Quarterly report pursuant to Section 13 or 15(d)

Cash Equivalents and Investments (Schedule of Cash Equivalents and Available-for-Sale Securities) (Details)

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Cash Equivalents and Investments (Schedule of Cash Equivalents and Available-for-Sale Securities) (Details) - USD ($)
Sep. 30, 2018
Dec. 31, 2017
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost $ 9,382,000 $ 11,735,000
Gross Unrealized Losses (1,000) (1,000)
Fair Value 9,381,000 11,734,000
Cash Equivalents 6,763,000 6,193,000
Short-Term Investments 2,618,322 5,540,744
Cash Equivalents [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 6,763,000 6,193,000
Fair Value 6,763,000 6,193,000
Cash Equivalents 6,763,000 6,193,000
Cash Equivalents [Member] | Money Market Funds [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 6,763,000 6,193,000
Fair Value 6,763,000 6,193,000
Cash Equivalents 6,763,000 6,193,000
Investments [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 2,619,000 5,542,000
Gross Unrealized Losses (1,000) (1,000)
Fair Value 2,618,000 5,541,000
Short-Term Investments 2,618,000 5,541,000
Investments [Member] | Commercial Paper [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 2,619,000 997,000
Gross Unrealized Losses (1,000)  
Fair Value 2,618,000 997,000
Short-Term Investments $ 2,618,000 997,000
Investments [Member] | Corporate Notes/Bonds [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost   4,545,000
Gross Unrealized Losses   (1,000)
Fair Value   4,544,000
Short-Term Investments   $ 4,544,000