Financial Instruments (Narrative) (Details) $ in Millions, $ in Billions		1 Months Ended		3 Months Ended			9 Months Ended
	Mar. 31, 2019 CAD ($)	Mar. 31, 2019 USD ($)	Mar. 31, 2019 CAD ($)	Sep. 30, 2020 USD ($)	Sep. 30, 2019 USD ($)	Mar. 31, 2019 USD ($)	Sep. 30, 2020 USD ($)	Sep. 30, 2019 USD ($)	Dec. 31, 2019 USD ($)	Mar. 31, 2019 CAD ($)
Derivative [Line Items]
Long-term debt				$ 29,300			$ 29,300		$ 28,000
Loss on Cronos-related financial instruments				105	$ 636		202	$ 1,327
Not Designated as Hedging Instrument [Member] | Forward Contracts [Member]
Derivative [Line Items]
Derivative asset, notional amount		$ 1,800				$ 1,800				$ 2.4
Loss on Cronos-related financial instruments						$ 31
Cronos [Member]
Derivative [Line Items]
Equity method investments, purchase price	$ 2.4	$ 1,800	$ 2.4
Foreign Currency Denominated Debt [Member]
Derivative [Line Items]
Debt instrument, fair value disclosure				5,368			5,368		5,057
Long-term debt				4,960			4,960		4,741
Net Investment Hedging [Member] | Foreign currency contracts [Member]
Derivative [Line Items]
Derivative, notional amount				1,402			1,402		2,246
Reported Value Measurement [Member]
Derivative [Line Items]
Long-term debt, fair value				29,300			29,300		28,000
Fair Value, Inputs, Level 2 [Member] | Estimate of Fair Value Measurement [Member]
Derivative [Line Items]
Long-term debt, fair value				$ 33,800			$ 33,800		$ 30,700