Equity Incentive Plans and Stock-Based Compensation (Details 2) - Employee Stock Option [Member] - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Number of Shares
Outstanding, at the beginning of the period (in shares)	3,235,891
Options granted (in shares)	0	551,479
Options exercised (in shares)	(704,851)
Options forfeited (in shares)	(33,967)
Outstanding, at the end of the period (in shares)	2,497,073
Vested or expected to vest at the end of the period (in shares)	2,473,989
Options exercisable at the end of the period (in shares)	1,972,769
Weighted Average Exercise Price
Outstanding at the beginning of the year (in dollars per shares)	$ 10.25
Options granted (in dollars per share)	0.00
Options exercised (in dollars per share)	6.89
Options forfeited (in dollars per share)	8.58
Outstanding at the end of the period (in dollars per shares)	11.22
Vested or expected to vest at the end of the period (in dollars per share)	11.20
Options exercisable at the end of the period (in dollars per share)	$ 10.82
Weighted Average Remaining Contractual Term
Outstanding	4 years 8 months 19 days
Vested or expected to vest	4 years 8 months 9 days
Options exercisable	3 years 8 months 12 days
Aggregate Intrinsic Value
Outstanding	$ 2,779
Vested or expected to vest	2,779
Options exercisable	$ 2,779