Short-term investment

12 Months Ended

Dec. 31, 2018

Investments, Debt and Equity Securities [Abstract]

Short-term investment

Short-term investment

As of December 31, 2017, the Company held a certificate of deposit of $4.5 million, with an original maturity at the date of purchase of one year. It was classified as Level 2 security in the fair value hierarchy. The certificate of deposit matured in the first quarter of 2018.