Segment Information (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014 segment	Dec. 31, 2013	Dec. 31, 2012
Segment Reporting Information [Line Items]
Number of operating segments									3
Net Interest Income	$ 19,031	$ 18,791	$ 18,321	$ 18,196	$ 18,388	$ 17,192	$ 16,712	$ 16,225	$ 74,339	$ 68,517	$ 66,248
Net Gains on Sales of Loans									1,892	2,645	3,234
Net Gains on Securities									1,481	2,429	1,667
Trust and Investment Product Fees									3,675	3,358	2,657
Insurance Revenues									7,255	6,217	5,524
Noncash Items:
Provision for Loan Losses									150	350	2,412
Depreciation and Amortization									4,810	4,461	4,688
Income Tax Expense (Benefit)									12,069	11,464	10,669
Segment Profit (Loss)	7,644	7,708	6,687	6,305	6,589	6,483	6,532	5,809	28,344	25,413	24,055
Segment Assets	2,237,099				2,163,827				2,237,099	2,163,827	2,006,300
Core Banking
Segment Reporting Information [Line Items]
Number of offices	37								37
Net Interest Income									74,801	69,634	68,311
Net Gains on Sales of Loans									1,892	2,645	3,234
Net Gains on Securities									1,481	2,065	1,667
Trust and Investment Product Fees									4	6	5
Insurance Revenues									29	39	23
Noncash Items:
Provision for Loan Losses									150	350	2,412
Depreciation and Amortization									4,527	3,944	4,099
Income Tax Expense (Benefit)									12,258	12,387	11,999
Segment Profit (Loss)									27,589	25,389	25,118
Segment Assets	2,242,456				2,171,837				2,242,456	2,171,837	2,006,992
Trust and Investment Advisory Services
Segment Reporting Information [Line Items]
Net Interest Income									16	21	21
Net Gains on Sales of Loans									0	0	0
Net Gains on Securities									0	0	0
Trust and Investment Product Fees									3,671	3,355	2,657
Insurance Revenues									38	31	36
Noncash Items:
Provision for Loan Losses									0	0	0
Depreciation and Amortization									23	28	24
Income Tax Expense (Benefit)									(156)	(32)	(187)
Segment Profit (Loss)									(259)	(70)	(298)
Segment Assets	11,401				11,663				11,401	11,663	11,551
Insurance
Segment Reporting Information [Line Items]
Net Interest Income									4	17	34
Net Gains on Sales of Loans									0	0	0
Net Gains on Securities									0	0	0
Trust and Investment Product Fees									0	0	0
Insurance Revenues									7,188	6,147	5,465
Noncash Items:
Provision for Loan Losses									0	0	0
Depreciation and Amortization									110	339	415
Income Tax Expense (Benefit)									737	320	181
Segment Profit (Loss)									1,059	425	250
Segment Assets	6,429				5,636				6,429	5,636	8,333
Other
Segment Reporting Information [Line Items]
Net Interest Income									(482)	(1,155)	(2,118)
Net Gains on Sales of Loans									0	0	0
Net Gains on Securities									0	364	0
Trust and Investment Product Fees									0	(3)	(5)
Insurance Revenues									0	0	0
Noncash Items:
Provision for Loan Losses									0	0	0
Depreciation and Amortization									150	150	150
Income Tax Expense (Benefit)									(770)	(1,211)	(1,324)
Segment Profit (Loss)									(45)	(331)	(1,015)
Segment Assets	$ (23,187)				$ (25,309)				$ (23,187)	$ (25,309)	$ (20,576)