Stock-based Compensation - Options (Details) - Options [Member] - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016	Dec. 31, 2016
Number of options outstanding [Roll Forward]
Options outstanding, beginning of period (in shares)			3,294,000
Granted (in shares)	0	0	60,000	68,000
Exercised (in shares)			(289,000)
Canceled and expired (in shares)			(14,000)
Options outstanding, end of period (in shares)	3,051,000		3,051,000		3,294,000
Options vested and unvested options expected to vest, net of forfeitures, end of period (in shares)	2,997,000		2,997,000
Options exercisable, end of period (in shares)	1,677,000		1,677,000
Weighted average exercise price [Roll Forward]
Options outstanding, beginning of period (in dollars per share)			$ 3.38
Granted (in dollars per share)			5.95
Exercised (in dollars per share)			3.06
Canceled and expired (in dollars per share)			2.18
Options outstanding, end of period (in dollars per share)	$ 3.47		3.47		$ 3.38
Options vested as of March 31, 2015 and unvested options expected to vest, net of forfeitures (in dollars per share)	3.46		3.46
Options exercisable, end of period (in dollars per share)	$ 3.35		3.35
Weighted-average grant date fair value of stock options granted (in dollars per share)			$ 2.76	$ 1.01
Weighted average Remaining Contractual Life [Abstract]
Options outstanding			6 years 11 months 5 days		7 years 2 months 23 days
Options vested and unvested options expected to vest, net of forfeitures, end of period			6 years 10 months 24 days
Option exercisable, end of period			5 years 6 months 29 days
Aggregate Intrinsic Value [Abstract]
Options outstanding, beginning of period			$ 5,301
Options outstanding, end of period	$ 8,805		8,805		$ 5,301
Options vested and expected to vest, end of period	8,690		8,690
Options exercisable, end of period	$ 5,054		$ 5,054
Closing price (in dollars per share)	$ 6.35		$ 6.35