CONSOLIDATED STATEMENTS OF CASH FLOWS (UNAUDITED) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Operating activities
Net income	$ 116,605	$ 93,285
Adjustments to reconcile net income to cash provided by operating activities:
Depreciation and amortization	90,809	84,948
Demand side management program amortization	1,257	1,392
Deferred income taxes	66,372	49,182
Amortization of investment tax credits	(740)	(651)
Allowance for equity funds used during construction	(5,923)	(2,726)
Net realized and unrealized hedging and derivative transactions	(164)	6,496
Changes in operating assets and liabilities:
Accounts receivable	41,048	30,996
Accrued unbilled revenues	49,579	112,150
Inventories	42,434	56,836
Prepayments and other	(10,662)	(3,250)
Accounts payable	(18,383)	(124,292)
Net regulatory assets and liabilities	67,907	10,147
Other current liabilities	10,870	39,057
Pension and other employee benefit obligations	(44,273)	(39,547)
Change in other noncurrent assets	3,779	(6,434)
Change in other noncurrent liabilities	1,720	(1,297)
Net cash provided by operating activities	412,235	306,292
Investing activities
Utility capital/construction expenditures	(226,948)	(152,420)
Allowance for equity funds used during construction	5,923	2,726
Investments in utility money pool arrangement	(276,000)	(383,000)
Repayments from utility money pool arrangement	76,000	363,000
Net cash used in investing activities	(421,025)	(169,694)
Financing activities
Repayments of short-term borrowings, net	(154,000)	0
Borrowings under utility money pool arrangement	14,000	0
Repayments under utility money pool arrangement	(14,000)	0
Proceeds from issuance of long-term debt	493,164	0
Repayments of long-term debt	(250,000)	0
Dividends paid to parent	(66,803)	(134,004)
Net cash provided by (used in) financing activities	22,361	(134,004)
Net change in cash and cash equivalents	13,571	2,594
Cash and cash equivalents at beginning of period	5,150	3,763
Cash and cash equivalents at end of period	18,721	6,357
Supplemental disclosure of cash flow information:
Cash paid for interest (net of amounts capitalized)	(54,770)	(44,384)
Cash (paid) received for income taxes, net	(16,308)	3,623
Supplemental disclosure of non-cash investing and financing transactions:
Property, plant and equipment additions in accounts payable	$ 81,470	$ 60,020