Condensed Consolidated Statement of Changes in Equity (unaudited) - USD ($) $ in Millions	Total	Series B Preferred Stock	Series C Preferred Stock	Cumulative Effect, Period of Adoption, Adjustment	Cumulative Effect, Period of Adoption, Adjusted Balance	Common stock and paid-in capital	Common stock and paid-in capital Cumulative Effect, Period of Adoption, Adjusted Balance	Preferred stock	Preferred stock Series B Preferred Stock	Preferred stock Series C Preferred Stock	Preferred stock Cumulative Effect, Period of Adoption, Adjusted Balance	Accumulated deficit	Accumulated deficit Cumulative Effect, Period of Adoption, Adjustment	Accumulated deficit Cumulative Effect, Period of Adoption, Adjusted Balance	Accumulated other comprehensive income	Accumulated other comprehensive income Cumulative Effect, Period of Adoption, Adjusted Balance	Treasury stock	Treasury stock Cumulative Effect, Period of Adoption, Adjusted Balance
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Adoption of Accounting Standards Update 2016-13	$ 14,416			$ (1,017)	$ 13,399	$ 21,438	$ 21,438	$ 0			$ 0	$ (4,057)	$ (1,017)	$ (5,074)	$ 123	$ 123	$ (3,088)	$ (3,088)
Beginning balance at Dec. 31, 2019	14,416			$ (1,017)	$ 13,399	21,438	$ 21,438	0			$ 0	(4,057)	$ (1,017)	$ (5,074)	123	$ 123	(3,088)	$ (3,088)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	(78)											(78)
Share-based compensation	61					61
Other comprehensive income (loss)	692														692
Common stock repurchases	(104)																(104)
Common stock dividends	(144)											(144)
Ending balance at Jun. 30, 2020	13,826					21,499		0				(5,296)			815		(3,192)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Adoption of Accounting Standards Update 2016-13	13,519					21,470		0				(5,465)			706		(3,192)
Beginning balance at Mar. 31, 2020	13,519					21,470		0				(5,465)			706		(3,192)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	241											241
Share-based compensation	29					29
Other comprehensive income (loss)	109														109
Common stock dividends	(72)											(72)
Ending balance at Jun. 30, 2020	13,826					21,499		0				(5,296)			815		(3,192)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Adoption of Accounting Standards Update 2016-13	13,826					21,499		0				(5,296)			815		(3,192)
Adoption of Accounting Standards Update 2016-13	14,703					21,544						(4,278)			631		(3,194)
Beginning balance at Dec. 31, 2020	14,703					21,544						(4,278)			631		(3,194)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	1,696											1,696
Net proceeds from issuance of series preferred stock		$ 1,335	$ 989						$ 1,335	$ 989
Share-based compensation	87					87
Other comprehensive income (loss)	(415)														(415)
Common stock repurchases	(721)																(721)
Common stock dividends	(144)											(144)
Ending balance at Jun. 30, 2021	17,530					21,631		2,324				(2,726)			216		(3,915)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Adoption of Accounting Standards Update 2016-13	14,625					21,566		0				(3,555)			27		(3,413)
Beginning balance at Mar. 31, 2021	14,625					21,566		0				(3,555)			27		(3,413)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	900											900
Net proceeds from issuance of series preferred stock		$ 1,335	$ 989						$ 1,335	$ 989
Share-based compensation	65					65
Other comprehensive income (loss)	189														189
Common stock repurchases	(502)																(502)
Common stock dividends	(71)											(71)
Ending balance at Jun. 30, 2021	17,530					21,631		2,324				(2,726)			216		(3,915)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Adoption of Accounting Standards Update 2016-13	$ 17,530					$ 21,631		$ 2,324				$ (2,726)			$ 216		$ (3,915)