Loan Portfolio and Credit Quality Impaired Loans With and Without Related Allowance (Details) - USD ($) $ in Thousands		3 Months Ended		6 Months Ended		12 Months Ended
		Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016	Dec. 31, 2016
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	[1]	$ 14,482	$ 24,889	$ 14,482	$ 24,889	$ 14,594
Impaired Financing Receivable, with Related Allowance, Recorded Investment	[1]	9,535	12,952	9,535	12,952	11,436
Impaired Financing Receivable, Recorded Investment	[1]	24,017	37,841	24,017	37,841	26,030
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance		19,345	34,516	19,345	34,516	20,815
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance		9,964	13,381	9,964	13,381	11,865
Impaired Financing Receivable, Unpaid Principal Balance		29,309	47,897	29,309	47,897	32,680
Impaired Financing Receivable, Related Allowance		981	1,101	981	1,101	1,135
Impaired Financing Receivable, Related Allowance		981	1,101	981	1,101	1,135
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment		15,860	25,364	16,525	24,057	22,323
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment		9,661	12,940	10,391	14,226	13,276
Impaired Financing Receivable, Average Recorded Investment		25,521	38,304	26,916	38,283	35,599
Impaired Financing Receivable, with No Related Allowance, Interest Income, Cash Basis Method		894	620	1,254	727	1,540
Impaired Financing Receivable, with Related Allowance, Interest Income, Cash Basis Method		119	114	233	238	458
Impaired Financing Receivable, Interest Income, Cash Basis Method		1,013	734	1,487	965	1,998
Commercial and industrial [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	[1]	1,771	8,595	1,771	8,595	1,793
Impaired Financing Receivable, with Related Allowance, Recorded Investment	[1]	0	37	0	37	0
Impaired Financing Receivable, Recorded Investment	[1]	1,771	8,632	1,771	8,632	1,793
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance		2,377	10,622	2,377	10,622	2,155
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance		0	37	0	37	0
Impaired Financing Receivable, Unpaid Principal Balance		2,377	10,659	2,377	10,659	2,155
Impaired Financing Receivable, Related Allowance		0	22	0	22	0
Impaired Financing Receivable, Related Allowance		0	22	0	22	0
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment		1,667	5,668	1,703	4,107	5,288
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment		0	44	0	31	31
Impaired Financing Receivable, Average Recorded Investment		1,667	5,712	1,703	4,138	5,319
Impaired Financing Receivable, with No Related Allowance, Interest Income, Cash Basis Method		12	59	25	71	249
Impaired Financing Receivable, with Related Allowance, Interest Income, Cash Basis Method		0	0	0	1	1
Impaired Financing Receivable, Interest Income, Cash Basis Method		12	59	25	72	250
Commercial Tax Exempt [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	[1]	0	0	0	0	0
Impaired Financing Receivable, with Related Allowance, Recorded Investment	[1]	0	0	0	0	0
Impaired Financing Receivable, Recorded Investment	[1]	0	0	0	0	0
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance		0	0	0	0	0
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance		0	0	0	0	0
Impaired Financing Receivable, Unpaid Principal Balance		0	0	0	0	0
Impaired Financing Receivable, Related Allowance		0	0	0	0	0
Impaired Financing Receivable, Related Allowance		0	0	0	0	0
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment		1,084	0	1,859	0	0
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment		0	0	0	0	0
Impaired Financing Receivable, Average Recorded Investment		1,084	0	1,859	0	0
Impaired Financing Receivable, with No Related Allowance, Interest Income, Cash Basis Method		80	0	80	0	0
Impaired Financing Receivable, with Related Allowance, Interest Income, Cash Basis Method		0	0	0	0	0
Impaired Financing Receivable, Interest Income, Cash Basis Method		80	0	80	0	0
Commercial real estate [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	[1]	2,879	7,780	2,879	7,780	4,488
Impaired Financing Receivable, with Related Allowance, Recorded Investment	[1]	6,996	7,233	6,996	7,233	7,115
Impaired Financing Receivable, Recorded Investment	[1]	9,875	15,013	9,875	15,013	11,603
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance		6,429	14,088	6,429	14,088	9,647
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance		7,425	7,662	7,425	7,662	7,544
Impaired Financing Receivable, Unpaid Principal Balance		13,854	21,750	13,854	21,750	17,191
Impaired Financing Receivable, Related Allowance		453	640	453	640	548
Impaired Financing Receivable, Related Allowance		453	640	453	640	548
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment		3,358	9,794	3,824	10,764	8,520
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment		7,011	7,266	7,042	7,294	7,230
Impaired Financing Receivable, Average Recorded Investment		10,369	17,060	10,866	18,058	15,750
Impaired Financing Receivable, with No Related Allowance, Interest Income, Cash Basis Method		724	504	970	542	1,032
Impaired Financing Receivable, with Related Allowance, Interest Income, Cash Basis Method		96	78	171	158	314
Impaired Financing Receivable, Interest Income, Cash Basis Method		820	582	1,141	700	1,346
Construction and land [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	[1]	232	861	232	861	179
Impaired Financing Receivable, with Related Allowance, Recorded Investment	[1]	0	0	0	0	0
Impaired Financing Receivable, Recorded Investment	[1]	232	861	232	861	179
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance		568	1,793	568	1,793	507
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance		0	0	0	0	0
Impaired Financing Receivable, Unpaid Principal Balance		568	1,793	568	1,793	507
Impaired Financing Receivable, Related Allowance		0	0	0	0	0
Impaired Financing Receivable, Related Allowance		0	0	0	0	0
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment		190	2,337	181	1,797	1,069
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment		0	0	0	943	507
Impaired Financing Receivable, Average Recorded Investment		190	2,337	181	2,740	1,576
Impaired Financing Receivable, with No Related Allowance, Interest Income, Cash Basis Method		0	0	0	0	48
Impaired Financing Receivable, with Related Allowance, Interest Income, Cash Basis Method		0	0	0	0	0
Impaired Financing Receivable, Interest Income, Cash Basis Method		0	0	0	0	48
Residential [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	[1]	9,600	7,653	9,600	7,653	8,134
Impaired Financing Receivable, with Related Allowance, Recorded Investment	[1]	2,503	5,682	2,503	5,682	4,284
Impaired Financing Receivable, Recorded Investment	[1]	12,103	13,335	12,103	13,335	12,418
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance		9,971	8,013	9,971	8,013	8,506
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance		2,503	5,682	2,503	5,682	4,284
Impaired Financing Receivable, Unpaid Principal Balance		12,474	13,695	12,474	13,695	12,790
Impaired Financing Receivable, Related Allowance		507	439	507	439	565
Impaired Financing Receivable, Related Allowance		507	439	507	439	565
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment		9,561	7,565	8,958	7,389	7,446
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment		2,613	5,630	3,312	5,958	5,505
Impaired Financing Receivable, Average Recorded Investment		12,174	13,195	12,270	13,347	12,951
Impaired Financing Receivable, with No Related Allowance, Interest Income, Cash Basis Method		78	57	179	114	211
Impaired Financing Receivable, with Related Allowance, Interest Income, Cash Basis Method		23	36	62	79	143
Impaired Financing Receivable, Interest Income, Cash Basis Method		101	93	241	193	354
Home equity [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	[1]	0	0	0	0	0
Impaired Financing Receivable, with Related Allowance, Recorded Investment	[1]	36	0	36	0	37
Impaired Financing Receivable, Recorded Investment	[1]	36	0	36	0	37
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance		0	0	0	0	0
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance		36	0	36	0	37
Impaired Financing Receivable, Unpaid Principal Balance		36	0	36	0	37
Impaired Financing Receivable, Related Allowance		21	0	21	0	22
Impaired Financing Receivable, Related Allowance		21	0	21	0	22
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment		0	0	0	0	0
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment		37	0	37	0	3
Impaired Financing Receivable, Average Recorded Investment		37	0	37	0	3
Impaired Financing Receivable, with No Related Allowance, Interest Income, Cash Basis Method		0	0	0	0	0
Impaired Financing Receivable, with Related Allowance, Interest Income, Cash Basis Method		0	0	0	0	0
Impaired Financing Receivable, Interest Income, Cash Basis Method		0	0	0	0	0
Consumer and other [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	[1]	0	0	0	0	0
Impaired Financing Receivable, with Related Allowance, Recorded Investment	[1]	0	0	0	0	0
Impaired Financing Receivable, Recorded Investment	[1]	0	0	0	0	0
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance		0	0	0	0	0
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance		0	0	0	0	0
Impaired Financing Receivable, Unpaid Principal Balance		0	0	0	0	0
Impaired Financing Receivable, Related Allowance		0	0	0	0	0
Impaired Financing Receivable, Related Allowance		0	0	0	0	0
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment		0	0	0	0	0
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment		0	0	0	0	0
Impaired Financing Receivable, Average Recorded Investment		0	0	0	0	0
Impaired Financing Receivable, with No Related Allowance, Interest Income, Cash Basis Method		0	0	0	0	0
Impaired Financing Receivable, with Related Allowance, Interest Income, Cash Basis Method		0	0	0	0	0
Impaired Financing Receivable, Interest Income, Cash Basis Method		$ 0	$ 0	$ 0	$ 0	$ 0

[1] Recorded investment represents the client loan balance net of historical charge-offs and historical nonaccrual interest paid, which was applied to principal.