Stockholders' Equity (Details) (USD $) In Millions, except Share data, unless otherwise specified	1 Months Ended	3 Months Ended		6 Months Ended			0 Months Ended							6 Months Ended
	Feb. 28, 2011	Jun. 30, 2011	Mar. 31, 2011	Jun. 30, 2011	Jun. 30, 2010	Dec. 31, 2010	Apr. 11, 2011 Senior Secured Notes due 2014 [Member]	Mar. 30, 2011 Senior Secured Notes due 2014 [Member]	Apr. 11, 2011 Senior Secured Notes due 2015 [Member]	Mar. 30, 2011 Senior Secured Notes due 2015 [Member]	Jun. 30, 2011 Securitization Facility [Member]	Jun. 30, 2011 Revolving Credit Facility [Member]	Jun. 30, 2011 Letter of Credit [Member]	Jun. 30, 2011 Maximum [Member]	Feb. 28, 2011 Maximum [Member]	Feb. 28, 2011 Minimum [Member]
Sale of preferred stock	2,587,500	2,600,000		2,600,000		0
Net proceeds from issuance of 6.25% mandatory convertible preferred stock	$ 249.7
Conversion rate of preferred stock															2.6717	2.1899
Convertible preferred stock dividend, rate				6.25%
Initial liquidation preference per share		$ 100		$ 100
Preferred stock dividend per year per share				$ 6.25
Annualized dividend on mandatory convertible preferred stock				16.2
Percentage of notes to be redeemed at option of company														35.00%
Redemption of debt							44.1	124.7	134.8	86.3
Losses on debt extinguishment		45.7	31.8	(77.5)	(1.4)
Premium on extinguishment of debt		42.2	28.2
Write off of notes discount and issuance cost upon redemption		3.5	3.6
Credit facility term (in years)												5
Credit agreement, maximum borrowing capacity											150	150	100
Threshold for maximum secured leverage ratio		130		130
Credit facility default threshold, other debt		$ 50