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Fair Value Assets, Level 1 to Level 2 Transfers, Number

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Fair Value Assets, Level 2 to Level 1 Transfers, Number

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Fair Value Assets, Level 2 to Level 3 Transfers, Number

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Fair Value Assets, Level 3 to Level 2 Transfers, Number

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Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]

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- Definition

Investment portfolio valued using dealer quotes.

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Percentage of investment portfolio valued using external pricing services.

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Percentage of investment portfolio valued using internal valuation models.

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Amount of credit risk valuation adjustment to derivative liabilities to properly reflect the credit quality of the entity.

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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
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-Topic 860
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-Section 50
-Paragraph 4D
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Amount of investments classified as other.

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Fair Value Measurements - Additional Information (Detail) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020 USD ($)	Jun. 30, 2019	Jun. 30, 2020 USD ($)	Jun. 30, 2019	Dec. 31, 2019 USD ($)
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Fair Value Assets, Level 1 to Level 2 Transfers, Number	0	0	0	0
Derivative Credit Risk Valuation Adjustment, Derivative Liabilities	$ 0		$ 0		$ 0
Other investments	401		401		478
Derivative liabilities	$ 134		$ 134		$ 90
Weighted average discounted rate of estimated future premium payments to be paid by the VIEs	2.10%		2.10%		2.40%
Fair Value Assets, Level 2 to Level 1 Transfers, Number	0	0	0	0
Fair Value Assets, Level 2 to Level 3 Transfers, Number	0	0	0	0
Fair Value Assets, Level 3 to Level 2 Transfers, Number	0	0	0	0
Fair Value Measured at Net Asset Value Per Share [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Other investments	$ 299		$ 299		$ 296
Fixed Income Securities [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Percentage of investment portfolio valued using dealer quotes	4.00%		4.00%		4.00%
Minimum [Member] \| Fixed Income Securities [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Percentage of investment portfolio valued using internal valuation models	2.00%		2.00%		2.00%
Maximum [Member] \| Fixed Income Securities [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Percentage of investment portfolio valued using external pricing services	94.00%		94.00%		94.00%
Variable Interest Entity [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Weighted average discounted rate of estimated future premium payments to be paid by the VIEs	3.00%		3.00%		2.70%