Computation of Earnings Per Share (Detail) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Basic and diluted loss per share:
Loss available to common stockholders	$ (417)	$ (448)
Weighted average shares outstanding, basic and diluted	332	330
Loss per share, basic and diluted	$ (1.26)	$ (1.36)
4.5 % Senior Limited Subordination Convertible Notes
Potentially dilutive shares excluded from diluted per share amounts:
Potentially dilutive shares excluded from diluted per share amounts	5	5
4.5% Convertible Notes
Potentially dilutive shares excluded from diluted per share amounts:
Potentially dilutive shares excluded from diluted per share amounts	12	12
6% Convertible Junior Subordinated Debentures
Potentially dilutive shares excluded from diluted per share amounts:
Potentially dilutive shares excluded from diluted per share amounts	4	4
6% Senior Convertible Notes
Potentially dilutive shares excluded from diluted per share amounts:
Potentially dilutive shares excluded from diluted per share amounts	40	40
Restricted Stock And Stock Options
Potentially dilutive shares excluded from diluted per share amounts:
Potentially dilutive shares excluded from diluted per share amounts	4	7