Equity - Common Stock (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011	Dec. 31, 2011
Common Stock [Details]
Common shares, authorized	500		500
Common shares, outstanding	296		295
Total issuances - shares	0.8	1.0
Issuance through 401(k) and or IPP - shares	0	0
Total issuances - net proceeds	$ 3	$ 8
Issuances through 401(k) and or IPP - net proceeds	$ 0	$ 1