CONSOLIDATED STATEMENT OF CHANGES IN EQUITY - USD ($) $ in Millions	Total	Preferred Stock [Member]	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Loss [Member]	As Previously Reported [Member] Retained Earnings [Member]	As Previously Reported [Member] Accumulated Other Comprehensive Loss [Member]	Cumulative Effect, Period of Adoption, Adjustment [Member]	[1]	Cumulative Effect, Period of Adoption, Adjustment [Member] Retained Earnings [Member]	Cumulative Effect, Period of Adoption, Adjustment [Member] Student Loan [Member] Retained Earnings [Member]	Cumulative Effect, Period of Adoption, Reclassification [Member] Retained Earnings [Member]	Cumulative Effect, Period of Adoption, Reclassification [Member] Accumulated Other Comprehensive Loss [Member]
Balance at beginning of period at Dec. 31, 2017		$ 1,265
Balance at beginning of period, common equity at Dec. 31, 2017			$ 0	$ 18,130	$ 1,227	$ (518)	$ 1,130	$ (431)	$ 91
Balance at beginning of period, common equity (Accounting Standards Update 2016-01 [Member]) at Dec. 31, 2017											$ 10		$ (4)	$ 4
Balance at beginning of period, common equity (Accounting Standards Update 2018-02 [Member]) at Dec. 31, 2017													91	(91)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Return of capital to parent				0
Employee benefit plans				6
Net income (loss)	$ 320				320
Cash dividends declared on preferred stock					(76)
Other comprehensive income, net of tax	152					152
Balance at end of period, common equity at Dec. 31, 2018	19,241		$ 0	18,136	1,498	(366)	1,471	(366)			$ 27
Balance at end of period at Dec. 31, 2018	20,506	$ 1,265
Beginning balance (shares) at Dec. 31, 2017		1,265	714
Ending balance (shares) at Dec. 31, 2018		1,265	714
Accounting Standards Update [Extensible List]											us-gaap:AccountingStandardsUpdate201602Member
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Return of capital to parent				(2,400)
Employee benefit plans				0
Net income (loss)	113				113
Cash dividends declared on preferred stock					(77)
Other comprehensive income, net of tax	87					87
Balance at end of period, common equity at Dec. 31, 2019	16,991		$ 0	15,736	1,618	(277)	$ 1,534	$ (279)
Balance at end of period, common equity (Accounting Standards Update 2016-13 [Member]) at Dec. 31, 2019											$ 84	$ 2	$ (2)	$ 2
Balance at end of period at Dec. 31, 2019	18,256	$ 1,265
Ending balance (shares) at Dec. 31, 2019		1,265	714
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Return of capital to parent				0
Employee benefit plans				10
Net income (loss)	(940)				(940)
Cash dividends declared on preferred stock					(77)
Other comprehensive income, net of tax	956					956
Balance at end of period, common equity at Dec. 31, 2020	17,026		$ 0	$ 15,746	$ 601	$ 679
Balance at end of period at Dec. 31, 2020	$ 18,291	$ 1,265
Ending balance (shares) at Dec. 31, 2020		1,265	714

[1] Reflects the adoption of new accounting guidance in 2018 which resulted in a cumulative effect adjustment as of January 1, 2018 to reclassify the stranded tax effects resulting from the change in the Federal corporate income tax rate from accumulated other comprehensive income (loss) to retained earnings.