Allowance for Credit Losses - Loan Balances by Year of Origination and Internally Assigned Risk Rating (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	$ 799,142	$ 1,360,684
Year two	966,097	1,214,746
Year three	1,150,182	831,734
Year four	712,097	565,201
Year five	477,370	610,556
More than five years	1,816,661	1,572,826
Revolving	1,058,098	1,041,199
Revolving-Term	27,703	28,914
Total	7,007,351	7,225,860
Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	793,541	1,355,291
Year two	958,356	1,136,715
Year three	1,060,518	792,352
Year four	676,582	502,350
Year five	408,589	494,436
More than five years	1,504,535	1,337,221
Revolving	1,039,420	1,011,297
Revolving-Term	24,166	25,726
Total	6,465,707	6,655,389
Special mention
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	168	5,274
Year two	5,474	47,302
Year three	56,894	19,350
Year four	13,343	24,802
Year five	40,492	57,026
More than five years	131,379	91,677
Revolving	11,861	24,296
Revolving-Term	121	123
Total	259,732	269,851
Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	5,433	118
Year two	2,268	30,083
Year three	32,019	20,032
Year four	22,172	33,648
Year five	28,289	57,105
More than five years	174,983	137,398
Revolving	6,818	5,607
Revolving-Term	3,415	3,066
Total	275,397	287,056
Doubtful
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	0	0
Year two	0	645
Year three	751	0
Year four	0	4,401
Year five	0	1,989
More than five years	5,764	6,529
Revolving	0	0
Revolving-Term	0	0
Total	6,514	13,564
Commercial
Financing Receivable, Credit Quality Indicator [Line Items]
Total	5,499,044	5,673,707
Commercial | Commercial real estate
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	179,504	334,086
Year two	326,979	476,203
Year three	504,625	417,944
Year four	370,957	320,140
Year five	287,320	415,184
More than five years	1,029,012	780,560
Revolving	41,898	47,830
Revolving-Term	0	0
Total	2,740,296	2,791,947
Commercial | Commercial and industrial
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	401,413	457,828
Year two	268,962	215,457
Year three	184,674	145,290
Year four	107,731	82,249
Year five	51,213	28,488
More than five years	146,667	221,609
Revolving	385,588	408,631
Revolving-Term	0	0
Total	1,546,247	1,559,552
Commercial | Commercial construction
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	61,289	132,813
Year two	130,376	230,907
Year three	189,721	63,535
Year four	48,374	2,921
Year five	1,853	6,346
More than five years	16,498	16,777
Revolving	19,761	12,778
Revolving-Term	0	0
Total	467,871	466,077
Commercial | Business banking
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	100,917	296,357
Year two	116,374	156,473
Year three	162,338	128,250
Year four	128,737	91,363
Year five	88,133	82,202
More than five years	367,340	298,779
Revolving	105,808	105,549
Revolving-Term	1,228	1,094
Total	1,070,875	1,160,067
Commercial | Pass | Commercial real estate
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	179,504	334,086
Year two	326,531	422,800
Year three	457,287	394,963
Year four	347,132	277,724
Year five	229,164	307,321
More than five years	778,930	615,217
Revolving	40,398	46,330
Revolving-Term	0	0
Total	2,358,945	2,398,441
Commercial | Pass | Commercial and industrial
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	395,929	454,131
Year two	265,953	199,453
Year three	153,588	140,049
Year four	102,789	68,607
Year five	45,641	27,645
More than five years	140,169	206,782
Revolving	370,282	383,082
Revolving-Term	0	0
Total	1,474,351	1,479,749
Commercial | Pass | Commercial construction
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	61,289	131,235
Year two	126,858	224,794
Year three	182,394	59,649
Year four	48,374	2,420
Year five	1,352	6,346
More than five years	5,131	4,555
Revolving	19,761	12,778
Revolving-Term	0	0
Total	445,159	441,777
Commercial | Pass | Business banking
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	100,800	296,254
Year two	115,666	154,335
Year three	158,725	123,207
Year four	123,708	86,552
Year five	85,193	77,238
More than five years	337,243	266,042
Revolving	104,566	103,571
Revolving-Term	455	291
Total	1,026,356	1,107,490
Commercial | Special mention | Commercial real estate
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	0	0
Year two	448	35,499
Year three	29,581	10,200
Year four	8,310	22,502
Year five	38,927	55,174
More than five years	112,654	75,022
Revolving	0	0
Revolving-Term	0	0
Total	189,920	198,397
Commercial | Special mention | Commercial and industrial
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	51	3,697
Year two	3,008	8,211
Year three	22,124	2,628
Year four	3,369	697
Year five	0	768
More than five years	1,141	1,046
Revolving	11,574	23,527
Revolving-Term	0	0
Total	41,266	40,574
Commercial | Special mention | Commercial construction
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	0	1,578
Year two	1,380	2,533
Year three	3,269	3,886
Year four	0	0
Year five	0	0
More than five years	8,421	8,593
Revolving	0	0
Revolving-Term	0	0
Total	13,071	16,590
Commercial | Special mention | Business banking
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	117	0
Year two	637	1,060
Year three	1,919	1,147
Year four	1,665	1,602
Year five	1,564	1,084
More than five years	6,958	6,866
Revolving	287	637
Revolving-Term	121	123
Total	13,270	12,519
Commercial | Substandard | Commercial real estate
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	0	0
Year two	0	17,259
Year three	17,007	12,781
Year four	15,516	19,914
Year five	19,229	50,700
More than five years	131,668	83,792
Revolving	1,500	1,500
Revolving-Term	0	0
Total	184,920	185,946
Commercial | Substandard | Commercial and industrial
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	5,433	0
Year two	0	7,793
Year three	8,962	2,613
Year four	1,573	8,544
Year five	5,572	75
More than five years	5,357	13,781
Revolving	3,733	2,022
Revolving-Term	0	0
Total	30,630	34,828
Commercial | Substandard | Commercial construction
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	0	0
Year two	2,138	3,580
Year three	4,058	0
Year four	0	501
Year five	500	0
More than five years	2,945	3,629
Revolving	0	0
Revolving-Term	0	0
Total	9,642	7,710
Commercial | Substandard | Business banking
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	0	103
Year two	72	1,078
Year three	1,694	3,896
Year four	3,364	3,209
Year five	1,376	3,880
More than five years	23,139	25,871
Revolving	954	1,341
Revolving-Term	651	680
Total	31,249	40,058
Commercial | Doubtful | Commercial real estate
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	0	0
Year two	0	645
Year three	751	0
Year four	0	0
Year five	0	1,989
More than five years	5,760	6,529
Revolving	0	0
Revolving-Term	0	0
Total	6,511	9,163
Commercial | Doubtful | Commercial and industrial
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	0	0
Year two	0	0
Year three	0	0
Year four	0	4,401
Year five	0	0
More than five years	0	0
Revolving	0	0
Revolving-Term	0	0
Total	0	4,401
Commercial | Doubtful | Commercial construction
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	0	0
Year two	0	0
Year three	0	0
Year four	0	0
Year five	0	0
More than five years	0	0
Revolving	0	0
Revolving-Term	0	0
Total	0	0
Commercial | Doubtful | Business banking
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	0	0
Year two	0	0
Year three	0	0
Year four	0	0
Year five	0	0
More than five years	0	0
Revolving	0	0
Revolving-Term	0	0
Total	0	0
Consumer
Financing Receivable, Credit Quality Indicator [Line Items]
Total	1,508,307	1,552,153
Consumer | Business banking
Financing Receivable, Credit Quality Indicator [Line Items]
Total		303,900
Consumer | Consumer real estate
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	43,351	120,736
Year two	111,123	122,544
Year three	98,869	69,931
Year four	51,411	65,133
Year five	46,628	76,254
More than five years	250,463	251,047
Revolving	468,158	439,020
Revolving-Term	23,875	22,667
Total	1,093,878	1,167,332
Consumer | Other consumer
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	12,668	18,864
Year two	12,283	13,162
Year three	9,955	6,784
Year four	4,887	3,395
Year five	2,223	2,082
More than five years	6,681	4,054
Revolving	36,886	27,391
Revolving-Term	2,600	5,153
Total	88,184	80,885
Consumer | Pass | Consumer real estate
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	43,351	120,736
Year two	111,065	122,171
Year three	98,684	67,700
Year four	49,815	63,653
Year five	45,224	73,805
More than five years	241,295	243,939
Revolving	467,802	438,888
Revolving-Term	22,670	22,667
Total	1,079,907	1,153,559
Consumer | Pass | Other consumer
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	12,668	18,849
Year two	12,283	13,162
Year three	9,842	6,784
Year four	4,764	3,395
Year five	2,016	2,082
More than five years	1,767	687
Revolving	36,611	26,647
Revolving-Term	1,040	2,767
Total	80,990	74,373
Consumer | Special mention | Consumer real estate
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	0	0
Year two	0	0
Year three	0	1,489
Year four	0	0
Year five	0	0
More than five years	2,205	150
Revolving	0	132
Revolving-Term	0	0
Total	2,205	1,771
Consumer | Special mention | Other consumer
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	0	0
Year two	0	0
Year three	0	0
Year four	0	0
Year five	0	0
More than five years	0	0
Revolving	0	0
Revolving-Term	0	0
Total	0	0
Consumer | Substandard | Consumer real estate
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	0	0
Year two	58	373
Year three	185	742
Year four	1,595	1,480
Year five	1,404	2,449
More than five years	6,963	6,958
Revolving	356	0
Revolving-Term	1,205	0
Total	11,766	12,002
Consumer | Substandard | Other consumer
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	0	15
Year two	0	0
Year three	113	0
Year four	123	0
Year five	208	0
More than five years	4,910	3,367
Revolving	275	744
Revolving-Term	1,560	2,386
Total	7,190	6,512
Consumer | Doubtful | Consumer real estate
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	0	0
Year two	0	0
Year three	0	0
Year four	0	0
Year five	0	0
More than five years	0	0
Revolving	0	0
Revolving-Term	0	0
Total	0	0
Consumer | Doubtful | Other consumer
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	0	0
Year two	0	0
Year three	0	0
Year four	0	0
Year five	0	0
More than five years	4	0
Revolving	0	0
Revolving-Term	0	0
Total	$ 4	$ 0