Fair Value Measurements - Assets and Liabilities Measured at Fair Value on a Recurring Basis using Significant Unobservable Inputs (Details) (Option contracts [Member], USD $) In Millions, unless otherwise specified	3 Months Ended	9 Months Ended
	Sep. 30, 2013	Sep. 30, 2013
Option contracts [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	$ (0.3)	$ 0.3
Total realized or unrealized gains (losses) included in earnings, net	0.5	0.1
Settlements, net	(0.2)	(0.4)
Balance at September 30, 2013	$ 0	$ 0