Common, Preferred and Treasury Stock (Share Acitivity within Common, Preferred and Treasury Stock) (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Values
Beginning Balance	$ 16,232	$ 15,870	$ 15,665
Shares acquired for treasury	(1,605)	(661)	(850)
Impact of stock transactions under stock compensation plans, net	67	80	75
Other	(6)	1	(2)
Ending Balance	16,385	16,232	15,870	$ 15,665
4.90% fixed-to-floating non-cumulative Series J perpetual preferred stock
Values
Issuance of preferred stock				297
Series I Preferred Stock
Values
Issuance of preferred stock					$ 441
Preferred stock Series H
Values
Issuance of preferred stock					$ 593
Common stock
Values
Beginning Balance	2,051	2,051	2,051
Ending Balance	$ 2,051	$ 2,051	$ 2,051	$ 2,051
Shares
Beginning balance	923,892,581	923,892,581	923,892,581
Ending balance	923,892,581	923,892,581	923,892,581	923,892,581
Preferred Stock
Values
Beginning Balance	$ 1,331	$ 1,331	$ 1,331
Ending Balance	$ 1,331	$ 1,331	$ 1,331	$ 1,331
Shares
Beginning balance	54,000	54,000	54,000
Ending balance	54,000	54,000	54,000	54,000
Treasury Stock
Values
Beginning Balance	$ (3,433)	$ (2,764)	$ (1,972)
Shares acquired for treasury	(1,588)	(668)	(847)
Impact of stock transactions under stock compensation plans, net	16	(4)	52
Other	3	3	3
Ending Balance	$ (5,002)	$ (3,433)	$ (2,764)	$ (1,972)
Shares
Beginning balance	173,413,282	138,812,267	99,845,629
Shares acquired for treasury	58,493,506	34,633,221	42,607,855
Impact of stock transactions under stock compensation plans, net	(1,693,503)	42,357	(3,593,406)
Other	(125,597)	(74,563)	(47,811)
Ending balance	230,087,688	173,413,282	138,812,267	99,845,629