Fair Value - Summary of Unobservable Inputs for the Embedded Derivatives of Interest Sensitive Contract Liabilities (Details) $ in Millions	Sep. 30, 2020 USD ($)	Dec. 31, 2019 USD ($)
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Available-for-sale securities	$ 73,988	$ 71,374
Level 3
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Available-for-sale securities	$ 5,468	$ 1,289
Nonperformance risk | Minimum
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Embedded derivative liability, measurement input	0.001	0.002
Nonperformance risk | Maximum
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Embedded derivative liability, measurement input	0.015	0.011
Nonperformance risk | Weighted Average [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Embedded derivative liability, measurement input	0.008	0.006
Option budget | Minimum
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Embedded derivative liability, measurement input	0.006	0.007
Option budget | Maximum
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Embedded derivative liability, measurement input	0.036	0.037
Option budget | Weighted Average [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Embedded derivative liability, measurement input	0.019	0.019
Surrender rate | Minimum
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Embedded derivative liability, measurement input	0.053	0.035
Surrender rate | Maximum
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Embedded derivative liability, measurement input	0.097	0.081
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	0.020	0.030
Measurement Input, Discount Rate [Member] | Maximum
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Debt Securities, Available-for-sale, Measurement Input	0.350	0.090
Measurement Input, Discount Rate [Member] | Weighted Average [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Debt Securities, Available-for-sale, Measurement Input	0.057	0.066
Embedded derivatives | Interest sensitive contract liabilities | Level 3
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Total liabilities measured at fair value	$ 11,741	$ 10,942