Equity Award Plans - Restricted Stock Units - Activity (Details) - RSUs
$ / shares in Units, $ in Thousands
3 Months Ended
Mar. 31, 2018
USD ($)
$ / shares
shares
Number of Shares  
Beginning balance (in shares) 0
Granted (in shares) 394,500
Ending balance (in shares) 394,500
Weighted-Average Grant Date Fair Value Per Share  
Beginning balance (in dollars per share) | $ / shares $ 0.00
Granted (in dollars per share) | $ / shares 7.46
Ending balance (in dollars per share) | $ / shares $ 7.46
Additional disclosures  
Weighted-Average Remaining Contractual Term - Balance (in years) 1 year 10 months 10 days
Number of Shares - Vested and expected to vest (in shares) 345,131
Weighted-Average Remaining Contractual Term - Vested and expected to vest (in years) 1 year 9 months 11 days
Aggregate Intrinsic Value  
Balance | $ $ 4,371
Vested and expected to vest | $ $ 3,824