Debt - Additional Information (Details) (USD $)	12 Months Ended			0 Months Ended		12 Months Ended												0 Months Ended	12 Months Ended		0 Months Ended				0 Months Ended			0 Months Ended		0 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Feb. 04, 2013 Senior Secured Credit Facility, due Oct 2017, variable rate 4.25%	Feb. 25, 2011 Senior Secured Credit Facility, due Oct 2017, variable rate 4.25%	Dec. 31, 2013 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%	Oct. 08, 2010 Senior Secured Credit Facility, due Oct 2017, variable rate 4.25%	Dec. 31, 2013 Revolving Credit Facility	Oct. 19, 2010 Revolving Credit Facility	Oct. 08, 2010 Revolving Credit Facility	Oct. 19, 2010 Revolving Credit Facility Maximum	Oct. 19, 2010 Revolving Credit Facility First Step Down	Oct. 19, 2010 Revolving Credit Facility First Step Down Maximum	Oct. 19, 2010 Revolving Credit Facility First Step Down Minimum	Oct. 19, 2010 Revolving Credit Facility Second Step Down	Oct. 19, 2010 Revolving Credit Facility Second Step Down Minimum	Feb. 25, 2011 Amended Senior Secured Revolving Credit Facility	Dec. 31, 2011 Amended Senior Secured Revolving Credit Facility	Dec. 31, 2013 Amended Senior Secured Revolving Credit Facility	Feb. 25, 2011 Amended Senior Secured Revolving Credit Facility Maximum	Feb. 25, 2011 Amended Senior Secured Revolving Credit Facility Minimum	Dec. 31, 2013 Second Amended Senior Secured Revolving Credit Facility	Feb. 04, 2013 Second Amended Senior Secured Revolving Credit Facility	Feb. 04, 2013 Second Amended Senior Secured Revolving Credit Facility Maximum	Feb. 04, 2013 Second Amended Senior Secured Revolving Credit Facility Minimum	Feb. 04, 2013 Second Amended Senior Secured Revolving Credit Facility First Step Down	Feb. 04, 2013 Second Amended Senior Secured Revolving Credit Facility First Step Down Maximum	Dec. 31, 2013 Second Amended Senior Secured Revolving Credit Facility First Step Down Maximum	Feb. 04, 2013 Second Amended Senior Secured Revolving Credit Facility First Step Down Minimum	Dec. 31, 2013 Second Amended Senior Secured Revolving Credit Facility First Step Down Minimum	Dec. 31, 2013 Second Amended Senior Secured Revolving Credit Facility Second Step Down	Feb. 04, 2013 Second Amended Senior Secured Revolving Credit Facility Second Step Down
Debt Instrument [Line Items]
Debt Instrument, Face Amount								$ 900,000,000			$ 50,000,000
Line of Credit Facility, Maximum Borrowing Capacity								250,000,000	150,000,000		50,000,000										75,000,000	50,000,000
LIBOR Rate Floor	1.50%																				1.50%	1.25%				1.00%
Debt Instrument, Basis Spread on Variable Rate	4.50%																				4.50%	3.00%				2.75%
Base Rate Floor	2.50%																				2.50%	2.25%				2.00%
Federal Funds Rate Additional Margin	0.50%																								3.50%	1.75%
One Month LIBOR Rate Floor	1.50%
One Month LIBOR Rate Additional Margin	1.00%																								4.50%	2.75%
One Month LIBOR Rate Additional Margin Uplift	3.50%
Upfront Fee on Debt, Percent	1.00%																								0.75%	0.50%		0.50%		0.375%
Percent of Excess Cash Flow Required For Mandatory Prepayment, Annual Mininum										50.00%			75.00%			100.00%							50.00%	50.00%			25.00%		25.00%		25.00%	0.00%	0.00%
Ratio of Indebtedness to Net Capital												5.75		5.75	5.25		5.25						5.75	4.75	5.75			5.75	5.75	5.25	5.25	5.25	5.25
Payments of Debt Restructuring Costs																		12,300,000
Payments of Debt Restructuring Costs, Recorded as Additional Discount on Debt																		7,400,000
Payments of Debt Restructuring Costs, Recorded as Deferred Financing Costs																		800,000
Debt modification costs	1,296,000	0	4,031,000																4,031,000
Proceeds from Lines of Credit				472,000,000	742,000,000
Senior Secured Credit Facility Due						467,200,000	472,000,000
Line of Credit Facility, Amount Outstanding																				0
Line of Credit Facility, Current Borrowing Capacity																				$ 10,900,000
Mandatory Prepayment of Debt, Percent per Quarter						0.25%
Mandatory Prepayment of Debt, Percent per Annum						1.00%
Debt Instrument, Interest Rate, Effective Percentage	5.00%