Acquisitions and Dispositions - Narrative (Details) $ / shares in Units, $ in Millions						3 Months Ended				6 Months Ended			12 Months Ended
	Jul. 15, 2021 USD ($) $ / shares	Mar. 15, 2021 USD ($)	Feb. 03, 2021 USD ($)	Jan. 26, 2021 USD ($)	Jan. 04, 2021 USD ($)	Jun. 30, 2021 USD ($) state $ / shares	Mar. 31, 2021 USD ($)	Mar. 31, 2021 USD ($)	Jun. 30, 2020 USD ($)	Dec. 31, 2021 USD ($)	Jun. 30, 2021 USD ($) state $ / shares	Jun. 30, 2020 USD ($)	Dec. 31, 2021 USD ($)	Mar. 29, 2021 USD ($)	Dec. 31, 2020 USD ($) $ / shares
Business Acquisition [Line Items]
Goodwill						$ 3,349					$ 3,349				$ 2,369
Long-term debt						7,996					7,996				$ 7,825
Amortization of purchased intangibles						$ 105			$ 29		$ 158	$ 57
Preferred stock, par value (in dollars per share) | $ / shares						$ 1					$ 1				$ 1
Redemption of preferred stock								$ 250
Proceeds from affiliates				$ 2,800
Definitive agreement with Wilton Reassurance														$ 220
Loss on disposition of operations, net of tax							$ 4,000				$ 3,971	$ 0
Noncumulative Preferred Stock | Subsequent Event
Business Acquisition [Line Items]
Redemption of preferred stock	$ 200
Noncumulative Preferred Stock | Series A
Business Acquisition [Line Items]
Preferred stock, par value (in dollars per share) | $ / shares						0.01					$ 0.01
Preferred stock, dividend rate, percentage								7.50%
Noncumulative Preferred Stock | Series B
Business Acquisition [Line Items]
Preferred stock, par value (in dollars per share) | $ / shares						0.01					0.01
Preferred stock, dividend rate, percentage								7.50%
Noncumulative Preferred Stock | Series C | Subsequent Event
Business Acquisition [Line Items]
Preferred stock, par value (in dollars per share) | $ / shares	$ 0.01
Preferred stock, dividend rate, percentage	7.50%
Non-Cumulative Convertible Preferred Stock | Series D
Business Acquisition [Line Items]
Preferred stock, par value (in dollars per share) | $ / shares						$ 0.01					$ 0.01
Depository Shares
Business Acquisition [Line Items]
Depository shares, as a ratio of preferred stock							0.025	0.025
Discontinued Operations, Held-for-sale
Business Acquisition [Line Items]
Amortized cost, net						$ 23,968					$ 23,968				$ 21,417
Equity securities, at fair value, cost						1,050					1,050				1,113
Other short term Investments, amortized cost						901					901				$ 993
Subordinated Debt
Business Acquisition [Line Items]
Repaid of subordinated notes		$ 72	$ 100
Subsequent acquisition (in percentage)			7.625%
Long-term debt						$ 350					$ 350
Senior Notes
Business Acquisition [Line Items]
Subsequent acquisition (in percentage)						6.75%					6.75%
SafeAuto
Business Acquisition [Line Items]
Number of states acquiree operates in | state						28					28
SafeAuto | Forecast
Business Acquisition [Line Items]
Cash to acquire businesses										$ 270
National General Holdings Corp.
Business Acquisition [Line Items]
Goodwill					$ 970
Purchase accounting fair value adjustment											$ 67
Amortization of purchased intangibles						$ 76					99
Amortization expense for the remainder of 2021						152					152
Amortization expense of present value of future profits						98					232
Fair value purchase accounting adjustments, increase in reserves											62
Fair value purchase accounting adjustments, reduction in investments											13
Fair value purchase accounting adjustments, increase in current and deferred tax liabilities											101
Business acquisition, transaction costs						$ 22					$ 22
National General Holdings Corp. | Noncumulative Preferred Stock | Series C | Subsequent Event
Business Acquisition [Line Items]
Preferred stock, dividend rate, percentage	7.50%
National General Holdings Corp. | Depository Shares | Subsequent Event
Business Acquisition [Line Items]
Depository shares, as a ratio of preferred stock	0.025
National General Holdings Corp. | Forecast
Business Acquisition [Line Items]
Amortization expense of present value of future profits													$ 85
National General Holdings Corp. | Minimum
Business Acquisition [Line Items]
Finite-lived intangible asset, useful life (in years)					3 years						6 months
National General Holdings Corp. | Maximum
Business Acquisition [Line Items]
Finite-lived intangible asset, useful life (in years)					10 years						12 months
National General Holdings Corp. | Allstate Protection
Business Acquisition [Line Items]
Goodwill					$ 608
Present value of future profits					317
National General Holdings Corp. | Protection Services
Business Acquisition [Line Items]
Goodwill					21
National General Holdings Corp. | Allstate Health and Benefits
Business Acquisition [Line Items]
Goodwill					$ 341