Revenue - Revenues Disaggregated by Product Technology (Details) - USD ($)	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Disaggregation of Revenue [Line Items]
Total Revenues	$ 12,791	$ 8,491
Air Pollution Control
Disaggregation of Revenue [Line Items]
Total Revenues	8,583	4,002
Air Pollution Control | Technology solutions
Disaggregation of Revenue [Line Items]
Total Revenues	7,722	3,348
Air Pollution Control | Spare parts
Disaggregation of Revenue [Line Items]
Total Revenues	300	269
Air Pollution Control | Ancillary revenue
Disaggregation of Revenue [Line Items]
Total Revenues	561	385
FUEL CHEM | Technology solutions
Disaggregation of Revenue [Line Items]
Total Revenues	$ 4,208	$ 4,489