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Accounting Pronouncements (Details) - Accounting Standards Update 2016-02 $ in Thousands | Jan. 01, 2019 USD ($)
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New Accounting Pronouncements or Change in Accounting Principle [Line Items] |
Right-of-use asset recognized | $ 7,747
Lease liability recognized | $ 7,868

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- 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

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- 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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- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details
Name: | us-gaap_NewAccountingPronouncementsOrChangeInAccountingPrincipleLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

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- Details
Name: | us-gaap_AdjustmentsForNewAccountingPronouncementsAxis=us-gaap_AccountingStandardsUpdate201602Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |