Reconciling Weighted-Average Number of Shares Used in Earnings Per Share Calculations (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Earnings Per Share Disclosure [Line Items]
Income from continuing operations	$ 60	$ 116	$ 222	$ 164
Less: Noncontrolling interests	4	2	10	9
Less: Preferred stock dividend requirements	8	8	23	23
Income from continuing operations available to common stockholders - Numerator basic	48	106	189	132
Preferred stock dividend requirements	8	8	23	23
Numerator diluted	56	114	212	155
Net income available to common stockholders - Numerator basic	48	102	189	125
Preferred stock dividend requirements	8	8	23	23
Numerator diluted	$ 56	$ 110	$ 212	$ 148
Weighted-average number of shares outstanding - Denominator basic	148.1	147.1	147.8	146.3
Employee compensation-related shares, including stock options	1.7	2.8	2.2	3.5
Conversion of preferred stock	64.7	64.7	64.7	65.5
Denominator diluted	214.5	214.6	214.7	215.3