Fair Value - Summary of Unobservable Inputs for the Embedded Derivatives of Interest Sensitive Contract Liabilities (Details) $ in Millions	Mar. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Available-for-sale securities	$ 92,429	$ 89,373
Level 3
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Available-for-sale securities	$ 5,982	$ 5,858
Nonperformance risk | Minimum
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Embedded derivative liability, measurement input	0.001	0.000
Nonperformance risk | Maximum
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Embedded derivative liability, measurement input	0.010	0.011
Nonperformance risk | Weighted Average [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Embedded derivative liability, measurement input	0.005	0.005
Option budget | Minimum
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Embedded derivative liability, measurement input	0.005	0.006
Option budget | Maximum
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Embedded derivative liability, measurement input	0.035	0.035
Option budget | Weighted Average [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Embedded derivative liability, measurement input	0.018	0.019
Surrender rate | Minimum
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Embedded derivative liability, measurement input	0.052	0.053
Surrender rate | Maximum
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Embedded derivative liability, measurement input	0.096	0.095
Surrender rate | Weighted Average [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Embedded derivative liability, measurement input	0.071	0.071
Measurement Input, Discount Rate [Member] | Minimum
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Debt Securities, Available-for-sale, Measurement Input	0.014	0.017
Measurement Input, Discount Rate [Member] | Maximum
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Debt Securities, Available-for-sale, Measurement Input	0.180	0.350
Measurement Input, Discount Rate [Member] | Weighted Average [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Debt Securities, Available-for-sale, Measurement Input	0.047	0.046
Embedded derivatives | Interest sensitive contract liabilities | Level 3
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Total liabilities measured at fair value	$ 12,473	$ 12,873