Revenue - Disaggregation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2026	Mar. 31, 2025	Mar. 31, 2026	Mar. 31, 2025
Disaggregation of Revenue [Line Items]
Revenues	$ 296,615	$ 278,631	$ 547,799	$ 520,062
Oil and gas (excludes petrochemical)
Disaggregation of Revenue [Line Items]
Revenues	112,744	101,167	210,633	196,846
Electric utility
Disaggregation of Revenue [Line Items]
Revenues	80,479	70,339	149,752	121,579
Commercial and other industrial
Disaggregation of Revenue [Line Items]
Revenues	54,446	40,369	95,071	84,669
Petrochemical
Disaggregation of Revenue [Line Items]
Revenues	27,551	43,704	50,329	76,887
Light rail traction power
Disaggregation of Revenue [Line Items]
Revenues	9,048	10,008	17,662	18,236
All others
Disaggregation of Revenue [Line Items]
Revenues	12,347	13,044	24,352	21,845
United States
Disaggregation of Revenue [Line Items]
Revenues	232,272	227,834	427,150	425,606
Canada
Disaggregation of Revenue [Line Items]
Revenues	29,823	33,970	62,282	65,664
Middle East and Africa
Disaggregation of Revenue [Line Items]
Revenues	13,618	8,282	23,490	12,840
Europe
Disaggregation of Revenue [Line Items]
Revenues	10,478	5,897	18,704	11,425
Asia/Pacific
Disaggregation of Revenue [Line Items]
Revenues	9,840	1,646	15,143	3,226
Mexico, Central and South America
Disaggregation of Revenue [Line Items]
Revenues	$ 584	$ 1,002	$ 1,030	$ 1,301