Summary of Accounting Policies (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Allowance for Doubtful Accounts
Allowance for doubtful accounts	$ 3.3	$ 5.2
Allowance for doubtful accounts
Activity in allowance for doubtful accounts
Balance at the Beginning of the period	5.2	5.2	4.6
Provision charged to expense	0.1	1.0	0.9
Provision charged to other accounts	(1.4)		0.3
Amounts written off, net of recoveries	(0.6)	(1.0)	(0.6)
Balance at the end of the period	$ 3.3	$ 5.2	$ 5.2