Income Taxes (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015	Dec. 31, 2016	Dec. 31, 2015
Income Tax [Line Items]
Effective income tax rate (as percent)	35.30%	37.10%	37.30%	38.60%
U.S. Federal statutory rate (as percent)	35.00%		35.00%
Gross unrecognized tax benefits, including interest and penalties	$ 44.6		$ 44.6			$ 38.9
Offsetting tax benefits	1.0		1.0			1.0
Net unrecognized tax benefits	$ 43.6		$ 43.6			$ 37.9
Scenario, Forecast
Income Tax [Line Items]
Expected annual effective income tax rate (as percent)					37.00%