Revenue - Disaggregation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2023	Mar. 31, 2022	Mar. 31, 2023	Mar. 31, 2022
Disaggregation of Revenue [Line Items]
Revenues	$ 171,444	$ 127,854	$ 298,302	$ 234,423
Oil and gas (excludes petrochemical)
Disaggregation of Revenue [Line Items]
Revenues	62,597	53,634	106,107	96,655
Petrochemical
Disaggregation of Revenue [Line Items]
Revenues	25,887	18,853	48,377	36,081
Electric utility
Disaggregation of Revenue [Line Items]
Revenues	42,668	30,374	71,075	51,907
Traction power
Disaggregation of Revenue [Line Items]
Revenues	7,317	10,054	14,389	21,426
Commercial and other industrial
Disaggregation of Revenue [Line Items]
Revenues	22,270	5,785	39,320	15,618
All others
Disaggregation of Revenue [Line Items]
Revenues	10,705	9,154	19,034	12,736
United States
Disaggregation of Revenue [Line Items]
Revenues	134,161	86,992	234,273	169,137
Canada
Disaggregation of Revenue [Line Items]
Revenues	21,995	22,053	40,491	37,178
Europe, Middle East and Africa
Disaggregation of Revenue [Line Items]
Revenues	11,957	15,551	18,516	23,381
Asia/Pacific
Disaggregation of Revenue [Line Items]
Revenues	1,788	1,646	2,564	2,590
Mexico, Central and South America
Disaggregation of Revenue [Line Items]
Revenues	$ 1,543	$ 1,612	$ 2,458	$ 2,137