XML 96 R64.htm IDEA: XBRL DOCUMENT v3.21.1

Share Capital (Other employee long-term incentives) (Details) - shares	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Restricted share units ("RSU")
Disclosure of classes of share capital [line items]
Shares outstanding	1,666,825	1,567,696
Granted	851,453	832,366
Forfeiture	(201,954)	(305,300)
Settled	(347,733)	(427,937)
Shares outstanding	1,968,591	1,666,825
Stock appreciation rights ("SAR")
Disclosure of classes of share capital [line items]
Shares outstanding	91,307	509,192
Granted	0	0
Forfeiture	(13,195)	(309,566)
Settled	(78,112)	(108,319)
Shares outstanding	0	91,307
Deferred share units ("DSU")
Disclosure of classes of share capital [line items]
Shares outstanding	688,427	645,413
Granted	176,418	208,882
Forfeiture	0	0
Settled	0	(165,868)
Shares outstanding	864,845	688,427
Performance share units ("PSU")
Disclosure of classes of share capital [line items]
Shares outstanding	1,082,153	983,441
Granted	475,623	423,628
Forfeiture	(75,892)	0
Settled	(247,866)	(324,916)
Shares outstanding	1,234,018	1,082,153

X

- Definition

Number Of Other Equity Instruments Settled In Share-Based Payment Arrangement

+ References

No definition available.

+ Details

Name:	agi_NumberOfOtherEquityInstrumentsSettledInShareBasedPaymentArrangement
Namespace Prefix:	agi_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

X

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

X

- Definition

The number of other equity instruments (ie other than share options) granted in a share-based payment arrangement.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IFRS
-Number 2
-IssueDate 2020-01-01
-Paragraph 47
-Subparagraph b
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IFRS&num=2&code=ifrs-tx-2020-en-r&anchor=para_47_b&doctype=Standard
-URIDate 2020-01-01

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Name IFRS
-Number 2
-IssueDate 2020-01-01
-Paragraph 45
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IFRS&num=2&code=ifrs-tx-2020-en-r&anchor=para_45&doctype=Standard
-URIDate 2020-01-01

+ Details

Name:	ifrs-full_NumberOfInstrumentsOtherEquityInstrumentsGranted
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:decimalItemType
Balance Type:	na
Period Type:	duration

X

- Definition

The number of other equity instruments (ie other than share options) forfeited in a share-based payment arrangement.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Name IFRS
-Number 2
-IssueDate 2020-01-01
-Paragraph 45
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IFRS&num=2&code=ifrs-tx-2020-en-r&anchor=para_45&doctype=Standard
-URIDate 2020-01-01

+ Details

Name:	ifrs-full_NumberOfOtherEquityInstrumentsForfeitedInSharebasedPaymentArrangement
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:decimalItemType
Balance Type:	na
Period Type:	duration

X

- Definition

The number of other equity instruments (ie other than share options) outstanding in a share-based payment arrangement.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Name IFRS
-Number 2
-IssueDate 2020-01-01
-Paragraph 45
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IFRS&num=2&code=ifrs-tx-2020-en-r&anchor=para_45&doctype=Standard
-URIDate 2020-01-01

+ Details

Name:	ifrs-full_NumberOfOtherEquityInstrumentsOutstandingInSharebasedPaymentArrangement
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:decimalItemType
Balance Type:	na
Period Type:	instant

X

- Details

Name:	ifrs-full_TypesOfSharebasedPaymentArrangementsAxis=agi_RestrictedShareUnitsRSUMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	ifrs-full_TypesOfSharebasedPaymentArrangementsAxis=agi_StockAppreciationRightsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	ifrs-full_TypesOfSharebasedPaymentArrangementsAxis=agi_DeferredShareUnitsDSUMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	ifrs-full_TypesOfSharebasedPaymentArrangementsAxis=agi_PerformanceShareUnitsPSUMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: