Segment Reporting (Tables)

3 Months Ended

Mar. 31, 2017

Segment Reporting [Abstract]

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

	Three Months Ended March 31,
In thousands	Utility		Gas Storage		Other			Total
2017
Operating revenues	$	292,726	$	4,541	$	56		$	297,323
Depreciation and amortization	19,624		1,461		—			21,085
Income (loss) from operations	75,823		606		(201		)	76,228
Net income (loss)	40,192		61		57			40,310
Capital expenditures	38,854		70		—			38,924
Total assets at March 31, 2017	2,799,638		254,260		16,758			3,070,656
2016
Operating revenues	$	250,104	$	5,369	$	56		$	255,529
Depreciation and amortization	18,760		1,634		—			20,394
Income from operations	72,295		1,726		51			74,072
Net income	35,852		736		53			36,641
Capital expenditures	29,177		877		—			30,054
Total assets at March 31, 2016	2,726,696		260,535		14,802			3,002,033
Total assets at December 31, 2016	2,806,627		256,333		16,841			3,079,801

Utility Margin [Table Text Block]

	Three Months Ended March 31,
In thousands	2017		2016
Utility margin calculation:
Utility operating revenues (1)	$	292,726	$	250,104
Less: Utility cost of gas	143,611		108,411
Environmental remediation expense	6,954		5,029
Utility margin	$	142,161	$	136,664