Loans, Allowance for Loan Losses and Credit Quality (Int Inc. Recognized on Impaired Loans by Portfolio) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Interest income recognized on impaired loans
Average Recorded Investment	$ 76,414	$ 44,558	$ 79,369	$ 45,318
Interest Income Recognized	461	385	1,510	1,165
WITH NO RELATED ALLOWANCE RECORDED: [Member]
Interest income recognized on impaired loans
Average Recorded Investment	58,096	23,672	60,830	24,169
Interest Income Recognized	277	226	959	695
WITH AN ALLOWANCE RECORDED: [Member]
Interest income recognized on impaired loans
Average Recorded Investment	18,318	20,886	18,539	21,149
Interest Income Recognized	184	159	551	470
Commercial and Industrial [Member] | WITH NO RELATED ALLOWANCE RECORDED: [Member]
Interest income recognized on impaired loans
Average Recorded Investment	33,935	2,444	36,329	2,584
Interest Income Recognized	18	16	179	48
Commercial and Industrial [Member] | WITH AN ALLOWANCE RECORDED: [Member]
Interest income recognized on impaired loans
Average Recorded Investment	1,698	2,097	1,768	2,135
Interest Income Recognized	21	4	65	13
Commercial Real Estate [Member] | WITH NO RELATED ALLOWANCE RECORDED: [Member]
Interest income recognized on impaired loans
Average Recorded Investment	14,569	11,549	14,798	11,775
Interest Income Recognized	151	115	460	348
Commercial Real Estate [Member] | WITH AN ALLOWANCE RECORDED: [Member]
Interest income recognized on impaired loans
Average Recorded Investment	4,569	6,854	4,599	6,977
Interest Income Recognized	65	42	195	126
Small Business [Member] | WITH NO RELATED ALLOWANCE RECORDED: [Member]
Interest income recognized on impaired loans
Average Recorded Investment	682	646	702	679
Interest Income Recognized	5	5	17	18
Small Business [Member] | WITH AN ALLOWANCE RECORDED: [Member]
Interest income recognized on impaired loans
Average Recorded Investment	305	367	315	384
Interest Income Recognized	3	6	11	17
Residential Real Estate [Member] | WITH NO RELATED ALLOWANCE RECORDED: [Member]
Interest income recognized on impaired loans
Average Recorded Investment	3,928	4,255	3,962	4,286
Interest Income Recognized	51	42	152	134
Residential Real Estate [Member] | WITH AN ALLOWANCE RECORDED: [Member]
Interest income recognized on impaired loans
Average Recorded Investment	9,752	10,004	9,838	10,071
Interest Income Recognized	79	92	234	272
Consumer Home Equity [Member] | WITH NO RELATED ALLOWANCE RECORDED: [Member]
Interest income recognized on impaired loans
Average Recorded Investment	4,883	4,616	4,935	4,677
Interest Income Recognized	50	45	146	138
Consumer Home Equity [Member] | WITH AN ALLOWANCE RECORDED: [Member]
Interest income recognized on impaired loans
Average Recorded Investment	1,765	1,299	1,782	1,310
Interest Income Recognized	14	13	41	36
Consumer - Other [Member] | WITH NO RELATED ALLOWANCE RECORDED: [Member]
Interest income recognized on impaired loans
Average Recorded Investment	99	162	104	168
Interest Income Recognized	2	3	5	9
Consumer - Other [Member] | WITH AN ALLOWANCE RECORDED: [Member]
Interest income recognized on impaired loans
Average Recorded Investment	229	265	237	272
Interest Income Recognized	$ 2	$ 2	$ 5	$ 6