Income Taxes - Reconciliation of unrecognized tax benefit (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Unrecognized Tax Benefits, Beginning of Period	$ 3.4	$ 2.7	$ 6.7
Unrecognized Tax Benefits, Increase Resulting from Prior Period Tax Positions	1.0	1.2	0.8
Unrecognized Tax Benefits, Increase Resulting from Current Period Tax Positions	0.1	0.1	0.0
Unrecognized Tax Benefits, Decrease Resulting from Settlements with Taxing Authorities of Lapse of Applicate Statute of Limitations	(0.6)	(0.6)	(4.8)
Unrecognized Tax Benefits, End of Period	$ 3.9	$ 3.4	$ 2.7