Claim and Claim Adjustment Expense Reserves - Excess Workers' Compensation LPT (Details) - USD ($) $ in Millions	6 Months Ended
Jun. 30, 2022	Jun. 30, 2021
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Claims paid	$ 2,575	$ 2,266

Amount, after effects of reinsurance, of payments to settle insured claims and pay costs incurred in the claims settlement process.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
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Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
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-SubTopic 10
-Section 45
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