Segment Information Reconciliation of Total Segment Margin to Income (Loss) Before Income Taxes (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Segment Information [Abstract]
Total segment margin	$ 350	$ 194	$ 575	$ 347
Operation and maintenance	(93)	(73)	(171)	(142)
General and administrative	(54)	(18)	(87)	(51)
Gain (loss) on asset sales, net	0	(1)	2	(2)
Depreciation, depletion and amortization	(168)	(68)	(262)	(133)
Income from unconsolidated affiliates	47	31	90	66
Interest expense, net	(78)	(41)	(134)	(78)
Loss on debt refinancing, net	0	(7)	0	(7)
Other income and deductions, net	(7)	(7)	(5)	(21)
(LOSS) INCOME BEFORE INCOME TAXES	$ (3)	$ 10	$ 8	$ (21)