Capital Stock (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Basic:
Income attributable to common stock	$ 778	$ 1,115
Income (loss) attributable to common stock, shares	385	383
Income (loss) attributable to common stock, per share	$ 2.02	$ 2.91
Effect of Dilutive Securities:
Mandatory Convertible Preferred Stock, Income	19	19
Mandatory Convertible Preferred Stock	12	12
Stock options and other	2	2
Diluted:
Income (loss) attributable to common stock, including assumed conversions, Amount	$ 797	$ 1,134
Income (loss) attributable to common stock, including assumed conversions, Shares	399	397
Income (loss) attributable to common stock, including assumed conversions, per share	$ 2.00	$ 2.86