Revenue - Summary of Revenue Disaggregated by Service Type, and Contract Type (Detail) - USD ($)	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	$ 253,408,000	$ 261,699,000	$ 805,588,000	$ 740,257,000	$ 1,371,305,000	$ 1,289,256,000
Centuri
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	454,300,000	395,204,000	767,162,000	655,221,000	1,634,226,000	1,409,263,000
Master services agreement | Centuri
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	375,860,000	290,075,000	611,515,000	484,539,000	1,229,388,000	1,014,517,000
Bid contract | Centuri
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	78,440,000	105,129,000	155,647,000	170,682,000	404,838,000	394,746,000
Unit priced contracts | Centuri
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	355,487,000	329,236,000	591,172,000	526,557,000	1,323,034,000	1,102,335,000
Fixed priced contracts | Centuri
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	4,426,000	27,025,000	42,965,000	52,566,000	107,697,000	138,658,000
Time and materials contracts | Centuri
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	94,387,000	38,943,000	133,025	76,098	203,495,000	168,270,000
Gas infrastructure services | Centuri
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	323,817,000	300,346,000	521,709,000	493,894,000	1,205,197,000	1,072,082,000
Electric power infrastructure services | Centuri
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	61,366,000	3,994,000	113,667,000	9,396,000	136,900,000	19,350,000
Other | Centuri
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	$ 69,117,000	$ 90,864,000	$ 131,786,000	$ 151,931,000	$ 292,129,000	$ 317,831,000