STATEMENTS 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	$ 89,901	$ 78,067	$ 67,750
Adjustments to reconcile net income to cash provided by operating activities:
Depreciation and amortization	109,207	106,207	106,897
Demand side management program amortization	1,811	2,034	1,793
Deferred income taxes	55,508	25,312	30,373
Amortization of investment tax credits	(275)	(341)	(298)
Allowance for equity funds used during construction	(5,342)	(4,188)	(4,082)
Provision for bad debts	3,655	3,990	3,765
Net derivative losses (gains)	268	268	(2,698)
Changes in operating assets and liabilities:
Accounts receivable	(23,518)	1,691	11,919
Accrued unbilled revenues	6,042	(4,399)	(7,922)
Inventories	(5,726)	(2,702)	19,935
Prepayments and other	(2,480)	10,920	(10,558)
Accounts payable	(1,527)	(17,015)	(5,788)
Net regulatory assets and liabilities	6,090	(20,082)	43,946
Other current liabilities	5,717	3,902	(3,236)
Pension and other employee benefit obligations	(7,576)	(4,213)	(11,229)
Change in other noncurrent assets	1,509	(2,868)	(11,067)
Change in other noncurrent liabilities	(4,299)	747	(7,989)
Net cash provided by operating activities	228,965	177,330	221,511
Investing activities
Utility capital/construction expenditures	(308,223)	(309,408)	(211,866)
Proceeds from the sale of assets	0	87,823	0
Allowance for equity funds used during construction	5,342	4,188	4,082
Investments in utility money pool arrangement	(40,300)	(204,200)	(990,800)
Receipts from utility money pool arrangement	40,300	281,200	1,004,300
Other, net	221	0	0
Net cash used in investing activities	(302,660)	(140,397)	(194,284)
Financing activities
Proceeds (repayment of) from short-term borrowings, net	(49,000)	49,000	0
Proceeds from issuance of long-term debt	193,137	0	0
Repayment of long-term debt	(101,800)	(25,000)	(100,057)
Borrowings under utility money pool arrangement	293,500	483,200	0
Repayments under utility money pool arrangement	(288,500)	(483,200)	0
Capital contributions from parent	89,631	583	16,243
Dividends paid to parent	(64,401)	(67,101)	(66,845)
Net cash provided by (used in) financing activities	72,567	(42,518)	(150,659)
Net change in cash and cash equivalents	(1,128)	(5,585)	(123,432)
Cash and cash equivalents at beginning of year	1,778	7,363	130,795
Cash and cash equivalents at end of year	650	1,778	7,363
Supplemental disclosure of cash flow information:
Cash paid for interest (net of amounts capitalized)	(57,122)	(57,969)	(69,619)
Cash paid for income taxes, net	(2,245)	(7,277)	(20,118)
Supplemental disclosure of non-cash investing transactions:
Property, plant and equipment additions in accounts payable	$ 23,570	$ 9,539	$ 12,432