CONSOLIDATED STATEMENTS OF CASH FLOWS (USD $) In Thousands, unless otherwise specified	6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012
Operating activities:
Net income (loss)	$ 168,380	$ 146,171
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Depreciation	178,480	163,558
Amortization	12,177	24,890
Conservation amortization	56,576	62,921
Deferred income taxes and tax credits, net	69,635	52,657
Net unrealized (gain) loss on derivative instruments	(53,496)	(76,850)
Funding of pension liability	(10,200)	(11,400)
Derivative contracts classified as financing activities due to merger	26,013	47,423
AFUDC - Equity	(11,222)	(14,485)
Regulatory Assets	(66,102)	(110,088)
Regulatory liabilities	10,341	37,752
Other long-term assets	10,842	7,302
Other long-term liabilities	54,837	45,284
Change in certain current assets and liabilities:
Accounts receivable and unbilled revenue	136,457	174,353
Materials and supplies	(2,184)	(13,722)
Fuel and gas inventory	11,104	31,138
Income taxes	4,795	1,892
Prepayments and other	(7,340)	(4,190)
Purchased gas adjustment	(18,078)	23,671
Accounts payable	(74,666)	(86,438)
Taxes payable	(11,589)	(10,835)
Accrued expenses and other	(15,507)	6,621
Net cash provided by operating activities	469,253	497,625
Investing activities:
Construction expenditures - excluding equity AFUDC	(326,082)	(398,900)
Proceeds from disposition of assets	108,166	0
Restricted cash	(1,023)	639
Other	(5,119)	(28,410)
Net cash used in investing activities	(224,058)	(426,671)
Financing activities:
Change in short-term debt and leases, net	(184,789)	9,211
Dividends paid	(84,609)	(88,444)
Long-term notes and bonds issued	161,860	1,314,000
Redemption of bonds and notes	(216,860)	(1,273,000)
Derivative contracts classified as financing activities due to merger	(26,013)	(47,423)
Issuance cost of bonds and other	(2,722)	(6,400)
Net cash provided by (used in) financing activities	(353,133)	(92,056)
Net increase (decrease) in cash and cash equivalents	(107,938)	(21,102)
Cash and cash equivalents at beginning of period	135,542	37,235
Cash and cash equivalents at end of period	27,604	16,133
Supplemental cash flow information:
Cash payments for interest (net of capitalized interest)	162,588	170,262
Cash payments (refunds) for income taxes	(4,500)	(1,898)
Subsidiaries [Member]
Operating activities:
Net income (loss)	206,601	193,588
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Depreciation	178,480	163,558
Amortization	12,177	24,890
Conservation amortization	56,576	62,921
Deferred income taxes and tax credits, net	90,940	77,611
Net unrealized (gain) loss on derivative instruments	(45,365)	(49,715)
Funding of pension liability	(10,200)	(11,400)
AFUDC - Equity	(11,222)	(14,485)
Regulatory Assets	(66,102)	(110,088)
Regulatory liabilities	10,341	37,752
Other long-term assets	14,921	10,875
Other long-term liabilities	33,285	31,394
Change in certain current assets and liabilities:
Accounts receivable and unbilled revenue	130,617	174,193
Materials and supplies	(2,184)	(13,722)
Fuel and gas inventory	11,104	31,138
Income taxes	4,795	1,892
Prepayments and other	(7,340)	(4,190)
Purchased gas adjustment	(18,078)	23,671
Accounts payable	(68,819)	(86,555)
Taxes payable	(11,589)	(10,835)
Accrued expenses and other	(17,586)	(14,296)
Net cash provided by operating activities	491,352	518,197
Investing activities:
Construction expenditures - excluding equity AFUDC	(326,082)	(398,900)
Proceeds from disposition of assets	108,166	0
Restricted cash	(1,023)	639
Other	(4,902)	(7,635)
Net cash used in investing activities	(223,841)	(405,896)
Financing activities:
Change in short-term debt and leases, net	(184,789)	9,211
Dividends paid	(188,064)	(137,329)
Long-term notes and bonds issued	161,860	0
Redemption of bonds and notes	(161,860)	0
Issuance cost of bonds and other	(2,725)	(563)
Net cash provided by (used in) financing activities	(375,578)	(128,681)
Net increase (decrease) in cash and cash equivalents	(108,067)	(16,380)
Cash and cash equivalents at beginning of period	135,530	31,010
Cash and cash equivalents at end of period	27,463	14,630
Supplemental cash flow information:
Cash payments for interest (net of capitalized interest)	122,892	106,823
Cash payments (refunds) for income taxes	$ (4,500)	$ (1,898)