Condensed Consolidated Statements of Operations (Parenthetical) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Income Statement [Abstract]
Reduction of research and development expenses	$ 0	$ 2,489,000	$ 0	$ 5,265,000