Redeemable Preferred Stock (Details) $ / shares in Units, € in Millions				12 Months Ended
	Aug. 26, 2014 $ / shares shares	May. 08, 2013 EUR (€) item	May. 08, 2013 USD ($) item $ / shares shares	Dec. 31, 2015 $ / shares shares	Dec. 31, 2014 $ / shares shares	May. 31, 2013 shares
Redeemable preferred stock
Redeemable stock issued (in shares)				5,231	5,231
Redeemable stock issued, par value (in dollars per share) | $ / shares				$ 0.01	$ 0.01
Weighted average exercise price of warrants (in dollars per share) | $ / shares					$ 4.00
Common Stock
Redeemable preferred stock
Shares issued upon conversion of redeemable stock (in shares)					5,521,676
Series C redeemable convertible preferred stock
Redeemable preferred stock
Redeemable stock issued (in shares)						10,431
Shares issued upon conversion of redeemable stock (in shares)				5,200
Air Liquide | Series C redeemable convertible preferred stock
Redeemable preferred stock
Redeemable stock issued (in shares)			10,431	5,231
Redeemable stock issued, par value (in dollars per share) | $ / shares			$ 0.01
Number of directors entitled to designate on board under Securities Purchase Agreement | item		1	1
Dividend rate				8.00%
Aggregate purchase price of shares issued		€ 2	$ 2,595,400
Conversion price per share | $ / shares	$ 0.2343
Shares issued upon conversion of redeemable stock (in shares)	(5,200)
Adjusted conversion price per share | $ / shares				$ 0.2343	$ 0.2343
Air Liquide | Series C redeemable convertible preferred stock | Common Stock
Redeemable preferred stock
Shares issued upon conversion of redeemable stock (in shares)	5,521,676