Segment Information (Tables)

3 Months Ended

Mar. 31, 2018

Segment Reporting [Abstract]

Schedule of Segment Reporting Information

The following tables present revenues from external customers, intersegment revenues, and segment net income for the two reportable segments (thousands of dollars):

	Natural Gas Operations		Construction Services			Other			Total
Three months ended March 31, 2018
Revenues from external customers	$	494,313	$	232,859		$	—		$	727,172
Intersegment revenues		—		27,158			—			27,158
Total	$	494,313	$	260,017		$	—		$	754,330
Segment net income (loss)	$	90,349	$	(11,001	)	$	(257	)	$	79,091
Three months ended March 31, 2017
Revenues from external customers	$	462,602	$	170,839		$	—		$	633,441
Intersegment revenues		—		21,296			—			21,296
Total	$	462,602	$	192,135		$	—		$	654,737
Segment net income (loss)	$	76,938	$	(7,334	)	$	(296	)	$	69,308
	Natural Gas Operations		Construction Services			Other			Total
Twelve months ended March 31, 2018
Revenues from external customers	$	1,334,019	$	1,211,345		$	—		$	2,545,364
Intersegment revenues		—		103,021			—			103,021
Total	$	1,334,019	$	1,314,366		$	—		$	2,648,385
Segment net income (loss)	$	170,229	$	34,693		$	(1,298	)	$	203,624
Twelve months ended March 31, 2017
Revenues from external customers	$	1,258,914	$	1,027,835		$	—		$	2,286,749
Intersegment revenues		—		97,230			—			97,230
Total	$	1,258,914	$	1,125,065		$	—		$	2,383,979
Segment net income (loss)	$	118,778	$	27,421		$	(296	)	$	145,903