Condensed Consolidated Statement of Cash Flows (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Cash flows from operating activities:
Net Income	$ 88,975	$ 74,783
Adjustments to reconcile net income to net cash provided by (used in) operating activities:
Depreciation and amortization	76,466	66,102
Allowance for equity funds used during construction (equity AFUDC)	(3,366)	(2,414)
Changes in operating assets and liabilities:
Receivables - affiliates	(268)	5,156
Receivables - others	(6,116)	(3,529)
Transportation and exchange gas receivable	(1,872)	2,539
Inventories	(4,196)	(892)
Payables - affiliates	(5,473)	14,502
Payables - others	(9,242)	(24,137)
Accrued liabilities	11,735	(7,866)
Reserve for rate refunds	10,574	0
Asset retirement obligation removal costs	(1,847)	(7,873)
Other, net	4,641	9,131
Net cash provided by operating activities	160,011	125,502
Cash flows from financing activities:
Cash distributions to parent	(65,000)	(54,259)
Cash contributions from parent	55,000	34,000
Other, net	7,542	(5,931)
Net cash used in financing activities	(2,458)	(26,190)
Cash flows from investing activities:
Property, plant and equipment additions, net of equity AFUDC*	(85,816)	(61,611)
Disposal of property, plant and equipment, net	1,423	3,438
Advances to affiliate, net	(73,178)	(39,755)
Contributions to unconsolidated affiliates	0	(3,998)
Purchase of ARO Trust investments	(8,938)	(7,766)
Proceeds from sale of ARO Trust investments	8,577	10,305
Other, net	333	13
Net cash used in investing activities	(157,599)	(99,374)
Decrease in cash	(46)	(62)
Cash at beginning of period	185	164
Cash at end of period	$ 139	$ 102