Equity - Reconciliation of Total Equity (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012		Jun. 30, 2011
Beginning balance			$ 10,025		$ 10,027
Net income			214	[1]	361	[1]
Other comprehensive income			1		(17)
Issuance of shares through offerings and stock-based compensation plans (See Note 6C)			31		47
Dividends declared			(369)		(367)
Distributions to noncontrolling interests			(2)		(2)
Ending balance	9,900	10,049	9,900		10,049
Notes To Reconciliation Of Total Equity [Details]
Net income	64	178	216		363
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			213		360
Other comprehensive income			1		(17)
Issuance of shares through offerings and stock-based compensation plans (See Note 6C)			31		47
Dividends declared			(369)		(367)
Distributions to noncontrolling interests			0		0
Ending balance	9,897	10,046	9,897		10,046
Noncontrolling Interests
Beginning balance			4		4
Net income			1		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)
Ending balance	$ 3	$ 3	$ 3		$ 3

[1] For the six months ended June 30, 2012, consolidated net income of $216 million includes $2 million attributable to preferred shareholders of subsidiaries. For the six months ended June 30, 2011, consolidated net income of $363 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.