Income Taxes - Deferred Tax Assets (Liabilities) (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Deferred tax assets
Deferred revenue	$ 277	$ 306
Net operating loss carry forwards	3,503	3,233
Property, plant and equipment	65	58
Other	343	326
Gross deferred tax assets	4,188	3,923
Less valuation allowance	(1,170)	(892)
Net deferred tax assets	3,018	3,031
Deferred tax liabilities
Deferred revenue	(34)	(41)
Property, plant and equipment	(1,264)	(974)
Intangible assets	(1,773)	(1,898)
Other	(33)	(29)
Gross deferred tax liabilities	(3,104)	(2,942)
Net deferred tax (liabilities) assets	$ (86)
Net deferred tax (liabilities) assets		$ 89