Summary of Significant Accounting Policies (tables)

6 Months Ended

Jun. 30, 2013

Accounting Policies [Abstract]

Schedule of Regulatory Assets [Table Text Block]

	Regulatory Assets
	June 30,				December 31,
In thousands	2013		2012		2012
Current:
Unrealized loss on derivatives(1)	$	9,392	$	29,407	$	10,796
Other(2)	16,560		35,890		41,652
Total current	$	25,952	$	65,297	$	52,448
Non-current:
Unrealized loss on derivatives(1)	$	1,754	$	2,130	$	578
Pension balancing(3)	20,327		10,611		14,727
Income tax asset	53,065		63,452		55,879
Pension and other postretirement benefit liabilities(3)	191,312		162,767		182,688
Environmental costs(4)	120,224		113,369		121,144
Other(2)	6,970		9,961		7,239
Total non-current	$	393,652	$	362,290	$	382,255

Schedule of Regulatory Liabilities [Table Text Block]

	Regulatory Liabilities
	June 30,				December 31,
In thousands	2013		2012		2012
Current:
Gas costs	$	6,353	$	12,980	$	9,100
Unrealized gain on derivatives(1)	547		2,142		1,950
Other(2)	9,744		5,626		9,742
Total current	$	16,644	$	20,748	$	20,792
Non-current:
Gas costs	$	481	$	1,504	$	—
Unrealized gain on derivatives(1)	1,054		1,170		3,639
Accrued asset removal costs	289,105		274,756		281,213
Other(2)	3,562		2,865		3,261
Total non-current	$	294,202	$	280,295	$	288,113