Consolidated Statements of Shareholders' Equity - USD ($) $ in Millions	Total	Cumulative effect of change in accounting principle - Reserve for Credit Losses	Preferred Shares [Member]	Common Shares [Member]	Additional Paid-in Capital [Member]	Accumulated Other Comprehensive Loss [Member]	Retained Earnings [Member]	Retained Earnings [Member] Cumulative effect of change in accounting principle - Reserve for Credit Losses	Series B Preferred Stock [Member]	Series B Preferred Stock [Member] Retained Earnings [Member]	Series C Preferred Stock [Member]	Series C Preferred Stock [Member] Retained Earnings [Member]
Beginning Balance at Dec. 31, 2018	$ 22,290		$ 0	$ 170	$ 12,218	$ (2,597)	$ 12,499
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	5,066						5,066
Other comprehensive loss	(64)					(64)	0
Repurchase of common shares	(3,325)			(6)	(517)		(2,802)
Other changes, primarily employee plans	127			1	168		(42)
Cash dividends declared preferred									$ (19)	$ (19)	$ (42)	$ (42)
Cash dividends declared common	(1,008)						(1,008)
Ending Balance at Sep. 30, 2019	23,025		0	165	11,869	(2,661)	13,652
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Preferred stock, dividend per share (in dollars per share)									$ 26.00		$ 49.00
Beginning Balance at Jun. 30, 2019	23,092		0	167	11,980	(2,606)	13,551
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	1,755						1,755
Other comprehensive loss	(55)					(55)	0
Repurchase of common shares	(1,450)			(2)	(170)		(1,278)
Other changes, primarily employee plans	58				59		(1)
Cash dividends declared preferred											$ (21)	(21)
Cash dividends declared common	(354)						(354)
Ending Balance at Sep. 30, 2019	23,025		0	165	11,869	(2,661)	13,652
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Preferred stock, dividend per share (in dollars per share)											$ 24.50
Beginning Balance at Dec. 31, 2019	$ 23,071	$ (882)	0	163	11,774	(2,737)	13,871	$ (882)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Accounting Standards Update [Extensible List]	us-gaap:AccountingStandardsUpdate201613Member
Ending Balance at Jan. 01, 2020								(882)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Impact of new accounting guidance, tax		288
Beginning Balance at Dec. 31, 2019	$ 23,071	(882)	0	163	11,774	(2,737)	13,871	$ (882)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	1,697						1,697
Other comprehensive loss	(135)					(135)	0
Repurchase of common shares	(875)			(2)	(105)		(768)
Other changes, primarily employee plans	102				149		(47)
Cash dividends declared preferred									$ (27)	(27)	$ (38)	(38)
Cash dividends declared common	(1,044)						(1,044)
Ending Balance at Sep. 30, 2020	21,869		0	161	11,818	(2,872)	12,762
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Preferred stock, dividend per share (in dollars per share)									$ 36.44		$ 43.99
Impact of new accounting guidance, net of tax		$ 1,170
Beginning Balance at Jun. 30, 2020	21,062		0	161	11,760	(2,911)	12,052
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	1,073						1,073
Other comprehensive loss	39					39	0
Other changes, primarily employee plans	59				58		1
Cash dividends declared preferred									$ (7)	$ (7)	$ (9)	$ (9)
Cash dividends declared common	(348)						(348)
Ending Balance at Sep. 30, 2020	$ 21,869		$ 0	$ 161	$ 11,818	$ (2,872)	$ 12,762
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Preferred stock, dividend per share (in dollars per share)									$ 9.98		$ 9.20