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 ($)
Mar. 31, 2018
Dec. 31, 2017
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost $ 11,777,000 $ 11,735,000
Gross Unrealized Losses (7,000) (1,000)
Fair Value 11,770,000 11,734,000
Cash Equivalents 5,751,000 6,193,000
Short-Term Investments 6,018,503 5,540,744
Cash Equivalents [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 5,751,000 6,193,000
Fair Value 5,751,000 6,193,000
Cash Equivalents 5,751,000 6,193,000
Cash Equivalents [Member] | Money Market Funds [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 5,751,000 6,193,000
Fair Value 5,751,000 6,193,000
Cash Equivalents 5,751,000 6,193,000
Investments [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 6,026,000 5,542,000
Gross Unrealized Losses (7,000) (1,000)
Fair Value 6,019,000 5,541,000
Short-Term Investments 6,019,000 5,541,000
Investments [Member] | Commercial Paper [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 1,988,000 997,000
Gross Unrealized Losses (2,000)  
Fair Value 1,986,000 997,000
Short-Term Investments 1,986,000 997,000
Investments [Member] | Corporate Notes/Bonds [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 4,038,000 4,545,000
Gross Unrealized Losses (5,000) (1,000)
Fair Value 4,033,000 4,544,000
Short-Term Investments $ 4,033,000 $ 4,544,000