Organization and Significant Accounting Policies - Goodwill (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Goodwill [Roll Forward]
Beginning Carrying Amount		$ 2,116	$ 2,116	$ 21,051
Acquired Goodwill		0	0	4,465
Impairment Charge		0	0	(23,400)
Ending Carrying Amount	$ 2,116	2,116	2,116	2,116
FUEL CHEM Segment
Goodwill [Roll Forward]
Beginning Carrying Amount		2,116	2,116	2,116
Acquired Goodwill		0	0	0
Impairment Charge		0	0	0
Ending Carrying Amount	2,116	2,116	2,116	2,116
APC Technology Segment
Goodwill [Roll Forward]
Beginning Carrying Amount		0	0	18,935
Acquired Goodwill		0	0	4,465
Impairment Charge	(23,400)	0	0	(23,400)
Ending Carrying Amount	$ 0	$ 0	$ 0	$ 0