Stockholders' Equity - Additional Durational Information (Detail) (USD $) In Millions, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Stockholders Equity Note [Line Items]
Number of shares underlying TSOs sold to selected financial institutions under the TSO program	635,047
Number of shares underlying TSOs sold to selected financial institutions under the TSO program, total value	$ 167
Number of shares underlying TSOs sold to selected financial institutions under the TSO program, average per share price	$ 262.74
Number of shares underlying TSOs sold to selected financial institutions under the TSO program, average premium per share price	$ 11.09
Total grant date fair value of stock options vested	561	690	690
Aggregate intrinsic value of all options and warrants exercised	$ 674	$ 794	$ 566
Employee stock options
Stockholders Equity Note [Line Items]
Stock Plans, terms	10 years	10 years	10 years
Stock Plans, vesting period	4 years	4 years	4 years
Restricted Stock Units (RSUs)
Stockholders Equity Note [Line Items]
Stock Plans, vesting period	4 years	4 years	4 years