Long-Term Debt (Details) (USD $)	12 Months Ended			0 Months Ended			0 Months Ended						0 Months Ended																			12 Months Ended					12 Months Ended		1 Months Ended	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2012	Dec. 31, 2012 March 2013 Amended Credit Facility Credit Facility	Mar. 08, 2013 March 2013 Amended Credit Facility Credit Facility Subsequent event	Dec. 31, 2012 March 2013 Amended Credit Facility Credit Facility Scheduled Principal Payments	Dec. 31, 2012 March 2013 Amended Credit Facility Credit Facility Estimated Excess Cash Flow Principal Payments	Mar. 08, 2013 March 2013 Amended Credit Facility Credit Facility Maximum March 8, 2013 to June 29, 2014 Subsequent event	Mar. 08, 2013 March 2013 Amended Credit Facility Credit Facility Maximum June 30, 2014 to June 29, 2015 Subsequent event	Mar. 08, 2013 March 2013 Amended Credit Facility Credit Facility Maximum June 30, 2015 and thereafter Subsequent event	Mar. 08, 2013 March 2013 Amended Credit Facility Credit Facility Minimum March 8, 2013 to June 29, 2014 Subsequent event	Mar. 08, 2013 March 2013 Amended Credit Facility Credit Facility Minimum June 30, 2014 to June 29, 2015 Subsequent event	Mar. 08, 2013 March 2013 Amended Credit Facility Credit Facility Minimum June 30, 2015 and thereafter Subsequent event	Mar. 08, 2013 March 2013 Amended Credit Facility Term Loans Subsequent event	Mar. 15, 2013 March 2013 Amended Credit Facility Term Loans Subsequent event	Mar. 08, 2013 March 2013 Amended Credit Facility Term Loans Greater than 3.00 Subsequent event	Mar. 08, 2013 March 2013 Amended Credit Facility Term Loans 2.25 to 3.00 Subsequent event	Mar. 08, 2013 March 2013 Amended Credit Facility Term Loans 1.25 to 2.25 Subsequent event	Mar. 08, 2013 March 2013 Amended Credit Facility Term Loans Less than 1.25 Subsequent event	Mar. 08, 2013 March 2013 Amended Credit Facility Term Loans Maximum 2.25 to 3.00 Subsequent event	Mar. 08, 2013 March 2013 Amended Credit Facility Term Loans Maximum 1.25 to 2.25 Subsequent event	Mar. 08, 2013 March 2013 Amended Credit Facility Term Loans Maximum Less than 1.25 Subsequent event	Mar. 08, 2013 March 2013 Amended Credit Facility Term Loans Minimum Greater than 3.00 Subsequent event	Mar. 08, 2013 March 2013 Amended Credit Facility Term Loans Minimum 2.25 to 3.00 Subsequent event	Mar. 08, 2013 March 2013 Amended Credit Facility Term Loans Minimum 1.25 to 2.25 Subsequent event	Mar. 08, 2013 March 2013 Amended Credit Facility Term Loans March 31, 2013 and prior Subsequent event	Mar. 08, 2013 March 2013 Amended Credit Facility Term Loans June 30, 2013 Subsequent event	Mar. 08, 2013 March 2013 Amended Credit Facility Term Loans September 30, 2013 Subsequent event	Mar. 08, 2013 March 2013 Amended Credit Facility Term Loans December 31, 2013 Subsequent event	Mar. 08, 2013 March 2013 Amended Credit Facility Term Loans Each quarter thereafter Subsequent event	Dec. 31, 2012 March 2013 Amended Credit Facility Revolving Loans	Mar. 08, 2013 March 2013 Amended Credit Facility Revolving Loans Subsequent event	Dec. 31, 2012 July 2011 Credit Facility Credit Facility	Dec. 31, 2011 July 2011 Credit Facility Credit Facility	Dec. 31, 2012 July 2011 Credit Facility Term Loans	Dec. 31, 2011 July 2011 Credit Facility Term Loans	Jul. 31, 2011 July 2011 Credit Facility Term Loans	Dec. 31, 2012 July 2011 Credit Facility Revolving Loans	Jul. 31, 2011 July 2011 Credit Facility Revolving Loans	May 31, 2011 May 2011 Credit Facility Revolving Loans	Dec. 31, 2010 2009 Credit Facility Credit Facility	Dec. 31, 2009 2009 Credit Facility Credit Facility
Long-term debt
Less unamortized discount	$ (4,517,000)	$ (3,732,000)
Subtotal	483,033,000	453,918,000																																457,650,000	487,550,000
Less current portion	(4,900,000)	(76,950,000)
Long-term debt, net of current portion	478,133,000	376,968,000
Maximum borrowing capacity																															50,000,000					490,000,000	120,000,000	120,000,000	150,000,000		185,000,000
Original issue discount (as a percent)																																		1.00%
Increase in effective borrowing rate (as a percent)																																		0.18%			0.42%
Variable rate basis													LIBOR
Applicable margin (as a percent)													6.00%																					4.50%
Interest rate for term loan (as a percent)													7.25%
Minimum quarterly principal payment																									1,225,000	8,575,000	8,575,000	8,575,000	6,125,000
Excess Cash Flow Prepayment as a Percentage of Consolidated EBITDA															75.00%	50.00%	25.00%	0.00%
Principal payment				50,000,000										25,000,000
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																														46,600,000
Letters of credit outstanding																														3,400,000
Debt issuance costs	12,019,000																																12,000,000
Effective interest rate under the Term Loans (as a percent)													7.90%																					6.40%
Consolidated leverage ratio							4.00	3.50	3.25										3.00	2.25	1.25	3.00	2.25	1.25								3.38
Consolidated fixed charge coverage ratio										105.00%	110.00%	110.00%																				330.00%
Maturity period																																							5 years
Principal payments required for the next five years
2013			76,950,000		76,950,000
2014			28,300,000		24,500,000	3,800,000
2015			32,000,000		24,500,000	7,500,000
2016			37,200,000		24,500,000	12,700,000
2017			24,500,000		24,500,000
Write-off of deferred loan fees to interest expense																																								2,900,000
Reclassification of accumulated interest rate swap losses from accumulated other comprehensive loss to interest expense																																								$ 2,100,000