Components of Income Before Taxes (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income Tax Disclosure [Abstract]
Domestic	$ 665.0	$ 595.6	$ 574.1
Foreign	40.9	39.8	50.8
Income before Income Taxes	$ 705.9	$ 635.4	$ 624.9