Investments in Equity Securities (Investment in Cronos Narrative) (Details) - Cronos Group Inc. [Member] $ / shares in Units, shares in Millions, $ in Billions			6 Months Ended
	Mar. 31, 2019 USD ($) shares	Mar. 31, 2019 CAD ($)	Jun. 30, 2020 USD ($) director board_member shares	Jun. 30, 2020 CAD ($)	Dec. 31, 2019 USD ($)	Mar. 31, 2019 $ / shares
Investments [Line Items]
Number of ordinary shares owned (approximately) (in shares) | shares	149.8
Ownership percentage (approximately)	45.00%		45.00%
Equity method investments, purchase price	$ 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			$ 1,223,000,000		$ 1,305,000,000
Equity method investment, difference between carrying amount and fair value, percentage (approximately)			(7.00%)	(7.00%)
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			36.0
Payments for derivative instrument, investing activities	$ 500,000,000
Equity method investment, aggregate exercise price			$ 400,000,000	$ 0.6
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			78.0
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			$ 1,100,000,000	$ 1.5
Common Stock [Member]
Investments [Line Items]
Equity method investments			1,017,000,000		1,002,000,000
Equity method investment, impairment			0
Fair Value, Inputs, Level 1 [Member]
Investments [Line Items]
Fair value of equity investment			$ 900,000,000		$ 1,200,000,000