Stock-based compensation (Tables)

12 Months Ended

Dec. 31, 2011

Stock-based compensation [Abstract]

Components of stock-based compensation expense recognized in the Consolidated Statements of Income

	2011			2010			2009
Stock options	$	85		$	124		$	115
Restricted stock units		188			182			134
Performance units		68			47			35
Total stock-based compensation expense, pre-tax		341			353			284
Tax benefit from stock-based compensation expense		(124	)		(120	)		(97	)
Total stock-based compensation expense, net of tax	$	217		$	233		$	187

Weighted average assumptions used and the resulting weighted average grant date fair value of employee stock options

	2011		2010		2009
Closing price of our common stock on grant date	$	54.66	$	58.32	$	50.65
Expected volatility		23.5%		28.0%		39.6%
Expected life (in years)		5.9		6.6		4.6
Risk-free interest rate		2.5%		3.2%		2.1%
Expected dividend yield		2.0%		0%		0%
Fair value of stock options granted	$	11.39	$	20.97	$	18.35

Stock options information

	Options (in millions)			Weighted- average exercise price		Weighted- average remaining contractual life (years)		Aggregate intrinsic value (in millions)
Balance unexercised at December 31, 2010		46.8		$	58.66
Granted		2.3		$	54.66
Exercised		(5.0	)	$	50.22
Expired/forfeited		(9.9	)	$	60.43
Balance unexercised at December 31, 2011		34.2		$	59.11		3.8	$	245
Vested or expected to vest at December 31, 2011		33.8		$	59.15		3.7	$	242
Exercisable at December 31, 2011		23.6		$	61.49		2.3	$	135

Restricted stock units Information

	Units (in millions)			Weighted-average grant date fair value
Balance nonvested at December 31, 2010		9.3		$	52.67
Granted		4.0		$	51.83
Vested		(3.4	)	$	52.06
Forfeited		(0.9	)	$	52.77
Balance nonvested at December 31, 2011		9.0		$	52.64

Weighted average assumptions used and the resulting weighted average grant date fair value of performance units

	2011		2010		2009
Closing price of our common stock on grant date	$	51.67	$	56.90	$	47.63
Volatility		32.8%		34.7%		34.3%
Risk-free interest rate		1.2%		1.3%		1.2%
Expected dividend yield		0.1%		0%		0%
Fair value of unit	$	49.50	$	62.06	$	48.22