CONSOLIDATED STATEMENTS OF OPERATIONS (USD $) In Millions, unless otherwise specified	9 Months Ended	3 Months Ended	12 Months Ended
	Dec. 31, 2012 Successor [Member]	Mar. 25, 2012 Predecessor [Member]	Dec. 31, 2011 Predecessor [Member]	Dec. 31, 2010 Predecessor [Member]
Operating revenues	$ 1,263	$ 443	$ 1,997	$ 1,789
Operating expenses:
Cost of natural gas and other energy	521	197	965	818
Operating, maintenance and general	340	105	373	345
Depreciation and amortization	179	49	204	196
Taxes, other than on income and revenues	37	11	42	43
Total operating expenses	1,077	362	1,584	1,402
Operating income	186	81	413	387
Other income (expenses):
Interest expense	(131)	(50)	(218)	(216)
Earnings from unconsolidated investments	(7)	16	99	105
Other, net	2	(2)	0	2
Total other expenses, net	(136)	(36)	(119)	(109)
Income from continuing operations before income tax expense	50	45	294	278
Income tax expense	39	12	80	80
Income (Loss) from Continuing Operations	11	33	214	198
Income (Loss) from Discontinued Operations	28	17	41	27
Net income (loss)	$ 39	$ 50	$ 255	$ 225