Quarterly report pursuant to Section 13 or 15(d)


6 Months Ended
Jun. 30, 2018
Fair Value Disclosures [Abstract]  
Cash and Cash Equivalents, Policy [Policy Text Block] As of June 30, 2018, cash and cash equivalents include the Company’s investments in debt securities, comprising municipal notes and bonds and corporate debt, commercial paper, money market funds and time deposits. The Company considers all highly liquid investments with original maturities of three months or less when purchased and have insignificant interest rate risk to be cash equivalents.  Debt securities classified as cash equivalents are required to be accounted for in accordance with ASC 320, Investments - Debt and Equity Securities. As such, the Company determined its investments in debt securities held at June 30, 2018 should be classified as available-for-sale and are carried at fair value with unrealized gains and losses reported in accumulated other comprehensive income in stockholders’ equity. The cost of debt securities is adjusted for amortization of premiums and discounts to maturity. This amortization is included in other income. Realized gains and losses, as well as interest income, are also included in other income. The fair values of securities are based on quoted market prices.
Fair Value of Financial Instruments, Policy [Policy Text Block] The carrying amounts of the Company’s financial instruments, including cash and cash equivalents and accounts payable, approximate fair value because of their short maturities. The carrying amount of the noncurrent restricted cash approximates fair value since, absent the restrictions, the underlying assets would be included in cash and cash equivalents. The Company’s cash equivalents are valued based on level 1 inputs which consist of quoted prices in active markets.