Supplementary Cash Flow Information - Additional Information (Details) - CAD ($) $ in Thousands	12 Months Ended
Mar. 31, 2018	Mar. 31, 2017
Disclosure Of Cash Flow Statement [Abstract]
Accounts payable and accrued liabilities	$ 49,679	$ 3,860
Property, plant and equipment and assets in process purchases	49,627	3,770
Share issue costs	52	90
Accounts payable and accrued liabilities, recognized	3,860	946
Property, plant and equipment and assets in process purchases, recognized	3,770	877
Share issue costs, recognized	$ 90	$ 69

Purchases of property, plant, and equipment and assets in process that remain in accounts payable or accrued liabilities at period end.

No definition available.

Name:	cgc_AccountsPayableAndAccruedLiabilitiesRelatingToPropertyPlantAndEquipmentAndAssetsInProcessPurchases
Namespace Prefix:	cgc_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

Purchases of property, plant, and equipment and assets in process that remain in accounts payable or accrued liabilities recognized at period end.

No definition available.

Name:	cgc_AccountsPayableAndAccruedLiabilitiesRelatingToPropertyPlantAndEquipmentAndAssetsInProcessPurchasesRecognized
Namespace Prefix:	cgc_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

Share issue costs that were incurred and expensed and remain in accounts payable or accrued liabilities at period end.

No definition available.

Name:	cgc_AccountsPayableAndAccruedLiabilitiesRelatingToShareIssueCosts
Namespace Prefix:	cgc_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

Share issue costs that were incurred and expensed and remain in accounts payable or accrued liabilities recognized at period end.

No definition available.

Name:	cgc_AccountsPayableAndAccruedLiabilitiesRelatingToShareIssueCostsRecognized
Namespace Prefix:	cgc_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

Disclosure of cash flow statement.

No definition available.

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

Accounts payable and accrued liability balances that relate specifically to financing and investing activities.

No definition available.

Name:	cgc_NonCashAccountsPayableAndAccruedLiabilitiesRelatingToFinancingAndInvestingActivities
Namespace Prefix:	cgc_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

Accounts payable and accrued liability balances that relate specifically to financing and investing activities recognized.

No definition available.

Name:	cgc_NonCashAccountsPayableAndAccruedLiabilitiesRelatingToFinancingAndInvestingActivitiesRecognized
Namespace Prefix:	cgc_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration