Fair Value Measurements - Fair Value and Carrying Value of Financial Instruments (Details) - USD ($) $ in Millions	Sep. 30, 2023	Jan. 01, 2023	Dec. 31, 2022		Jan. 01, 2021
Assets
Debt securities	$ 41,388		$ 44,762
Equity securities	277		393	[1]
Mortgage loans	10,136		10,967
Policy loans	4,368		4,377	[1]
Freestanding derivative instruments	925		1,270	[1]
FHLBI capital stock	108		146
Cash and cash equivalents	2,760		4,298
Reinsurance recoverable, net of allowance for credit losses of $33 and $15 at September 30, 2023 and December 31, 2022, respectively	26,212	$ 29,046	29,046	[1]	$ 35,116
Market risk benefit assets, at fair value	6,815	4,865	4,865	[1]	690
Separate account assets	202,903		195,906	[1]
Liabilities
Market risk benefit liabilities, at fair value	3,917	$ 5,662	5,662	[1]	$ 10,690
Reserves for guaranteed investment contracts	863		1,128
Trust instruments supported by funding agreements	5,900		5,887
FHLB funding agreements	1,949		2,004
Funds withheld payable under reinsurance treaties	19,973		22,957	[1]
Long-term debt	2,635		2,635
Securities lending payable	28		36
Freestanding derivative instruments	2,548		2,065	[1]
Repurchase agreements	0		1,012
FHLB advances	180
Separate account liabilities	202,903		195,906	[1]
Variable Interest Entity, Primary Beneficiary
Assets
Equity securities	92		127
Liabilities
Securities lending payable	2		4
Carrying Value
Assets
Debt securities	41,388		44,762
Equity securities	277		393
Mortgage loans	10,612		11,549
Limited partnerships	3,221		3,212
Policy loans	4,368		4,377
Freestanding derivative instruments	925		1,270
FHLBI capital stock	108		146
Cash and cash equivalents	2,760		4,298
Reinsurance recoverable, net of allowance for credit losses of $33 and $15 at September 30, 2023 and December 31, 2022, respectively	167		221
Market risk benefit assets, at fair value	6,815		4,865
Separate account assets	202,903		195,906
Liabilities
Annuity reserves	35,362		37,357
Market risk benefit liabilities, at fair value	3,917		5,662
Reserves for guaranteed investment contracts	863		1,128
Trust instruments supported by funding agreements	5,900		5,887
FHLB funding agreements	1,949		2,004
Funds withheld payable under reinsurance treaties	19,973		22,957
Long-term debt	2,635		2,635
Securities lending payable	28		36
Freestanding derivative instruments	2,548		2,065
Notes issued by consolidated VIEs	2,011		1,732
Repurchase agreements	0		1,012
FHLB advances	180		0
Separate account liabilities	202,903		195,906
Fair Value
Assets
Debt securities	41,388		44,762
Equity securities	277		393
Mortgage loans	9,815		10,841
Limited partnerships	3,221		3,212
Policy loans	4,368		4,377
Freestanding derivative instruments	925		1,270
FHLBI capital stock	108		146
Cash and cash equivalents	2,760		4,298
Reinsurance recoverable, net of allowance for credit losses of $33 and $15 at September 30, 2023 and December 31, 2022, respectively	167		221
Market risk benefit assets, at fair value	6,815		4,865
Separate account assets	202,903		195,906
Liabilities
Annuity reserves	29,861		32,377
Market risk benefit liabilities, at fair value	3,917		5,662
Reserves for guaranteed investment contracts	820		1,099
Trust instruments supported by funding agreements	5,592		5,760
FHLB funding agreements	1,699		2,104
Funds withheld payable under reinsurance treaties	19,973		22,957
Long-term debt	2,322		2,344
Securities lending payable	28		36
Freestanding derivative instruments	2,548		2,065
Notes issued by consolidated VIEs	2,011		1,732
Repurchase agreements	0		1,012
FHLB advances	180		0
Separate account liabilities	$ 202,903		$ 195,906

[1] (1) Recast for the adoption of ASU 2018-12. See Notes 1 and 2 to the Condensed Consolidated Financial Statements.