Fair Value of Financial Assets and Liabilities - Derivative Instruments (Change in Fair Value of Derivative and Warrant Liabilities) (Details)	3 Months Ended
	Mar. 31, 2017 USD ($)
Derivatives And Fair Value [Line Items]
Balance, derivative liability	$ 2,443,000
Changes in estimated fair value	(114,000)
Balance, derivative liability	2,329,000
Dilutive Financing Derivative Liability [Member]
Derivatives And Fair Value [Line Items]
Balance, derivative liability	126,000
Changes in estimated fair value	(3,000)
Balance, derivative liability	123,000
November 2016 Warrant Derivative Liability [Member]
Derivatives And Fair Value [Line Items]
Balance, derivative liability	2,043,000
Changes in estimated fair value	(82,000)
Balance, derivative liability	1,961,000
June 2016 Offering Liability [Member]
Derivatives And Fair Value [Line Items]
Balance, derivative liability	274,000
Changes in estimated fair value	(29,000)
Balance, derivative liability	$ 245,000