Parent Only Financial Information Parent Only Statement of Cash Flows (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Cash Flows from Operating Activities:
Net Income	$ 29,326	$ 26,534	$ 24,662
Stock-Based Compensation Expense	351	287	308
Stock-Based Compensation Expense	351	287	308
Net Cash Provided By Operating Activities	37,827	34,695	28,926
Cash Flows from Investing Activities:
Proceeds from the Sale of Securities Available-for-Sale	107,175	97,930	66,551
Purchases of Securities Available-for-Sale	(117,262)	(134,950)	(201,820)
Proceeds from the Maturities and Calls of Securities Held-to-Maturity	49,244	56,461	48,409
Net Cash Used In Investing Activities	(148,566)	(157,789)	(229,539)
Cash Flows from Financing Activities:
Shares Issued for Stock Option Exercises, net	1,190	2,404	918
Shares Issued for Dividend Reinvestment Plans	1,684	1,743	886
Tax Benefit for Exercises of Stock Options	0	188	59
Purchase of Treasury Stock	(3,248)	(2,141)	(1,498)
Cash Dividends Paid	(13,599)	(13,092)	(12,700)
Net Cash Provided By Financing Activities	126,222	129,381	205,386
Net Increase (Decrease) in Cash and Cash Equivalents	15,483	6,287	4,773
Cash and Cash Equivalents at Beginning of Year	57,355	51,068	46,295
Cash and Cash Equivalents at End of Year	72,838	57,355	51,068
Interest on Deposits and Borrowings	6,957	5,341	4,856
Parent Company [Member]
Cash Flows from Operating Activities:
Net Income	29,326	26,534	24,662
Undistributed Net Income of Subsidiaries	(17,310)	(15,283)	(11,509)
Stock-Based Compensation Expense	233	196	227
Stock-Based Compensation Expense	351	287	308
Changes in Other Assets and Other Liabilities	(1,530)	(1,177)	(1,419)
Net Cash Provided By Operating Activities	11,070	10,557	12,269
Cash Flows from Investing Activities:
Proceeds from the Sale of Securities Available-for-Sale	0	0	47
Purchases of Securities Available-for-Sale	0	0	(47)
Proceeds from the Maturities and Calls of Securities Held-to-Maturity	1,000	0	0
Net Cash Used In Investing Activities	1,000	0	0
Cash Flows from Financing Activities:
Shares Issued for Stock Option Exercises, net	1,190	2,404	918
Shares Issued Under the Employee Stock Purchase Plan	496	493	494
Shares Issued for Dividend Reinvestment Plans	1,684	1,743	886
Tax Benefit for Exercises of Stock Options	0	188	59
Purchase of Treasury Stock	(3,248)	(2,141)	(1,498)
Cash Dividends Paid	(13,599)	(13,092)	(12,700)
Net Cash Provided By Financing Activities	(13,477)	(10,405)	(11,841)
Net Increase (Decrease) in Cash and Cash Equivalents	(1,407)	152	428
Cash and Cash Equivalents at Beginning of Year	3,593	3,441	3,013
Cash and Cash Equivalents at End of Year	2,186	3,593	3,441
Interest on Deposits and Borrowings	$ 781	$ 691	$ 619