Consolidated Statements of Stockholders' Equity - USD ($) $ in Millions	Total	Series C Preferred Stock	Series D Preferred Stock	Preferred Stock	Preferred Stock Series C Preferred Stock	Preferred Stock Series D Preferred Stock	Common Stock	Retained Earnings	Accumulated Other Comprehensive Income (Loss)	Cumulative Effect to Retained Earnings Retained Earnings	Cumulative Effect to Retained Earnings Accumulated Other Comprehensive Income (Loss)
Balance as of beginning-of-year at Dec. 31, 2020				$ 0			$ 5,082	$ 8,686	$ 8,931	$ (6,273)	$ 4,627
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock compensation/issued for benefit plans							85
Net income (loss)	$ 3,778							3,778
Retirement of common stock/cancellation of shares							(432)	(673)
Common stock dividends declared								(322)
Other comprehensive income (loss), net of tax	(3,574)								(3,574)
Balance as of end-of-year at Dec. 31, 2021	19,915			0			4,735	5,196	9,984
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of preferred stock					$ 493	$ 493
Stock compensation/issued for benefit plans							40
Net income (loss)	1,358							1,358
Retirement of common stock/cancellation of shares							(231)	(319)
Preferred stock dividends declared	0	$ 0	$ 0
Common stock dividends declared								(311)
Other comprehensive income (loss), net of tax	(16,336)								(16,336)
Balance as of end-of-year at Dec. 31, 2022	5,102			986			4,544	5,924	(6,352)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock compensation/issued for benefit plans							61
Net income (loss)	(752)							(752)
Preferred stock dividends declared	(82)	$ (36)	$ (46)					(82)
Common stock dividends declared								(312)
Other comprehensive income (loss), net of tax	2,876								2,876
Balance as of end-of-year at Dec. 31, 2023	$ 6,893			$ 986			$ 4,605	$ 4,778	$ (3,476)