Financial Instruments - Credit Losses (Details) - USD ($) $ in Millions		3 Months Ended
	Jan. 01, 2020	Sep. 30, 2020	Jun. 30, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Dec. 31, 2018
Receivables [Abstract]
Accounting Standards Update [Extensible List]	us-gaap:AccountingStandardsUpdate201613Member
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total Equity		$ (132,038)	$ (134,386)	$ (145,208)	$ (156,892)	$ (157,451)	$ (155,642)
Related Party Transaction [Line Items]
Allowance for credit loss		666		849
Trade receivable		8,100
Non-trade receivable		3,100
Retained Earnings
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total Equity		(163,509)	$ (166,122)	$ (174,945)	$ (183,783)	$ (183,442)	$ (180,987)
Investments and Advances
Related Party Transaction [Line Items]
Allowance for credit loss		560
Government Joint Venture Partners
Related Party Transaction [Line Items]
Allowance for credit loss		265
Reduction in allowance for credit losses		$ 550
Cumulative Effect, Period of Adoption, Adjustment | Retained Earnings
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total Equity	$ 25