Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 460
-SubTopic 10
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-Section 50
-Paragraph 3
-Publisher FASB
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Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 450
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-Name Accounting Standards Codification
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-Publisher FASB
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Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 450
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Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 450
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-Section 50
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-URI https://asc.fasb.org//1943274/2147483076/450-20-50-4

Reference 5: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 450
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
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-URI https://asc.fasb.org//1943274/2147483076/450-20-50-9

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Topic 450
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-Name Accounting Standards Codification
-Section 50
-Paragraph 9
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-Publisher FASB
-URI https://asc.fasb.org//1943274/2147483076/450-20-50-9

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Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

Contingencies: (Third-Party Guarantees) (Details) $ in Millions, $ in Millions	Aug. 31, 2022 CAD ($)	Aug. 31, 2022 USD ($)	Mar. 31, 2022 CAD ($)	Mar. 31, 2022 USD ($)	Oct. 17, 2020 CAD ($)	Oct. 17, 2020 USD ($)
Canadian Government
Loss Contingencies [Line Items]
Project contribution from government			$ 27	$ 22	$ 173	$ 131
Medicago Inc. \| Financial Guarantee
Loss Contingencies [Line Items]
Reduction of guarantee obligation	$ 123	$ 93