BALANCE FROM CONTRACTS WITH CUSTOMERS - Narrative (Details) - CAD ($) $ in Millions	12 Months Ended
Mar. 31, 2021	Mar. 31, 2020
Disclosure of disaggregation of revenue from contracts with customers [line items]
Revenue that was included in contract liability balance	$ 517.7	$ 532.2
(Reversal of) revenue from performance obligations satisfied or partially satisfied in previous periods	(8.9)	$ 29.8
Remaining performance obligations	$ 4,438.7
No later than 1 year
Disclosure of disaggregation of revenue from contracts with customers [line items]
Percentage of entity's revenue expected to be recognised	35.00%
Later than one year
Disclosure of disaggregation of revenue from contracts with customers [line items]
Percentage of entity's revenue expected to be recognised	21.00%

Revenue, Remaining Performance Obligation, Percentage

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- Definition

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

+ References

No definition available.

+ Details

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- Definition

The amount of revenue from performance obligations satisfied (or partially satisfied) in previous periods. [Refer: Performance obligations [member]; Revenue from contracts with customers]

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IFRS
-Number 15
-IssueDate 2020-01-01
-Paragraph 116
-Subparagraph c
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IFRS&num=15&code=ifrs-tx-2020-en-r&anchor=para_116_c&doctype=Standard
-URIDate 2020-01-01

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- Definition

The amount of revenue that was included in the contract liability balance at the beginning of the period. [Refer: Contract liabilities; Revenue from contracts with customers]

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IFRS
-Number 15
-IssueDate 2020-01-01
-Paragraph 116
-Subparagraph b
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IFRS&num=15&code=ifrs-tx-2020-en-r&anchor=para_116_b&doctype=Standard
-URIDate 2020-01-01

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- Definition

The amount of the transaction price allocated to the performance obligations that are unsatisfied (or partially unsatisfied) as of the end of the reporting period. The transaction price is the amount of consideration to which an entity expects to be entitled in exchange for transferring promised goods or services to a customer, excluding amounts collected on behalf of third parties (for example, some sales taxes). [Refer: Performance obligations [member]]

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IFRS
-Number 15
-IssueDate 2020-01-01
-Paragraph 120
-Subparagraph a
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-URIDate 2020-01-01

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