Loans, Allowance for Loan Losses and Credit Quality (ALLL - by category) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Summary of changes in allowance for loan losses
Beginning Balance	$ 62,557	$ 59,479	$ 60,643	$ 61,566
Charge-offs	(847)	(817)	(2,009)	(5,523)
Recoveries	450	1,048	1,026	2,017
Provision for loan losses	1,075	0	3,575	1,650
Ending Balance	63,235	59,710	63,235	59,710
Ending Balance: Individually Evaluated for Impairment	1,097	1,417	1,097	1,417	$ 1,342
Ending Balance: Collectively Evaluated for Impairment	62,138	58,293	62,138	58,293
Commercial and Industrial [Member]
Summary of changes in allowance for loan losses
Beginning Balance	14,788	13,544	13,256	16,921
Charge-offs	(218)	(124)	(355)	(3,715)
Recoveries	108	404	179	604
Provision for loan losses	430	(994)	2,028	(980)
Ending Balance	15,108	12,830	15,108	12,830
Ending Balance: Individually Evaluated for Impairment	7	71	7	71	10
Ending Balance: Collectively Evaluated for Impairment	15,101	12,759	15,101	12,759
Commercial Real Estate [Member]
Summary of changes in allowance for loan losses
Beginning Balance	32,095	30,947	31,453	30,369
Charge-offs	(82)	0	(82)	0
Recoveries	29	286	67	343
Provision for loan losses	226	(233)	830	288
Ending Balance	32,268	31,000	32,268	31,000
Ending Balance: Individually Evaluated for Impairment	34	49	34	49	42
Ending Balance: Collectively Evaluated for Impairment	32,234	30,951	32,234	30,951
Construction Loans [Member]
Summary of changes in allowance for loan losses
Beginning Balance	5,216	4,814	5,698	4,522
Charge-offs	0	0	0	0
Recoveries	0	0	0	0
Provision for loan losses	(189)	806	(671)	1,098
Ending Balance	5,027	5,620	5,027	5,620
Ending Balance: Individually Evaluated for Impairment	0	0	0	0
Ending Balance: Collectively Evaluated for Impairment	5,027	5,620	5,027	5,620
Small Business [Member]
Summary of changes in allowance for loan losses
Beginning Balance	1,709	1,613	1,577	1,502
Charge-offs	(111)	(164)	(237)	(258)
Recoveries	10	17	29	96
Provision for loan losses	160	140	399	266
Ending Balance	1,768	1,606	1,768	1,606
Ending Balance: Individually Evaluated for Impairment	1	1	1	1	1
Ending Balance: Collectively Evaluated for Impairment	1,767	1,605	1,767	1,605
Residential Real Estate [Member]
Summary of changes in allowance for loan losses
Beginning Balance	2,909	2,693	2,822	2,621
Charge-offs	0	(43)	(148)	(182)
Recoveries	9	15	12	29
Provision for loan losses	153	111	385	308
Ending Balance	3,071	2,776	3,071	2,776
Ending Balance: Individually Evaluated for Impairment	874	1,020	874	1,020	1,007
Ending Balance: Collectively Evaluated for Impairment	2,197	1,756	2,197	1,756
Consumer Home Equity [Member]
Summary of changes in allowance for loan losses
Beginning Balance	5,468	5,353	5,390	5,238
Charge-offs	(87)	(81)	(261)	(217)
Recoveries	71	65	128	167
Provision for loan losses	102	89	297	238
Ending Balance	5,554	5,426	5,554	5,426
Ending Balance: Individually Evaluated for Impairment	168	257	168	257	265
Ending Balance: Collectively Evaluated for Impairment	5,386	5,169	5,386	5,169
Consumer Other [Member]
Summary of changes in allowance for loan losses
Beginning Balance	372	515	447	393
Charge-offs	(349)	(405)	(926)	(1,151)
Recoveries	223	261	611	778
Provision for loan losses	193	81	307	432
Ending Balance	439	452	439	452
Ending Balance: Individually Evaluated for Impairment	13	19	13	19	$ 17
Ending Balance: Collectively Evaluated for Impairment	$ 426	$ 433	$ 426	$ 433