Deferred Revenue (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Deferred Revenue Arrangement [Line Items]
Deferred revenue, advances received	$ 12,225	$ 31,625
Deferred revenue	50,634	113,319	$ 118,414
Deferred revenue, current	$ 15,111	$ 31,612
Supply Agreement | Minimum
Deferred Revenue Arrangement [Line Items]
Deferred revenue, average initial contract term	one
Supply Agreement | Maximum
Deferred Revenue Arrangement [Line Items]
Deferred revenue, average initial contract term	fifteen