XML 83 R51.htm IDEA: XBRL DOCUMENT v3.21.1

Decommissioning Liabilities (Details) - Provision for decommissioning, restoration and rehabilitation costs [member] - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Reconciliation of changes in other provisions [abstract]
Beginning balance	$ 59.0	$ 44.9
Reclamation expenditures		(2.0)
Accretion expense	2.6	2.8
Reclamation, Care and Maintenance Expenses	3.5	1.9
Revisions to expected discounted cash flows	17.1	13.3
Ending balance	$ 75.2	$ 59.0

X

- Definition

Reclamation Expenses

+ References

No definition available.

+ Details

Name:	agi_ReclamationExpenses
Namespace Prefix:	agi_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

X

- Definition

The increase (decrease) in other provisions resulting from a change in discount rate. [Refer: Other provisions]

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 37
-IssueDate 2020-01-01
-Paragraph 84
-Subparagraph e
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=37&code=ifrs-tx-2020-en-r&anchor=para_84_e&doctype=Standard
-URIDate 2020-01-01

+ Details

Name:	ifrs-full_IncreaseDecreaseThroughChangeInDiscountRateOtherProvisions
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

X

- Definition

The increase in other provisions through adjustments arising from the passage of time. [Refer: Other provisions]

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 37
-IssueDate 2020-01-01
-Paragraph 84
-Subparagraph e
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=37&code=ifrs-tx-2020-en-r&anchor=para_84_e&doctype=Standard
-URIDate 2020-01-01

+ Details

Name:	ifrs-full_IncreaseDecreaseThroughTimeValueOfMoneyAdjustmentOtherProvisions
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

X

- Definition

The amount of provisions other than provisions for employee benefits. [Refer: Provisions]

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 37
-IssueDate 2020-01-01
-Paragraph 84
-Subparagraph a
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=37&code=ifrs-tx-2020-en-r&anchor=para_84_a&doctype=Standard
-URIDate 2020-01-01

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 1
-IssueDate 2020-01-01
-Paragraph 78
-Subparagraph d
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=1&code=ifrs-tx-2020-en-r&anchor=para_78_d&doctype=Standard
-URIDate 2020-01-01

+ Details

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

X

- Definition

The amount used (ie incurred and charged against the provision) for other provisions. [Refer: Other provisions]

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 37
-IssueDate 2020-01-01
-Paragraph 84
-Subparagraph c
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=37&code=ifrs-tx-2020-en-r&anchor=para_84_c&doctype=Standard
-URIDate 2020-01-01

+ Details

Name:	ifrs-full_ProvisionUsedOtherProvisions
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

X

- References

No definition available.

+ Details

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

X

- Details

Name:	ifrs-full_ClassesOfProvisionsAxis=ifrs-full_ProvisionForDecommissioningRestorationAndRehabilitationCostsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: