Fair Value Measurements (Change in Fair Value of Derivative Liabilities) (Details)	3 Months Ended
	Mar. 31, 2019 USD ($)
Derivatives And Fair Value [Line Items]
Balance, derivative liability	$ 22,000
Changes in estimated fair value	11,000
Balance, derivative liability	33,000
June 2016 Offering Liability [Member]
Derivatives And Fair Value [Line Items]
Balance, derivative liability	1,000
Balance, derivative liability	1,000
November 2016 Warrants [Member]
Derivatives And Fair Value [Line Items]
Balance, derivative liability	21,000
Changes in estimated fair value	11,000
Balance, derivative liability	$ 32,000