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

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	9 Months Ended	12 Months Ended
	Jun. 30, 2021	Sep. 30, 2021 USD ($)	Dec. 31, 2020 USD ($)
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Assets, fair value		$ 5,103	$ 3,267
Liabilities, fair value		3,439	3,409
Fixed indexed annuities \| Discounted cash flow
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Liabilities, fair value		$ 3,439	$ 3,404
Minimum \| Fixed indexed annuities \| Discounted cash flow
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Market value of option	0.00%	0.00%
Swap rates	0.08%	0.01%
Mortality multiplier	100.00%	100.00%
Surrender rates	0.25%	0.25%
Partial withdrawals	2.00%	2.00%
Non-performance spread	0.74%	0.30%
Option cost	0.05%	0.00%
Maximum \| Fixed indexed annuities \| Discounted cash flow
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Market value of option	67.65%	28.41%
Swap rates	1.65%	2.41%
Mortality multiplier	100.00%	100.00%
Surrender rates	55.00%	70.00%
Partial withdrawals	3.50%	21.74%
Non-performance spread	0.74%	0.93%
Option cost	16.61%	4.97%
Weighted Average \| Fixed indexed annuities \| Discounted cash flow
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Market value of option	2.25%	2.48%
Swap rates	0.87%	1.21%
Mortality multiplier	100.00%	100.00%
Surrender rates	5.24%	6.19%
Partial withdrawals	2.58%	2.72%
Non-performance spread	0.74%	0.62%
Option cost	2.25%	1.81%
Insurance Subsidiary \| Minimum \| Discounted cash flow \| Discount rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Equity securities			0.1060
Insurance Subsidiary \| Maximum \| Discounted cash flow \| Discount rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Equity securities			0.1060
Insurance Subsidiary \| Weighted Average \| Discounted cash flow \| Discount rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Equity securities			0.1060
Asset-backed securities \| Broker-quoted
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Assets, fair value		$ 3,105	$ 1,175
Asset-backed securities \| Third-Party Valuation
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Assets, fair value		$ 139	175
Asset-backed securities \| Minimum \| Broker-quoted
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Offered quotes	85.00%	53.66%
Asset-backed securities \| Minimum \| Third-Party Valuation
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Offered quotes	0.00%	95.55%
Asset-backed securities \| Maximum \| Broker-quoted
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Offered quotes	126.15%	145.43%
Asset-backed securities \| Maximum \| Third-Party Valuation
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Offered quotes	107.25%	107.08%
Asset-backed securities \| Weighted Average \| Broker-quoted
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Offered quotes	103.96%	97.03%
Asset-backed securities \| Weighted Average \| Third-Party Valuation
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Offered quotes	79.87%	103.58%
Commercial mortgage-backed securities \| Broker-quoted
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Assets, fair value		$ 36	26
Commercial mortgage-backed securities \| Minimum \| Broker-quoted
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Offered quotes	131.59%	101.04%
Commercial mortgage-backed securities \| Maximum \| Broker-quoted
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Offered quotes	131.59%	127.33%
Commercial mortgage-backed securities \| Weighted Average \| Broker-quoted
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Offered quotes	131.59%	117.40%
Corporates \| Broker-quoted
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Assets, fair value		$ 344	388
Corporates \| Discounted cash flow
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Assets, fair value		13
Corporates \| Third-Party Valuation
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Assets, fair value		$ 756	901
Corporates \| Minimum \| Broker-quoted
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Offered quotes	75.20%	93.33%
Corporates \| Minimum \| Discounted cash flow
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Debt securities		0.4400
Corporates \| Minimum \| Third-Party Valuation
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Offered quotes	88.42%	86.58%
Corporates \| Maximum \| Broker-quoted
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Offered quotes	114.68%	113.92%
Corporates \| Maximum \| Discounted cash flow
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Debt securities		1.0000
Corporates \| Maximum \| Third-Party Valuation
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Offered quotes	125.83%	121.41%
Corporates \| Weighted Average \| Broker-quoted
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Offered quotes	103.36%	103.68%
Corporates \| Weighted Average \| Discounted cash flow
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Debt securities		0.7800
Corporates \| Weighted Average \| Third-Party Valuation
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Offered quotes	109.47%	108.34%
Hybrids \| Third-Party Valuation
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Assets, fair value			4
Hybrids \| Minimum \| Third-Party Valuation
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Offered quotes	112.06%
Hybrids \| Maximum \| Third-Party Valuation
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Offered quotes	112.06%
Hybrids \| Weighted Average \| Third-Party Valuation
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Offered quotes	112.06%
Municipals \| Third-Party Valuation
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Assets, fair value		$ 43	43
Municipals \| Minimum \| Third-Party Valuation
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Offered quotes	133.53%	134.75%
Municipals \| Maximum \| Third-Party Valuation
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Offered quotes	133.53%	134.75%
Municipals \| Weighted Average \| Third-Party Valuation
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Offered quotes	133.53%	134.75%
Residential mortgage-backed securities \| Broker-quoted
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Assets, fair value		$ 394	483
Residential mortgage-backed securities \| Minimum \| Broker-quoted
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Offered quotes	112.58%	0.00%
Residential mortgage-backed securities \| Maximum \| Broker-quoted
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Offered quotes	112.58%	115.44%
Residential mortgage-backed securities \| Weighted Average \| Broker-quoted
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Offered quotes	112.58%	115.44%
Foreign Governments \| Third-Party Valuation
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Assets, fair value		$ 18	$ 17
Foreign Governments \| Minimum \| Third-Party Valuation
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Offered quotes	107.87%	108.78%
Foreign Governments \| Maximum \| Third-Party Valuation
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Offered quotes	113.80%	116.83%
Foreign Governments \| Weighted Average \| Third-Party Valuation
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Offered quotes	109.72%	111.29%
Short-Term \| Broker-quoted
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Assets, fair value		$ 192
Short-Term \| Minimum \| Broker-quoted
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Offered quotes		100.00%
Short-Term \| Maximum \| Broker-quoted
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Offered quotes		100.00%
Short-Term \| Weighted Average \| Broker-quoted
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Offered quotes		100.00%
Equity securities \| Minimum \| Broker-quoted \| EBITDA Multiple
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Equity securities		6.6	6.6
Equity securities \| Maximum \| Broker-quoted \| EBITDA Multiple
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Equity securities		6.6	6.6
Equity securities \| Weighted Average \| Broker-quoted \| EBITDA Multiple
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Equity securities		6.6	6.6
Equity securities \| Insurance Subsidiary \| Broker-quoted
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Assets, fair value		$ 3
Equity securities \| Insurance Subsidiary \| Discounted cash flow
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Assets, fair value		4	$ 3
Equity securities \| Insurance Subsidiary \| Income-Approach
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Assets, fair value		$ 3	$ 1
Yield		2.49%	2.61%
Equity securities \| Insurance Subsidiary \| Black Scholes model
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Assets, fair value		$ 2	$ 1
Equity securities \| Insurance Subsidiary \| Minimum \| Broker-quoted
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Offered quotes		44.00%
Equity securities \| Insurance Subsidiary \| Minimum \| Discounted cash flow \| Discount rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Equity securities		0.1337
Equity securities \| Insurance Subsidiary \| Minimum \| Black Scholes model \| Risk Free Rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Equity securities		0.0050	0.0029
Equity securities \| Insurance Subsidiary \| Minimum \| Black Scholes model \| Strike Price
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Equity securities		1.50	1.50
Equity securities \| Insurance Subsidiary \| Minimum \| Black Scholes model \| Volatility
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Equity securities		1.5000	0.0100
Equity securities \| Insurance Subsidiary \| Minimum \| Black Scholes model \| Dividend Yield
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Equity securities		0.0000	0.0000
Equity securities \| Insurance Subsidiary \| Maximum \| Broker-quoted
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Offered quotes		100.00%
Equity securities \| Insurance Subsidiary \| Maximum \| Discounted cash flow \| Discount rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Equity securities		0.1337
Equity securities \| Insurance Subsidiary \| Maximum \| Black Scholes model \| Risk Free Rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Equity securities		0.0050	0.0029
Equity securities \| Insurance Subsidiary \| Maximum \| Black Scholes model \| Strike Price
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Equity securities		1.50	1.50
Equity securities \| Insurance Subsidiary \| Maximum \| Black Scholes model \| Volatility
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Equity securities		1.5000	0.0100
Equity securities \| Insurance Subsidiary \| Maximum \| Black Scholes model \| Dividend Yield
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Equity securities		0.0000	0.0000
Equity securities \| Insurance Subsidiary \| Weighted Average \| Broker-quoted
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Offered quotes		78.00%
Equity securities \| Insurance Subsidiary \| Weighted Average \| Discounted cash flow \| Discount rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Equity securities		0.1337
Equity securities \| Insurance Subsidiary \| Weighted Average \| Black Scholes model \| Risk Free Rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Equity securities		0.0050	0.0029
Equity securities \| Insurance Subsidiary \| Weighted Average \| Black Scholes model \| Strike Price
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Equity securities		1.50	1.50
Equity securities \| Insurance Subsidiary \| Weighted Average \| Black Scholes model \| Volatility
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Equity securities		1.5000	0.0100
Equity securities \| Insurance Subsidiary \| Weighted Average \| Black Scholes model \| Dividend Yield
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Equity securities		0.0000	0.0000
Other long-term investments \| Third-Party Valuation
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Assets, fair value			$ 27
Market value of fund	100.00%
Other long-term investments \| Black Scholes model
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Assets, fair value		$ 31
Market value of fund		100.00%
Credit linked note \| Broker-quoted
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Assets, fair value		$ 20	23
Offered quotes	100.00%	100.00%
Future policy benefits \| Discounted cash flow
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Liabilities, fair value			$ 5
Risk margin to reflect uncertainty	0.50%
Future policy benefits \| Minimum \| Discounted cash flow
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Non-performance spread	0.00%