CONDENSED BALANCE SHEETS (Parenthetical) (USD $) In Thousands, except Share data, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
CONDENSED BALANCE SHEETS
Accounts receivable, allowance (in dollars)	$ 364	$ 222
Convertible preferred stock, par value (in dollars per share)	$ 0.001	$ 0.001
Convertible preferred stock, shares authorized	60,187,700	59,147,999
Convertible preferred stock, shares issued	59,989,268	53,084,507
Convertible preferred stock, shares outstanding	59,989,268	53,084,507
Common stock, par value (in dollars per share)	$ 0.001	$ 0.001
Common stock, shares authorized	77,000,000	77,000,000
Common stock, shares issued	992,578	667,684
Common stock, shares outstanding	992,578	667,684