Reinsurance - Schedule of Assets and Liabilities Held in Support of Reserves (Details) - USD ($) $ in Millions	Sep. 30, 2026	Dec. 31, 2025
Assets
Total assets	$ 13,276	$ 15,195
Liabilities
Total liabilities	13,066	14,960
Derivatives related to funds withheld under reinsurance treaties
Liabilities
Net fair value, derivative asset	1,985	1,748
Funds withheld embedded derivative \| Derivatives related to funds withheld under reinsurance treaties
Liabilities
Net fair value, derivative asset	1,983	1,752
Location, Statement of Financial Position, Balance [Axis]: us-gaap:AccruedInvestmentIncomeReceivable
Assets
Total assets	78	92
Location, Statement of Financial Position, Balance [Axis]: us-gaap:CashAndCashEquivalentsAtCarryingValue
Assets
Total assets	258	375
Location, Statement of Financial Position, Balance [Axis]: us-gaap:DebtSecuritiesAvailableForSaleExcludingAccruedInterest
Assets
Total assets	6,156	7,947
Location, Statement of Financial Position, Balance [Axis]: us-gaap:DerivativeAssets
Assets
Total assets	2	(4)
Location, Statement of Financial Position, Balance [Axis]: us-gaap:EquitySecuritiesFvNiCurrentAndNoncurrent
Assets
Total assets	45	88
Location, Statement of Financial Position, Balance [Axis]: us-gaap:FundsHeldUnderReinsuranceAgreementsLiability
Liabilities
Total liabilities	13,066	14,960
Location, Statement of Financial Position, Balance [Axis]: us-gaap:LoansInsurancePolicy
Assets
Total assets	3,548	3,548
Location, Statement of Financial Position, Balance [Axis]: us-gaap:OtherAssets
Assets
Total assets	(7)	5
Location, Statement of Financial Position, Balance [Axis]: us-gaap:OtherInvestments
Assets
Total assets	685	712
Location, Statement of Financial Position, Balance [Axis]: jxn:DebtSecuritiesFairValueOption
Assets
Total assets	180	6
Location, Statement of Financial Position, Balance [Axis]: jxn:FinancingReceivableExcludingAccruedInterestAndFairValueOptionAfterAllowanceForCreditLoss
Assets
Total assets	1,774	2,102
Location, Statement of Financial Position, Balance [Axis]: jxn:FinancingReceivableFairValueOption
Assets
Total assets	$ 557	$ 324