197,397	831,734
2018	777,580	565,201
2017	517,769	610,556
2016 and Prior	2,014,783	1,572,826
Revolving	1,027,762	1,041,199
Revolving-Term	28,225	28,914
Total	7,183,168	7,225,860
Pass
Financing Receivable, Credit Quality Indicator [Line Items]
2021	429,585	1,355,291
2020	1,176,989	1,136,715
2019	1,098,741	792,352
2018	738,120	502,350
2017	462,653	494,436
2016 and Prior	1,673,313	1,337,221
Revolving	1,002,104	1,011,297
Revolving-Term	24,770	25,726
Total	6,606,275	6,655,389
Special mention
Financing Receivable, Credit Quality Indicator [Line Items]
2021	0	5,274
2020	7,532	47,302
2019	68,876	19,350
2018	13,283	24,802
2017	24,342	57,026
2016 and Prior	133,387	91,677
Revolving	18,005	24,296
Revolving-Term	122	123
Total	265,547	269,851
Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
2021	5,476	118
2020	72	30,083
2019	29,134	20,032
2018	26,177	33,648
2017	30,773	57,105
2016 and Prior	200,579	137,398
Revolving	7,653	5,607
Revolving-Term	3,332	3,066
Total	303,198	287,056
Doubtful
Financing Receivable, Credit Quality Indicator [Line Items]
2021	0	0
2020	0	645
2019	645	0
2018	0	4,401
2017	0	1,989
2016 and Prior	7,503	6,529
Revolving	0	0
Revolving-Term	0	0
Total	8,148	13,564
Commercial
Financing Receivable, Credit Quality Indicator [Line Items]
Total	5,676,683	5,673,707
Commercial | Commercial real estate
Financing Receivable, Credit Quality Indicator [Line Items]
2021	96,988	334,086
2020	319,656	476,203
2019	497,992	417,944
2018	400,461	320,140
2017	300,796	415,184
2016 and Prior	1,118,080	780,560
Revolving	46,354	47,830
Revolving-Term	0	0
Total	2,780,327	2,791,947
Commercial | Commercial and industrial
Financing Receivable, Credit Quality Indicator [Line Items]
2021	257,902	457,828
2020	481,453	215,457
2019	203,334	145,290
2018	118,255	82,249
2017	61,054	28,488
2016 and Prior	193,891	221,609
Revolving	383,699	408,631
Revolving-Term	0	0
Total	1,699,588	1,559,552
Commercial | Commercial construction
Financing Receivable, Credit Quality Indicator [Line Items]
2021	24,730	132,813
2020	131,133	230,907
2019	202,255	63,535
2018	53,248	2,921
2017	2,560	6,346
2016 and Prior	22,301	16,777
Revolving	13,232	12,778
Revolving-Term	0	0
Total	449,459	466,077
Commercial | Business banking
Financing Receivable, Credit Quality Indicator [Line Items]
2021	34,568	296,357
2020	121,591	156,473
2019	171,003	128,250
2018	139,513	91,363
2017	93,638	82,202
2016 and Prior	395,703	298,779
Revolving	112,001	105,549
Revolving-Term	1,061	1,094
Total	1,069,078	1,160,067
Commercial | Pass | Commercial real estate
Financing Receivable, Credit Quality Indicator [Line Items]
2021	96,988	334,086
2020	319,206	422,800
2019	444,668	394,963
2018	376,347	277,724
2017	258,362	307,321
2016 and Prior	850,342	615,217
Revolving	44,872	46,330
Revolving-Term	0	0
Total	2,390,785	2,398,441
Commercial | Pass | Commercial and industrial
Financing Receivable, Credit Quality Indicator [Line Items]
2021	252,427	454,131
2020	478,363	199,453
2019	168,546	140,049
2018	110,278	68,607
2017	55,096	27,645
2016 and Prior	179,887	206,782
Revolving	361,828	383,082
Revolving-Term	0	0
Total	1,606,425	1,479,749
Commercial | Pass | Commercial construction
Financing Receivable, Credit Quality Indicator [Line Items]
2021	24,730	131,235
2020	127,643	224,794
2019	195,245	59,649
2018	53,248	2,420
2017	2,059	6,346
2016 and Prior	10,856	4,555
Revolving	13,232	12,778
Revolving-Term	0	0
Total	427,012	441,777
Commercial | Pass | Business banking
Financing Receivable, Credit Quality Indicator [Line Items]
2021	34,568	296,254
2020	121,017	154,335
2019	167,764	123,207
2018	134,358	86,552
2017	89,027	77,238
2016 and Prior	362,534	266,042
Revolving	110,572	103,571
Revolving-Term	265	291
Total	1,020,105	1,107,490
Commercial | Special mention | Commercial real estate
Financing Receivable, Credit Quality Indicator [Line Items]
2021	0	0
2020	450	35,499
2019	35,420	10,200
2018	8,342	22,502
2017	22,541	55,174
2016 and Prior	113,614	75,022
Revolving	0	0
Revolving-Term	0	0
Total	180,367	198,397
Commercial | Special mention | Commercial and industrial
Financing Receivable, Credit Quality Indicator [Line Items]
2021	0	3,697
2020	3,090	8,211
2019	28,623	2,628
2018	3,562	697
2017	180	768
2016 and Prior	1,289	1,046
Revolving	17,718	23,527
Revolving-Term	0	0
Total	54,461	40,574
Commercial | Special mention | Commercial construction
Financing Receivable, Credit Quality Indicator [Line Items]
2021	0	1,578
2020	3,490	2,533
2019	2,862	3,886
2018	0	0
2017	0	0
2016 and Prior	8,478	8,593
Revolving	0	0
Revolving-Term	0	0
Total	14,830	16,590
Commercial | Special mention | Business banking
Financing Receivable, Credit Quality Indicator [Line Items]
2021	0	0
2020	502	1,060
2019	1,972	1,147
2018	1,379	1,602
2017	1,621	1,084
2016 and Prior	7,759	6,866
Revolving	287	637
Revolving-Term	122	123
Total	13,642	12,519
Commercial | Substandard | Commercial real estate
Financing Receivable, Credit Quality Indicator [Line Items]
2021	0	0
2020	0	17,259
2019	17,259	12,781
2018	15,772	19,914
2017	19,894	50,700
2016 and Prior	146,624	83,792
Revolving	1,482	1,500
Revolving-Term	0	0
Total	201,030	185,946
Commercial | Substandard | Commercial and industrial
Financing Receivable, Credit Quality Indicator [Line Items]
2021	5,476	0
2020	0	7,793
2019	6,165	2,613
2018	4,415	8,544
2017	5,778	75
2016 and Prior	12,715	13,781
Revolving	4,153	2,022
Revolving-Term	0	0
Total	38,701	34,828
Commercial | Substandard | Commercial construction
Financing Receivable, Credit Quality Indicator [Line Items]
2021	0	0
2020	0	3,580
2019	4,148	0
2018	0	501
2017	501	0
2016 and Prior	2,967	3,629
Revolving	0	0
Revolving-Term	0	0
Total	7,616	7,710
Commercial | Substandard | Business banking
Financing Receivable, Credit Quality Indicator [Line Items]
2021	0	103
2020	72	1,078
2019	1,267	3,896
2018	3,777	3,209
2017	2,990	3,880
2016 and Prior	25,409	25,871
Revolving	1,141	1,341
Revolving-Term	674	680
Total	35,330	40,058
Commercial | Doubtful | Commercial real estate
Financing Receivable, Credit Quality Indicator [Line Items]
2021	0	0
2020	0	645
2019	645	0
2018	0	0
2017	0	1,989
2016 and Prior	7,499	6,529
Revolving	0	0
Revolving-Term	0	0
Total	8,144	9,163
Commercial | Doubtful | Commercial and industrial
Financing Receivable, Credit Quality Indicator [Line Items]
2021	0	0
2020	0	0
2019	0	0
2018	0	4,401
2017	0	0
2016 and Prior	0	0
Revolving	0	0
Revolving-Term	0	0
Total	0	4,401
Commercial | Doubtful | Commercial construction
Financing Receivable, Credit Quality Indicator [Line Items]
2021	0	0
2020	0	0
2019	0	0
2018	0	0
2017	0	0
2016 and Prior	0	0
Revolving	0	0
Revolving-Term	0	0
Total	0	0
Commercial | Doubtful | Business banking
Financing Receivable, Credit Quality Indicator [Line Items]
2021	0	0
2020	0	0
2019	0	0
2018	0	0
2017	0	0
2016 and Prior	0	0
Revolving	0	0
Revolving-Term	0	0
Total	0	0
Consumer
Financing Receivable, Credit Quality Indicator [Line Items]
Total	1,506,485	1,552,153
Consumer | Business banking
Financing Receivable, Credit Quality Indicator [Line Items]
Total	321,800	303,900
Consumer | Consumer real estate
Financing Receivable, Credit Quality Indicator [Line Items]
2021	20,000	120,736
2020	116,640	122,544
2019	111,128	69,931
2018	60,255	65,133
2017	56,942	76,254
2016 and Prior	277,553	251,047
Revolving	436,952	439,020
Revolving-Term	24,630	22,667
Total	1,104,099	1,167,332
Consumer | Other consumer
Financing Receivable, Credit Quality Indicator [Line Items]
2021	872	18,864
2020	14,119	13,162
2019	11,686	6,784
2018	5,848	3,395
2017	2,778	2,082
2016 and Prior	7,255	4,054
Revolving	35,525	27,391
Revolving-Term	2,534	5,153
Total	80,618	80,885
Consumer | Pass | Consumer real estate
Financing Receivable, Credit Quality Indicator [Line Items]
2021	20,000	120,736
2020	116,640	122,171
2019	110,942	67,700
2018	58,166	63,653
2017	55,435	73,805
2016 and Prior	267,411	243,939
Revolving	436,449	438,888
Revolving-Term	23,550	22,667
Total	1,088,594	1,153,559
Consumer | Pass | Other consumer
Financing Receivable, Credit Quality Indicator [Line Items]
2021	872	18,849
2020	14,119	13,162
2019	11,576	6,784
2018	5,723	3,395
2017	2,673	2,082
2016 and Prior	2,283	687
Revolving	35,151	26,647
Revolving-Term	955	2,767
Total	73,354	74,373
Consumer | Special mention | Consumer real estate
Financing Receivable, Credit Quality Indicator [Line Items]
2021	0	0
2020	0	0
2019	0	1,489
2018	0	0
2017	0	0
2016 and Prior	2,246	150
Revolving	0	132
Revolving-Term	0	0
Total	2,246	1,771
Consumer | Special mention | Other consumer
Financing Receivable, Credit Quality Indicator [Line Items]
2021	0	0
2020	0	0
2019	0	0
2018	0	0
2017	0	0
2016 and Prior	0	0
Revolving	0	0
Revolving-Term	0	0
Total	0	0
Consumer | Substandard | Consumer real estate
Financing Receivable, Credit Quality Indicator [Line Items]
2021	0	0
2020	0	373
2019	186	742
2018	2,089	1,480
2017	1,506	2,449
2016 and Prior	7,896	6,958
Revolving	503	0
Revolving-Term	1,080	0
Total	13,260	12,002
Consumer | Substandard | Other consumer
Financing Receivable, Credit Quality Indicator [Line Items]
2021	0	15
2020	0	0
2019	109	0
2018	125	0
2017	104	0
2016 and Prior	4,968	3,367
Revolving	374	744
Revolving-Term	1,579	2,386
Total	7,260	6,512
Consumer | Doubtful | Consumer real estate
Financing Receivable, Credit Quality Indicator [Line Items]
2021	0	0
2020	0	0
2019	0	0
2018	0	0
2017	0	0
2016 and Prior	0	0
Revolving	0	0
Revolving-Term	0	0
Total	0	0
Consumer | Doubtful | Other consumer
Financing Receivable, Credit Quality Indicator [Line Items]
2021	0	0
2020	0	0
2019	0	0
2018	0	0
2017	0	0
2016 and Prior	4	0
Revolving	0	0
Revolving-Term	0	0
Total	$ 4	$ 0