Income Taxes - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Components of Income Tax Expense (Benefit) [Line Items]
Effective income tax rate	25.30%	(8.60%)	36.50%
Favorable impact of tax law changes regarding Global Intangible Low Taxes Income regulations	$ 13
Unfavorable impact of non-deductible goodwill impairment		$ 779
Tax Cuts and Jobs Act, income tax expense			$ 92
Net deferred tax liabilities	86
Deferred tax liabilities, long-term	247	241
Net deferred tax assets		89
Deferred tax assets, net, noncurrent	161	330
Uncertain tax benefits	923	952	$ 970
Deferred tax assets, valuation allowance	1,170	892
Unrecognized tax benefits that would impact effective tax rate	33	30
Unrecognized tax benefits, accrued interest	9	$ 8
Reasonably possible decrease in unrecognized tax benefits for uncertain tax positions previously taken	(2)
Federal
Components of Income Tax Expense (Benefit) [Line Items]
Operating loss carryforwards	12,900
Uncertain tax benefits	4,100
State
Components of Income Tax Expense (Benefit) [Line Items]
Operating loss carryforwards	8,300
Uncertain tax benefits	618
Foreign
Components of Income Tax Expense (Benefit) [Line Items]
Operating loss carryforwards	$ 7,200