Long-Term Debt (Details) (USD $)				1 Months Ended								1 Months Ended											1 Months Ended
	Mar. 31, 2013	Dec. 31, 2012	Mar. 31, 2013 Credit Facility	Mar. 31, 2013 Term Loans	Mar. 31, 2013 March 2013 Amended Credit Facility Credit Facility	Mar. 31, 2013 March 2013 Amended Credit Facility Credit Facility Maximum March 8, 2013 to June 29, 2014	Mar. 31, 2013 March 2013 Amended Credit Facility Credit Facility Maximum June 30, 2014 to June 29, 2015	Mar. 31, 2013 March 2013 Amended Credit Facility Credit Facility Maximum June 30, 2015 and thereafter	Mar. 31, 2013 March 2013 Amended Credit Facility Credit Facility Minimum March 8, 2013 to June 29, 2014	Mar. 31, 2013 March 2013 Amended Credit Facility Credit Facility Minimum June 30, 2014 to June 29, 2015	Mar. 31, 2013 March 2013 Amended Credit Facility Credit Facility Minimum June 30, 2015 and thereafter	Mar. 31, 2013 March 2013 Amended Credit Facility Term Loans	Mar. 31, 2013 March 2013 Amended Credit Facility Term Loans Greater than 3.00	Mar. 31, 2013 March 2013 Amended Credit Facility Term Loans 2.25 to 3.00	Mar. 31, 2013 March 2013 Amended Credit Facility Term Loans 1.25 to 2.25	Mar. 31, 2013 March 2013 Amended Credit Facility Term Loans Less than 1.25	Mar. 31, 2013 March 2013 Amended Credit Facility Term Loans Maximum 2.25 to 3.00	Mar. 31, 2013 March 2013 Amended Credit Facility Term Loans Maximum 1.25 to 2.25	Mar. 31, 2013 March 2013 Amended Credit Facility Term Loans Maximum Less than 1.25	Mar. 31, 2013 March 2013 Amended Credit Facility Term Loans Minimum Greater than 3.00	Mar. 31, 2013 March 2013 Amended Credit Facility Term Loans Minimum 2.25 to 3.00	Mar. 31, 2013 March 2013 Amended Credit Facility Term Loans Minimum 1.25 to 2.25	Mar. 31, 2013 March 2013 Amended Credit Facility Term Loans June 30, 2013	Mar. 31, 2013 March 2013 Amended Credit Facility Term Loans September 30, 2013	Mar. 31, 2013 March 2013 Amended Credit Facility Term Loans December 31, 2013	Mar. 31, 2013 March 2013 Amended Credit Facility Term Loans Each quarter thereafter	Mar. 31, 2013 March 2013 Amended Credit Facility Revolving Loans	Jul. 31, 2011 July 2011 Credit Facility Credit Facility	Jul. 31, 2011 July 2011 Credit Facility Term Loans	Mar. 31, 2013 July 2011 Credit Facility Term Loans	Dec. 31, 2012 July 2011 Credit Facility Term Loans	Jul. 31, 2011 July 2011 Credit Facility Revolving Loans
Long-term debt
Less unamortized discount	$ (3,303,000)	$ (3,732,000)
Subtotal	403,122,000	453,918,000																												406,425,000	457,650,000
Less current portion	(35,650,000)	(76,950,000)
Long-term debt, net of current portion	367,472,000	376,968,000
Maximum borrowing capacity																											50,000,000		490,000,000			120,000,000
Original issue discount (as a percent)																													1.00%
Increase in effective borrowing rate (as a percent)					0.12%																							0.46%
Variable rate basis												LIBOR
Applicable margin (as a percent)												6.00%
Interest rate for term loan (as a percent)												7.25%
Minimum quarterly principal payment																							8,575,000	8,575,000	8,575,000	6,125,000
Estimated principal payment based on a percentage of ECF												3,800,000
Excess Cash Flow Prepayment as a Percentage of Consolidated EBITDA													75.00%	50.00%	25.00%	0.00%
Principal payment				50,000,000
Additional principal payment required												50,000,000
Interest rate terms																											bear interest at the alternative base rate or LIBOR, plus the applicable margin for each rate that fluctuates with the consolidated leverage ratio
Funds available under credit facility																											47,000,000
Letters of credit outstanding																											3,000,000
Debt issuance costs					2,600,000																							12,000,000
Effective interest rate under the Term Loans (as a percent)				8.00%
Write-off of previously existing debt issuance costs to interest expense					1,300,000
Reduction in maximum borrowing capacity																											$ 70,000,000
Consolidated leverage ratio			3.09			4.00	3.50	3.25									3.00	2.25	1.25	3.00	2.25	1.25
Consolidated fixed charge coverage ratio			3.95						1.05	1.10	1.10