Revenue - Summary of Revenue Disaggregated by Service Type, and Contract Type (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	$ 203,082	$ 200,256	$ 966,941	$ 1,005,844	$ 1,346,391	$ 1,374,724
Centuri
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	580,392	515,250	1,408,698	1,282,412	1,877,264	1,698,853
Master services agreement | Centuri
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	437,914	410,283	1,076,961	1,021,798	1,438,540	1,291,397
Bid contract | Centuri
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	142,478	104,967	331,737	260,614	438,724	407,456
Unit price contracts | Centuri
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	377,284	415,404	985,673	1,006,577	1,359,352	1,316,404
Fixed price contracts | Centuri
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	46,379	37,539	109,935	80,503	142,356	152,890
Time and materials contracts | Centuri
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	156,729	62,307	313,090	195,332	375,556	229,559
Gas infrastructure services | Centuri
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	387,578	364,241	935,444	885,950	1,288,468	1,160,017
Electric power infrastructure services | Centuri
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	115,386	70,610	282,992	184,277	346,432	202,844
Other | Centuri
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	$ 77,428	$ 80,399	$ 190,262	$ 212,185	$ 242,364	$ 335,992