Subsequent Events (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	1 Months Ended	0 Months Ended	1 Months Ended	0 Months Ended	12 Months Ended									0 Months Ended	12 Months Ended		12 Months Ended					12 Months Ended		12 Months Ended
	Aug. 31, 2011	Feb. 26, 2013 Subsequent Event	Aug. 31, 2011 Subsequent Event	Feb. 26, 2013 Subsequent Event Dividend Declared [Member]	Dec. 31, 2012 Amended Senior Secured Revolving Credit Facility	Dec. 31, 2012 Second Amended Senior Secured Revolving Credit Facility Subsequent Event October 2010 Refinancing	Dec. 31, 2012 Second Amended Senior Secured Revolving Credit Facility Subsequent Event Percent Excess Cash Flow Required for Prepayment if Consolidated Leverate Ratio is 5.75 or Greater [Member] October 2010 Refinancing	Dec. 31, 2012 Second Amended Senior Secured Revolving Credit Facility Subsequent Event Percent Excess Cash Flow Required for Prepayment if Consolidated Leverate Ratio is 5.75 or Greater [Member] Minimum	Dec. 31, 2012 Second Amended Senior Secured Revolving Credit Facility Subsequent Event Percent Excess Cash Flow Required for Prepayment if Consolidated Leverate Ratio is Between 5.25 and 5.75 [Member] October 2010 Refinancing	Dec. 31, 2012 Second Amended Senior Secured Revolving Credit Facility Subsequent Event Percent Excess Cash Flow Required for Prepayment if Consolidated Leverate Ratio is Between 5.25 and 5.75 [Member] Minimum	Dec. 31, 2012 Second Amended Senior Secured Revolving Credit Facility Subsequent Event Percent Excess Cash Flow Required for Prepayment if Consolidated Leverate Ratio is Between 5.25 and 5.75 [Member] Maximum	Dec. 31, 2012 Second Amended Senior Secured Revolving Credit Facility Subsequent Event Percent Excess Cash Flow Required for Prepayment if Consolidated Leverate Ratio is Less Than 5.25 [Member] October 2010 Refinancing	Dec. 31, 2012 Second Amended Senior Secured Revolving Credit Facility Subsequent Event Percent Excess Cash Flow Required for Prepayment if Consolidated Leverate Ratio is Less Than 5.25 [Member] Maximum	Feb. 25, 2011 Senior Secured Credit Facility, due Oct 2017, variable rate 4.25%	Dec. 31, 2012 Senior Secured Credit Facility, due Oct 2017, variable rate 4.25%	Dec. 31, 2011 Senior Secured Credit Facility, due Oct 2017, variable rate 4.25%	Dec. 31, 2012 Senior Secured Revolving Credit Facility Amended Senior Secured Revolving Credit Facility Subsequent Event October 2010 Refinancing	Dec. 31, 2012 Senior Secured Revolving Credit Facility Amended Senior Secured Revolving Credit Facility Subsequent Event October 2010 Refinancing London Interbank Offered Rate (LIBOR) [Member]	Dec. 31, 2012 Senior Secured Revolving Credit Facility Amended Senior Secured Revolving Credit Facility Subsequent Event October 2010 Refinancing Base Rate [Member]	Dec. 31, 2012 Senior Secured Revolving Credit Facility Second Amended Senior Secured Revolving Credit Facility Subsequent Event London Interbank Offered Rate (LIBOR) [Member]	Dec. 31, 2012 Senior Secured Revolving Credit Facility Second Amended Senior Secured Revolving Credit Facility Subsequent Event Base Rate [Member]	Dec. 31, 2012 Senior Secured Revolving Credit Facility Second Amended Senior Secured Revolving Credit Facility Subsequent Event October 2010 Refinancing	Dec. 31, 2012 Senior Secured Revolving Credit Facility Second Amended Senior Secured Revolving Credit Facility Subsequent Event Leverage Ratio Below 4.75 Resulting in Reduction in Unused Commitment Fee [Member]	Dec. 31, 2012 Senior Secured Revolving Credit Facility Second Amended Senior Secured Revolving Credit Facility Subsequent Event Leverage Ratio Below 4.75 Resulting in Reduction in Unused Commitment Fee [Member] October 2010 Refinancing	Dec. 31, 2012 Term Loans Amended Senior Secured Revolving Credit Facility Subsequent Event October 2010 Refinancing London Interbank Offered Rate (LIBOR) [Member]	Dec. 31, 2012 Term Loans Amended Senior Secured Revolving Credit Facility Subsequent Event October 2010 Refinancing Base Rate [Member]	Dec. 31, 2012 Term Loans Second Amended Senior Secured Revolving Credit Facility Subsequent Event London Interbank Offered Rate (LIBOR) [Member]	Dec. 31, 2012 Term Loans Second Amended Senior Secured Revolving Credit Facility Subsequent Event Base Rate [Member]	Dec. 31, 2012 Term Loans Second Amended Senior Secured Revolving Credit Facility Subsequent Event October 2010 Refinancing London Interbank Offered Rate (LIBOR) [Member]
Subsequent Event [Line Items]
Debt Instrument, Basis Spread on Variable Rate																		4.50%	3.50%	2.75%	1.75%				3.00%				2.75%
LIBOR Rate Floor					2.25%																				1.25%		1.00%
Mandatory Prepayment of Debt, Percent per Annum						1.00%									1.00%
Line of Credit Facility, Unused Capacity, Commitment Fee Percentage																	0.75%					0.50%		0.375%
Percent of Excess Cash Flow Required Applied as a Prepayment							50.00%		25.00%			0.00%
Ratio of Indebtedness to Net Capital								5.75		5.25	5.75		5.25										4.75
Base Rate Floor					1.25%																					2.25%		2.00%
Senior secured credit facility due															$ 472.0	$ 682.5
Proceeds from Lines of Credit														742.0
Common stock dividend authorized				$ 0.75
Authorized amount under stock repurchase program	$ 45	$ 100	$ 45