Changes in Equity (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Stockholders Equity Note [Line Items]
Beginning Balance	$ 1,838	$ 1,786
Total comprehensive income	130	32
Preferred stock dividends	(8)	(8)
Common stock dividends	(7)
Dividends attributable to noncontrolling interests		(2)
Stock compensation	5	8
Stock withheld for employee taxes		(2)
Ending Balance	1,958	1,814
To US Parent
Stockholders Equity Note [Line Items]
Beginning Balance	1,737	1,687
Total comprehensive income	126	27
Preferred stock dividends	(8)	(8)
Common stock dividends	(7)
Stock compensation	5	8
Stock withheld for employee taxes		(2)
Ending Balance	1,853	1,712
Attributable to Non- controlling Interests
Stockholders Equity Note [Line Items]
Beginning Balance	101	99
Total comprehensive income	4	5
Dividends attributable to noncontrolling interests		(2)
Ending Balance	$ 105	$ 102