Long-duration Contracts - Significant Inputs and Assumptions (Details) $ in Millions	Sep. 30, 2026 USD ($)	Dec. 31, 2025 USD ($)	Sep. 30, 2025 USD ($)	Dec. 31, 2024 USD ($)
Market Risk Benefit [Line Items]
Net liability	$ 4,497	$ 4,716	$ 4,612	$ 3,715
Nonperformance risk \| Discounted cash flow \| Minimum
Market Risk Benefit [Line Items]
Market risk benefit, measurement input (in percent)	0.004		0.004
Nonperformance risk \| Discounted cash flow \| Maximum
Market Risk Benefit [Line Items]
Market risk benefit, measurement input (in percent)	0.011		0.010
Nonperformance risk \| Discounted cash flow \| Weighted average
Market Risk Benefit [Line Items]
Market risk benefit, measurement input (in percent)	0.010		0.009
Option budget \| Discounted cash flow \| Minimum
Market Risk Benefit [Line Items]
Market risk benefit, measurement input (in percent)	0.005		0.005
Option budget \| Discounted cash flow \| Maximum
Market Risk Benefit [Line Items]
Market risk benefit, measurement input (in percent)	0.059		0.060
Option budget \| Discounted cash flow \| Weighted average
Market Risk Benefit [Line Items]
Market risk benefit, measurement input (in percent)	0.030		0.026
Surrender rate \| Discounted cash flow \| Minimum
Market Risk Benefit [Line Items]
Market risk benefit, measurement input (in percent)	0.046		0.037
Surrender rate \| Discounted cash flow \| Maximum
Market Risk Benefit [Line Items]
Market risk benefit, measurement input (in percent)	0.093		0.079
Surrender rate \| Discounted cash flow \| Weighted average
Market Risk Benefit [Line Items]
Market risk benefit, measurement input (in percent)	0.058		0.052
Measurement Input, Utilization Rate \| Discounted cash flow \| Minimum
Market Risk Benefit [Line Items]
Market risk benefit, measurement input (in percent)	0.286		0.286
Measurement Input, Utilization Rate \| Discounted cash flow \| Maximum
Market Risk Benefit [Line Items]
Market risk benefit, measurement input (in percent)	0.950		0.950
Measurement Input, Utilization Rate \| Discounted cash flow \| Weighted average
Market Risk Benefit [Line Items]
Market risk benefit, measurement input (in percent)	0.892		0.861