Consolidated Balance Sheet (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Current Assets:
Cash	$ 185	$ 164
Receivables:
Trade less allowance of $0 ($407 in 2011)	116,847	107,585
Affiliates	2,656	5,903
Advances to affiliate	312,165	253,611
Other	8,928	14,004
Transportation and exchange gas receivables	2,876	4,914
Gas in storage, at original cost	812	822
Gas available for customer nomination, at average cost	8,600	349
Material and supplies, at lower of average cost or market	36,506	34,437
Regulatory assets	36,706	37,877
Other	14,342	12,973
Total current assets	540,623	472,639
Investments, at cost plus equity in undistributed earnings	55,603	56,994
Property, Plant and Equipment:
Natural gas transmission plant	8,506,189	8,089,338
Less-Accumulated depreciation and amortization	2,954,276	2,801,104
Total property, plant and equipment, net	5,551,913	5,288,234
Other Assets:
Regulatory assets	214,912	207,945
Other	47,764	50,471
Total other assets	262,676	258,416
Total assets	6,410,815	6,076,283
Payables:
Trade	107,795	93,862
Affiliates	32,006	16,937
Cash overdrafts	11,512	14,844
Transportation and exchange gas payables	3,513	2,784
Property and other taxes	13,326	11,672
Interest	20,784	25,947
Regulatory liabilities	14,624	1,958
Customer advances	11,020	20,221
Asset retirement obligations	43,472	57,403
Other	36,107	23,189
Current maturities of long-term debt	0	324,321
Total current liabilities	294,159	593,138
Long-Term Debt	1,428,323	1,029,397
Other Long-Term Liabilities:
Asset retirement obligations	253,398	245,365
Regulatory liabilities	232,888	182,848
Other	5,339	6,182
Total other long-term liabilities	491,625	434,395
Contingent Liabilities and Commitments (Note 2)
Owner's Equity:
Member's capital	1,993,412	1,841,888
Retained earnings	2,204,018	2,177,811
Accumulated other comprehensive income (loss)	(722)	(346)
Total owner's equity	4,196,708	4,019,353
Total liabilities and owner's equity	$ 6,410,815	$ 6,076,283