Stock-based Awards (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014
Additional disclosure
Stock-based compensation expense	$ 7,531	$ 9,440	$ 26,151	$ 20,978
Options
Number of Options
Outstanding at the beginning of period (in shares)			25,589,876
Granted (in shares)			2,403,722
Exercised (in shares)			(1,492,738)
Canceled/forfeited (in shares)			(974,257)
Outstanding at the end of the period (in shares)	25,526,603		25,526,603		25,589,876
Weighted-Average Exercise Price
Outstanding at the beginning of period (in dollars per share)			$ 9.79
Granted (in dollars per share)			12.46
Exercised (in dollars per share)			3.73
Canceled/forfeited (in dollars per share)			11.19
Outstanding at the end of the period (in dollars per share)	$ 10.34		$ 10.34		$ 9.79
Additional disclosure
Weighted average remaining contractual life (in years)			7 years 1 day		7 years 6 months 20 days
Remaining stock-based compensation expense for unvested awards	$ 54,800		$ 54,800
Weighted average period over which remaining stock based compensation expense for unvested awards is expected to be recognized			2 years 8 months 6 days
Stock-based compensation expense	6,200	8,600	$ 20,500	19,800
Restricted stock units
Additional disclosure
Remaining stock-based compensation expense for unvested awards	16,600		$ 16,600
Weighted average period over which remaining stock based compensation expense for unvested awards is expected to be recognized			3 years 4 months 16 days
Stock-based compensation expense	$ 1,400	$ 800	$ 5,700	$ 1,200