Segment Reporting (Tables)

12 Months Ended

Dec. 31, 2017

Segment Reporting [Abstract]

Schedule of Segment Reporting Information, by Segment [Table Text Block]

In thousands	Utility		Other		Total
2017
Operating revenues	$	732,942	$	22,096	$	755,038
Depreciation and amortization	79,734		1,319		81,053
Income from operations	132,807		12,452		145,259
Net income from continuing operations(1)	60,509		11,564		72,073
Capital expenditures	211,672		1,653		213,325
Total assets at December 31, 2017(3)	2,961,326		64,546		3,025,872
2016
Operating revenues	$	650,477	$	17,696	$	668,173
Depreciation and amortization	76,289		1,315		77,604
Income from operations	130,570		13,539		144,109
Net income from continuing operations(2)	54,567		7,852		62,419
Capital expenditures	138,074		283		138,357
Total assets at December 31, 2016(3)	2,806,627		62,759		2,869,386
2015
Operating revenues	$	702,210	$	15,678	$	717,888
Depreciation and amortization	74,410		1,312		75,722
Income from operations	119,215		11,822		131,037
Net income from continuing operations(2)	53,391		6,635		60,026
Capital expenditures	115,272		1,040		116,312
Total assets at December 31, 2015(3)	2,791,623		64,335		2,855,958

⁽¹⁾ Includes $1.0 million of tax expense in Utility and $4.4 million of tax benefit in Other from the enactment of the TCJA. The TCJA was enacted December 22, 2017 and resulted in the federal tax rate changing from 35% to 21%.

⁽²⁾  Includes $2.0 million in 2016 and $9.1 million in 2015 of after-tax regulatory environmental disallowance charges in Utility.

⁽³⁾  Total assets exclude assets related to discontinued operations of $13.9 million, $210.4 million and $213.5 million as of December 31, 2017, 2016, and 2015, respectively.

Utility Margin [Table Text Block]

In thousands	2017		2016		2015
Utility margin calculation:
Utility operating revenues	$	732,942	$	650,477	$	702,210
Less: Utility cost of gas	325,019		260,588		327,305
Environmental remediation expense	15,291		13,298		3,513
Utility margin	$	392,632	$	376,591	$	371,392