Segment Reporting (tables)

3 Months Ended

Mar. 31, 2013

Segment Reporting [Abstract]

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

	Three Months Ended Three Months Ended March 31,
In thousands	Utility		Gas Storage		Other			Total
2013
Operating revenues	$	269,659	$	8,146	$	56		$	277,861
Depreciation and amortization	17,188		1,619		—			18,807
Income from operations	70,228		3,957		21			74,206
Net income (loss)	36,031		1,636		(28		)	37,639
Capital expenditures	22,388		286		—			22,674
Total assets at March 31, 2013	2,501,724		288,795		15,980			2,806,499
2012
Operating revenues	$	302,905	$	6,679	$	55		$	309,639
Depreciation and amortization	16,338		1,612		—			17,950
Income from operations	75,964		2,679		23			78,666
Net income	39,468		806		10			40,284
Capital expenditures	19,656		791		—			20,447
Total assets at March 31, 2012	2,420,194		286,756		15,923			2,722,873
Total assets at December 31, 2012	2,505,655		291,568		15,897			2,813,120

Utility Margin [Table Text Block]

	Three Months Ended March 31,
In thousands	2013		2012
Utility margin calculation:
Utility operating revenues	$	269,659	$	302,905
Less: Utility cost of gas	142,359		169,755
Utility margin	$	127,300	$	133,150