XML 74 R43.htm IDEA: XBRL DOCUMENT
v3.19.1

Acquisition of Richmond Mines Ltd. (Narrative) (Details) - Richmont Mines Ltd [Member] $ in Millions | Nov. 23, 2017 USD ($) shares
--- | ---
Disclosure of detailed information about business combination [line items] |
Conversion of Richmont units to Alamos units (note 5) | shares | 88,398,804
Number of shares issued, business combination, value | $ 615.3
Share based compensation, acquisitions | $ 12.1
Ordinary shares [member] |
Disclosure of detailed information about business combination [line items] |
Conversion ratio of shares | 1.385

X
- Definition Acquisitions Through Business Combinations, Share Based Compensation + References No definition available. + Details
Name: | agi_AcquisitionsThroughBusinessCombinationsShareBasedCompensation
Namespace Prefix: | agi_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Business Combination, Shares Issued, Value + References No definition available. + Details
Name: | agi_BusinessCombinationSharesIssuedValue
Namespace Prefix: | agi_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Business Combinations, Conversion Ratio of Shares + References No definition available. + Details
Name: | agi_BusinessCombinationsConversionRatioofShares
Namespace Prefix: | agi_
Data Type: | xbrli:pureItemType
Balance Type: | na
Period Type: | instant

X
- Definition Number of Shares Issued, Business Combination + References No definition available. + Details
Name: | agi_NumberofSharesIssuedBusinessCombination
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_DisclosureOfBusinessCombinationsLineItems
Namespace Prefix: | ifrs-full_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | ifrs-full_BusinessCombinationsAxis=agi_RichmontMinesLtdMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | ifrs-full_ClassesOfShareCapitalAxis=ifrs-full_OrdinarySharesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |