Loans, Allowance for Loan Losses and Credit Quality (ALLL - by category) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017
Summary of changes in allowance for loan losses
Beginning Balance	$ 60,862	$ 62,318	$ 60,643	$ 61,566
Charge-offs	(569)	(4,198)	(1,162)	(4,706)
Recoveries	264	309	576	969
Provision for loan losses	2,000	1,050	2,500	1,650
Ending Balance	62,557	59,479	62,557	59,479
Ending Balance: Individually Evaluated for Impairment	1,187	1,536	1,187	1,536	$ 1,342
Ending Balance: Collectively Evaluated for Impairment	61,370	57,943	61,370	57,943
Commercial and Industrial [Member]
Summary of changes in allowance for loan losses
Beginning Balance	13,533	16,518	13,256	16,921
Charge-offs	(4)	(3,591)	(137)	(3,591)
Recoveries	59	13	71	200
Provision for loan losses	1,200	604	1,598	14
Ending Balance	14,788	13,544	14,788	13,544
Ending Balance: Individually Evaluated for Impairment	8	70	8	70	10
Ending Balance: Collectively Evaluated for Impairment	14,780	13,474	14,780	13,474
Commercial Real Estate [Member]
Summary of changes in allowance for loan losses
Beginning Balance	31,459	30,743	31,453	30,369
Charge-offs	0	0	0	0
Recoveries	18	26	38	57
Provision for loan losses	618	178	604	521
Ending Balance	32,095	30,947	32,095	30,947
Ending Balance: Individually Evaluated for Impairment	74	166	74	166	42
Ending Balance: Collectively Evaluated for Impairment	32,021	30,781	32,021	30,781
Construction Loans [Member]
Summary of changes in allowance for loan losses
Beginning Balance	5,679	5,023	5,698	4,522
Charge-offs	0	0	0	0
Recoveries	0	0	0	0
Provision for loan losses	(463)	(209)	(482)	292
Ending Balance	5,216	4,814	5,216	4,814
Ending Balance: Individually Evaluated for Impairment	0	0	0	0
Ending Balance: Collectively Evaluated for Impairment	5,216	4,814	5,216	4,814
Small Business [Member]
Summary of changes in allowance for loan losses
Beginning Balance	1,593	1,533	1,577	1,502
Charge-offs	(102)	(24)	(126)	(94)
Recoveries	10	13	19	79
Provision for loan losses	208	91	239	126
Ending Balance	1,709	1,613	1,709	1,613
Ending Balance: Individually Evaluated for Impairment	1	1	1	1	1
Ending Balance: Collectively Evaluated for Impairment	1,708	1,612	1,708	1,612
Residential Real Estate [Member]
Summary of changes in allowance for loan losses
Beginning Balance	2,837	2,716	2,822	2,621
Charge-offs	(109)	(116)	(148)	(139)
Recoveries	1	2	3	14
Provision for loan losses	180	91	232	197
Ending Balance	2,909	2,693	2,909	2,693
Ending Balance: Individually Evaluated for Impairment	859	1,036	859	1,036	1,007
Ending Balance: Collectively Evaluated for Impairment	2,050	1,657	2,050	1,657
Consumer Home Equity [Member]
Summary of changes in allowance for loan losses
Beginning Balance	5,359	5,345	5,390	5,238
Charge-offs	(95)	(122)	(174)	(136)
Recoveries	23	26	57	102
Provision for loan losses	181	104	195	149
Ending Balance	5,468	5,353	5,468	5,353
Ending Balance: Individually Evaluated for Impairment	231	243	231	243	265
Ending Balance: Collectively Evaluated for Impairment	5,237	5,110	5,237	5,110
Consumer Other [Member]
Summary of changes in allowance for loan losses
Beginning Balance	402	440	447	393
Charge-offs	(259)	(345)	(577)	(746)
Recoveries	153	229	388	517
Provision for loan losses	76	191	114	351
Ending Balance	372	515	372	515
Ending Balance: Individually Evaluated for Impairment	14	20	14	20	$ 17
Ending Balance: Collectively Evaluated for Impairment	$ 358	$ 495	$ 358	$ 495