Debt (Details Textual) (USD $)	1 Months Ended	12 Months Ended				12 Months Ended
	Jan. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2012 Credit Facility [Member]	Nov. 30, 2012 Credit Facility [Member]	Dec. 31, 2004 Senior Notes [Member]
Debt (Textual) [Abstract]
Issuance of 8.625% senior notes						$ 150,000,000
Percentage of Senior Note Redeemed						8.625%
Senior notes due date						2014
Redeemed principle amount of senior notes	61,800,000	39,600,000	20,600,000
Total consideration on redemption of senior notes	62,700,000	40,600,000	20,500,000
Accrued interest on redemption	1,800,000	685,000	312,000
Loss on extinguishment of debt	1,500,000	1,500,000	160,000
Unamortized debt issuance costs	594,000	466,000	317,000
Amount of senior secured revolving credit facility					30,000,000
Maturity date of credit facility					2017
Percentage of federal funds effective rate				0.50%
Percentage of eurodollar rate				1.00%
Cost related to obtaining the credit facility				246,000
Outstanding indebtedness under the Credit Facility				$ 0