Loans (Past Due Loans) (Details) - USD ($) $ in Thousands		Sep. 30, 2017	Dec. 31, 2016
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total past due		$ 16,447	$ 24,422
Current		3,306,631	3,209,949
Total loans	[1]	3,323,078	3,234,371
Commercial Mortgages [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total past due		5,887	8,708
Current		1,079,648	1,065,478
Total loans		1,085,535	1,074,186
Commercial Construction & Development [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total past due		0	0
Current		126,257	121,371
Total loans		126,257	121,371
Commercial & Industrial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total past due		455	1,154
Current		587,869	574,955
Total loans		588,324	576,109
Residential Mortgage [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total past due		7,802	12,226
Current		1,163,359	1,082,598
Total loans		1,171,161	1,094,824
Homeowner Construction [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total past due		0	0
Current		24,376	27,924
Total loans		24,376	27,924
Home Equity Lines [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total past due		815	681
Current		259,065	263,519
Total loans		259,880	264,200
Home Equity Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total past due		1,453	1,510
Current		33,324	35,762
Total loans		34,777	37,272
Other Consumer [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total past due		35	143
Current		32,733	38,342
Total loans		32,768	38,485
30-59
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total past due		3,165	8,154
30-59 | Commercial Mortgages [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total past due		0	901
30-59 | Commercial Construction & Development [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total past due		0	0
30-59 | Commercial & Industrial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total past due		8	409
30-59 | Residential Mortgage [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total past due		1,530	5,381
30-59 | Homeowner Construction [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total past due		0	0
30-59 | Home Equity Lines [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total past due		761	655
30-59 | Home Equity Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total past due		847	776
30-59 | Other Consumer [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total past due		19	32
60-89
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total past due		2,373	755
60-89 | Commercial Mortgages [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total past due		0	0
60-89 | Commercial Construction & Development [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total past due		0	0
60-89 | Commercial & Industrial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total past due		21	0
60-89 | Residential Mortgage [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total past due		1,748	652
60-89 | Homeowner Construction [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total past due		0	0
60-89 | Home Equity Lines [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total past due		54	26
60-89 | Home Equity Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total past due		549	76
60-89 | Other Consumer [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total past due		1	1
Over 90
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total past due		10,909	15,513
Over 90 | Commercial Mortgages [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total past due		5,887	7,807
Over 90 | Commercial Construction & Development [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total past due		0	0
Over 90 | Commercial & Industrial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total past due		426	745
Over 90 | Residential Mortgage [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total past due		4,524	6,193
Over 90 | Homeowner Construction [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total past due		0	0
Over 90 | Home Equity Lines [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total past due		0	0
Over 90 | Home Equity Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total past due		57	658
Over 90 | Other Consumer [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total past due		$ 15	$ 110

[1] Includes net unamortized loan origination costs of $3.9 million and $3.0 million, respectively, at September 30, 2017 and December 31, 2016 and net unamortized premiums on purchased loans of $781 thousand and $783 thousand, respectively, at September 30, 2017 and December 31, 2016.