Investments - Summary of Amortized Cost and Estimated Fair Value of Available-for-Sale Investments, Excluding VIE Investments (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
Jun. 30, 2023	Jun. 30, 2023	Dec. 31, 2022	Jun. 30, 2022
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Allowance for Credit Loss	$ 1	$ 1	$ 0	$ 0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	30	30	31
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	24	24	53
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	764	764	400
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	85	85	53
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	109	109	106
Fixed maturity securities, at fair value	1,953	1,953
Debt Securities, Available-for-Sale, Allowance for Credit Loss, Period Increase (Decrease)	0	1
Short-term Investments [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Unrealized Loss Position	37	37	86
Debt Securities, Available-for-sale, Allowance for Credit Loss	0	0	0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	0	0	0
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	37	37	78
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	0	0	0
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	0	0	8
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	0	0	0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	0	0	0
Fixed maturity securities, at fair value	365	365	507
Fixed Income Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Unrealized Loss Position	1,319	1,319	1,183
Debt Securities, Available-for-sale, Allowance for Credit Loss	1	1	0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	30	30	31
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	556	556	791
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	24	24	53
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	764	764	392
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	85	85	53
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	109	109	106
Fixed maturity securities, at fair value	1,552	1,552	1,395
Fixed Income Securities [Member] \| Municipal Bonds [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Unrealized Loss Position	38	38	28
Debt Securities, Available-for-sale, Allowance for Credit Loss	0	0	0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	0	0	0
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	22	22	21
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	0	0	1
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	16	16	7
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	2	2	1
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	2	2	2
Fixed maturity securities, at fair value	63	63	43
Fixed Income Securities [Member] \| Corporate Debt Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Unrealized Loss Position	656	656	559
Debt Securities, Available-for-sale, Allowance for Credit Loss	0	0	0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	0	0	1
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	209	209	280
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	9	9	21
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	447	447	279
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	53	53	42
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	62	62	63
Fixed maturity securities, at fair value	674	674	598
Fixed Income Securities [Member] \| Foreign Obligations [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Unrealized Loss Position	83	83	73
Debt Securities, Available-for-sale, Allowance for Credit Loss	0	0	0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	0	0	0
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	36	36	27
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	2	2	2
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	47	47	47
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	9	9	7
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	11	11	9
Fixed maturity securities, at fair value	83	83	76
Fixed Income Securities [Member] \| US Government Debt Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Unrealized Loss Position	66	66	58
Debt Securities, Available-for-sale, Allowance for Credit Loss	0	0	0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	0	0	0
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	27	27	40
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	2	2	3
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	40	40	19
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	2	2	1
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	4	4	4
Fixed maturity securities, at fair value	71	71	65
Fixed Income Securities [Member] \| Residential Mortgage-Backed Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Unrealized Loss Position	165	165	132
Debt Securities, Available-for-sale, Allowance for Credit Loss	1	1	0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	26	26	28
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	74	74	132
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	2	2	19
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	91	91	0
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	15	15	0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	17	17	19
Fixed maturity securities, at fair value	238	238	238
Fixed Income Securities [Member] \| Collateralized Debt Obligations [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Unrealized Loss Position	117	117	126
Debt Securities, Available-for-sale, Allowance for Credit Loss	0	0	0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	0	0	0
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	0	0	90
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	0	0	3
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	117	117	36
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	3	3	1
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	3	3	4
Fixed maturity securities, at fair value	138	138	137
Fixed Income Securities [Member] \| Asset-backed Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Unrealized Loss Position	179	179	203
Debt Securities, Available-for-sale, Allowance for Credit Loss	0	0	0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	3	3	2
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	173	173	198
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	9	9	4
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	6	6	5
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	1	1	1
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	10	10	5
Fixed maturity securities, at fair value	268	268	224
Fixed Income Securities [Member] \| Commercial Mortgage Backed Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Unrealized Loss Position	15	15	3
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	15	15	3
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	0	0	0
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	0	0	0
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	0	0	0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	0	0	0
Fixed maturity securities, at fair value	16	16
Fixed Income Securities [Member] \| Collateralized Mortgage Backed Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Allowance for Credit Loss	0	0	0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	0	0	0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	0	0	0
Fixed maturity securities, at fair value	16	16	15
Fixed Income Investments And Other Investments [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Allowance for Credit Loss	1	1	0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	30	30	31
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	109	109	106
Fixed maturity securities, at fair value	1,917	1,917	1,902
Collateral Pledged [Member] \| Fixed Income Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	0	0	0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	0	0	0
Fixed maturity securities, at fair value	36	36	64
Collateral Pledged [Member] \| Fixed Income Securities [Member] \| Short-term Investments [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Allowance for Credit Loss	0	0	0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	0	0	0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	0	0	0
Fixed maturity securities, at fair value	36	36	64
Asset Pledged as Collateral [Member] \| Fixed Income Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Allowance for Credit Loss	$ 0	$ 0	$ 0

Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Amount, before tax, of unrealized loss in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Amount of allowance for credit loss on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Amount of increase (decrease) in allowance for credit loss of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in continuous unrealized loss position for more than 12 months, without allowance for credit loss. Includes beneficial interest in securitized financial asset.

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