Redeemable Preferred Stock (Details) - USD ($)				1 Months Ended	3 Months Ended		6 Months Ended	12 Months Ended
	Apr. 05, 2017	Dec. 22, 2016	May 08, 2013	Dec. 31, 2016	Sep. 30, 2017	Mar. 31, 2017	Jun. 30, 2017	Dec. 31, 2017	Jun. 30, 2018
Redeemable preferred stock
Payments for redemption of preferred stock							$ 3,700,000
Series C Redeemable Convertible Preferred Stock
Redeemable preferred stock
Shares issued (in shares)					2,611
Redeemable stock issued, par value (in dollars per share)					$ 0.01
Redeemable stock issued, stated value (in dollars per share)								$ 0.01	$ 0.01
Redeemable convertible Preferred Stock, shares outstanding								2,620	2,620
Series C Redeemable Convertible Preferred Stock | Air Liquide
Redeemable preferred stock
Dividend rate								8.00%
Aggregate purchase price of shares issued			$ 248.794
Adjusted conversion price per share								$ 0.2343	$ 0.2343
Series D Redeemable Convertible Preferred Stock
Redeemable preferred stock
Shares issued (in shares)		18,500		18,500
Redeemable stock issued, par value (in dollars per share)				$ 0.01
Shares of common stock that can be purchased from warrants issued				7,381,500
Redeemable stock issued, stated value (in dollars per share)				$ 0.01
Net proceeds from public offering				$ 15,600,000
Shares redeemed (in shares)						3,700
Payments for redemption of preferred stock						$ 3,700,000
Shares issued upon conversion of redeemable stock (in shares)	9,548,393
Conversion price per share	$ 1.55