Share-based Compensation (Details Textual) (USD $)	12 Months Ended					1 Months Ended		12 Months Ended							1 Months Ended		12 Months Ended								1 Months Ended	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2013 Maximum [Member]	Dec. 31, 2013 Minimum [Member]	Jan. 31, 2011 2005 Stock option plan [Member]	Jan. 31, 2006 2005 Stock option plan [Member]	Dec. 31, 2013 2005 Stock option plan [Member]	Dec. 31, 2012 2005 Stock option plan [Member]	Dec. 31, 2011 2005 Stock option plan [Member]	Dec. 31, 2013 2005 Plan SARs [Member]	Dec. 31, 2013 Stock Options [Member]	Dec. 31, 2012 Stock Options [Member]	Dec. 31, 2011 Stock Options [Member]	May 14, 2010 SARs Grant [Member]	Apr. 04, 2007 SARs Grant [Member]	Dec. 31, 2013 SARs Grant [Member] vesting_increment	Dec. 31, 2012 SARs Grant [Member]	Dec. 31, 2011 SARs Grant [Member]		Dec. 31, 2009 SARs Grant [Member]	Dec. 31, 2008 SARs Grant [Member]	Dec. 31, 2013 SARs Grant [Member] Maximum [Member]	Dec. 31, 2013 SARs Grant [Member] Minimum [Member]	May 14, 2010 2010 SARS Exchange [Member]	Dec. 31, 2013 April 28, 2008 SARs Market Grant [Member] trading_day	Dec. 31, 2011 April 28, 2008 SARs Market Grant [Member] trading_day	Dec. 31, 2008 April 28, 2008 SARs Market Grant [Member]	Dec. 31, 2013 March 3, 2009 SARs Market Grant [Member] trading_day	Dec. 31, 2009 March 3, 2009 SARs Market Grant [Member]	Dec. 31, 2011 April 28, 2008 SARs Grant [Member]	Dec. 31, 2012 Awards Vest Based On Time [Member] SARs Grant [Member]	Dec. 31, 2012 Awards Vest Based On Time And Performance [Member] SARs Grant [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares authorized								1,000,000
Award maximum number of shares per employee								300,000
Expiration period of options and SARs				10 years	5 years
Income tax benefits related to share-based compensation arrangements	$ 3,100,000	$ 2,300,000	$ 1,300,000
Shares for which company granted options							484,876
Shares covered by options, expired						340,352
Stock options granted								0	0	0
Shares available for issuance in future grants								855,476
Shares registered for issuance to the public under 2005 plan								1,000,000
Exercised, Shares Covered by Options										(36,001)
Intrinsic value of stock options exercised (less than $0.1 million)										100,000
SARs granted (in shares)															95,100	190,200	0	204,500	242,041		212,850	196,900						77,500		93,250		89,600	114,900
Exercise price per SAR (in dollars per share)															$ 14.12	$ 29.49
Net effect of SARs compensation income												0	0	0											300,000
Increment percentage											25.00%
SAR, vesting rule, period to achieve specified target price																										12 months			12 months
SAR, vesting rule, number of trading days required during period to achieve specified target price																										20	20		20,000
SAR, vesting rule, trading period to achieve specified target price																										60 days	60 days		60 days
Equal vesting increments after each subsequent anniversary																	3
Vesting period																							4 years	3 years
SARs forfeited (in shares)																	41,114	22,360	22,720	[1]											13,123
Unrecognized compensation costs related to the unvested portion of SARs																	$ 600,000
Period over which compensation cost expected to be realized																	11 months

[1] Of the SARs granted in 2008, 13,123 were canceled in 2011 due to the closing price of the Company’s common stock not achieving a specified price target for twenty trading days during any sixty day trading day period.