Income Taxes - Narrative (Details) $ in Millions	3 Months Ended				6 Months Ended
	Sep. 30, 2020 USD ($)	Jun. 30, 2020 USD ($)	Jun. 30, 2019 USD ($)	Mar. 31, 2019 USD ($)	Jun. 30, 2020 USD ($) Installment	Jun. 30, 2019 USD ($)	Mar. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)
Income Taxes [Line Items]
Income tax expense (benefit)		$ (186)	$ 26		$ 63	$ 32
Income (loss) before income taxes		(889)	82		(1,257)	44
Net discrete tax adjustments		$ 2	$ 6	$ 7	$ 293	$ 13
U.S. statutory rate		21.00%	21.00%		21.00%	21.00%
Non-cash goodwill impairment charge					$ 182
Deferred tax asset, tax credit carryforwards, foreign		$ 118			$ 118			$ 403
CARES act of 2020, net operating loss carryback period					5 years
Number of equal annual installments to receive refund alternative minimum tax credit carryforwards | Installment					2
Scenario Forecast
Income Taxes [Line Items]
CARES Act Of 2020 refundable alternative minimum tax credit carryforwards	$ 5
Foreign Tax Authority
Income Taxes [Line Items]
Tax credit carryforward, valuation allowance		298			$ 298		$ 295	3
Valuation allowance		993			$ 993			969
Tax credit carryforward expiration year					2025
Deferred tax assets		1,300			$ 1,300			$ 1,200
Foreign Tax Authority | Beginning Year
Income Taxes [Line Items]
Tax credit carryforward expiration year					2025
Foreign Tax Authority | Ending Year
Income Taxes [Line Items]
Tax credit carryforward expiration year					2030
Domestic and State and Local Authority
Income Taxes [Line Items]
Net deferred tax assets		1,100			$ 1,100
Net deferred tax assets, unlimited lives		900			900
Net deferred tax assets, limited lives		200			$ 200
Net deferred tax assets, expiration period					after 2025
Valuation allowance		308			$ 308
Luxembourg
Income Taxes [Line Items]
Change in enacted tax rate, amount			$ 6
Luxembourg | Foreign Tax Authority
Income Taxes [Line Items]
Valuation allowance		$ 893			$ 893