Revenue - Disaggregation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Disaggregation of Revenue [Line Items]
Revenues	$ 106,569	$ 106,575
Oil and gas (excludes petrochemical)
Disaggregation of Revenue [Line Items]
Revenues	43,021	40,028
Petrochemical
Disaggregation of Revenue [Line Items]
Revenues	17,228	9,165
Electric utility
Disaggregation of Revenue [Line Items]
Revenues	21,533	28,171
Traction power
Disaggregation of Revenue [Line Items]
Revenues	11,372	13,361
All others
Disaggregation of Revenue [Line Items]
Revenues	13,415	15,850
United States
Disaggregation of Revenue [Line Items]
Revenues	82,145	80,586
Canada
Disaggregation of Revenue [Line Items]
Revenues	15,125	14,091
Europe, Middle East and Africa
Disaggregation of Revenue [Line Items]
Revenues	7,830	8,256
Asia/Pacific
Disaggregation of Revenue [Line Items]
Revenues	944	2,716
Mexico, Central and South America
Disaggregation of Revenue [Line Items]
Revenues	$ 525	$ 926