Equity Incentive Plans and Stock-Based Compensation (Details 3) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2012	Nov. 14, 2017
Aggregate Intrinsic Value
Share Price					$ 14.56
Options
Number of Shares
Outstanding, at the beginning of the period (in shares)	7,008,833	8,995,017	11,441,646
Options granted (in shares)	558,426	500,000	362,335
Options exercised (in shares)	(1,278,856)	(1,405,077)	(1,184,141)
Stock options forfeited (in shares)	(1,978,042)	(1,081,107)	(1,624,823)
Outstanding, at the end of the period (in shares)	4,310,361	7,008,833	8,995,017
Vested or expected to vest at the end of the period (in shares)	4,250,520
Options exercisable at the end of the period (in shares)	3,428,595
Weighted Average Exercise Price
Outstanding at the beginning of the year (in dollars per shares)	$ 9.34	$ 10.01	$ 10.73
Options granted (in dollars per share)	12.95	12.29	11.27
Options exercised (in dollars per share)	7.34	7.27	7.42
Options forfeited (in dollars per share)	10.68	18.98	17.22
Outstanding at the end of the period (in dollars per shares)	9.78	$ 9.34	$ 10.01
Vested or expected to vest at the end of the period (in dollars per share)	9.74
Options exercisable at the end of the period (in dollars per share)	$ 9.11
Weighted Average Remaining Contractual Term (in years)
Outstanding (in years)	5 years 6 months 4 days
Vested or expected to vest (in years)	5 years 5 months 16 days
Options exercisable (in years)	4 years 9 months
Aggregate Intrinsic Value
Outstanding	$ 20,967
Vested or expected to vest	20,876
Options exercisable	$ 19,331
Share Price	$ 14.22
Total number of in-the-money outstanding (in shares)	3,833,131
Total number of in-the-money exercisable (in shares)	3,020,652
Stock Options with Market Condition
Number of Shares
Outstanding, at the beginning of the period (in shares)	1,135,000
Options granted (in shares)				1,795,000
Outstanding, at the end of the period (in shares)	0	1,135,000