Equity - Reconciliation of Total Equity (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2010	Sep. 30, 2010	Jun. 30, 2010	Mar. 31, 2010	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Beginning balance				$ 10,027				$ 9,455	$ 10,027	$ 9,455	$ 8,693
Cumulative effect of change in accounting principle										(2)
Net income									578	859	757
Other comprehensive loss									(40)	(38)	29
Issuance of shares through offerings and stock-based compensation plans (See Note 5D)									53	434	623
Allocation of ESOP shares									0	21	21
Stock-based compensation expense									38	27	36
Dividends declared									(628)	(726)	(704)
Distributions to noncontrolling interests									(3)	(2)	(1)
Other									0	(1)	1
Ending balance	10,025				10,027				10,025	10,027	9,455
Notes To Reconciliation Of Total Equity [Details]
Net income	(74)	293	178	185	128	365	180	190	582	863	761
Noncontrolling Interests
Beginning balance				4				6	4	6	6
Cumulative effect of change in accounting principle										(2)
Net income									3	3	0
Distributions to noncontrolling interests									(3)	(2)	(1)
Other									0	(1)	1
Ending balance	$ 4				$ 4				$ 4	$ 4	$ 6