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] 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, 2018		$ 1,265
Balance at beginning of period, common equity at Dec. 31, 2018			$ 0	$ 18,136	$ 1,498	$ (366)	$ 1,471	$ (366)
Balance at beginning of period, common equity (Accounting Standards Update 2016-13 [Member]) at Dec. 31, 2018									$ 0	$ 0	$ 0	$ 0
Balance at beginning of period, common equity (Accounting Standards Update 2016-02 [Member]) at Dec. 31, 2018									$ 27
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Return of capital to parent				(2,400)
Employee benefit plans				(2)
Net income (loss)	$ 230				230
Cash dividends declared on preferred stock					(38)
Other comprehensive income, net of tax	311					311
Balance at end of period, common equity at Jun. 30, 2019	17,369		0	15,734	1,690	(55)
Balance at end of period at Jun. 30, 2019	18,634	1,265
Accounting Standards Update [Extensible List] | Accounting Standards Update 2016-13 [Member]									us-gaap:accountingstandardsupdate201613member	us-gaap:accountingstandardsupdate201613member	us-gaap:accountingstandardsupdate201613member	us-gaap:accountingstandardsupdate201613member
Balance at beginning of period at Dec. 31, 2018		1,265
Balance at beginning of period, common equity at Dec. 31, 2018			0	18,136	1,498	(366)	1,471	(366)
Balance at beginning of period, common equity (Accounting Standards Update 2016-13 [Member]) at Dec. 31, 2018									$ 0	$ 0	$ 0	$ 0
Balance at beginning of period, common equity (Accounting Standards Update 2016-02 [Member]) at Dec. 31, 2018									27
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, common equity (Accounting Standards Update 2016-02 [Member]) at Dec. 31, 2019									$ 0
Balance at end of period at Dec. 31, 2019	18,256	1,265
Balance at beginning of period at Mar. 31, 2019		1,265
Balance at beginning of period, common equity at Mar. 31, 2019			0	15,736	1,607	(287)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Employee benefit plans				(2)
Net income (loss)	121				121
Cash dividends declared on preferred stock					(38)
Other comprehensive income, net of tax	232					232
Balance at end of period, common equity at Jun. 30, 2019	17,369		0	15,734	1,690	(55)
Balance at end of period at Jun. 30, 2019	18,634	1,265
Balance at beginning of period at Dec. 31, 2019	18,256	1,265
Balance at beginning of period, common equity at Dec. 31, 2019	16,991		0	15,736	1,618	(277)	$ 1,534	$ (279)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Return of capital to parent				0
Employee benefit plans				10
Net income (loss)	(1,276)				(1,276)
Cash dividends declared on preferred stock					(39)
Other comprehensive income, net of tax	1,107					1,107
Balance at end of period, common equity at Jun. 30, 2020	16,879		0	15,746	303	830
Balance at end of period at Jun. 30, 2020	18,144	1,265
Balance at beginning of period at Mar. 31, 2020		1,265
Balance at beginning of period, common equity at Mar. 31, 2020			0	15,741	335	978
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Employee benefit plans				5
Net income (loss)	7				7
Cash dividends declared on preferred stock					(39)
Other comprehensive income, net of tax	(148)					(148)
Balance at end of period, common equity at Jun. 30, 2020	16,879		$ 0	$ 15,746	$ 303	$ 830
Balance at end of period at Jun. 30, 2020	$ 18,144	$ 1,265