Segment Information (Segment Financial Information) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Segment Reporting Information [Line Items]
Net Interest Income	$ 24,917	$ 24,560	$ 74,455	$ 70,015
Net Gains on Sales of Loans	952	1,004	2,598	2,607
Net Gains on Securities	575	458	575	1,426
Trust and Investment Product Fees	1,301	1,191	3,894	3,435
Insurance Revenues	1,728	1,661	6,112	5,993
Noncash Items:
Provision for Loan Losses	250	0	1,100	1,200
Depreciation and Amortization	1,179	1,139	3,496	3,366
Income Tax Expense (Benefit)	3,511	4,106	10,757	10,120
Segment Profit (Loss)	9,660	10,185	29,055	25,119
Segment Assets	3,072,889		3,072,889		$ 2,955,994
Operating Segments | Core Banking
Segment Reporting Information [Line Items]
Net Interest Income	25,109	24,721	75,017	70,492
Net Gains on Sales of Loans	952	1,004	2,598	2,607
Net Gains on Securities	572	458	572	1,426
Trust and Investment Product Fees	0	(6)	2	(3)
Insurance Revenues	11	6	25	14
Noncash Items:
Provision for Loan Losses	250	0	1,100	1,200
Depreciation and Amortization	1,091	1,065	3,235	3,129
Income Tax Expense (Benefit)	3,669	4,249	10,906	10,349
Segment Profit (Loss)	9,621	10,168	28,377	25,049
Segment Assets	3,068,999		3,068,999		2,958,585
Operating Segments | Trust and Investment Advisory Services
Segment Reporting Information [Line Items]
Net Interest Income	2	0	4	0
Net Gains on Sales of Loans	0	0	0	0
Net Gains on Securities	0	0	0	0
Trust and Investment Product Fees	1,300	1,205	3,894	3,446
Insurance Revenues	2	15	15	28
Noncash Items:
Provision for Loan Losses	0	0	0	0
Depreciation and Amortization	5	0	12	2
Income Tax Expense (Benefit)	31	51	114	115
Segment Profit (Loss)	41	69	151	152
Segment Assets	1,981		1,981		1,851
Operating Segments | Insurance
Segment Reporting Information [Line Items]
Net Interest Income	2	2	6	5
Net Gains on Sales of Loans	0	0	0	0
Net Gains on Securities	0	0	0	0
Trust and Investment Product Fees	0	0	0	0
Insurance Revenues	1,715	1,640	6,072	5,951
Noncash Items:
Provision for Loan Losses	0	0	0	0
Depreciation and Amortization	19	10	57	61
Income Tax Expense (Benefit)	67	80	542	648
Segment Profit (Loss)	102	122	849	999
Segment Assets	10,071		10,071		8,494
Other
Segment Reporting Information [Line Items]
Net Interest Income	(196)	(163)	(572)	(482)
Net Gains on Sales of Loans	0	0	0	0
Net Gains on Securities	3	0	3	0
Trust and Investment Product Fees	1	(8)	(2)	(8)
Insurance Revenues	0	0	0	0
Noncash Items:
Provision for Loan Losses	0	0	0	0
Depreciation and Amortization	64	64	192	174
Income Tax Expense (Benefit)	(256)	(274)	(805)	(992)
Segment Profit (Loss)	(104)	$ (174)	(322)	$ (1,081)
Segment Assets	$ (8,162)		$ (8,162)		$ (12,936)