Income Taxes (Uncertain Tax Positions) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Income Tax Contingency [Line Items]
Percentage of likelihood for realization of benefit upon ultimate settlement		50.00%
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns
Beginning balance	$ 0.0
Changes in prior year tax positions	0.1
Tax positions taken during the current year	0.2
Ending balance	0.3	$ 0.0
Permanent Differences
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns
Beginning balance	0.0
Changes in prior year tax positions	0.1
Tax positions taken during the current year	0.2
Ending balance	0.3	0.0
Temporary Differences
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns
Beginning balance	0.0
Changes in prior year tax positions	0.0
Tax positions taken during the current year	0.0
Ending balance	0.0	0.0
Interest and Penalties Net of Tax Benefit
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns
Beginning balance	0.0
Changes in prior year tax positions	0.0
Tax positions taken during the current year	0.0
Ending balance	$ 0.0	$ 0.0