Summary of Significant Accounting Policies (tables)

9 Months Ended

Sep. 30, 2012

Accounting Policies [Abstract]

Schedule of Regulatory Assets [Table Text Block]

Regulatory Assets
Thousands	September 30, 2012		September 30, 2011		December 31, 2011
Current:
Unrealized loss on derivatives(1)	$	17,156	$	46,651	$	57,317
Pension and other postretirement benefit liabilities(2)	15,491		10,988		15,491
Other(3)	21,244		19,095		21,865
Total current	$	53,891	$	76,734	$	94,673
Non-current:
Unrealized loss on derivatives(1)	$	615	$	7,429	$	6,536
Pension balancing(2)	13,134		3,989		6,008
Income tax asset	58,437		70,241		65,264
Pension and other postretirement benefit liabilities(2)	158,894		110,007		170,512
Environmental costs(4)	128,173		122,454		105,670
Other(3)	8,439		14,637		17,402
Total non-current	$	367,692	$	328,757	$	371,392

Schedule of Regulatory Liabilities [Table Text Block]

Regulatory Liabilities
Thousands	September 30, 2012		September 30, 2011		December 31, 2011
Current:
Gas costs	$	10,069	$	16,991	$	17,994
Unrealized gain on derivatives(1)	6,771		3,932		2,853
Other(3)	7,970		7,670		10,199
Total current	$	24,810	$	28,593	$	31,046
Non-current:
Gas costs	$	596	$	1,250	$	8,420
Unrealized gain on derivatives(1)	5,608		227		—
Accrued asset removal costs	278,897		263,123		267,355
Other(3)	2,996		2,307		2,607
Total non-current	$	288,097	$	266,907	$	278,382