Income Taxes Income Tax - Unrecognized tax benefits additional information (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Taxes [Line Items]
Unrecognized Tax Benefits that Would Impact Effective Tax Rate	$ 9.3
Unrecognized Tax Benefits, Income Tax Penalties and Interest Accrued	1.7	$ 1.0
Unrecognized Tax Benefits, Income Tax Penalties and Interest Expense	0.8	$ 0.3	$ 0.1
Significant Change in Unrecognized Tax Benefits is Reasonably Possible, Amount of Unrecorded Benefit	$ 1.2
Domestic Tax Authority
Income Taxes [Line Items]
Year Which Prior Year's Tax Returns Are No Longer Subject to Tax Examination	Dec. 31, 2014
State and Local Jurisdiction
Income Taxes [Line Items]
Year Which Prior Year's Tax Returns Are No Longer Subject to Tax Examination	Dec. 31, 2014
Foreign Tax Authority
Income Taxes [Line Items]
Year Which Prior Year's Tax Returns Are No Longer Subject to Tax Examination	Dec. 31, 2012