Revenue - Summary of Revenue from Contracts With Customers Disaggregated by Service Type, and Contract Type (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Disaggregation of Revenue [Line Items]
Revenues	$ 261,699	$ 248,242	$ 740,257	$ 713,882	$ 1,289,256	$ 1,242,203
Centuri Construction Group Inc [Member]
Disaggregation of Revenue [Line Items]
Revenues	395,204	300,307	655,221	492,442	1,409,263	1,133,272
Master Services Agreement [Member] | Centuri Construction Group Inc [Member]
Disaggregation of Revenue [Line Items]
Revenues	290,075	208,361	484,539	355,553	1,014,517	825,980
Bid Contract [Member] | Centuri Construction Group Inc [Member]
Disaggregation of Revenue [Line Items]
Revenues	105,129	91,946	170,682	136,889	394,746	307,292
Unit Priced Contracts [Member] | Centuri Construction Group Inc [Member]
Disaggregation of Revenue [Line Items]
Revenues	345,390	272,427	579,675	450,098	1,249,602	974,107
Fixed-price Contract [Member] | Centuri Construction Group Inc [Member]
Disaggregation of Revenue [Line Items]
Revenues	49,814	27,880	75,546	42,344	159,661	159,165
Replacement Gas Construction [Member] | Centuri Construction Group Inc [Member]
Disaggregation of Revenue [Line Items]
Revenues	256,070	181,512	413,421	301,950	899,537	733,927
New Gas Construction [Member] | Centuri Construction Group Inc [Member]
Disaggregation of Revenue [Line Items]
Revenues	44,276	40,226	80,473	73,305	172,545	197,100
Other Construction [Member] | Centuri Construction Group Inc [Member]
Disaggregation of Revenue [Line Items]
Revenues	$ 94,858	$ 78,569	$ 161,327	$ 117,187	$ 337,181	$ 202,245