Loans, Allowance for Loan Losses and Credit Quality (ALLL - by category) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Summary of changes in allowance for loan losses
Beginning Balance	$ 60,643	$ 61,566
Charge-offs	(593)	(508)
Recoveries	312	660
Provision for loan losses	500	600
Ending Balance	60,862	62,318
Ending Balance: Individually Evaluated for Impairment	1,257	5,055	$ 1,342
Ending Balance: Collectively Evaluated for Impairment	59,605	57,263
Commercial and Industrial [Member]
Summary of changes in allowance for loan losses
Beginning Balance	13,256	16,921
Charge-offs	(133)	0
Recoveries	12	187
Provision for loan losses	398	(590)
Ending Balance	13,533	16,518
Ending Balance: Individually Evaluated for Impairment	9	3,558	10
Ending Balance: Collectively Evaluated for Impairment	13,524	12,960
Commercial Real Estate [Member]
Summary of changes in allowance for loan losses
Beginning Balance	31,453	30,369
Charge-offs	0	0
Recoveries	20	31
Provision for loan losses	(14)	343
Ending Balance	31,459	30,743
Ending Balance: Individually Evaluated for Impairment	37	173	42
Ending Balance: Collectively Evaluated for Impairment	31,422	30,570
Construction Loans [Member]
Summary of changes in allowance for loan losses
Beginning Balance	5,698	4,522
Charge-offs	0	0
Recoveries	0	0
Provision for loan losses	(19)	501
Ending Balance	5,679	5,023
Ending Balance: Individually Evaluated for Impairment	0	0
Ending Balance: Collectively Evaluated for Impairment	5,679	5,023
Small Business [Member]
Summary of changes in allowance for loan losses
Beginning Balance	1,577	1,502
Charge-offs	(24)	(70)
Recoveries	9	66
Provision for loan losses	31	35
Ending Balance	1,593	1,533
Ending Balance: Individually Evaluated for Impairment	3	2	1
Ending Balance: Collectively Evaluated for Impairment	1,590	1,531
Residential Real Estate [Member]
Summary of changes in allowance for loan losses
Beginning Balance	2,822	2,621
Charge-offs	(39)	(23)
Recoveries	2	12
Provision for loan losses	52	106
Ending Balance	2,837	2,716
Ending Balance: Individually Evaluated for Impairment	944	1,066	1,007
Ending Balance: Collectively Evaluated for Impairment	1,893	1,650
Consumer Home Equity [Member]
Summary of changes in allowance for loan losses
Beginning Balance	5,390	5,238
Charge-offs	(79)	(14)
Recoveries	34	76
Provision for loan losses	14	45
Ending Balance	5,359	5,345
Ending Balance: Individually Evaluated for Impairment	248	235	265
Ending Balance: Collectively Evaluated for Impairment	5,111	5,110
Consumer Other [Member]
Summary of changes in allowance for loan losses
Beginning Balance	447	393
Charge-offs	(318)	(401)
Recoveries	235	288
Provision for loan losses	38	160
Ending Balance	402	440
Ending Balance: Individually Evaluated for Impairment	16	21	$ 17
Ending Balance: Collectively Evaluated for Impairment	$ 386	$ 419