Fair Value Measurements (Change in Fair Value of Derivative Liabilities) (Details)	3 Months Ended
	Mar. 31, 2018 USD ($)
Derivatives And Fair Value [Line Items]
Balance, derivative liability	$ 292,000
Changes in estimated fair value	79,000
Exercised warrants	(184,000)
Balance, derivative liability	187,000
Dilutive Financing Derivative Liability [Member]
Derivatives And Fair Value [Line Items]
Balance, derivative liability	155,000
November 2016 Warrants [Member]
Derivatives And Fair Value [Line Items]
Balance, derivative liability	260,000
Changes in estimated fair value	79,000
Exercised warrants	(184,000)
Balance, derivative liability	155,000
June 2016 Offering Liability [Member]
Derivatives And Fair Value [Line Items]
Balance, derivative liability	32,000
Balance, derivative liability	$ 32,000