Derivative and Financial Instruments - Financial Instruments at fair value (Details) - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019
Schedule Of Available For Sale Securities [Line Items]
Cash and cash equivalents	$ 3,908	$ 5,088
Short-term Investments	3,866	3,028
Investments and long-term receivables	8,707	8,687
Carrying (Reported) Amount, Fair Value Disclosure [Member]
Schedule Of Available For Sale Securities [Line Items]
Cash and cash equivalents	19	9
Short-term Investments	236	99
Investments and long-term receivables	204	133
Corporate Bonds [Member] \| Remaining maturities within one year [Member] \| Carrying (Reported) Amount, Fair Value Disclosure [Member]
Schedule Of Available For Sale Securities [Line Items]
Cash and cash equivalents	0	1
Short-term Investments	126	59
Investments and long-term receivables	0	0
Corporate Bonds [Member] \| Remaining Maturities Greater Than One Year Through Five Years [Member] \| Carrying (Reported) Amount, Fair Value Disclosure [Member]
Schedule Of Available For Sale Securities [Line Items]
Cash and cash equivalents	0	0
Short-term Investments	0	0
Investments and long-term receivables	140	99
Commercial Paper [Member] \| Remaining maturities within one year [Member] \| Carrying (Reported) Amount, Fair Value Disclosure [Member]
Schedule Of Available For Sale Securities [Line Items]
Cash and cash equivalents	19	8
Short-term Investments	110	30
Investments and long-term receivables	0	0
U.S. Government Obligations [Member] \| Remaining maturities within one year [Member] \| Carrying (Reported) Amount, Fair Value Disclosure [Member]
Schedule Of Available For Sale Securities [Line Items]
Cash and cash equivalents	0	0
Short-term Investments	0	10
Investments and long-term receivables	0	0
U.S. Government Obligations [Member] \| Remaining Maturities Greater Than One Year Through Five Years [Member] \| Carrying (Reported) Amount, Fair Value Disclosure [Member]
Schedule Of Available For Sale Securities [Line Items]
Cash and cash equivalents	0	0
Short-term Investments	0	0
Investments and long-term receivables	21	15
U.S. Government Agency Obligations [Member] \| Remaining Maturities Greater Than One Year Through Five Years [Member] \| Carrying (Reported) Amount, Fair Value Disclosure [Member]
Schedule Of Available For Sale Securities [Line Items]
Cash and cash equivalents	0	0
Short-term Investments	0	0
Investments and long-term receivables	5	0
Asset-backed Securities [Member] \| Remaining Maturities Greater Than One Year Through Five Years [Member] \| Carrying (Reported) Amount, Fair Value Disclosure [Member]
Schedule Of Available For Sale Securities [Line Items]
Cash and cash equivalents	0	0
Short-term Investments	0	0
Investments and long-term receivables	$ 38	$ 19

Amount of investments including trading securities, held-to-maturity securities, and short-term investments classified as other and current but excluding investement in Cenovus Energy Common Shares.

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