Fair Value Measurements - Schedule of Carrying Amount and Fair Value by Hierarchy of Certain Financial Instruments Not Reported at Fair Value (Details) - USD ($) $ in Millions	Sep. 30, 2026	Dec. 31, 2025
Assets
Mortgage loans	$ 10,711	$ 9,887
Policy loans	863	889
FHLBI capital stock	90	119
Liabilities
Annuity reserves	44,943	39,059
Guaranteed investment contracts and funding agreements	11,432	11,021
Funds withheld payable under reinsurance treaties	11,325	12,989
Debt	2,769	2,030
Securities lending payable	29	35
Repurchase agreements	500	1,001
Separate account liabilities	237,319	236,496
Fair Value
Assets
Mortgage loans	10,240	9,624
Policy loans	863	889
FHLBI capital stock	90	119
Liabilities
Annuity reserves	40,453	38,552
Guaranteed investment contracts and funding agreements	11,062	11,077
Funds withheld payable under reinsurance treaties	11,325	12,989
Debt	2,461	1,877
Securities lending payable	29	35
Repurchase agreements	500	1,001
Separate account liabilities	237,319	236,496
Fair Value \| Level 1
Assets
Mortgage loans	0	0
Policy loans	0	0
FHLBI capital stock	90	119
Liabilities
Annuity reserves	0	0
Guaranteed investment contracts and funding agreements	0	0
Funds withheld payable under reinsurance treaties	0	0
Debt	0	0
Securities lending payable	0	0
Repurchase agreements	0	0
Separate account liabilities	0	0
Fair Value \| Level 2
Assets
Mortgage loans	0	0
Policy loans	0	0
FHLBI capital stock	0	0
Liabilities
Annuity reserves	0	0
Guaranteed investment contracts and funding agreements	0	0
Funds withheld payable under reinsurance treaties	0	0
Debt	2,461	1,877
Securities lending payable	29	35
Repurchase agreements	500	1,001
Separate account liabilities	237,319	236,496
Fair Value \| Level 3
Assets
Mortgage loans	10,240	9,624
Policy loans	863	889
FHLBI capital stock	0	0
Liabilities
Annuity reserves	40,453	38,552
Guaranteed investment contracts and funding agreements	11,062	11,077
Funds withheld payable under reinsurance treaties	11,325	12,989
Debt	0	0
Securities lending payable	0	0
Repurchase agreements	0	0
Separate account liabilities	$ 0	$ 0

Funds Held Under Reinsurance Agreements, Liability, Excluding At Fair Value Under Fair Value Option

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Amount, including accrued interest, to be repaid to counterparty to repurchase agreement when carrying amount or market value if higher, of security or other asset sold under repurchase agreement exceeds 10 percent of total assets.

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Fair value portion of debt instrument payable, including, but not limited to, notes payable and loans payable.

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Fair value portion of investments in Federal Home Loan Bank (FHLBank) stock.

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Fair value portion of liability related to investment contracts for example, but not limited to, guaranteed investment contract or annuities.

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Fair value portion of loan receivable, including, but not limited to, mortgage loans held for investment, finance receivables held for investment, policy loans on insurance contracts.

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Amount, after the effects of master netting arrangements, of securities loaned to entities in exchange for collateral. Includes liabilities not subject to a master netting arrangement and not elected to be offset.

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