Short-term Investments - Narrative (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Securities Purchased Under Agreements to Resell and Other Short Term Investment Securities [Line Items]
Short-term investments	$ 15,955	$ 24,870
US Treasury Bill Securities
Securities Purchased Under Agreements to Resell and Other Short Term Investment Securities [Line Items]
Short-term investments	$ 16,000	24,800
Interest rate on U.S. Treasury Bills	1.40%
U.S. Treasury Security, Maturing on March 12, 2020 | US Treasury Bill Securities
Securities Purchased Under Agreements to Resell and Other Short Term Investment Securities [Line Items]
Short-term investments		$ 8,900
Interest rate on U.S. Treasury Bills		1.80%
U.S. Treasury Security, Maturing on June 11, 2020 | US Treasury Bill Securities
Securities Purchased Under Agreements to Resell and Other Short Term Investment Securities [Line Items]
Short-term investments		$ 15,900
Interest rate on U.S. Treasury Bills		1.40%