Income Taxes Income Taxes (Details) - USD ($) $ in Millions	3 Months Ended			9 Months Ended
	Sep. 30, 2018	Jun. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Income Tax Disclosure [Abstract]
Discrete tax items		$ 6.6
Change in enacted tax rate				2.10%
Effective tax rate prior to impact of change in enacted tax rate				22.50%
Effective tax rate	23.10%		38.80%	24.60%	34.40%
TCJA one-time tax expense				$ 51.0