Fair Value of Financial Instruments - Quantitative Information of Unobservable Inputs Used for Level Three Fair Value Measurements of Financial Instruments on Recurring Basis (Detail) $ in Millions	9 Months Ended
	Sep. 30, 2020 USD ($)
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Assets, fair value	$ 2,850
Liabilities, fair value	3,166
Broker-quoted | Asset-backed securities
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Assets, fair value	768
Broker-quoted | Commercial mortgage-backed securities
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Assets, fair value	26
Broker-quoted | Corporates
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Assets, fair value	319
Broker-quoted | Residential mortgage-backed securities
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Assets, fair value	501
Broker-quoted | Credit Linked Note
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Assets, fair value	$ 23
Offered quotes	100.00%
Third-Party Valuation | Asset-backed securities
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Assets, fair value	$ 176
Third-Party Valuation | Corporates
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Assets, fair value	948
Third-Party Valuation | Hybrids
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Assets, fair value	4
Third-Party Valuation | Municipals
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Assets, fair value	42
Third-Party Valuation | Foreign Governments
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Assets, fair value	16
Black Scholes model | Investment in unconsolidated affiliates
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Assets, fair value	$ 23
Market value of fund	100.00%
Future policy benefits | Discounted cash flow
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Risk margin to reflect uncertainty	0.50%
Future policy benefits | Discounted cash flow | Future policy benefits, nonperformance risk spread
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Liabilities, fair value	$ 5
Fixed indexed annuities | Discounted cash flow
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Liabilities, fair value	$ 3,161
Minimum | Broker-quoted | Asset-backed securities
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Offered quotes	99.37%
Minimum | Broker-quoted | Commercial mortgage-backed securities
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Offered quotes	131.09%
Minimum | Broker-quoted | Corporates
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Offered quotes	0.00%
Minimum | Broker-quoted | Residential mortgage-backed securities
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Offered quotes	0.00%
Minimum | Broker-quoted | Equity securities | EBITDA Multiple
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Equity securities	6.5
Minimum | Third-Party Valuation | Asset-backed securities
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Offered quotes	0.00%
Minimum | Third-Party Valuation | Corporates
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Offered quotes	80.78%
Minimum | Third-Party Valuation | Hybrids
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Offered quotes	111.51%
Minimum | Third-Party Valuation | Municipals
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Offered quotes	128.08%
Minimum | Third-Party Valuation | Foreign Governments
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Offered quotes	101.68%
Minimum | Black Scholes model | Equity securities | Risk Free Rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Equity securities	0.0026
Minimum | Black Scholes model | Equity securities | Strike Price
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Equity securities	1.50
Minimum | Black Scholes model | Equity securities | Volatility
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Equity securities	0.0100
Minimum | Black Scholes model | Equity securities | Dividend Yield
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Equity securities	0.0000
Minimum | Discounted cash flow | Discount rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Equity securities	0.0740
Minimum | Future policy benefits | Discounted cash flow | Future policy benefits, nonperformance risk spread
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Non-performance spread	0.00%
Minimum | Fixed indexed annuities | Discounted cash flow
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Non-performance spread	1.07%
Market value of option	0.00%
Treasury rates	0.08%
Mortality multiplier	80.00%
Surrender rates	0.25%
Partial withdrawals	2.00%
Option cost	0.05%
Maximum | Broker-quoted | Asset-backed securities
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Offered quotes	124.37%
Maximum | Broker-quoted | Commercial mortgage-backed securities
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Offered quotes	131.09%
Maximum | Broker-quoted | Corporates
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Offered quotes	112.66%
Maximum | Broker-quoted | Residential mortgage-backed securities
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Offered quotes	109.63%
Maximum | Broker-quoted | Equity securities | EBITDA Multiple
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Equity securities	6.5
Maximum | Third-Party Valuation | Asset-backed securities
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Offered quotes	117.07%
Maximum | Third-Party Valuation | Corporates
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Offered quotes	124.57%
Maximum | Third-Party Valuation | Hybrids
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Offered quotes	111.51%
Maximum | Third-Party Valuation | Municipals
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Offered quotes	128.08%
Maximum | Third-Party Valuation | Foreign Governments
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Offered quotes	102.09%
Maximum | Black Scholes model | Equity securities | Risk Free Rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Equity securities	0.0026
Maximum | Black Scholes model | Equity securities | Strike Price
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Equity securities	1.50
Maximum | Black Scholes model | Equity securities | Volatility
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Equity securities	0.0100
Maximum | Black Scholes model | Equity securities | Dividend Yield
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Equity securities	0.0000
Maximum | Discounted cash flow | Discount rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Equity securities	0.0740
Maximum | Fixed indexed annuities | Discounted cash flow
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Non-performance spread	1.07%
Market value of option	50.69%
Treasury rates	1.46%
Mortality multiplier	80.00%
Surrender rates	55.00%
Partial withdrawals	3.50%
Option cost	16.61%
Weighted Average | Broker-quoted | Asset-backed securities
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Offered quotes	(105.85%)
Weighted Average | Broker-quoted | Commercial mortgage-backed securities
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Offered quotes	(131.09%)
Weighted Average | Broker-quoted | Corporates
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Offered quotes	(103.37%)
Weighted Average | Broker-quoted | Residential mortgage-backed securities
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Offered quotes	(109.63%)
Weighted Average | Broker-quoted | Equity securities | EBITDA Multiple
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Equity securities	4.6
Weighted Average | Third-Party Valuation | Asset-backed securities
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Offered quotes	(80.57%)
Weighted Average | Third-Party Valuation | Corporates
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Offered quotes	(107.32%)
Weighted Average | Third-Party Valuation | Hybrids
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Offered quotes	(111.51%)
Weighted Average | Third-Party Valuation | Municipals
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Offered quotes	(128.08%)
Weighted Average | Third-Party Valuation | Foreign Governments
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Offered quotes	(101.81%)
Weighted Average | Black Scholes model | Equity securities | Risk Free Rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Equity securities	0.0026
Weighted Average | Black Scholes model | Equity securities | Strike Price
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Equity securities	1.50
Weighted Average | Black Scholes model | Equity securities | Volatility
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Equity securities	0.0100
Weighted Average | Black Scholes model | Equity securities | Dividend Yield
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Equity securities	0.0000
Weighted Average | Discounted cash flow | Discount rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Equity securities	0.0222
Weighted Average | Fixed indexed annuities | Discounted cash flow
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Non-performance spread	(1.07%)
Market value of option	(2.22%)
Treasury rates	(0.77%)
Mortality multiplier	(80.00%)
Surrender rates	(4.81%)
Partial withdrawals	(2.56%)
Option cost	(2.22%)
Insurance Subsidiary | Income-Approach | Equity securities
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Assets, fair value	$ 1
Yield	2.61%
Insurance Subsidiary | Black Scholes model | Equity securities
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Assets, fair value	$ 1
Insurance Subsidiary | Discounted cash flow | Equity securities
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Assets, fair value	$ 2