Parent Only Financial Information Parent Only Statement of Cash Flows (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Cash Flows from Operating Activities:
Net Income	$ 24,662	$ 23,360	$ 21,795
Gains on the Sale of Securities Available-for-Sale	172	137	527
Stock-Based Compensation Expense	308	360	372
Stock-Based Compensation Expense	308	360	372
Net Cash Provided By Operating Activities	28,926	30,641	36,673
Cash Flows from Investing Activities:
Proceeds from the Sale of Securities Available-for-Sale	66,551	49,928	16,295
Purchases of Securities Available-for-Sale	(201,820)	(113,953)	(136,416)
Net Cash Used In Investing Activities	(229,539)	(67,693)	(149,015)
Cash Flows from Financing Activities:
Stock Options Exercised	918	1,454	1,254
Shares Issued Under the Employee Stock Purchase Plan	494	488	477
Shares Issued for Dividend Reinvestment Plans	886	0	1,280
Tax Benefit from Exercise of Stock Options	59	25	23
Purchases of Treasury Stock	(1,498)	(2,455)	(1,709)
Cash Dividends Paid	(12,700)	(12,407)	(12,109)
Net Cash Provided By Financing Activities	205,386	33,367	113,490
Net Increase (Decrease) in Cash and Cash Equivalents	4,773	(3,685)	1,148
Cash and Cash Equivalents at Beginning of Year	46,295	49,980	48,832
Cash and Cash Equivalents at End of Year	51,068	46,295	49,980
Interest on Deposits and Borrowings	4,856	5,932	8,067
Shares Issued for Acquisition of Subsidiary	0	91	233
Parent Company [Member]
Cash Flows from Operating Activities:
Net Income	24,662	23,360	21,795
Undistributed Net Income of Subsidiaries	(11,509)	(10,344)	(9,155)
Stock-Based Compensation Expense	227	197	198
Stock-Based Compensation Expense	308	360	372
Changes in Other Assets and Other Liabilities	(1,419)	(1,014)	(990)
Net Cash Provided By Operating Activities	12,269	12,559	12,220
Cash Flows from Investing Activities:
Proceeds from the Sale of Securities Available-for-Sale	47	45	45
Purchases of Securities Available-for-Sale	(47)	(45)	(45)
Net Cash Used In Investing Activities	0	0	0
Cash Flows from Financing Activities:
Stock Options Exercised	918	1,454	1,254
Shares Issued Under the Employee Stock Purchase Plan	494	488	477
Shares Issued for Dividend Reinvestment Plans	(886)	0	(1,280)
Tax Benefit from Exercise of Stock Options	59	25	23
Purchases of Treasury Stock	(1,498)	(2,455)	(1,709)
Cash Dividends Paid	(12,700)	(12,407)	(12,109)
Net Cash Provided By Financing Activities	(11,841)	(12,895)	(10,784)
Net Increase (Decrease) in Cash and Cash Equivalents	428	(336)	1,436
Cash and Cash Equivalents at Beginning of Year	3,013	3,349	1,913
Cash and Cash Equivalents at End of Year	3,441	3,013	3,349
Interest on Deposits and Borrowings	619	620	640
Shares Issued for Acquisition of Subsidiary	$ 0	$ 91	$ 233