Income Taxes - Narrative (Details)	3 Months Ended	12 Months Ended
	Mar. 31, 2019 USD ($)	Dec. 31, 2019 USD ($) jurisdiction	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Sep. 30, 2017 USD ($)
Income Tax
Number of non-U.S. tax jurisdictions in which the entity is operating | jurisdiction		20
Non-U.K. tax rate differentials		$ 4,000,000	$ 7,000,000	$ 1,000,000
Tax expense (benefit) from foreign exchange transactions		0
Gross operating loss carryforwards		2,107,000,000
Net deferred tax assets before valuation allowance		618,000,000	398,000,000
Net operating loss carryforwards		519,000,000	313,000,000
Valuation allowance on net deferred tax assets		585,000,000	220,000,000
Deferred income taxes		33,000,000	178,000,000
Non-current deferred tax assets		33,000,000	178,000,000
Operating loss carryforwards, valuation allowance		197,000,000
Unrecognized tax benefits which, if recognized, would affect the effective tax rate		$ 1,000,000	14,000,000	13,000,000
Number of months from the reporting date during which unrecognized tax benefit would result in change in income tax		12 years
U.S. income tax reform		$ 0	$ 0	34,000,000
Foreign earnings repatriated	$ 12,000,000
Luxembourg
Income Tax
Gross operating loss carryforwards		864,000,000
United States
Income Tax
Deferred tax asset, provisional income tax expense				3,000,000
Deferred tax asset due to basis step up					$ 77,000,000
Deferred tax asset due to basis set up, Tax Cuts and Jobs Act of 2017				36,000,000
Aggregate income tax provision					$ 73,000,000
U.S. income tax reform		30,000,000		$ 34,000,000
Germany
Income Tax
Valuation allowance on net deferred tax assets		162,000,000
Minimum
Income Tax
Decrease in the unrecognized tax benefits reasonably possible, low end of range		0
Expiration in 2028
Income Tax
Gross operating loss carryforwards		$ 226,000,000