Income Taxes (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended			6 Months Ended	9 Months Ended			0 Months Ended	9 Months Ended
	Sep. 30, 2013 item	Jun. 30, 2013	Sep. 30, 2012	Jun. 30, 2013	Sep. 30, 2013 item	Sep. 30, 2012	Dec. 31, 2012	Jun. 30, 2013 Federal	Sep. 30, 2013 Federal	Sep. 30, 2013 State Minimum	Sep. 30, 2013 State Maximum
Income Taxes
Reversal of valuation allowance against the company's deferred tax assets		$ 187.5
Valuation allowance against deferred tax assets	25.9	46.4		46.4	25.9		258.9
Pretax income required for the realization of federal NOLs and federal deductible temporary differences								550
Number of consecutive quarters of earnings considered for valuation allowance	5				5
Tax period within which temporary differences related to previously impaired inventory will be reversed if annual pretax income remains at current levels in future years				5 years
Period of cumulative pretax loss position considered in the evaluation of negative evidence				3 years
Deferred tax assets, net	$ 213.4				$ 213.4		$ 258.9
Period of net operating losses carryforward									20 years	10 years	20 years
Period of federal tax credit carryforwards									20 years
Overall effective income tax (benefit) expense rate (as a percent)	0.80%		0.20%		(154.50%)	1.80%