Summary of Significant Accounting Policies (Tables)

9 Months Ended

Sep. 30, 2016

Accounting Policies [Abstract]

Schedule of Regulatory Assets [Table Text Block]

	Regulatory Assets
	September 30,				December 31,
In thousands	2016		2015		2015
Current:
Unrealized loss on derivatives(1)	$	5,205	$	21,949	$	22,092
Gas costs	10,164		19,274		8,717
Environmental costs(2)	9,734		12,364		9,270
Decoupling(3)	16,028		19,391		18,775
Other(4)	14,149		9,734		10,324
Total current	$	55,280	$	82,712	$	69,178
Non-current:
Unrealized loss on derivatives(1)	$	1,682	$	3,540	$	3,447
Pension balancing(5)	48,637		41,193		43,748
Income taxes	40,106		44,767		43,049
Pension and other postretirement benefit liabilities	174,282		189,111		184,223
Environmental costs(2)	64,279		37,443		76,584
Gas costs	712		2,098		1,949
Decoupling(3)	1,006		4,331		6,349
Other(4)	10,484		11,470		11,362
Total non-current	$	341,188	$	333,953	$	370,711

Schedule of Regulatory Liabilities [Table Text Block]

	Regulatory Liabilities
	September 30,				December 31,
In thousands	2016		2015		2015
Current:
Gas costs	$	12,001	$	22,499	$	14,157
Unrealized gain on derivatives(1)	4,857		2,939		2,659
Other(4)	11,063		8,689		13,111
Total current	$	27,921	$	34,127	$	29,927
Non-current:
Gas costs	$	765	$	6,357	$	8,869
Unrealized gain on derivatives(1)	1,151		299		27
Accrued asset removal costs(6)	336,699		324,467		327,047
Other(4)	3,528		3,367		3,344
Total non-current	$	342,143	$	334,490	$	339,287