Income Taxes - Change In Valuation Allowance (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Change in valuation allowance
Increase in valuation allowance for current year increase in net operating losses	$ 51,848
Increase (decrease) in valuation allowance for current year net increase (decrease) in deferred tax assets other than net operating losses	(5,609)
Decrease in valuation allowance as a result of foreign currency fluctuation	6,306
Increase in valuation allowance due to change in tax rates	372
Net increase in valuation allowance	52,917	$ 16,416	$ 12,503
U.S.
Change in valuation allowance
Increase in valuation allowance for current year increase in net operating losses	51,848
Increase (decrease) in valuation allowance for current year net increase (decrease) in deferred tax assets other than net operating losses	(5,742)
Decrease in valuation allowance as a result of foreign currency fluctuation	6,306
Net increase in valuation allowance	52,412	15,720	12,771
Foreign
Change in valuation allowance
Increase (decrease) in valuation allowance for current year net increase (decrease) in deferred tax assets other than net operating losses	133
Increase in valuation allowance due to change in tax rates	372
Net increase in valuation allowance	$ 505	$ 696	$ (268)