Stockholders' Equity - Summary of Stock Option Activity And Weighted Average Exercise Prices (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Options
Options outstanding, beginning balance (in shares)	9,144	10,769	9,724
Granted (in shares)	635	857	3,827
Exercised (in shares)	(325)	(646)	(1,098)
Cancelled or expired (in shares)	(1,685)	(1,837)	(1,684)
Options outstanding, ending balance (in shares)	7,769	9,144	10,769
Options vested and expected to vest	7,348	8,356	9,043
Options exercisable	5,580	5,401	4,737
Weighted Average Exercise Price
Options outstanding, beginning balance (in dollars per share)	$ 11.05	$ 10.95	$ 10.86
Granted (in dollars per share)	7.32	10.06	11.04
Exercised (in dollars per share)	5.66	4.41	7.10
Cancelled (in dollars per share)	11.49	12.22	12.70
Options outstanding, ending balance (in dollars per share)	10.88	11.05	10.95
Options vested and expected to vest (in dollars per share)	11.00	11.08	10.89
Options exercisable (in dollars per share)	$ 11.31	$ 10.95	$ 10.01
Weighted Average Remaining Contractual Term (in years)
Options outstanding	6 years 18 days	6 years 7 months 28 days	7 years 4 days
Options vested and expected to vest	5 years 10 months 24 days	6 years 5 months 27 days	6 years 8 months 9 days
Options exercisable	5 years 3 months 7 days	5 years 7 months 6 days	5 years 3 months 11 days
Aggregate Intrinsic Value
Options outstanding	$ 2,641	$ 2,117	$ 38,752
Options vested and expected to vest	2,529	2,117	33,566
Options exercisable	$ 2,347	$ 2,117	$ 22,083