Consolidated Statements of Changes in Stockholders' Equity - USD ($) $ in Millions	Total	Preferred stock	Common stock	Additional paid-in capital	Retained earnings	Accumulated other comprehensive income	Shares held in RSU Trust, at cost	Treasury stock, at cost
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance at beginning of year, adjusted					$ 103,939
Beginning balance at Dec. 31, 2012		$ 9,058	$ 4,105	$ 94,604	104,223	$ 4,102	$ (21)	$ (12,002)
Cumulative effect of change in accounting principle at Dec. 31, 2012					(284)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of preferred stock		3,900
Redemption of preferred stock		(1,800)
Shares issued and commitments to issue common stock for employee stock-based compensation awards, and related tax effects				(752)
Other				(24)
Net income	$ 17,886				17,886
Dividends declared:
Preferred stock					(805)
Common stock ($1.72, $1.58 and $1.44 per share for 2015, 2014 and 2013, respectively)					(5,585)
Other comprehensive income/(loss)	(2,903)					(2,903)
Purchase of treasury stock			(4,789)					(4,789)
Reissuance from treasury stock								1,944
Ending balance at Dec. 31, 2013	210,857	11,158	4,105	93,828	115,435	1,199	(21)	(14,847)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance at beginning of year, adjusted					115,435
Cumulative effect of change in accounting principle at Dec. 31, 2013					0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of preferred stock		8,905
Redemption of preferred stock		0
Shares issued and commitments to issue common stock for employee stock-based compensation awards, and related tax effects				(508)
Other				(50)
Net income	21,745				21,745
Dividends declared:
Preferred stock					(1,125)
Common stock ($1.72, $1.58 and $1.44 per share for 2015, 2014 and 2013, respectively)					(6,078)
Other comprehensive income/(loss)	990					990
Purchase of treasury stock			(4,760)					(4,760)
Reissuance from treasury stock								1,751
Ending balance at Dec. 31, 2014	231,727	20,063	4,105	93,270	129,977	2,189	(21)	(17,856)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance at beginning of year, adjusted					129,977
Cumulative effect of change in accounting principle at Dec. 31, 2014					0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of preferred stock		6,005
Redemption of preferred stock		0
Shares issued and commitments to issue common stock for employee stock-based compensation awards, and related tax effects				(436)
Other				(334)
Net income	24,442				24,442
Dividends declared:
Preferred stock					(1,515)
Common stock ($1.72, $1.58 and $1.44 per share for 2015, 2014 and 2013, respectively)					(6,484)
Other comprehensive income/(loss)	(1,997)					(1,997)
Purchase of treasury stock			$ (5,616)					(5,616)
Reissuance from treasury stock								1,781
Ending balance at Dec. 31, 2015	$ 247,573	$ 26,068		$ 92,500	$ 146,420	$ 192	$ (21)	$ (21,691)