Earnings Per Share (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Numerator for earnings (loss) per share, basic
Income (loss) from continuing operations attributable to controlling interest	$ 528	$ (27)	$ 319	$ 295
Undistributed earnings allocable to participating securities				(2)
Income (loss) from continuing operations available to shareholders	528	(27)	319	293
Denominator for earnings (loss) per share, basic
Weighted-average shares outstanding	359	320	354	320
Weighted-average shares for per share calculation, basic	359	320	354	320
Per share earnings (loss) from continuing operations, basic	$ 1.47	$ (0.08)	$ 0.90	$ 0.92
Numerator for earnings (loss) per share, diluted
Income (loss) from continuing operations attributable to controlling interest	528	(27)	319	295
Undistributed earnings allocable to participating securities				(2)
Income (loss) from continuing operations available to shareholders	$ 528	$ (27)	$ 319	$ 293
Denominator for earnings (loss) per share, diluted
Weighted-average shares outstanding	359	320	354	320
Weighted-average shares for per share calculation, diluted	359	320	354	320
Per share earnings (loss) from continuing operations, diluted	$ 1.47	$ (0.08)	$ 0.90	$ 0.92
1.50% Series B Convertible Senior Notes due December 2037
Anti-dilutive securities
Interest rate on convertible debt not having effect on earning per share calculation (as a percent)	1.50%		1.50%
1.50% Series C Convertible Senior Notes due December 2037
Anti-dilutive securities
Interest rate on convertible debt not having effect on earning per share calculation (as a percent)	1.50%		1.50%
Share-based awards
Anti-dilutive securities
Share-based awards excluded from earnings per share calculation	1.9	2.9	1.9	1.8