Consolidated Statement of Cash Flows (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Cash flows from operating activities:
Net Income	$ 279,658	$ 270,776	$ 280,357
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	260,069	252,131	247,543
Allowance for equity funds used during construction (Equity AFUDC)	(10,588)	(8,539)	(7,835)
Changes in operating assets and liabilities:
Receivables - affiliates	(982)	1,702	(3,192)
Receivables - others	(11,155)	6,714	(25,759)
Transportation and exchange gas receivable	(2,497)	4,833	3,399
Inventories	50,295	(46,261)	36,667
Payables - affiliates	(1,832)	(23,485)	(7,461)
Payables - others	14,577	15,888	(51,868)
Accrued liabilities	26,637	405	(24,587)
Asset retirement obligation removal costs	(43,666)	(6,990)	(10,063)
Reserve for rate refunds	0	(564)	(13,798)
Other, net	11,128	42,873	27,393
Net cash provided by operating activities	571,644	509,483	450,796
Cash flows from financing activities:
Additions to long-term debt	372,518	0	0
Retirement of long-term debt	(300,000)	0	0
Debt issue costs	(3,846)	0	0
Cash distributions	(219,000)	(333,791)	(145,000)
Cash contributions from parent	115,000	75,000	0
Other	(4,681)	1,146	4,101
Net cash used in financing activities	(40,009)	(257,645)	(140,899)
Cash flows from investing activities:
Property, plant and equipment additions, net of equity AFUDC*	(385,671)	(376,502)	(303,458)
Disposal of property, plant and equipment, net	2,698	13,959	(2,328)
Advances to affiliates, net	(144,773)	126,999	189
Purchase of long-term investments	(14,834)	0	0
Purchase of ARO Trust investments	(41,310)	(46,952)	(45,604)
Proceeds from sale of ARO Trust investments	56,576	31,001	40,713
Other, net	(4,305)	(303)	271
Net cash used in investing activities	(531,619)	(251,798)	(310,217)
Increase (decrease) in cash	16	40	(320)
Cash at beginning of period	148	108	428
Cash at end of period	$ 164	$ 148	$ 108