Quarterly Impact of Adoption of ASU 2017-11 (Unaudited) (Details) - USD ($) $ in Thousands	3 Months Ended						6 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Jun. 30, 2018	Jun. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2018	Dec. 31, 2017
Statement of Operations [Abstract]
Change in fair value of warrant liability gain (loss)	$ 1,053	$ 263	$ (40)	$ (421)	$ (657)	$ 671	$ 222	$ 14	$ 1,275	$ (407)	$ 0	$ (595)
ASU 2017-11 [Member]
Statement of Operations [Abstract]
Change in fair value of warrant liability gain (loss)	(1,053)	(263)	43				(220)		(1,273)
Balance Sheet [Abstract]
Fair value of warrant liability	1,342	264	24				264		1,342
Balances Without the Adoption of ASU 2017-11 [Member] | ASU 2017-11 [Member]
Statement of Operations [Abstract]
Change in fair value of warrant liability gain (loss)	(79)	(23)	1				(22)		(101)
Balance Sheet [Abstract]
Fair value of warrant liability	104	0	1				0		104
Effect of Adoption Higher/(Lower) [Member] | ASU 2017-11 [Member]
Statement of Operations [Abstract]
Change in fair value of warrant liability gain (loss)	(974)	(240)	42				(198)		(1,172)
Balance Sheet [Abstract]
Fair value of warrant liability	$ 1,238	$ 264	$ 23				$ 264		$ 1,238