Investments and Fair Value Measurements Additional Information (Details)			6 Months Ended
Jun. 30, 2019	Dec. 31, 2018	Jun. 30, 2019
Investments, Debt and Equity Securities [Abstract]
Original maturity of highly liquid investments included in cash and cash equivalents			40 months
Weighted average maturity	7 months	4 months

Marketable Securities, Weighted Average Remaining Maturity, At Period End

No definition available.

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Namespace Prefix:	algn_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration