Loans (Past Due Loans) (Details) - USD ($) $ in Thousands		Mar. 31, 2018	Dec. 31, 2017
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total past due		$ 19,358	$ 20,075
Current		3,368,048	3,353,996
Total loans	[1]	3,387,406	3,374,071
30-59
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total past due		13,030	8,304
60-89
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total past due		1,535	2,351
Over 90
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total past due		4,793	9,420
Commercial Real Estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total past due		0	4,960
Current		1,217,278	1,205,535
Total loans	[2]	1,217,278	1,210,495
Commercial Real Estate | 30-59
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total past due		0	6
Commercial Real Estate | 60-89
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total past due		0	0
Commercial Real Estate | Over 90
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total past due		0	4,954
Commercial & Industrial
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total past due		3,295	4,076
Current		600,535	608,258
Total loans	[3]	603,830	612,334
Commercial & Industrial | 30-59
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total past due		2,898	3,793
Commercial & Industrial | 60-89
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total past due		0	2
Commercial & Industrial | Over 90
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total past due		397	281
Total Commercial
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total past due		3,295	9,036
Current		1,817,813	1,813,793
Total loans		1,821,108	1,822,829
Total Commercial | 30-59
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total past due		2,898	3,799
Total Commercial | 60-89
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total past due		0	2
Total Commercial | Over 90
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total past due		397	5,235
Residential Real Estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total past due		11,806	7,855
Current		1,238,084	1,219,393
Total loans	[4]	1,249,890	1,227,248
Residential Real Estate | 30-59
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total past due		6,909	1,678
Residential Real Estate | 60-89
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total past due		789	2,274
Residential Real Estate | Over 90
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total past due		4,108	3,903
Home Equity
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total past due		4,235	3,141
Current		281,488	289,326
Total loans		285,723	292,467
Home Equity | 30-59
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total past due		3,203	2,798
Home Equity | 60-89
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total past due		744	75
Home Equity | Over 90
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total past due		288	268
Other
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total past due		22	43
Current		30,663	31,484
Total loans	[5]	30,685	31,527
Other | 30-59
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total past due		20	29
Other | 60-89
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total past due		2	0
Other | Over 90
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total past due		0	14
Total Consumer
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total past due		4,257	3,184
Current		312,151	320,810
Total loans		316,408	323,994
Total Consumer | 30-59
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total past due		3,223	2,827
Total Consumer | 60-89
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total past due		746	75
Total Consumer | Over 90
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total past due		$ 288	$ 282

[1] Includes net unamortized loan origination costs of $4.1 million and $3.8 million, respectively, at March 31, 2018 and December 31, 2017 and net unamortized premiums on purchased loans of $855 thousand and $878 thousand, respectively, at March 31, 2018 and December 31, 2017.

[2] Commercial real estate loans consist of commercial mortgages primarily secured by income producing property, as well as construction and development loans. Construction and development loans are made to businesses for land development or the on-site construction of industrial, commercial, or residential buildings.

[3] Commercial & industrial consist of loans to businesses and individuals, a substantial portion of which are fully or partially collateralized by real estate.

[4] Residential real estate loans consist of mortgage and homeowner construction loans secured by one- to four- family residential properties.

[5] Other consumer loans consists of loans to individuals secured by general aviation aircraft and other personal installment loans.