Income Tax Expense - Gross Unrecognized Income Tax Benefits (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Gross Unrecognized Income Tax Benefits [Roll Forward]
Balance at January 1	$ 2.0	$ 1.2	$ 2.7
Additions for Tax Positions Related to the Current Year	0.5	0.0	0.1
Additions for Tax Positions Related to Prior Years	0.7	1.0	1.3
Reduction for Tax Positions Related to Prior Years	(0.7)	0.0	0.0
Reductions for Settlements	0.0	0.0	(2.9)
Lapse of Statute	(0.1)	(0.2)	0.0
Balance as of December 31	2.4	2.0	1.2
Unrecognized Tax Benefits that Would Impact Effective Tax Rate	0.5
Unrecognized Tax Benefits, Accrued Interest	$ 0.0	$ 0.0	$ 0.5
Unrecognized Tax Benefits, Interest Expense	immaterial	immaterial	immaterial
Unrecognized Tax Benefits, Penalties	$ 0.0	$ 0.0	$ 0.0
Material Changes to Unrecognized Tax Benefits Expected During Next 12 Months	$ 0.0