Summary of Significant Accounting Policies (tables)

3 Months Ended

Mar. 31, 2013

Accounting Policies [Abstract]

Schedule of Regulatory Assets [Table Text Block]

	Regulatory Assets
	March 31,				December 31,
In thousands	2013		2012		2012
Current:
Unrealized loss on derivatives(1)	$	3,450	$	53,697	$	10,796
Pension and other postretirement benefit liabilities(2)	17,247		15,491		17,247
Other(3)	18,304		21,302		24,405
Total current	$	39,001	$	90,490	$	52,448
Non-current:
Unrealized loss on derivatives(1)	$	642	$	3,947	$	578
Pension balancing(2)	17,322		8,367		14,727
Income tax asset	53,065		63,452		55,879
Pension and other postretirement benefit liabilities(2)	178,377		166,639		182,688
Environmental costs(4)	125,671		108,007		121,144
Other(3)	9,376		13,720		7,239
Total non-current	$	384,453	$	364,132	$	382,255

Schedule of Regulatory Liabilities [Table Text Block]

	Regulatory Liabilities
	March 31,				December 31,
In thousands	2013		2012		2012
Current:
Gas costs	$	8,694	$	35,584	$	9,100
Unrealized gain on derivatives(1)	8,054		1,824		1,950
Other(3)	11,491		12,933		9,742
Total current	$	28,239	$	50,341	$	20,792
Non-current:
Gas costs	$	1,407	$	14,462	$	—
Unrealized gain on derivatives(1)	2,836		52		3,639
Accrued asset removal costs	285,437		270,837		281,213
Other(3)	3,455		2,780		3,261
Total non-current	$	293,135	$	288,131	$	288,113