Long-term Debt and Other Long-Term Liabilities - Additional Information (Details) - CAD ($)	12 Months Ended
Mar. 31, 2018	Mar. 31, 2017
Annual Interest Rate 4.9% Mortgage Payable Due August 1, 2021
Disclosure Of Detailed Information About Borrowings [Line Items]
Borrowings, maturity	August 1, 2021	August 1, 2021
Interest rate	4.90%	4.90%
Annual Interest Rate of 5.3% Mortgage Payable Due December 1, 2019
Disclosure Of Detailed Information About Borrowings [Line Items]
Borrowings, maturity	December 1, 2019	December 1, 2019
Interest rate	5.30%	5.30%
Annual Interest Rate of 4.8% Mortgage Payable Due December 1, 2020
Disclosure Of Detailed Information About Borrowings [Line Items]
Borrowings, maturity	December 1, 2020	December 1, 2020
Interest rate	4.80%	4.80%
Revolving Line of Credit \| Canada \| CIBC Prime Rate
Disclosure Of Detailed Information About Borrowings [Line Items]
Description of variable interest basis	CIBC prime rate plus 1.2%	CIBC prime rate plus 1.2%
Adjustment to Prime Rate for Borrowings	1.20%	1.20%
Variable interest rate term	5 years	5 years
Revolving Line of Credit \| Canada \| Maximum
Disclosure Of Detailed Information About Borrowings [Line Items]
Revolving lines of credit	$ 5,500,000	$ 5,500,000
Term Loan 10% Due October 1, 2024
Disclosure Of Detailed Information About Borrowings [Line Items]
Borrowings, maturity	October 1, 2024	October 1, 2024
Interest rate	10.00%	10.00%
Term of mortgage payable	10 years
Rent expenses	$ 27,000

Amount of additional rent associated with lease agreement.

No definition available.

Name:	cgc_AdditionalMonthlyRent
Namespace Prefix:	cgc_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Amended lease term.

+ References

No definition available.

+ Details

Name:	cgc_AmendedLeaseTerm
Namespace Prefix:	cgc_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Description of variable interest basis.

+ References

No definition available.

+ Details

Name:	cgc_DescriptionOfVariableInterestBasis
Namespace Prefix:	cgc_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Variable interest rate term.

+ References

No definition available.

+ Details

Name:	cgc_VariableInterestRateTerm
Namespace Prefix:	cgc_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

The adjustment to the basis (reference rate) used for calculation of the interest rate on borrowings. [Refer: Borrowings]

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Name IFRS
-Number 7
-IssueDate 2017-01-01
-Paragraph 7
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IFRS&num=7&date=2017-03-01&anchor=para_7&doctype=Standard
-URIDate 2017-03-09

+ Details

Name:	ifrs-full_BorrowingsAdjustmentToInterestRateBasis
Namespace Prefix:	ifrs-full_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

The interest rate on borrowings. [Refer: Borrowings]

+ References

+ Details

Name:	ifrs-full_BorrowingsInterestRate
Namespace Prefix:	ifrs-full_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

The maturity of borrowings. [Refer: Borrowings]

+ References

+ Details

Name:	ifrs-full_BorrowingsMaturity
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- 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

Name:	ifrs-full_DisclosureOfDetailedInformationAboutBorrowingsLineItems
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

The amount of undrawn borrowing facilities that may be available for future operating activities and to settle capital commitments. [Refer: Capital commitments]

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Name IAS
-Number 7
-IssueDate 2017-01-01
-Paragraph 50
-Subparagraph a
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=7&date=2017-03-01&anchor=para_50_a&doctype=Standard
-URIDate 2017-03-09

+ Details

Name:	ifrs-full_UndrawnBorrowingFacilities
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Details

Name:	ifrs-full_BorrowingsByNameAxis=cgc_FourPointNinePercentAnnualInterestRateMortgagePayableDueAugustOneTwoThousandTwentyOneMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	ifrs-full_BorrowingsByNameAxis=cgc_FivePointThreePercentAnnualInterestRateMortgagePayableDueDecemberOneTwoThousandNineteenMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	ifrs-full_BorrowingsByNameAxis=cgc_FourPointEightPercentAnnualInterestRateMortgagePayableDueDecemberOneTwoThousandTwentyMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	ifrs-full_BorrowingsByNameAxis=cgc_RevolvingLineOfCreditMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	ifrs-full_GeographicalAreasAxis=country_CA
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	ifrs-full_TypesOfInterestRatesAxis=cgc_CIBCPrimeRateMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	ifrs-full_RangeAxis=ifrs-full_TopOfRangeMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	ifrs-full_BorrowingsByNameAxis=cgc_TenPercentTermLoanDueOctoberOneTwoThousandTwentyFourMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: