Fair Value of Assets and Liabilities - Quantitative information about the significant unobservable inputs used in level 3 fair value measurements (Details) - Equity-indexed and forward starting options in life and annuity product contracts - Projected option cost - Significant unobservable inputs (Level 3) $ in Millions	Mar. 31, 2021 USD ($)
Quantitative information about the significant unobservable inputs
Fair value	$ (435)
Minimum
Quantitative information about the significant unobservable inputs
Measurement input	0.010
Maximum
Quantitative information about the significant unobservable inputs
Measurement input	0.042
Weighted Average
Quantitative information about the significant unobservable inputs
Measurement input	0.0283