Segment Information (Tables)

12 Months Ended

Dec. 31, 2017

Segment Reporting [Abstract]

Accounts Receivable for Services

Accounts receivable for these services, which are not eliminated during consolidation, are presented in the table below (in thousands).

	December 31, 2017		December 31, 2016
Accounts receivable for Centuri services	$	12,987	$	10,585

Schedule of Revenues by Geographic Area

The following table presents the amount of revenues for both segments by geographic area (thousands of dollars):

	December 31, 2017		December 31, 2016		December 31, 2015
Revenues (a)
United States	$	2,345,134	$	2,256,600	$	2,289,133
Canada		203,658		203,890		174,492
Total	$	2,548,792	$	2,460,490	$	2,463,625

(a) Revenues are attributed to countries based on the location of customers.

Schedule of Segment Reporting Information

The financial information pertaining to the natural gas operations and construction services segments for each of the three years in the period ended December 31, 2017 is as follows (thousands of dollars):

2017	Gas Operations		Construction Services		Other			Total
Revenues from unaffiliated customers	$	1,302,308	$	1,149,325	$	—		$	2,451,633
Intersegment sales		—		97,159		—			97,159
Total	$	1,302,308	$	1,246,484	$	—		$	2,548,792
Interest revenue	$	2,784	$	3	$	—		$	2,787
Interest expense	$	69,733	$	7,986	$	345		$	78,064
Depreciation and amortization	$	201,922	$	49,029	$	—		$	250,951
Income tax expense	$	63,135	$	2,390	$	(437	)	$	65,088
Segment net income	$	156,818	$	38,360	$	(1,337	)	$	193,841
Segment assets	$	5,482,669	$	752,496	$	1,901		$	6,237,066
Capital expenditures	$	560,448	$	63,201	$	—		$	623,649
2016	Gas Operations		Construction Services		Other			Total
Revenues from unaffiliated customers	$	1,321,412	$	1,040,957	$	—		$	2,362,369
Intersegment sales		—		98,121		—			98,121
Total	$	1,321,412	$	1,139,078	$	—		$	2,460,490
Interest revenue	$	1,848	$	1	$	—		$	1,849
Interest expense	$	66,997	$	6,663	$	—		$	73,660
Depreciation and amortization	$	233,463	$	55,669	$	—		$	289,132
Income tax expense	$	58,584	$	19,884	$	—		$	78,468
Segment net income	$	119,423	$	32,618	$	—		$	152,041
Segment assets	$	5,001,756	$	579,370	$	—		$	5,581,126
Capital expenditures	$	457,120	$	72,411	$	—		$	529,531
2015	Gas Operations		Construction Services		Other			Total
Revenues from unaffiliated customers	$	1,454,639	$	904,870	$	—		$	2,359,509
Intersegment sales		—		104,116		—			104,116
Total	$	1,454,639	$	1,008,986	$	—		$	2,463,625
Interest revenue	$	1,754	$	419	$	—		$	2,173
Interest expense	$	64,095	$	7,784	$	—		$	71,879
Depreciation and amortization	$	213,455	$	56,656	$	—		$	270,111
Income tax expense	$	61,355	$	18,547	$	—		$	79,902
Segment net income	$	111,625	$	26,692	$	—		$	138,317
Segment assets	$	4,822,845	$	535,840	$	—		$	5,358,685
Capital expenditures	$	438,289	$	49,711	$	—		$	488,000