Investments in Equity Securities (Investment in Cronos Narrative) (Details) - Cronos [Member] $ / shares in Units, shares in Thousands, $ in Billions			1 Months Ended		9 Months Ended
	Oct. 27, 2020 USD ($)	Mar. 31, 2019 CAD ($)	Mar. 31, 2019 USD ($) shares	Mar. 31, 2019 CAD ($)	Sep. 30, 2020 USD ($) director board_member shares	Sep. 30, 2020 CAD ($)	Jun. 30, 2020	Dec. 31, 2019 USD ($)	Mar. 31, 2019 $ / shares
Investments [Line Items]
Number of ordinary shares owned (approximately) (in shares) | shares			149,800		156,600
Ownership percentage (approximately)			45.00%		44.00%		45.00%
Equity method investments, purchase price		$ 2.4	$ 1,800,000,000	$ 2.4
Equity method investment, warrant exercised, ownership percentage (approximately)			55.00%	55.00%
Payments to acquire equity method investments			$ 400,000,000
Payments for deferred tax liability			300,000,000
Number of directors nominated | director					4
Equity method investment, number of independent directors nominated | director					1
Number of members on the Board of Directors | board_member					7
Equity method investments					$ 1,087,000,000			$ 1,305,000,000
Equity method investment, difference between carrying amount and fair value, percentage (approximately)					20.00%	20.00%
Equity Contract, Preemptive Rights [Member]
Investments [Line Items]
Equity method investment, shares purchased, (CAD per share) | $ / shares									$ 16.25
Equity method investment, number of shares eligible for purchase (approximately) (in shares) | shares					35,000
Payments for derivative instrument, investing activities			$ 500,000,000
Equity method investment, aggregate exercise price						$ 0.6
Equity Contract, Preemptive Rights [Member] | Subsequent Event [Member]
Investments [Line Items]
Equity method investment, aggregate exercise price	$ 400,000,000
Equity Contract, Warrant [Member]
Investments [Line Items]
Equity method investment, shares purchased, (CAD per share) | $ / shares									$ 19.00
Equity method investment, number of shares eligible for purchase (approximately) (in shares) | shares					79,000
Equity method investment, percentage of shares eligible for purchase			10.00%
Payments for derivative instrument, investing activities			$ 1,200,000,000
Equity method investment, aggregate exercise price						$ 1.5
Equity Contract, Warrant [Member] | Subsequent Event [Member]
Investments [Line Items]
Equity method investment, aggregate exercise price	$ 1,100,000,000
Common Stock [Member]
Investments [Line Items]
Equity method investments					$ 986,000,000			1,002,000,000
Equity method investment, impairment					0
Fair Value, Inputs, Level 1 [Member]
Investments [Line Items]
Fair value of equity investment					$ 800,000,000			$ 1,200,000,000