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Credit Facilities - Additional Information (Detail) (USD $)
12 Months Ended
Dec. 31, 2014
Mar. 22, 2013
Line of Credit Facility [Line Items]    
Line of credit, available borrowings   $ 50,000,000us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity
Current borrowing capacity   10,000,000us-gaap_LineOfCreditFacilityCurrentBorrowingCapacity
Minimum unrestricted cash balance requirement 50,000,000algn_MinimumUnrestrictedCashBalanceToBeMaintained  
Interest rate on borrowings at LIBOR plus, minimum 1.75%us-gaap_DebtInstrumentInterestRateStatedPercentageRateRangeMinimum  
Interest rate on borrowings at LIBOR plus, maximum 1.75%us-gaap_DebtInstrumentInterestRateStatedPercentageRateRangeMaximum  
Line of credit, amount outstanding $ 0us-gaap_LineOfCredit