Assets Held for Sale - Schedule of Assets Classified as Held for Sale (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Loss on write-down of assets held for sale	$ 2,580	$ 0	$ 2,580	$ 0
Energy Chemistry Technologies | Disposal Group, Held-for-sale, Not Discontinued Operations
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Loss on write-down of assets held for sale	2,600
Property and equipment, net	4,830		4,830		$ 4,998
Valuation allowance	(2,580)		(2,580)		0
Assets held for sale, net	$ 2,250		$ 2,250		$ 4,998