Goodwill (Changes in the Carrying Value of Goodwill) (Details) - USD ($)	3 Months Ended				12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Changes in the carrying value of goodwill:
Goodwill, net					$ 37,180,000
Goodwill impairment recognized	$ 0	$ 0	$ 0	$ 0	(37,180,000)	$ 0	$ 0
Goodwill, net					0	37,180,000
Energy Chemistry Technologies
Changes in the carrying value of goodwill:
Goodwill, gross					37,180,000	37,180,000
Accumulated impairment losses					0	0
Goodwill, net					37,180,000	37,180,000
Goodwill impairment recognized					(37,180,000)	0
Acquisition goodwill recognized					0	0
Goodwill, gross	37,180,000				37,180,000	37,180,000	37,180,000
Accumulated impairment losses	0				(37,180,000)	0	0
Goodwill, net	$ 37,180,000				$ 0	$ 37,180,000	$ 37,180,000