Market risk benefits (MRB Roll-Forward) (Details) - USD ($) $ in Millions		3 Months Ended	12 Months Ended
		Sep. 30, 2024	Dec. 31, 2024	Dec. 31, 2023
Minimum
Market Risk Benefit [Line Items]
Long-Duration Contracts, Assumptions by Product and Guarantee, Lapse Rate			0.50%	0.50%
Annuitization rate			0.00%	0.00%
Maximum
Market Risk Benefit [Line Items]
Long-Duration Contracts, Assumptions by Product and Guarantee, Lapse Rate			27.30%	30.00%
Annuitization rate			100.00%	100.00%
Weighted Average
Market Risk Benefit [Line Items]
Long-Duration Contracts, Assumptions by Product and Guarantee, Lapse Rate	[1]		3.40%	4.00%
Annuitization rate	[1]		4.50%	4.50%
Long-Duration Insurance, Other | Variable Annuity [Member]
Market Risk Benefit [Line Items]
Balance - beginning of period			$ 771	$ 800
Balance, beginning of period, before effect of changes in the instrument-specific credit risk			749	776
Interest rate changes			(130)	26
Effect of changes in equity markets	[2]		(125)	(195)
Effect of changes in volatilities			1	20
Market Risk Benefit, Increase (Decrease) from Actual Policyholder Behavior Different from Expected			55	18
Market Risk Benefit, Increase (Decrease) from Future Expected Policyholder Behavior Assumption		$ 87	87	89
Effect of timing and all other			(45)	15
Balance, end of period, before effect of changes in the instrument-specific credit risk			592	749
Effect of changes in the instrument-specific credit risk			15	22
Balance - end of period			$ 607	$ 771
Average attained age of all policyholders under all benefits reinsured, years			74 years	74 years
Market Risk Benefit, Net Amount at Risk	[3]		$ 1,520	$ 1,872
Market Risk Benefits Other Gains (Losses)			$ (297)	$ (334)

[1] The weighted-average lapse and annuitization rates are determined by weighting each treaty's rates by the MRB contract's fair value.

[2] Market movements are predominantly driven by changes in equities.

[3] The net amount at risk is defined as the present value of future claim payments assuming policy account values and guaranteed values are fixed at the valuation date, and reinsurance coverage ends at the earlier of the maturity of the underlying variable annuity policy or the reinsurance treaty. No withdrawals, lapses, and mortality improvements are assumed in the projection. GLB-related risks contain conservative mortality and annuitization assumptions.