Stock-Based Compensation (Details) (Stock options, USD $)	3 Months Ended	12 Months Ended
	Mar. 31, 2014	Dec. 31, 2013
Stock options
Shares
Options Outstanding at beginning of the period (in shares)	5,770,544
Granted (in shares)	12,750
Exercised (in shares)	(107,814)
Canceled (in shares)	(7,527)
Options Outstanding at the end of the period (in shares)	5,667,953	5,770,544
Options Vested and Expected to Vest at the end of the period (in shares)	5,627,995
Options Exercisable at the end of the period (in shares)	3,371,583
Shares Available for Grant under the 2008 Plan (in shares)	2,097,719
Weighted Average Exercise Price Per Share
Options Outstanding at beginning of the period (in dollars per share)	$ 8.17
Granted (in dollars per share)	$ 26.37
Exercised (in dollars per share)	$ 6.10
Canceled (in dollars per share)	$ 10.46
Options Outstanding at the end of the period (in dollars per share)	$ 8.25	$ 8.17
Options Vested and Expected to Vest at the end of the period (in dollars per share)	$ 8.21
Options Exercisable at the end of the period (in dollars per share)	$ 6.22
Weighted Average Remaining Contractual Term
Options Outstanding at beginning of the period	6 years 9 months 18 days	7 years
Options Outstanding at the end of the period	6 years 9 months 18 days	7 years
Options Vested and Expected to Vest at the end of the period	6 years 9 months 18 days
Options Exercisable at the end of the period	5 years 6 months
Additional information
Weighted average grant-date fair value (in dollars per share)	$ 16.91