Weighted Average Common Shares and Share Repurchase Plan - Additional Information (Detail) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013	May 31, 2014	Mar. 31, 2013
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Out-of-the-money stock options	124,357	3,680,344	1,214,422	4,661,606
Repurchase of outstanding common stock					$ 6,500,000,000	$ 4,000,000,000
Number of shares purchased			30,100,000
Shares purchased value			2,669,000,000	500,000,000
Additional amount of common stock that may be repurchased under this board authorized plan	$ 2,300,000,000		$ 2,300,000,000
Average cost per share of share repurchased			$ 88.67
Restricted Stock
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Shares granted			1,073,179	1,205,569
Performance Share Units
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Shares granted			298,222	279,093
Equity Option
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Shares granted			162,911