Equity - Reconciliation of Total Equity (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2012		Mar. 31, 2011
Beginning balance	$ 10,025		$ 10,027
Net income	150	[1]	183	[1]
Other comprehensive income	5		4
Issuance of shares through offerings and stock-based compensation plans (See Note 6C)	17		19
Dividends declared	(184)		(183)
Distributions to noncontrolling interests	(2)		(2)
Other	0		2
Ending balance	10,011		10,050
Notes To Reconciliation Of Total Equity [Details]
Net income	152		185
Net income attributable to preferred shareholders of subsidiaries excluded from reconciliation of total equity	2		2
Total Common Stock Equity
Beginning balance	10,021		10,023
Net income	150		184
Other comprehensive income	5		4
Issuance of shares through offerings and stock-based compensation plans (See Note 6C)	17		19
Dividends declared	(184)		(183)
Distributions to noncontrolling interests	0		0
Other	0		0
Ending balance	10,009		10,047
Noncontrolling Interests
Beginning balance	4		4
Net income	0		(1)
Other comprehensive income	0		0
Issuance of shares through offerings and stock-based compensation plans (See Note 6C)	0		0
Dividends declared	0		0
Distributions to noncontrolling interests	(2)		(2)
Other	0		2
Ending balance	$ 2		$ 3

[1] For the three months ended March 31, 2012, consolidated net income of $152 million includes $2 million attributable to preferred shareholders of subsidiaries. For the three months ended March 31, 2011, consolidated net income of $185 million includes $2 million attributable to preferred shareholders of subsidiaries. Income attributable to preferred shareholders of subsidiaries is not a component of total equity and is excluded from the table above.