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	6 Months Ended
	Jun. 30, 2020 USD ($)
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Assets, fair value	$ 2,920
Liabilities, fair value	2,957
Broker-quoted | Asset-backed securities
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Assets, fair value	763
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	317
Broker-quoted | Residential mortgage-backed securities
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Assets, fair value	509
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	$ 253
Third-Party Valuation | Corporates
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Assets, fair value	947
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	40
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	$ 21
Market value of fund	100.00%
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	$ 2,952
Minimum | Broker-quoted | Asset-backed securities
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Offered quotes	98.66%
Minimum | Broker-quoted | Commercial mortgage-backed securities
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Offered quotes	89.90%
Minimum | Broker-quoted | Corporates
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Offered quotes	13.70%
Minimum | Broker-quoted | Residential mortgage-backed securities
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Offered quotes	0.00%
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	84.04%
Minimum | Third-Party Valuation | Hybrids
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Offered quotes	109.54%
Minimum | Third-Party Valuation | Municipals
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Offered quotes	122.62%
Minimum | Third-Party Valuation | Foreign Governments
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Offered quotes	98.72%
Minimum | Future policy benefits | Discounted cash flow
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Risk margin to reflect uncertainty	0.00%
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	1.19%
Market value of option	0.00%
Treasury rates	0.13%
Mortality multiplier	80.00%
Surrender rates	0.50%
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	122.19%
Maximum | Broker-quoted | Commercial mortgage-backed securities
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Offered quotes	126.22%
Maximum | Broker-quoted | Corporates
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Offered quotes	111.18%
Maximum | Broker-quoted | Residential mortgage-backed securities
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Offered quotes	106.86%
Maximum | Third-Party Valuation | Asset-backed securities
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Offered quotes	112.65%
Maximum | Third-Party Valuation | Corporates
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Offered quotes	124.53%
Maximum | Third-Party Valuation | Hybrids
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Offered quotes	109.54%
Maximum | Third-Party Valuation | Municipals
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Offered quotes	122.62%
Maximum | Third-Party Valuation | Foreign Governments
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Offered quotes	99.90%
Maximum | Future policy benefits | Discounted cash flow
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Risk margin to reflect uncertainty	0.50%
Maximum | Fixed indexed annuities | Discounted cash flow
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Non-performance spread	1.19%
Market value of option	40.32%
Treasury rates	1.41%
Mortality multiplier	80.00%
Surrender rates	75.00%
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	(104.48%)
Weighted Average | Broker-quoted | Commercial mortgage-backed securities
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Offered quotes	(125.18%)
Weighted Average | Broker-quoted | Corporates
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Offered quotes	(102.46%)
Weighted Average | Broker-quoted | Residential mortgage-backed securities
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Offered quotes	(106.86%)
Weighted Average | Third-Party Valuation | Asset-backed securities
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Offered quotes	(83.58%)
Weighted Average | Third-Party Valuation | Corporates
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Offered quotes	(105.51%)
Weighted Average | Third-Party Valuation | Hybrids
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Offered quotes	(109.54%)
Weighted Average | Third-Party Valuation | Municipals
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Offered quotes	(122.62%)
Weighted Average | Third-Party Valuation | Foreign Governments
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Offered quotes	(99.53%)
Weighted Average | Future policy benefits | Discounted cash flow
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Risk margin to reflect uncertainty	(0.50%)
Weighted Average | Fixed indexed annuities | Discounted cash flow
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Non-performance spread	(1.19%)
Market value of option	(2.22%)
Treasury rates	(0.77%)
Mortality multiplier	(80.00%)
Surrender rates	(5.72%)
Partial withdrawals	(2.55%)
Option cost	(2.19%)
Insurance Subsidiary | Income-Approach | Equity securities
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Assets, fair value	$ 1
Yield	2.61%