Loans, Allowance for Loan Losses and Credit Quality (Allowance Allocations) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016	Mar. 31, 2017	Dec. 31, 2016	Mar. 31, 2016	Dec. 31, 2015
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans and Leases Receivable, Allowance	$ 59,479	$ 57,727	$ 59,479	$ 57,727	$ 62,318	$ 61,566	$ 56,432	$ 55,825
Allowance for Loan and Lease Losses, Write-offs	(4,198)	(577)	(4,706)	(1,114)
Allowance for Loan and Lease Loss, Recovery of Bad Debts	309	1,272	969	1,891
Provision for loan losses	1,050	600	1,650	1,125
Allowance for loans based on collective and individual evaluation of impairment by loan category
Ending Balance: Collectively Evaluated for Impairment	6,177,446		6,177,446			5,903,916
Ending Balance: Individually Evaluated for Impairment	74,610		74,610			77,297
Financing Receivable, Net	4,466,376		4,466,376			4,355,968
Ending Balance: Total Loans by Group	6,269,696		6,269,696			5,999,605
Receivables Acquired with Deteriorated Credit Quality [Member]
Allowance for loans based on collective and individual evaluation of impairment by loan category
Financing Receivable, Net	17,640		17,640			18,392
Commercial and Industrial [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans and Leases Receivable, Allowance	13,544	14,027	13,544	14,027	16,518	16,921	13,485	13,802
Allowance for Loan and Lease Losses, Write-offs	(3,591)	(2)	(3,591)	(4)
Allowance for Loan and Lease Loss, Recovery of Bad Debts	13	649	200	787
Provision for loan losses	604	(105)	14	(558)
Allowance for loans based on collective and individual evaluation of impairment by loan category
Ending Balance: Collectively Evaluated for Impairment	874,664		874,664			862,875
Ending Balance: Individually Evaluated for Impairment	36,272		36,272			39,178
Financing Receivable, Net	910,936		910,936			902,053
Ending Balance: Total Loans by Group	910,936		910,936			902,053
Commercial and Industrial [Member] | Receivables Acquired with Deteriorated Credit Quality [Member]
Allowance for loans based on collective and individual evaluation of impairment by loan category
Financing Receivable, Net	0		0			0
Commercial Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans and Leases Receivable, Allowance	30,947	29,011	30,947	29,011	30,743	30,369	28,595	27,327
Allowance for Loan and Lease Losses, Write-offs	0	(25)	0	(25)
Allowance for Loan and Lease Loss, Recovery of Bad Debts	26	223	57	412
Provision for loan losses	178	218	521	1,297
Allowance for loans based on collective and individual evaluation of impairment by loan category
Ending Balance: Collectively Evaluated for Impairment	3,055,924		3,055,924			2,983,642
Ending Balance: Individually Evaluated for Impairment	17,065		17,065			16,813
Financing Receivable, Net	3,083,020		3,083,020			3,010,798
Ending Balance: Total Loans by Group	3,083,020		3,083,020			3,010,798
Commercial Real Estate [Member] | Receivables Acquired with Deteriorated Credit Quality [Member]
Allowance for loans based on collective and individual evaluation of impairment by loan category
Financing Receivable, Net	10,031		10,031			10,343
Construction Loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans and Leases Receivable, Allowance	4,814	5,216	4,814	5,216	5,023	4,522	5,100	5,366
Allowance for Loan and Lease Losses, Write-offs	0	0	0	0
Allowance for Loan and Lease Loss, Recovery of Bad Debts	0	0	0	0
Provision for loan losses	(209)	116	292	(150)
Allowance for loans based on collective and individual evaluation of impairment by loan category
Ending Balance: Collectively Evaluated for Impairment	340,757		340,757			320,391
Ending Balance: Individually Evaluated for Impairment	0		0			0
Financing Receivable, Net	340,757		340,757			320,391
Ending Balance: Total Loans by Group	340,757		340,757			320,391
Construction Loans [Member] | Receivables Acquired with Deteriorated Credit Quality [Member]
Allowance for loans based on collective and individual evaluation of impairment by loan category
Financing Receivable, Net	0		0			0
Small Business [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans and Leases Receivable, Allowance	1,613	1,441	1,613	1,441	1,533	1,502	1,341	1,264
Allowance for Loan and Lease Losses, Write-offs	(24)	(30)	(94)	(93)
Allowance for Loan and Lease Loss, Recovery of Bad Debts	13	73	79	94
Provision for loan losses	91	57	126	176
Allowance for loans based on collective and individual evaluation of impairment by loan category
Ending Balance: Collectively Evaluated for Impairment	130,804		130,804			121,855
Ending Balance: Individually Evaluated for Impairment	859		859			871
Financing Receivable, Net	131,663		131,663			122,726
Ending Balance: Total Loans by Group	131,663		131,663			122,726
Small Business [Member] | Receivables Acquired with Deteriorated Credit Quality [Member]
Allowance for loans based on collective and individual evaluation of impairment by loan category
Financing Receivable, Net	0		0			0
Residential Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans and Leases Receivable, Allowance	2,693	2,578	2,693	2,578	2,716	2,621	2,567	2,590
Allowance for Loan and Lease Losses, Write-offs	(116)	(8)	(139)	(27)
Allowance for Loan and Lease Loss, Recovery of Bad Debts	2	51	14	51
Provision for loan losses	91	(32)	197	(36)
Allowance for loans based on collective and individual evaluation of impairment by loan category
Ending Balance: Collectively Evaluated for Impairment	728,109		728,109			622,392
Ending Balance: Individually Evaluated for Impairment	13,879		13,879			14,175
Ending Balance: Total Loans by Group	749,392		749,392			644,426
Residential Real Estate [Member] | Receivables Acquired with Deteriorated Credit Quality [Member]
Allowance for loans based on collective and individual evaluation of impairment by loan category
Financing Receivable, Net	7,404		7,404			7,859
Consumer Home Equity [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans and Leases Receivable, Allowance	5,353	4,986	5,353	4,986	5,345	5,238	4,915	4,889
Allowance for Loan and Lease Losses, Write-offs	(122)	(190)	(136)	(337)
Allowance for Loan and Lease Loss, Recovery of Bad Debts	26	26	102	53
Provision for loan losses	104	235	149	381
Allowance for loans based on collective and individual evaluation of impairment by loan category
Ending Balance: Collectively Evaluated for Impairment	1,037,064		1,037,064			982,095
Ending Balance: Individually Evaluated for Impairment	6,190		6,190			5,863
Ending Balance: Total Loans by Group	1,043,459		1,043,459			988,147
Consumer Home Equity [Member] | Receivables Acquired with Deteriorated Credit Quality [Member]
Allowance for loans based on collective and individual evaluation of impairment by loan category
Financing Receivable, Net	205		205			189
Consumer Other [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans and Leases Receivable, Allowance	515	468	515	468	$ 440	393	$ 429	$ 587
Allowance for Loan and Lease Losses, Write-offs	(345)	(322)	(746)	(628)
Allowance for Loan and Lease Loss, Recovery of Bad Debts	229	250	517	494
Provision for loan losses	191	$ 111	351	$ 15
Allowance for loans based on collective and individual evaluation of impairment by loan category
Ending Balance: Collectively Evaluated for Impairment	10,124		10,124			10,666
Ending Balance: Individually Evaluated for Impairment	345		345			397
Ending Balance: Total Loans by Group	10,469		10,469			11,064
Consumer Other [Member] | Receivables Acquired with Deteriorated Credit Quality [Member]
Allowance for loans based on collective and individual evaluation of impairment by loan category
Financing Receivable, Net	$ 0		$ 0			$ 1