Inventory - Summary of Inventory (Detail) - CAD ($) $ in Thousands	Apr. 30, 2018	Apr. 30, 2017
Inventories [abstract]
Dore	$ 955	$ 922
Goods in transit	376	429
Work-in-process	662	377
Concentrate	595	189
Stockpile	118	196
Supplies	793	808
Inventory	$ 3,499	$ 2,921

A classification of current inventory representing the amount of inventories in transit. [Refer: Inventories]

Name:	ifrs-full_CurrentInventoriesInTransit
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

A classification of current inventory representing the amount of ore stockpiles. [Refer: Inventories]

+ References

+ Details

Name:	ifrs-full_CurrentOreStockpiles
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

The amount of current inventories. [Refer: Inventories]

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 2
-IssueDate 2017-01-01
-Paragraph 36
-Subparagraph b
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=2&date=2017-03-01&anchor=para_36_b&doctype=Standard
-URIDate 2017-03-09

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 1
-IssueDate 2017-01-01
-Paragraph 54
-Subparagraph g
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=1&date=2017-03-01&anchor=para_54_g&doctype=Standard
-URIDate 2017-03-09

Reference 3: http://www.xbrl.org/2003/role/exampleRef
-Name IAS
-Number 1
-IssueDate 2017-01-01
-Paragraph 68
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=1&date=2017-03-01&anchor=para_68&doctype=Standard
-URIDate 2017-03-09

+ Details

Name:	ifrs-full_Inventories
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

A classification of current inventory representing the amount of supplies to be used for the production process. [Refer: Inventories]

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Name IAS
-Number 2
-IssueDate 2017-01-01
-Paragraph 37
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=2&date=2017-03-01&anchor=para_37&doctype=Standard
-URIDate 2017-03-09

Reference 2: http://www.xbrl.org/2003/role/exampleRef
-Name IAS
-Number 1
-IssueDate 2017-01-01
-Paragraph 78
-Subparagraph c
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=1&date=2017-03-01&anchor=para_78_c&doctype=Standard
-URIDate 2017-03-09

+ Details

Name:	ifrs-full_ProductionSupplies
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

A classification of current inventory representing the amount of assets currently in production, which require further processes to be converted into finished goods or services. [Refer: Current finished goods; Inventories]

+ References

+ Details

Name:	ifrs-full_WorkInProgress
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Current concentrate inventories.

+ References

No definition available.

+ Details

Name:	sam_CurrentConcentrateInventories
Namespace Prefix:	sam_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Inventories [abstract]

+ References

No definition available.

+ Details

Name:	sam_InventoriesAbstract
Namespace Prefix:	sam_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Inventories product in dore.

+ References

No definition available.

+ Details

Name:	sam_InventoriesProductInDore
Namespace Prefix:	sam_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant