Liquidity and Going Concern - Narrative (Details) - USD ($)	1 Months Ended
	Jul. 31, 2018	Sep. 30, 2018	Dec. 31, 2017	Sep. 30, 2017	Dec. 31, 2016	May 19, 2015
Liquidity and Going Concern
Accumulated deficit		$ 232,000,000	$ 228,346,000
Cash		3,254,000	$ 2,807,000	$ 3,341,000	$ 7,839,000
Shares sold in rights offering	$ 2,200,000
Shelf Registration
Liquidity and Going Concern
Aggregate securities authorized						$ 50,000,000.0
Aggregate securities sold		$ 3,100,000