Quarterly report pursuant to Section 13 or 15(d)

Short Term Investments

Short Term Investments
6 Months Ended
Jun. 30, 2018
Investments, Debt and Equity Securities [Abstract]  
Investments in Debt and Marketable Equity Securities (and Certain Trading Assets) Disclosure [Text Block]
Short Term Investments
The following table summarizes the available-for-sale investments held
as of
June 30, 2018. There were no available-for-sale investments in prior periods.
June 30, 2018
U.S. government agency securities and treasuries
The amortized cost of the available-for-sale investments is adjusted for amortization of premiums and accretion of discounts to maturity. There were no material realized gains or losses recognized on the sale or maturity of available-for-sale investments during the three or six months ended June 30, 2018