Derivative and Financial Instruments - Financial Instruments at Cost Plus Accrued Interest (Details) - USD ($) $ in Millions	Jun. 30, 2021	Dec. 31, 2020
Schedule of Held-to-maturity Securities [Line Items]
Cash and Cash Equivalents, carried at cost plus accrued interest	$ 6,560	$ 2,978
Short-term investments, carried at cost plus accrued interest	2,016	3,320
Investments and long-term receivables carried at cost plus accrued interest	2	1
Cash [Member]
Schedule of Held-to-maturity Securities [Line Items]
Cash and Cash Equivalents, carried at cost plus accrued interest	899	597
Demand Deposits [Member]
Schedule of Held-to-maturity Securities [Line Items]
Cash and Cash Equivalents, carried at cost plus accrued interest	1,541	1,133
Time Deposits [Member] \| 1 to 90 days [Member]
Schedule of Held-to-maturity Securities [Line Items]
Cash and Cash Equivalents, carried at cost plus accrued interest	4,104	1,225
Short-term investments, carried at cost plus accrued interest	1,537	2,859
Time Deposits [Member] \| 91 to 180 days [Member]
Schedule of Held-to-maturity Securities [Line Items]
Short-term investments, carried at cost plus accrued interest	270	448
Time Deposits [Member] \| Within one year [Member]
Schedule of Held-to-maturity Securities [Line Items]
Short-term investments, carried at cost plus accrued interest	209	13
Time Deposits [Member] \| One year through eight years [Member]
Schedule of Held-to-maturity Securities [Line Items]
Investments and long-term receivables carried at cost plus accrued interest	2	1
U.S. Government Obligations [Member] \| 1 to 90 days [Member]
Schedule of Held-to-maturity Securities [Line Items]
Cash and Cash Equivalents, carried at cost plus accrued interest	16	23
Short-term investments, carried at cost plus accrued interest	$ 0	$ 0