Summary of Significant Accounting Policies - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Jan. 01, 2021	Dec. 31, 2020
Summary of Significant Accounting Policies [Line Items]
Stockholders' equity	$ (51,301)	$ (43,454)	$ (69,034)	$ (65,935)	$ (67,199)
Earning pattern of reinsurance contract extension (in years)	24 months
Accumulated Other Comprehensive Income (Loss)
Summary of Significant Accounting Policies [Line Items]
Stockholders' equity	$ 14,037	22,616	(5,071)		(13,511)
Retained Earnings
Summary of Significant Accounting Policies [Line Items]
Stockholders' equity	$ (37,516)	$ (34,893)	$ (25,695)		(15,504)
Cumulative effect of change in accounting principle
Summary of Significant Accounting Policies [Line Items]
Stockholders' equity					1,264
Cumulative effect of change in accounting principle | Accumulated Other Comprehensive Income (Loss)
Summary of Significant Accounting Policies [Line Items]
Stockholders' equity					2,197
Cumulative effect of change in accounting principle | Retained Earnings
Summary of Significant Accounting Policies [Line Items]
Stockholders' equity					$ (933)
Cumulative effect of change in accounting principle | Minimum | ASU 2018-12 | Accumulated Other Comprehensive Income (Loss)
Summary of Significant Accounting Policies [Line Items]
Stockholders' equity				(2,200)
Cumulative effect of change in accounting principle | Minimum | ASU 2018-12 | Retained Earnings
Summary of Significant Accounting Policies [Line Items]
Stockholders' equity				$ (933)
Building | Maximum
Summary of Significant Accounting Policies [Line Items]
Useful life (in years)	40 years
Furniture and Fixtures | Maximum
Summary of Significant Accounting Policies [Line Items]
Useful life (in years)	10 years
Capitalized Software Costs | Maximum
Summary of Significant Accounting Policies [Line Items]
Useful life (in years)	10 years