Balance Sheet Components - Schedule of Intangible Assets (Details) - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2008
Intangible assets, net
Acquired intangible assets	$ 910,000	$ 910,000		$ 910,000
Less: accumulated amortization	(910,000)	(778,000)
Total intangible assets, net		132,000
Amortization of intangible assets	$ 132,000	$ 150,000	$ 182,000