Income Taxes - Narrative (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Dec. 31, 2017	Mar. 31, 2017
Income Tax Disclosure [Abstract]
Effective income tax rate (percent)	24.80%		40.00%
Gross unrecognized tax benefit	$ 6.1	$ 5.9
Expected change in unrecognized tax benefits	3.1
Accrued interest on income taxes	1.0	1.1
Accrued penalties on income taxes, less than	$ 0.1	0.1
Tax Cuts and Jobs Act of 2017, incomplete accounting, provisional income tax expense (benefit)		$ (77.5)