Financial Instruments (Narrative) (Details) $ in Billions				3 Months Ended
	Mar. 31, 2019 USD ($)	Mar. 31, 2019 CAD ($)	Mar. 07, 2019 CAD ($)	Mar. 31, 2020 USD ($)	Mar. 31, 2019 USD ($)	Dec. 31, 2019 USD ($)	Mar. 07, 2019 USD ($)	Mar. 07, 2019 CAD ($)
Derivative [Line Items]
Short-term borrowings				$ 3,000,000,000.0		$ 0
Derivative, gain (loss) on derivative, net				(137,000,000)	$ (425,000,000)
Not Designated as Hedging Instrument [Member] | Forward Contracts [Member]
Derivative [Line Items]
Derivative asset, notional amount							$ 1,800,000,000	$ 2.4
Derivative, gain (loss) on derivative, net					$ 31,000,000
Cronos Group Inc. [Member]
Derivative [Line Items]
Equity method investments, purchase price	$ 1,800,000,000	$ 2.4	$ 2.4
Foreign Currency Denominated Debt [Member]
Derivative [Line Items]
Debt instrument, fair value disclosure				4,595,000,000		5,057,000,000
Long-term debt				4,666,000,000		4,741,000,000
Net Investment Hedging [Member] | Foreign currency contracts [Member]
Derivative [Line Items]
Derivative, notional amount				2,246,000,000		2,246,000,000
Reported Value Measurement [Member]
Derivative [Line Items]
Long-term debt, fair value				27,000,000,000.0		28,000,000,000.0
Fair Value, Inputs, Level 2 [Member] | Estimate of Fair Value Measurement [Member]
Derivative [Line Items]
Long-term debt, fair value				$ 28,300,000,000		$ 30,700,000,000