Expected Credit Losses - Type Of Customer Receivable (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Expected Credit Losses
Accounts receivable and notes receivable, current	$ 2,425	$ 2,105
Contract assets, net	1,409	794
Long-term notes receivable, net of current portion	259	477
Total allowance for expected credit losses on customer receivables	$ 4,093	$ 3,376