Quarterly report pursuant to Section 13 or 15(d)

Short-term Investments (Details)

v3.19.1
Short-term Investments (Details) - USD ($)
$ in Thousands
Mar. 31, 2019
Dec. 31, 2018
Schedule of Held-to-maturity Securities [Line Items]    
Amortized Cost $ 26,110 $ 32,718
Unrealized Gains 5 14
Unrealized Losses (4) (15)
Fair Value 26,111 32,717
Commercial paper    
Schedule of Held-to-maturity Securities [Line Items]    
Amortized Cost 7,680 8,772
Unrealized Gains 0 0
Unrealized Losses 0 0
Fair Value 7,680 8,772
Overnight repurchase agreement    
Schedule of Held-to-maturity Securities [Line Items]    
Amortized Cost 5,000 9,000
Unrealized Gains 0 0
Unrealized Losses 0 0
Fair Value 5,000 9,000
U.S. government securities    
Schedule of Held-to-maturity Securities [Line Items]    
Amortized Cost 13,430 14,946
Unrealized Gains 5 14
Unrealized Losses (4) (15)
Fair Value $ 13,431 $ 14,945