Derivative and Financial Instruments - Financial Instruments at cost, plus accrued interest (Details) - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019
Schedule of Held-to-maturity Securities [Line Items]
Cash and Cash Equivalents, carried at cost plus accrued interest	$ 2,487	$ 5,079
Short-term investments, carried at cost plust accrued interest	3,759	2,929
Cash [Member]
Schedule of Held-to-maturity Securities [Line Items]
Cash and Cash Equivalents, carried at cost plus accrued interest	545	759
Demand Deposits [Member]
Schedule of Held-to-maturity Securities [Line Items]
Cash and Cash Equivalents, carried at cost plus accrued interest	1,182	1,483
Time Deposits [Member] \| Remaining maturities from 1 to 90 days [Member]
Schedule of Held-to-maturity Securities [Line Items]
Cash and Cash Equivalents, carried at cost plus accrued interest	755	2,030
Short-term investments, carried at cost plust accrued interest	2,961	1,395
Time Deposits [Member] \| Remaining maturities from 91 to 180 days [Member]
Schedule of Held-to-maturity Securities [Line Items]
Cash and Cash Equivalents, carried at cost plus accrued interest	0	0
Short-term investments, carried at cost plust accrued interest	741	465
Time Deposits [Member] \| Remaining maturities within one year [Member]
Schedule of Held-to-maturity Securities [Line Items]
Cash and Cash Equivalents, carried at cost plus accrued interest	0	0
Short-term investments, carried at cost plust accrued interest	7	0
Commercial Paper [Member] \| Remaining maturities from 1 to 90 days [Member]
Schedule of Held-to-maturity Securities [Line Items]
Cash and Cash Equivalents, carried at cost plus accrued interest	0	413
Short-term investments, carried at cost plust accrued interest	50	1,069
Government obligations [Member] \| Remaining maturities from 1 to 90 days [Member]
Schedule of Held-to-maturity Securities [Line Items]
Cash and Cash Equivalents, carried at cost plus accrued interest	5	394
Short-term investments, carried at cost plust accrued interest	$ 0	$ 0