Basis of Presentation - Effects of Adoption of ASU 2018-12, Stockholders' Equity (Details) - USD ($) $ in Millions	Sep. 30, 2023	Jun. 30, 2023	Dec. 31, 2022	Sep. 30, 2022	Jun. 30, 2022	Dec. 31, 2021	Dec. 31, 2020
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total equity	$ 15,158	$ 15,470	$ 15,201	$ 14,563	$ 15,714	$ 17,471
As Reported
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total equity			15,478		16,221	19,175
Accumulated Other Comprehensive Income (Loss)
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total equity	(3,473)	(3,160)	(3,320)	(3,679)	(2,913)	(1,320)	$ (1,516)
Accumulated Other Comprehensive Income (Loss) | As Reported
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total equity			(3,284)		(2,510)	186	581
Accumulated Other Comprehensive Income (Loss) | De-recognition of shadow reserves
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total equity							2,331
Accumulated Other Comprehensive Income (Loss) | Re-measurement of LFPB using an upper-medium grade fixed income instrument yield discount rate
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total equity							(4,428)
Accumulated Other Comprehensive Income (Loss) | Other adjustments
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total equity
Retained Earnings
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total equity	15,877	15,637	14,931	15,172	15,210	14,754	14,145
Retained Earnings | As Reported
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total equity			15,144		15,261	14,776	14,150
Retained Earnings | De-recognition of shadow reserves
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total equity
Retained Earnings | Re-measurement of LFPB using an upper-medium grade fixed income instrument yield discount rate
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total equity
Retained Earnings | Other adjustments
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total equity							(5)
Noncontrolling Interests
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total equity	$ 710	$ 867	852	$ 798	932	1,153	1,077
Noncontrolling Interests | As Reported
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total equity			$ 880		$ 985	$ 1,329	1,321
Noncontrolling Interests | De-recognition of shadow reserves
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total equity							270
Noncontrolling Interests | Re-measurement of LFPB using an upper-medium grade fixed income instrument yield discount rate
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total equity							(513)
Noncontrolling Interests | Other adjustments
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total equity							$ (1)