Income Taxes - Deferred Tax Assets (Liabilities) (Details) - USD ($)	Dec. 31, 2019	Dec. 31, 2018
Deferred tax assets
Deferred revenue	$ 306,000,000	$ 298,000,000
Net operating loss carry forwards	3,233,000,000	3,494,000,000
Property, plant and equipment	58,000,000	57,000,000
Other	326,000,000	309,000,000
Gross deferred tax assets	3,923,000,000	4,158,000,000
Less valuation allowance	(892,000,000)	(931,000,000)
Net deferred tax assets	3,031,000,000	3,227,000,000
Deferred tax liabilities
Deferred revenue	(41,000,000)	(45,000,000)
Property, plant and equipment	(974,000,000)	(853,000,000)
Intangible assets	(1,898,000,000)	(1,998,000,000)
Other	(29,000,000)	(25,000,000)
Gross deferred tax liabilities	(2,942,000,000)	(2,921,000,000)
Net deferred tax assets	$ 89,000,000	$ 306,000,000