CONSOLIDATED 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	$ 396,803	$ 399,720	$ 323,320
Adjustments to reconcile net income to cash provided by operating activities:
Depreciation and amortization	333,960	289,050	260,935
Demand side management program amortization	7,876	19,666	27,625
Deferred income taxes	226,555	154,861	197,348
Amortization of investment tax credits	(2,613)	(2,693)	(2,375)
Allowance for equity funds used during construction	(7,710)	(11,370)	(41,118)
Provision for bad debts	20,371	21,571	21,189
Net derivative losses (gains)	12,102	(23,112)	42,896
Changes in operating assets and liabilities:
Accounts receivable	(22,962)	16,807	7,082
Accrued unbilled revenues	(7,009)	16,418	40,573
Inventories	(30,939)	34,424	(19,700)
Prepayments and other	26,152	14,328	(44,555)
Accounts payable	40,754	(106,632)	(32,982)
Net regulatory assets and liabilities	46,334	17,098	(64,251)
Other current liabilities	29,843	16,067	(1,531)
Pension and other employee benefit obligations	(84,181)	(29,820)	(216,696)
Change in other noncurrent assets	4,116	(2,578)	375
Change in other noncurrent liabilities	(15,039)	(11,474)	(24,796)
Net cash provided by operating activities	974,413	812,331	473,339
Investing activities
Utility capital/construction expenditures	(726,830)	(571,746)	(627,421)
Allowance for equity funds used during construction	7,710	11,370	41,118
Acquisition of generation assets	0	(732,495)	0
Investments in utility money pool	(609,300)	(831,000)	(274,200)
Repayments from utility money pool	557,300	831,000	274,200
Net cash used in investing activities	(771,120)	(1,292,871)	(586,303)
Financing activities
Proceeds from (repayments of) short-term borrowings, net	(269,400)	174,400	55,000
Proceeds from issuance of long-term debt	246,305	395,313	394,570
Repayments of long-term debt, including reacquisition premiums	0	0	(200,000)
Borrowings under utility money pool arrangement	203,800	255,500	802,800
Repayments under utility money pool arrangement	(203,800)	(339,500)	(759,800)
Capital contributions from parent	60,800	260,116	108,813
Dividends paid to parent	(270,147)	(265,806)	(266,188)
Net cash (used in) provided by financing activities	(232,442)	480,023	135,195
Net change in cash and cash equivalents	(29,149)	(517)	22,231
Cash and cash equivalents at beginning of period	32,912	33,429	11,198
Cash and cash equivalents at end of period	3,763	32,912	33,429
Supplemental disclosure of cash flow information:
Cash paid for interest (net of amounts capitalized)	(172,266)	(156,906)	(147,186)
Cash received (paid) for income taxes, net	28,525	(63,999)	(6,155)
Supplemental disclosure of non-cash investing and financing transactions:
Property, plant and equipment additions in accounts payable	59,094	96,359	13,332
Storage assets under capital lease	$ 7,375	$ 12,628	$ 143,105