Condensed Consolidated Statements of Equity (Unaudited) (USD $) In Millions	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Treasury Stock [Member]	Noncontrolling Interest [Member]	Total
Balance at Dec. 31, 2010	$ 391	$ 631	$ 943	$ (150)	$ (2)	$ 23	$ 1,836
Balance (in Shares) at Dec. 31, 2010	78.0
Net income			142			11	153
Other comprehensive loss				(1)			(1)
Dividends on common stock		2	(70)				(68)
Distributions to noncontrolling interest						(16)	(16)
Benefit, dividend reinvestment and stock purchase plans	2	8			(2)		8
Benefit, dividend reinvestment and stock purchase plans (in Shares)	0.4
Purchase of treasury shares					(2)		(2)
Stock-based compensation expense (net of tax)		4					4
Balance at Jun. 30, 2011	393	645	1,015	(151)	(6)	18	1,914
Balance (in Shares) at Jun. 30, 2011	78.4
Balance at Dec. 31, 2011	586	1,989	967	(217)	(7)	21	3,339
Balance (in Shares) at Dec. 31, 2011	117.0
Net income			164			10	174
Other comprehensive loss				10			10
Dividends on common stock			(96)				(96)
Distributions to noncontrolling interest						(14)	(14)
Benefit, dividend reinvestment and stock purchase plans	3	9			(1)		11
Benefit, dividend reinvestment and stock purchase plans (in Shares)	0.5
Stock-based compensation expense (net of tax)		5					5
Balance at Jun. 30, 2012	$ 589	$ 2,003	$ 1,035	$ (207)	$ (8)	$ 17	$ 3,429
Balance (in Shares) at Jun. 30, 2012	117.5