Revenue Recognition - Deferred Revenue and Customer Deposits Rollforward (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Customer Contracts Liability, Current
Beginning balance	$ 14,432	$ 9,845
Deferred revenue and customer deposits	120,008	53,422
Recognition of revenue	(114,014)	(48,730)
Foreign exchange rate changes	848	(105)
End balance	$ 21,274	$ 14,432