Debt (Details) (USD $) In Millions, unless otherwise specified	0 Months Ended	1 Months Ended					0 Months Ended		3 Months Ended
	Mar. 25, 2013 5 1/4% Senior Notes due 2023	Mar. 31, 2013 5 1/4% Senior Notes due 2023 Debt redemption period April 15, 2018 to April 14, 2019	Mar. 31, 2013 5 1/4% Senior Notes due 2023 Debt redemption period April 15, 2019 to April 14, 2020	Mar. 31, 2013 5 1/4% Senior Notes due 2023 Debt redemption period April 15, 2020 to April 14, 2021	Mar. 31, 2013 5 1/4% Senior Notes due 2023 Debt redemption before April 15, 2016	Mar. 31, 2013 5 1/4% Senior Notes due 2023 Debt redemption on or after April 15, 2021	Apr. 09, 2013 6 3/4% senior notes, due 2015	Mar. 25, 2013 6 3/4% senior notes, due 2015	Mar. 31, 2013 6 3/4% senior notes, due 2015
Long Term Debt
Debt issued	$ 400.0
Effective interest rate ( as a percent)	5.25%							6.75%
Redemption price of debt instrument (as a percent)		102.625%	101.75%	100.875%	105.25%	100.00%	100.00%
Maximum redemption of debt instrument (as a percent)					35.00%
Redemption of debt							198.3	301.7
Expenses recorded for tender and call premiums, loss on early extinguishment of debt, unamortized debt issuance cost write-off, and tender expenses									$ 2.0