Amount of increase in allowance for credit loss on reinsurance recoverable, from recovery.

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Amount of expense (reversal of expense) for expected credit loss on reinsurance recoverable.

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Amount of allowance for credit loss on reinsurance recoverable.

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Amount of stockholders' equity (deficit), net of receivables from officers, directors, owners, and affiliates of the entity, attributable to both the parent and noncontrolling interests. Amount excludes temporary equity. Alternate caption for the concept is permanent equity.

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Reinsurance - Reinsurance Recoverable, Allowance for Credit Loss (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2019
Reinsurance Recoverable, Allowance for Credit Loss [Roll Forward]
Reinsurance Recoverable, Allowance for Credit Loss, Beginning Balance	$ 42	$ 52	$ 55	$ 48
Reinsurance Recoverable, Credit Loss Expense (Reversal)	1	1	(12)	3
Reinsurance Recoverable, Allowance for Credit Loss, Ending Balance	43	54	43	54
Reinsurance Recoverable, Allowance for Credit Loss, Recovery	0	1	0	1
Operating Segments [Member] \| Property, Liability and Casualty Insurance Product Line
Reinsurance Recoverable, Allowance for Credit Loss [Roll Forward]
Reinsurance Recoverable, Allowance for Credit Loss, Beginning Balance	39	49	52	48
Reinsurance Recoverable, Credit Loss Expense (Reversal)	1	1	(12)	2
Reinsurance Recoverable, Allowance for Credit Loss, Ending Balance	40	51	40	51
Reinsurance Recoverable, Allowance for Credit Loss, Recovery	0	1	0	1
Operating Segments [Member] \| Group Benefits
Reinsurance Recoverable, Allowance for Credit Loss [Roll Forward]
Reinsurance Recoverable, Allowance for Credit Loss, Beginning Balance	1	1	1	0
Reinsurance Recoverable, Credit Loss Expense (Reversal)	0	0	0	0
Reinsurance Recoverable, Allowance for Credit Loss, Ending Balance	1	1	1	1
Reinsurance Recoverable, Allowance for Credit Loss, Recovery	0	0	0	0
Corporate, Non-Segment [Member]
Reinsurance Recoverable, Allowance for Credit Loss [Roll Forward]
Reinsurance Recoverable, Allowance for Credit Loss, Beginning Balance	2	2	2	0
Reinsurance Recoverable, Credit Loss Expense (Reversal)	0	0	0	1
Reinsurance Recoverable, Allowance for Credit Loss, Ending Balance	2	2	2	2
Reinsurance Recoverable, Allowance for Credit Loss, Recovery	0	0	0	0
Uncollectible reinsurance
Reinsurance Recoverable, Allowance for Credit Loss [Roll Forward]
Reinsurance Recoverable, Allowance for Credit Loss, Beginning Balance	98	117	108	114
Reinsurance Recoverable, Allowance for Credit Loss, Ending Balance	99	111	99	111
Uncollectible reinsurance \| Operating Segments [Member] \| Property, Liability and Casualty Insurance Product Line
Reinsurance Recoverable, Allowance for Credit Loss [Roll Forward]
Reinsurance Recoverable, Allowance for Credit Loss, Beginning Balance	95	114	105	114
Reinsurance Recoverable, Allowance for Credit Loss, Ending Balance	96	108	96	108
Uncollectible reinsurance \| Operating Segments [Member] \| Group Benefits
Reinsurance Recoverable, Allowance for Credit Loss [Roll Forward]
Reinsurance Recoverable, Allowance for Credit Loss, Beginning Balance	1	1	1	0
Reinsurance Recoverable, Allowance for Credit Loss, Ending Balance	1	1	1	1
Uncollectible reinsurance \| Corporate, Non-Segment [Member]
Reinsurance Recoverable, Allowance for Credit Loss [Roll Forward]
Reinsurance Recoverable, Allowance for Credit Loss, Beginning Balance	2	2	2	0
Reinsurance Recoverable, Allowance for Credit Loss, Ending Balance	2	2	2	2
Disputes [Member]
Reinsurance Recoverable, Allowance for Credit Loss [Roll Forward]
Reinsurance Recoverable, Allowance for Credit Loss, Beginning Balance	56	65	53	66
Reinsurance Recoverable, Allowance for Credit Loss, Ending Balance	56	57	56	57
Disputes [Member] \| Operating Segments [Member] \| Property, Liability and Casualty Insurance Product Line
Reinsurance Recoverable, Allowance for Credit Loss [Roll Forward]
Reinsurance Recoverable, Allowance for Credit Loss, Beginning Balance	56	65	53	66
Reinsurance Recoverable, Allowance for Credit Loss, Ending Balance	56	57	56	57
Disputes [Member] \| Operating Segments [Member] \| Group Benefits
Reinsurance Recoverable, Allowance for Credit Loss [Roll Forward]
Reinsurance Recoverable, Allowance for Credit Loss, Beginning Balance	0	0	0	0
Reinsurance Recoverable, Allowance for Credit Loss, Ending Balance	0	0	0	0
Disputes [Member] \| Corporate, Non-Segment [Member]
Reinsurance Recoverable, Allowance for Credit Loss [Roll Forward]
Reinsurance Recoverable, Allowance for Credit Loss, Beginning Balance	0	0	0	0
Reinsurance Recoverable, Allowance for Credit Loss, Ending Balance	$ 0	$ 0	0	0
Cumulative Effect, Period of Adoption, Adjustment [Member] \| Accounting Standards Update 2016-13 [Member]
Reinsurance Recoverable, Past Due [Line Items]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest					$ 2
Cumulative Effect, Period of Adoption, Adjustment [Member] \| Accounting Standards Update 2016-13 [Member] \| Operating Segments [Member] \| Property, Liability and Casualty Insurance Product Line
Reinsurance Recoverable, Past Due [Line Items]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest					0
Cumulative Effect, Period of Adoption, Adjustment [Member] \| Accounting Standards Update 2016-13 [Member] \| Operating Segments [Member] \| Group Benefits
Reinsurance Recoverable, Past Due [Line Items]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest					1
Cumulative Effect, Period of Adoption, Adjustment [Member] \| Accounting Standards Update 2016-13 [Member] \| Corporate, Non-Segment [Member]
Reinsurance Recoverable, Past Due [Line Items]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest					$ 1
Cumulative Effect, Period of Adoption, Adjusted Balance [Member]
Reinsurance Recoverable, Allowance for Credit Loss [Roll Forward]
Reinsurance Recoverable, Allowance for Credit Loss, Beginning Balance			55	50
Cumulative Effect, Period of Adoption, Adjusted Balance [Member] \| Operating Segments [Member] \| Property, Liability and Casualty Insurance Product Line
Reinsurance Recoverable, Allowance for Credit Loss [Roll Forward]
Reinsurance Recoverable, Allowance for Credit Loss, Beginning Balance			52	48
Cumulative Effect, Period of Adoption, Adjusted Balance [Member] \| Operating Segments [Member] \| Group Benefits
Reinsurance Recoverable, Allowance for Credit Loss [Roll Forward]
Reinsurance Recoverable, Allowance for Credit Loss, Beginning Balance			1	1
Cumulative Effect, Period of Adoption, Adjusted Balance [Member] \| Corporate, Non-Segment [Member]
Reinsurance Recoverable, Allowance for Credit Loss [Roll Forward]
Reinsurance Recoverable, Allowance for Credit Loss, Beginning Balance			$ 2	$ 1