Stock-Based Compensation - Additional Information (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014	Dec. 31, 2014
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Unvested exercisable shares	845,410		845,410		469,000
Unvested exercisable shares, vesting period			3 years
Unvested options exercised			0	0
Weighted-average grant-date fair value of stock options granted			$ 4.78	$ 2.68
Total intrinsic value of options exercised			$ 5,200	$ 2,300
Total fair value of options vested			5,500	1,900
Stock-based compensation expense	$ 3,201	$ 2,463	6,421	$ 4,310
Total unrecognized compensation cost	18,300		$ 18,300		$ 12,100
Weighted-average period of recognition			3 years 1 month 6 days		2 years 9 months 18 days
Employee Stock
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense	$ 200		$ 1,500
Sale of shares	145,000		1,005,928
Restricted Stock Units (RSUs)
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock option plan, number of shares granted			170,000		947,342
Vesting starting period			2014-08
Vesting ending period			2017-08
Stock option plan, number of additional shares available for grant					372,342