Revenue - Disaggregation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Disaggregation of Revenue [Line Items]
Revenues	$ 126,858	$ 106,569
Oil and gas (excludes petrochemical)
Disaggregation of Revenue [Line Items]
Revenues	43,510	43,021
Petrochemical
Disaggregation of Revenue [Line Items]
Revenues	22,490	17,228
Electric utility
Disaggregation of Revenue [Line Items]
Revenues	28,407	21,533
Traction power
Disaggregation of Revenue [Line Items]
Revenues	7,072	11,372
Commercial and other industrial
Disaggregation of Revenue [Line Items]
Revenues	17,050	5,646
All others
Disaggregation of Revenue [Line Items]
Revenues	8,329	7,769
United States
Disaggregation of Revenue [Line Items]
Revenues	100,112	82,145
Canada
Disaggregation of Revenue [Line Items]
Revenues	18,496	15,125
Europe, Middle East and Africa
Disaggregation of Revenue [Line Items]
Revenues	6,559	7,830
Asia/Pacific
Disaggregation of Revenue [Line Items]
Revenues	776	944
Mexico, Central and South America
Disaggregation of Revenue [Line Items]
Revenues	$ 915	$ 525