Income Taxes - Narrative (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Income Tax Examination [Line Items]
Federal statutory tax rate	21.00%	35.00%
Statute of limitations minimum	3 years
Statute of limitations maximum	6 years
Non-current deferred tax assets			$ 70.5
Income tax expense benefit (expense)	$ 0.7	$ (0.9)
Decrease in deferred tax assets due to expiration and exercise of shared-based awards	$ 0.0	0.7
Deferred tax assets related to operating loss carryforwards			47.9
Deferred tax assets, may not be realized			$ 1.0
Excess Share-Based Compensation, 2015 and 2016 | Accumulated Deficit
Income Tax Examination [Line Items]
Net Change on derivatives designated as cash flow hedges, net of tax of $0.1		$ 6.5