Revenue - Disaggregation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Disaggregation of Revenue [Line Items]
Revenues	$ 192,365	$ 135,483	$ 490,667	$ 369,907
Oil and gas (excludes petrochemical)
Disaggregation of Revenue [Line Items]
Revenues	73,452	58,669	179,560	155,324
Petrochemical
Disaggregation of Revenue [Line Items]
Revenues	21,995	15,187	70,372	51,268
Electric utility
Disaggregation of Revenue [Line Items]
Revenues	43,824	30,173	114,899	82,079
Commercial and other industrial
Disaggregation of Revenue [Line Items]
Revenues	35,527	14,966	74,846	30,583
Traction power
Disaggregation of Revenue [Line Items]
Revenues	7,143	9,775	21,532	31,200
All others
Disaggregation of Revenue [Line Items]
Revenues	10,424	6,713	29,458	19,453
United States
Disaggregation of Revenue [Line Items]
Revenues	153,258	102,931	387,531	272,069
Canada
Disaggregation of Revenue [Line Items]
Revenues	21,765	23,599	62,255	60,777
Europe, Middle East and Africa
Disaggregation of Revenue [Line Items]
Revenues	12,004	6,697	30,521	30,078
Asia/Pacific
Disaggregation of Revenue [Line Items]
Revenues	2,338	1,645	4,903	4,235
Mexico, Central and South America
Disaggregation of Revenue [Line Items]
Revenues	$ 3,000	$ 611	$ 5,457	$ 2,748