Consolidated Statements of Changes in Stockholders' Equity (Unaudited) - 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
Beginning balance at Dec. 31, 2014		$ 20,063	$ 4,105	$ 93,270	$ 129,977	$ 2,189	$ (21)	$ (17,856)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of preferred stock		1,430
Shares issued and commitments to issue common stock for employee stock-based compensation awards, and related tax effects				(987)
Other				(38)
Cumulative effect of change in accounting principle at Dec. 31, 2014					0	0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	$ 5,914				5,914
Dividends declared:
Preferred stock					(324)
Common stock ($0.44 and $0.40 per share)					(1,519)
Other comprehensive income	241					241
Purchase of treasury stock								(1,900)
Reissuance from treasury stock								1,320
Ending balance at Mar. 31, 2015	235,864	21,493	4,105	92,245	134,048	2,430	(21)	(18,436)
Beginning balance at Dec. 31, 2015	247,573	26,068	4,105	92,500	146,420	192	(21)	(21,691)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of preferred stock		0
Shares issued and commitments to issue common stock for employee stock-based compensation awards, and related tax effects				(732)
Other				14
Cumulative effect of change in accounting principle at Dec. 31, 2015					(154)	154
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	5,520				5,520
Dividends declared:
Preferred stock					(412)
Common stock ($0.44 and $0.40 per share)					(1,644)
Other comprehensive income	436					436
Purchase of treasury stock								(1,696)
Reissuance from treasury stock								1,098
Ending balance at Mar. 31, 2016	$ 250,157	$ 26,068	$ 4,105	$ 91,782	$ 149,730	$ 782	$ (21)	$ (22,289)