Fair Value Measurements - Additional Information (Detail) - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Finance receivable	$ 76	$ 77
Loss and loss expense reserves	2,861	2,835
Life Policy Loans
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Finance receivable	33	32
Investment contract reserves:
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Loss and loss expense reserves	1,566	1,559
Investment contract reserves: \| Deferred annuities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Loss and loss expense reserves	754	760
Investment contract reserves: \| Structured Settlement Annuity
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Loss and loss expense reserves	151	151
Fair Value, Inputs, Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Cash and Cash Equivalents, Fair Value Disclosure	$ 486	$ 767

Fair value portion of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates.

No definition available.

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

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- Definition

Amount of accrued obligation to policyholders that relates to insured events under long-term life insurance contracts.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03.13(a)(1))
-URI http://asc.fasb.org/extlink&oid=119400593&loc=d3e572229-122910

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-Publisher FASB
-Name Accounting Standards Codification
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-Section 25
-Paragraph 11
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- Definition

Amount after allowance and deduction of deferred interest and fees, unamortized costs and premiums and discounts from face amounts, of loans and leases held in portfolio, including but not limited to, commercial and consumer loans. Excludes loans and leases covered under loss sharing agreements and loans held for sale.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=118952595&loc=d3e4428-111522

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
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-Subparagraph (SX 210.9-03.7)
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