Short-Term Investments - Additional Information (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Securities Purchased Under Agreements to Resell and Other Short Term Investment Securities [Line Items]
Short-term investments	$ 42,942	$ 42,994
Interest rate on U.S. Treasury Bills, maximum	1.00%	1.00%
US Treasury Bill Securities
Securities Purchased Under Agreements to Resell and Other Short Term Investment Securities [Line Items]
Short-term investments	$ 42,900	$ 43,000