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/(loss)	Shares held in RSU Trust, at cost	Treasury stock, at cost
Beginning balance at Dec. 31, 2016		$ 26,068	$ 4,105	$ 91,627	$ 162,440	$ (1,175)	$ (21)	$ (28,854)
Cumulative effect of changes in accounting principles at Dec. 31, 2016					0	0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares issued and commitments to issue common stock for employee shared-based compensation awards, and related tax effects				(865)
Other				(158)
Net income	$ 13,477				13,477
Dividends declared:
Preferred stock					(823)
Common stock ($1.12 and $1.00 per share)					(3,606)
Other comprehensive income/(loss)	783					783
Repurchase								(5,839)
Reissuance								1,324
Ending balance at Jun. 30, 2017	258,483	26,068	4,105	90,604	171,488	(392)	(21)	(33,369)
Beginning balance at Mar. 31, 2017						(923)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	7,029
Dividends declared:
Other comprehensive income/(loss)	531
Ending balance at Jun. 30, 2017	258,483	26,068	4,105	90,604	171,488	(392)	(21)	(33,369)
Beginning balance at Dec. 31, 2017	255,693	26,068	4,105	90,579	177,676	(119)	(21)	(42,595)
Cumulative effect of changes in accounting principles at Dec. 31, 2017					(183)	88
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares issued and commitments to issue common stock for employee shared-based compensation awards, and related tax effects				(1,076)
Other				(111)
Net income	17,028				17,028
Dividends declared:
Preferred stock					(788)
Common stock ($1.12 and $1.00 per share)					(3,852)
Other comprehensive income/(loss)	(1,107)					(1,107)
Repurchase								(9,639)
Reissuance								1,405
Ending balance at Jun. 30, 2018	257,458	26,068	4,105	89,392	189,881	(1,138)	(21)	(50,829)
Beginning balance at Mar. 31, 2018						(1,063)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	8,316
Dividends declared:
Other comprehensive income/(loss)	(75)
Ending balance at Jun. 30, 2018	$ 257,458	$ 26,068	$ 4,105	$ 89,392	$ 189,881	$ (1,138)	$ (21)	$ (50,829)