Summary of Significant Accounting Policies - Schedule of Revenue by Product Including Price Concessions (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Disaggregation of Revenue [Line Items]
Revenue recognized	$ 137,683	$ 168,501	$ 511,325	$ 472,224
Implicit price concessions included in total revenue	12,370	15,363	38,861	50,051
Aligner revenue, net of implicit price concessions
Disaggregation of Revenue [Line Items]
Revenue recognized	108,273	139,279	418,590	388,111
Financing revenue, net of implicit price concessions
Disaggregation of Revenue [Line Items]
Revenue recognized	10,887	12,042	33,140	37,428
Retainers and other products revenue
Disaggregation of Revenue [Line Items]
Revenue recognized	$ 18,523	$ 17,180	$ 59,595	$ 46,685