Weighted Average Common Shares - Additional Information (Detail) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Repurchase of outstanding common stock permitted	$ 6,500,000,000		$ 6,500,000,000
Common stock, shares purchased value	$ 20,000,000		$ 36,000,000	$ 1,765,000,000
Number of shares purchased	63,200,000		63,200,000
Shares purchased value	$ 5,300,000,000		$ 5,300,000,000
Restricted Stock
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Shares granted			1,122,724	1,028,883
Antidilutive Securities Excluded From Computation Of Earnings Per Share Amount	3,027,138		2,952,012
Performance Share Units
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Shares granted			362,873	298,222
Antidilutive Securities Excluded From Computation Of Earnings Per Share Amount	912,383		1,025,826
Stock Options
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Shares granted			521,773	162,911
Antidilutive Securities Excluded From Computation Of Earnings Per Share Amount	7,012,818	1,978,777	6,901,674	2,577,984