Condensed Consolidated Statements of Changes in Equity (Deficit) - USD ($) $ in Millions	Total	Senior Preferred Stock	Preferred Stock	Common Stock	Accumulated Deficit	Accumulated Other Comprehensive Income	Treasury Stock
Proceeds From Senior Preferred Stock Agreement With Us Treasury	$ 3,687	$ 3,687
Balance (shares) at Dec. 31, 2017		1,000,000	556,000,000	1,158,000,000
Balance at Dec. 31, 2017	(3,686)	$ 117,149	$ 19,130	$ 687	$ (133,805)	$ 553	$ (7,400)
Increase (Decrease) in Stockholders' Equity [Rollforward]
Preferred Stock, Dividends, Per Share, Cash Paid	0
Increase to senior preferred stock		3,687
Comprehensive income:
Net income	4,261				4,261
Other comprehensive income (loss), net of tax effect:
Changes in net unrealized gains on available-for-sale securities (net of tax of $2 and $15, respectively)	(57)					(57)
Reclassification adjustment for gains included in net income (net of tax of $12, and $70, respectively)	(263)					(263)
Prior service cost and actuarial gains, net of amortization for defined benefit plans (net of tax)	(3)					(3)
Reclassification related to Tax Cuts and Jobs Act					(117)	117
Other	(1)				(1)
Balance at Mar. 31, 2018	(3,938)	$ 120,836	$ 19,130	$ 687	(129,662)	(347)	(7,400)
Balance (shares) at Mar. 31, 2018		1,000,000	556,000,000	1,158,000,000
Balance (shares) at Dec. 31, 2017		1,000,000	556,000,000	1,158,000,000
Balance at Dec. 31, 2017	(3,686)	$ 117,149	$ 19,130	$ 687	(133,805)	553	(7,400)
Other comprehensive income (loss), net of tax effect:
Total comprehensive income	3,938
Balance at Dec. 31, 2018	$ 6,240	$ 120,836	$ 19,130	$ 687	(127,335)	322	(7,400)
Balance (shares) at Dec. 31, 2018		1,000,000	556,000,000	1,158,000,000
Other comprehensive income (loss), net of tax effect:
Senior preferred stock issued, shares	1,000,000
Proceeds From Senior Preferred Stock Agreement With Us Treasury	$ 0
Preferred Stock, Dividends, Per Share, Cash Paid	3,240				3,240
Net income	2,400				2,400
Changes in net unrealized gains on available-for-sale securities (net of tax of $2 and $15, respectively)	8					8
Reclassification adjustment for gains included in net income (net of tax of $12, and $70, respectively)	(44)					(44)
Prior service cost and actuarial gains, net of amortization for defined benefit plans (net of tax)	(3)					(3)
Total comprehensive income	2,361
Reclassification related to Tax Cuts and Jobs Act						0
Balance at Mar. 31, 2019	$ 5,361	$ 120,836	$ 19,130	$ 687	$ (128,175)	$ 283	$ (7,400)
Balance (shares) at Mar. 31, 2019		1,000,000	556,000,000	1,158,000,000
Other comprehensive income (loss), net of tax effect:
Senior preferred stock issued, shares	1,000,000