Stock-Based Compensation (Details) (Stock option, USD $) Share data in Thousands, except Per Share data, unless otherwise specified	3 Months Ended	6 Months Ended
	Jun. 30, 2013	Jun. 30, 2013
Stock option
Summary of stock option activity - Shares
Options outstanding at the beginning of the period (in shares)		3,899
Exercised (in shares)		(12)
Cancelled (in shares)		(8)
Options outstanding at the end of the period (in shares)	3,879	3,879
Options exercisable at the end of the period (in shares)	2,078	2,078
Options vested and expected to vest at the end of the period (in shares)	3,727	3,727
Summary of stock option activity - Weighted-Average Exercise Price (in dollars per share)
Options outstanding at the beginning of the period (in dollars per share)		$ 3.10
Exercised (in dollars per share)		$ 1.10
Cancelled (in dollars per share)		$ 3.22
Options outstanding at the end of the period (in dollars per share)	$ 3.11	$ 3.11
Options exercisable at the end of the period (in dollars per share)	$ 2.57	$ 2.57
Options vested and expected to vest at the end of the period (in dollars per share)	$ 3.08	$ 3.08
Weighted-Average Contractual Life (In Years)
Options outstanding at the end of the period		7 years 6 months 29 days
Options exercisable at the end of the period		6 years 9 months 25 days
Options vested and expected to vest at the end of the period		7 years 6 months 14 days
Aggregate Intrinsic Value
Options outstanding at the end of the period (in dollars)	$ 1,568,000	$ 1,568,000
Options exercisable at the end of the period (in dollars)	1,505,000	1,505,000
Options vested and expected to vest at the end of the period (in dollars)	1,565,000	1,565,000
Additional disclosures
Total grant date fair value of stock options vested	$ 700,000	$ 1,500,000