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Investments and Fair Value Measurements Investments in Privately Held Companies (Details) - USD ($) $ in Thousands | 3 Months Ended
--- | ---
Mar. 31, 2020 | Mar. 31, 2019
Debt Securities, Available-for-sale [Line Items] |  |
Impairments on long-lived assets | $ 2,900 | $ 3,975

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- Definition Impairments Of Equity Investments + References No definition available. + Details
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Namespace Prefix: | algn_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

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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_ScheduleOfAvailableForSaleSecuritiesLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration