Income Taxes - Carryforwards (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Operating Loss Carryforwards [Line Items]
R&D, AMT and state credit carry forwards	$ 26.7	$ 44.5
Federal
Operating Loss Carryforwards [Line Items]
NOL carry forwards	1,318.2
R&D, AMT and state credit carry forwards	25.3
State
Operating Loss Carryforwards [Line Items]
NOL carry forwards	1,337.8
R&D, AMT and state credit carry forwards	2.3
Foreign
Operating Loss Carryforwards [Line Items]
NOL carry forwards	186.2
R&D, AMT and state credit carry forwards	$ 0.0