Revenue from Contracts with Customers - Schedule of the Disaggregation of Revenue (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Disaggregation of Revenue [Line Items]
Operating revenue	$ 2,849,685	$ 2,854,390	$ 2,699,250
Operating segments
Disaggregation of Revenue [Line Items]
Operating revenue	2,868,593	2,869,444	2,715,233
Eliminations
Disaggregation of Revenue [Line Items]
Operating revenue	(18,908)	(15,054)	(15,983)
Fixed-price | Operating segments
Disaggregation of Revenue [Line Items]
Operating revenue	1,684,927	1,403,462	1,310,647
Unit-price | Operating segments
Disaggregation of Revenue [Line Items]
Operating revenue	217,563	176,580	208,396
Cost reimbursable | Operating segments
Disaggregation of Revenue [Line Items]
Operating revenue	966,103	1,289,402	1,196,190
Electrical & Mechanical
Disaggregation of Revenue [Line Items]
Operating revenue	2,023,911	2,125,543	1,988,729
Electrical & Mechanical | Operating segments
Disaggregation of Revenue [Line Items]
Operating revenue	2,031,447	2,134,867	1,997,840
Electrical & Mechanical | Eliminations
Disaggregation of Revenue [Line Items]
Operating revenue	(7,536)	(9,324)	(9,111)
Electrical & Mechanical | Commercial | Operating segments
Disaggregation of Revenue [Line Items]
Operating revenue	1,197,760	1,204,016	1,082,456
Electrical & Mechanical | Industrial | Operating segments
Disaggregation of Revenue [Line Items]
Operating revenue	322,661	473,339	405,730
Electrical & Mechanical | Institutional | Operating segments
Disaggregation of Revenue [Line Items]
Operating revenue	364,611	262,344	215,509
Electrical & Mechanical | Renewables | Operating segments
Disaggregation of Revenue [Line Items]
Operating revenue	36,975	55,402	151,100
Electrical & Mechanical | Service & other | Operating segments
Disaggregation of Revenue [Line Items]
Operating revenue	109,440	139,766	143,045
Electrical & Mechanical | Fixed-price | Operating segments
Disaggregation of Revenue [Line Items]
Operating revenue	1,299,059	1,049,626	1,002,117
Electrical & Mechanical | Unit-price | Operating segments
Disaggregation of Revenue [Line Items]
Operating revenue	61,964	81,786	91,565
Electrical & Mechanical | Cost reimbursable | Operating segments
Disaggregation of Revenue [Line Items]
Operating revenue	670,424	1,003,455	904,158
Transmission & Distribution
Disaggregation of Revenue [Line Items]
Operating revenue	825,774	728,847	710,521
Transmission & Distribution | Operating segments
Disaggregation of Revenue [Line Items]
Operating revenue	837,146	734,577	717,393
Transmission & Distribution | Eliminations
Disaggregation of Revenue [Line Items]
Operating revenue	(11,372)	(5,730)	(6,872)
Transmission & Distribution | Utility | Operating segments
Disaggregation of Revenue [Line Items]
Operating revenue	753,725	677,434	645,077
Transmission & Distribution | Transportation | Operating segments
Disaggregation of Revenue [Line Items]
Operating revenue	83,421	57,143	72,316
Transmission & Distribution | Fixed-price | Operating segments
Disaggregation of Revenue [Line Items]
Operating revenue	385,868	353,836	308,530
Transmission & Distribution | Unit-price | Operating segments
Disaggregation of Revenue [Line Items]
Operating revenue	155,599	94,794	116,831
Transmission & Distribution | Cost reimbursable | Operating segments
Disaggregation of Revenue [Line Items]
Operating revenue	$ 295,679	$ 285,947	$ 292,032