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Balance Sheet Components - Property and Equipment, net (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Sep. 30, 2019	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Property and Equipment, net
Property and equipment, gross		$ 64,807	$ 58,633
Less: Accumulated depreciation and amortization		(41,524)	(34,297)
Total Property and Equipment, net		23,283	24,336
Impairment		1,671	1,544	$ 576
Impairment of leasehold improvements	$ 1,200	1,200
Impairment of capitalized software	100	100
Impairment of right-of-use assets		400
Selling, general and administrative
Property and Equipment, net
Impairment	$ 1,700	1,700
Research and development
Property and Equipment, net
Impairment			1,500
Machinery and equipment
Property and Equipment, net
Property and equipment, gross		36,414	35,400
Furniture and fixtures
Property and Equipment, net
Property and equipment, gross		$ 1,376	1,319
Useful Life		3 years
Computer equipment
Property and Equipment, net
Property and equipment, gross		$ 1,828	2,117
Useful Life		3 years
Capitalized software held for internal use
Property and Equipment, net
Property and equipment, gross		$ 5,917	4,868
Useful Life		3 years
Impairment of capitalized software		$ 100
Leasehold improvements
Property and Equipment, net
Property and equipment, gross		11,556	10,916
Construction-in-process
Property and Equipment, net
Property and equipment, gross		$ 7,716	$ 4,013
Minimum \| Machinery and equipment
Property and Equipment, net
Useful Life		3 years
Maximum \| Machinery and equipment
Property and Equipment, net
Useful Life		5 years