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	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Option contracts [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	$ 0.3	$ 0.3	$ 3.5
Total realized or unrealized gains (losses) included in earnings, net	0.1	(0.2)	4.2
Settlements, net	(0.4)	0.2	(7.4)
Ending balance	$ 0	$ 0.3	$ 0.3