Liquidity and Going Concern - (Details) - USD ($)	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	May 19, 2015
Liquidity and Going Concern [Line Items]
Accumulated deficit	$ 228,346,000	$ 223,063,000
Cash	2,807,000	$ 7,839,000	$ 2,958,000
Replacement Shelf
Liquidity and Going Concern [Line Items]
Authorized amount				$ 50,000,000.0
Shelf registration securities sold	$ 3,100,000