Equity Plans (Details) (USD $)	3 Months Ended											0 Months Ended			3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2014 Incentive Plan [Member]	Mar. 31, 2014 Employee Stock Purchase Plan (ESPP) [Member]	Mar. 31, 2013 Employee Stock Purchase Plan (ESPP) [Member]	Mar. 31, 2014 Dividend Reinvestment and Stock Purchase Plan (DRSPP) [Member]	Mar. 31, 2013 Dividend Reinvestment and Stock Purchase Plan (DRSPP) [Member]	Mar. 31, 2014 Restricted Stock and Deferred Restricted Stock [Member]	Mar. 31, 2013 Restricted Stock and Deferred Restricted Stock [Member]	Mar. 31, 2014 Stock Options [Member]	Mar. 31, 2013 Stock Options [Member]	Jan. 31, 2014 Restricted Stock Units (RSUs) [Member]	Jan. 02, 2014 Restricted Stock Units (RSUs) [Member] vesting_installment	Mar. 31, 2014 Common Stock [Member] Employee Stock Purchase Plan (ESPP) [Member]	Mar. 31, 2014 Dividend Equivalent Rights [Member]	Mar. 31, 2013 Dividend Equivalent Rights [Member]	Apr. 14, 2014 Subsequent Event [Member] Common Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Remaining shares available for issuance under the Incentive Plan			1,119,807
Shares issuable upon exercise of Incentive Plan awards			315,914
Compensation costs charged to income:	$ 244,000	$ 347,000		$ 72,000	$ 58,000			$ 172,000	$ 289,000
Excess tax benefits realized from share options exercised and stock issuance	59,000	30,000						0	30,000	59,000	0
Proceeds from the exercise of stock options and similar instruments	476,000	345,000		406,000	328,000	26,000	17,000			44,000	0
Unrecognized compensation costs				49,000				1,132,000		0
Recognition period for unrecognized compensation cost								1 year 6 months 15 days
Number of equity instruments granted												3,845	21,790
Number of equal successive installments for vesting of stock awards													3
Grant date fair value of equity instruments granted												$ 26.39	$ 26.80
Liability accrued for Dividend Equivalent Rights															33,000	34,000
Decrease to retained earnings for compensation cost related to Dividend Equivalent Rights															33,000	34,000
Purchase price of common stock under ESPP, percent				85.00%
Maximum percentage of base compensation employees can designate for stock purchases under ESPP				10.00%
Number of shares authorized for issuance under the plan						3,000,000								270,400
Plan expense				$ 36,000	$ 21,000
Number of shares issued under the DRSPP						875	619
Shares Deregistered (in shares)																	2,993,744