Stockholders' Equity (Summary of Stockholders' Equity) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Common Stock [Member]
Balances			$ 15
Balances (in shares)			14,946,712
Conversion of notes payable and related accrued interest and fees to common stock			$ 76
Conversion of notes payable and related accrued interest and fees to common stock (in shares)			76,007,754
Issuance of common stock			$ 19
Issuance of common stock, shares			18,653,320
Issuance of stock options in lieu of cash compensation
Stock-based compensation expense
Issuance of common stock in exchange for services
Issuance of common stock in exchange for services, shares			88,333
Comprehensive loss
Balances	$ 110		$ 110
Balances (in shares)	109,696,119		109,696,119
Additional Paid-In Capital [Member]
Balances			$ 238,246
Conversion of notes payable and related accrued interest and fees to common stock			18,356
Issuance of common stock			2,762
Issuance of stock options in lieu of cash compensation			303
Stock-based compensation expense			3,455
Issuance of common stock in exchange for services			51
Comprehensive loss
Balances	$ 263,173		263,173
Accumulated Deficit [Member]
Balances			(262,597)
Conversion of notes payable and related accrued interest and fees to common stock
Issuance of common stock
Issuance of stock options in lieu of cash compensation
Stock-based compensation expense
Issuance of common stock in exchange for services
Comprehensive loss			(7,755)
Balances	(270,352)		(270,352)
Balances			(24,336)
Conversion of notes payable and related accrued interest and fees to common stock			18,432
Issuance of common stock			2,781
Issuance of stock options in lieu of cash compensation			303
Stock-based compensation expense			3,455
Issuance of common stock in exchange for services			51
Comprehensive loss	(2,668)	$ (6,154)	(7,755)	$ (11,702)
Balances	$ (7,069)		$ (7,069)