Income Taxes - Unrecognized Tax Benefits (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Unrecognized tax benefits [Roll Forward]
Balance as of beginning of period	$ 69.8	$ 47.6
Additions based on tax positions related to current period	2.5	0.9
Additions for tax positions of prior years	29.2	25.7
Expiration of statutes of limitations	(5.0)	(2.1)
Settlements of uncertain tax positions with tax authorities	(24.8)	(2.3)
Balance as of end of period	71.7	69.8	$ 47.6
Unrecognized tax benefits that would impact effective tax rate	21.4	67.7	44.6
Interest and penalties related to unrecognized tax benefits recorded in income tax expense	1.6	33.5	1.9
Accrued interest and penalties	$ 52.3	$ 43.8	$ 10.3