Accounting Policies (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022	Jun. 30, 2023	Dec. 31, 2022	Jun. 30, 2022	Dec. 31, 2021	Dec. 31, 2020
ASU 2018-12
Reinsurance recoverable	$ 699		$ 699			$ 665
Prepaid reinsurance premiums	69		69			51
Deferred policy acquisition costs	1,101	$ 1,033	1,101	$ 1,033	$ 1,109	1,013	$ 1,046	$ 916
Total assets	30,915		30,915			29,732
Life policy and investment contract reserves	2,920		2,920			3,015
Deferred income tax	997		997			1,054
Total liabilities	20,291		20,291			19,170
Retained earnings	12,018		12,018			11,711
Accumulated other comprehensive income	(827)		(827)			(614)
Total shareholders' equity	10,624	9,480	10,624	9,480		10,562
Total liabilities and shareholders' equity	30,915		30,915			29,732
Earned premiums	2,033	1,884	5,894	5,350
Insurance losses and contract holders' benefits	1,332	1,418	4,070	3,772
Underwriting, acquisition and insurance expenses	609	551	1,744	1,604
Deferred	(106)	(180)	2	(571)
Net Income (Loss)	(99)	(416)	660	(1,500)
Change in life policy reserves, reinsurance recoverable and other, net of tax	89	95	76	393
Other comprehensive income (loss)	(201)	(310)	(213)	(1,084)
Comprehensive Income (Loss)	$ (300)	$ (726)	$ 447	$ (2,584)
Basic (in USD per share)	$ (0.63)	$ (2.63)	$ 4.20	$ (9.42)
Diluted (in USD per share)	$ (0.63)	$ (2.63)	$ 4.17	$ (9.42)
Accounting Standards Update 2018-12
ASU 2018-12
Reinsurance recoverable						665			$ 287
Prepaid reinsurance premiums						51
Deferred policy acquisition costs						1,013			296
Total assets						29,732
Life policy and investment contract reserves						3,015
Deferred income tax						1,054
Total liabilities						19,170
Retained earnings						11,711
Accumulated other comprehensive income						(614)
Total shareholders' equity						10,562
Total liabilities and shareholders' equity						29,732
Earned premiums		$ 1,884		$ 5,350
Insurance losses and contract holders' benefits		1,418		3,772
Underwriting, acquisition and insurance expenses		551		1,604
Deferred		(180)		(571)
Net Income (Loss)		(416)		(1,500)
Change in life policy reserves, reinsurance recoverable and other, net of tax		95		393
Other comprehensive income (loss)		(310)		(1,084)
Comprehensive Income (Loss)		$ (726)		$ (2,584)
Basic (in USD per share)		$ (2.63)		$ (9.42)
Diluted (in USD per share)		$ (2.63)		$ (9.42)
Accounting Standards Update 2018-12 | As originally reported
ASU 2018-12
Reinsurance recoverable						640			217
Prepaid reinsurance premiums						79
Deferred policy acquisition costs						1,014			263
Total assets						29,736
Life policy and investment contract reserves						3,059
Deferred income tax						1,045
Total liabilities						19,205
Retained earnings						11,702
Accumulated other comprehensive income						(636)
Total shareholders' equity						10,531
Total liabilities and shareholders' equity						29,736
Earned premiums		$ 1,882		$ 5,345
Insurance losses and contract holders' benefits		1,418		3,766
Underwriting, acquisition and insurance expenses		551		1,604
Deferred		(180)		(571)
Net Income (Loss)		(418)		(1,499)
Change in life policy reserves, reinsurance recoverable and other, net of tax		0		1
Other comprehensive income (loss)		(405)		(1,476)
Comprehensive Income (Loss)		$ (823)		$ (2,975)
Basic (in USD per share)		$ (2.64)		$ (9.41)
Diluted (in USD per share)		$ (2.64)		$ (9.41)
Accounting Standards Update 2018-12 | Effect of Modified Retrospective Application Accounting Standards Update 2018-12
ASU 2018-12
Reinsurance recoverable						25
Prepaid reinsurance premiums						(28)
Deferred policy acquisition costs						(1)			$ 33
Total assets						(4)
Life policy and investment contract reserves						(44)
Deferred income tax						9
Total liabilities						(35)
Retained earnings						9
Accumulated other comprehensive income						22
Total shareholders' equity						31
Total liabilities and shareholders' equity						$ (4)
Earned premiums		$ 2		$ 5
Insurance losses and contract holders' benefits		0		6
Underwriting, acquisition and insurance expenses		0		0
Deferred		0		0
Net Income (Loss)		2		(1)
Change in life policy reserves, reinsurance recoverable and other, net of tax		95		392
Other comprehensive income (loss)		95		392
Comprehensive Income (Loss)		$ 97		$ 391
Basic (in USD per share)		$ 0.01		$ (0.01)
Diluted (in USD per share)		$ 0.01		$ (0.01)