Revenue - Disaggregation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2025	Mar. 31, 2024	Mar. 31, 2025	Mar. 31, 2024
Disaggregation of Revenue [Line Items]
Revenues	$ 278,631	$ 255,108	$ 520,062	$ 449,125
Oil and gas (excludes petrochemical)
Disaggregation of Revenue [Line Items]
Revenues	101,167	103,820	196,846	187,456
Petrochemical
Disaggregation of Revenue [Line Items]
Revenues	43,704	50,070	76,887	78,437
Electric utility
Disaggregation of Revenue [Line Items]
Revenues		47,502	121,579	88,205
Commercial and other industrial
Disaggregation of Revenue [Line Items]
Revenues	40,369	34,894	84,669	59,566
Light rail traction power
Disaggregation of Revenue [Line Items]
Revenues	10,008	4,517	18,236	8,862
All others
Disaggregation of Revenue [Line Items]
Revenues	13,044	14,305	21,845	26,599
United States
Disaggregation of Revenue [Line Items]
Revenues	227,834	216,933	425,606	376,793
Canada
Disaggregation of Revenue [Line Items]
Revenues	33,970	24,160	65,664	44,510
Europe
Disaggregation of Revenue [Line Items]
Revenues	5,897	8,265	11,425	14,797
Middle East and Africa
Disaggregation of Revenue [Line Items]
Revenues	8,282	2,803	12,840	6,078
Mexico, Central and South America
Disaggregation of Revenue [Line Items]
Revenues	1,002	2,159	1,301	4,816
Asia/Pacific
Disaggregation of Revenue [Line Items]
Revenues	$ 1,646	$ 788	$ 3,226	$ 2,131