Summary of Business and Significant Accounting Policies (Tables)

9 Months Ended

Sep. 30, 2012

Summary of Business and Significant Accounting Policies [Abstract]

Property and equipment, net estimated useful lives

Computer equipment and software	3-5 years
Furniture and fixtures	3-5 years
Leasehold improvements	Shorter of the lease term or estimated useful life

Fair value of stock option grant and stock purchase right granted under ESPP estimated on date of grant using Black-Scholes option pricing model

	Three Months  Ended September 30,		Nine Months  Ended September 30,
	2012	2011	2012	2011
Stock Options:
Expected volatility	54%	57% - 69%	54% - 57%	50% - 69%
Expected term (in years)	6.05	5.66	6.05	5.83
Risk-free interest rate	0.87% - 0.93%	0.00% - 3.03%	0.87% - 1.18%	0.00% - 3.03%
Dividend yield	—  %	—  %	—  %	—  %

	Three and Nine Months Ended
	September 30, 2012
ESPP:
Expected volatility		42	%
Expected term (in years)		0.58
Risk-free interest rate		0.16	%
Dividend yield		—	%

Changes in the allowance for doubtful accounts

	September 30, 2012
Balance at December 31, 2011	$	—
Add: bad debt expense		160
Less: recoveries		(12	)
Balance at end of period	$	148