Quarterly report pursuant to Section 13 or 15(d)

Fair Value Measurements (Schedule of Financial Assets and Liabilities Measured at Fair Value on a Recurring Basis) (Details)

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Fair Value Measurements (Schedule of Financial Assets and Liabilities Measured at Fair Value on a Recurring Basis) (Details) - USD ($)
$ in Thousands
Jun. 30, 2019
Dec. 31, 2018
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Cash equivalents $ 9,540  
Investments 4,001  
Assets (Liabilities) Net, fair value 13,541 $ 8,428
Fair Value, Inputs, Level 1 [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Cash equivalents 9,540  
Assets (Liabilities) Net, fair value 9,540 8,428
Fair Value, Inputs, Level 2 [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Investments 4,001  
Assets (Liabilities) Net, fair value 4,001  
Money Market Funds [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Cash equivalents 9,540 8,428
Money Market Funds [Member] | Fair Value, Inputs, Level 1 [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Cash equivalents 9,540 $ 8,428
Commercial Paper [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Investments 1,992  
Commercial Paper [Member] | Fair Value, Inputs, Level 2 [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Investments 1,992  
Corporate Notes/Bonds [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Investments 2,009  
Corporate Notes/Bonds [Member] | Fair Value, Inputs, Level 2 [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Investments $ 2,009