Balance Sheet Components - Prepaid Expenses and Other Current Assets (Details) (USD $)	Sep. 30, 2014		Dec. 31, 2013
Balance Sheet Components [Abstract]
Prepaid expenses and deposits for inventory	$ 3,525,000		$ 3,426,000
Other current assets	377,000	[1]	776,000	[1]
Prepaid expenses and other current assets	3,902,000		4,202,000
Rebate receivable			$ 500,000

[1] Other current assets at December 31, 2013, included a rebate receivable of approximately $0.5 million.