Investments in Equity Securities (Investment in Cronos Narrative) (Details) $ / shares in Units, shares in Millions, $ in Millions, $ in Billions				6 Months Ended
	Mar. 31, 2019 USD ($) shares	Mar. 31, 2019 CAD ($)	Mar. 07, 2019 CAD ($)	Jun. 30, 2019 USD ($) director board_member shares	Mar. 31, 2019 $ / shares
Investment [Line Items]
Payments to acquire equity method investments				$ 1,832
Cronos Group Inc. [Member]
Investment [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	$ 2.4	$ 2.4
Equity method investment, warrant exercised, ownership percentage (approximately)	55.00%	55.00%
Payments to acquire equity method investments	$ 400
Payments for deferred tax liability	300
Number of directors nominated | director				4
Number of members on the Board of Directors | board_member				7
Equity Contract, Preemptive Rights [Member] | Cronos Group Inc. [Member]
Investment [Line Items]
Equity method investment, shares purchased, (CAD per share) | $ / shares					$ 16.25
Equity method investment, number of shares eligible for purchase (in shares) | shares				40.0
Payments for derivative instrument, investing activities	$ 500
Equity Contract, Warrant [Member]
Investment [Line Items]
Equity method investment, percentage of shares eligible for purchase	10.00%
Equity Contract, Warrant [Member] | Cronos Group Inc. [Member]
Investment [Line Items]
Equity method investment, shares purchased, (CAD per share) | $ / shares					$ 19.00
Equity method investment, number of shares eligible for purchase (in shares) | shares	75.0
Payments for derivative instrument, investing activities	$ 1,200