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v3.19.2

Basis of Financial Statement Presentation (Details) $ in Thousands | Jan. 01, 2019 USD ($)
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Organization, Consolidation and Presentation of Financial Statements [Abstract] |
Right-of-use asset recognized | $ 7,747
Lease liability recognized | $ 7,868

X
- Definition Operating and Finance Lease, Liability + References No definition available. + Details
Name: | alg_OperatingAndFinanceLeaseLiability
Namespace Prefix: | alg_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Operating and Finance Lease, Right-of-Use Asset + References No definition available. + Details
Name: | alg_OperatingAndFinanceLeaseRightofUseAsset
Namespace Prefix: | alg_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

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- References No definition available. + Details
Name: | us-gaap_OrganizationConsolidationAndPresentationOfFinancialStatementsAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration