Fair Value of Financial Assets and Liabilities – Derivative Instruments (Fair Value of Financial Liabilities Measured on Recurring Basis) (Details) - USD ($)	May 09, 2019	Dec. 31, 2018
Schedule Of Derivative Liabilities At Fair Value [Line Items]
Total assets		$ 9,430,000
Asset acquisition derivative liability	$ 2,900,000	1,117,000
Total liabilities		1,117,000
June 2016 Offering Liability [Member]
Schedule Of Derivative Liabilities At Fair Value [Line Items]
Asset acquisition derivative liability		1,117,000
Fair Value, Inputs, Level 1 [Member]
Schedule Of Derivative Liabilities At Fair Value [Line Items]
Total assets		9,430,000
Total liabilities
Fair Value, Inputs, Level 1 [Member] | June 2016 Offering Liability [Member]
Schedule Of Derivative Liabilities At Fair Value [Line Items]
Asset acquisition derivative liability
Fair Value, Inputs, Level 2 [Member]
Schedule Of Derivative Liabilities At Fair Value [Line Items]
Total assets
Total liabilities
Fair Value, Inputs, Level 2 [Member] | June 2016 Offering Liability [Member]
Schedule Of Derivative Liabilities At Fair Value [Line Items]
Asset acquisition derivative liability
Fair Value, Inputs, Level 3 [Member]
Schedule Of Derivative Liabilities At Fair Value [Line Items]
Total assets
Total liabilities		1,117,000
Fair Value, Inputs, Level 3 [Member] | June 2016 Offering Liability [Member]
Schedule Of Derivative Liabilities At Fair Value [Line Items]
Asset acquisition derivative liability		1,117,000
Money Market Funds [Member]
Schedule Of Derivative Liabilities At Fair Value [Line Items]
Money market funds		9,430,000
Money Market Funds [Member] | Fair Value, Inputs, Level 1 [Member]
Schedule Of Derivative Liabilities At Fair Value [Line Items]
Money market funds		9,430,000
Money Market Funds [Member] | Fair Value, Inputs, Level 2 [Member]
Schedule Of Derivative Liabilities At Fair Value [Line Items]
Money market funds
Money Market Funds [Member] | Fair Value, Inputs, Level 3 [Member]
Schedule Of Derivative Liabilities At Fair Value [Line Items]
Money market funds