Revenue From Contracts With Customers - Summary of Allowance for Notes Receivable (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020
Financing Receivable Allowance For Credit Losses [Line Items]
Beginning balance	$ 18
Accounting Standards Update [Extensible List]		us-gaap:AccountingStandardsUpdate201613Member
Provision for credit losses	(6)	$ 1
Ending balance	$ 12	20
Cumulative Effect, Period of Adoption, Adjustment
Financing Receivable Allowance For Credit Losses [Line Items]
Beginning balance		$ 19