Summary of Accounting Policies (Details) - Allowance for doubtful accounts - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Activity in allowance for doubtful accounts
Balance at the Beginning of the period	$ 4.8	$ 3.3	$ 5.2
Provision charged to expense	0.3	1.2	0.1
Provision charged to other accounts	0.1	1.1	(1.4)
Amounts written off, net of recoveries	(0.5)	(0.8)	(0.6)
Balance at the end of the period	$ 4.7	$ 4.8	$ 3.3