Income Taxes - Operating Loss Carryforwards (Details) $ in Millions	Dec. 31, 2018 USD ($)
Operating Loss Carryforwards
Deferred tax asset relating to NOL carryforwards that have an indefinite life in several non U.S. jurisdictions	$ 1,670.0
Recognized valuation allowance relating to NOL carryforwards	1,700.0
Operating Loss Carryforwards
NOL carryforwards for state income tax purposes	780.0
U.S. Federal
Operating Loss Carryforwards
Net operating loss carryforwards	578.0
U.S. Federal | Between 2010 and 2036
Operating Loss Carryforwards
Net operating loss carryforwards	442.0
Non U.S. Federal Jurisdictions
Operating Loss Carryforwards
Net operating loss carryforwards	7,100.0
Non U.S. Federal Jurisdictions | From 2019 to 2038
Operating Loss Carryforwards
Net operating loss carryforwards	$ 526.0