Statement of Cash Flows (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
OPERATING ACTIVITIES:
Net income	$ 152,813	$ 149,527	$ 153,651
Adjustments to reconcile net income to net cash provided by (used in) operating activities:
Depreciation	90,486	87,915	86,373
Regulatory credits	(1,023)	(1,662)	(2,403)
(Gain) loss on sale of property, plant and equipment	6	0	(508)
Amortization of deferred charges and credits	1,491	2,293	5,050
Allowance for equity funds used during construction	(1,438)	(1,947)	(1,996)
Changes in current assets and liabilities:
Trade accounts receivable	270	1,927	(326)
Affiliated receivables, including income taxes	(132)	2,396	(3,284)
Exchange gas due from others	402	1,262	2,623
Materials and supplies	1,231	(1,759)	(143)
Other current assets	(54)	826	1,744
Trade accounts payable	(597)	(559)	(828)
Affiliated payable, including income taxes	(1,462)	(13,026)	350
Exchange gas due to others	(402)	(1,262)	(2,623)
Other accrued liabilities	827	985	(4,860)
Changes in noncurrent assets and liabilities:
Deferred charges	(2,829)	(5,865)	(3,362)
Other deferred credits	4,769	8,148	5,340
Net cash provided by operating activities	244,358	229,199	234,798
FINANCING ACTIVITIES:
Proceeds from issuance of long-term debt	0	8,000	0
Retirement of long-term debt	0	(8,000)	0
Capital contributions from parent	5,100	19,000	49,180
Distributions paid	(127,000)	(191,450)	(135,000)
Other	657	(1,209)	2,212
Net cash used in financing activities	(121,243)	(173,659)	(83,608)
Property, plant and equipment -
Capital expenditures	(115,111)	(120,236)	(152,580)
Proceeds from sales	(993)	3,913	2,234
Repayments from (advances to) affiliates	(6,979)	60,386	(787)
Net cash used in investing activities	(123,083)	(55,937)	(151,133)
NET INCREASE (DECREASE) IN CASH	32	(397)	57
CASH AT BEGINNING OF PERIOD	5	402	345
CASH AT END OF PERIOD	$ 37	$ 5	$ 402