Income Taxes - Unrecognized Tax Benefits (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]
Balance as of beginning of year	$ 1.0	$ 0.6	$ 0.3
Additions for tax positions of prior years	11.4	0.1	0.3
Additions for tax positions of current year	6.7	0.5	0.0
Reductions due to lapse of statutes and settlements	(1.0)	(0.2)	0.0
Balance as of the end of year	$ 18.1	$ 1.0	$ 0.6