Stock Option Information (Detail) (USD $) In Millions, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2011
Shares
Outstanding at end of year	9,357,000
Options exercisable at end of period	7,913,000
Weighted-average exercise price
Outstanding at end of year	$ 36.71
Options exercisable at end of period	$ 37.75
Employee Stock Option
Shares
Outstanding at beginning of year	9,690,000
Granted	891,000
Exercised	(28,000)
Forfeited or expired	(1,196,000)
Outstanding at end of year	9,357,000
Options exercisable at end of period	7,913,000
Weighted-average exercise price
Outstanding at beginning of year	$ 36.59
Granted	$ 33.98
Exercised	$ 26.83
Forfeited or expired	$ 33.94
Outstanding at end of year	$ 36.71
Options exercisable at end of period	$ 37.75
Aggregate intrinsic value
Outstanding at end of year	$ 6
Options exercisable at end of period	$ 4