Unaudited Quarterly Financial data and Restatement of Previously Issued Unaudited interim Condensed Consolidated Financial Statements - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended							6 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2020	Jun. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Right of use assets obtained in exchange for new operating lease liabilities												$ 58,500	$ 37,700
Research and development	$ 7,386	$ 4,873	$ 4,774	$ 4,882	$ 3,563	$ 3,608	$ 3,006	$ 9,647	$ 6,614	$ 17,033	$ 10,177	$ 27,848	15,059	$ 12,750
As previously Reported
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Research and development	11,964	9,757	10,412	9,341	8,028	8,933	7,373	20,169	16,306	32,133	24,334		33,675	33,907
Restatement Adjustments
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Research and development	$ (4,578)	$ (4,884)	$ (5,638)	(4,459)	$ (4,465)	$ (5,325)	$ (4,367)	$ (10,522)	$ (9,692)	$ (15,100)	$ (14,157)		(18,616)	(21,157)
Cost of Revenue													19,492	$ 21,157
Other Adjustments
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Research and development				$ 876									$ 876