Investments - Realized Gain (Loss) on Investments (Detail) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2020	Mar. 31, 2019
Investments, Debt and Equity Securities [Abstract]
Realized investment gains (losses) - sales and other	$ 4,934	$ 3,670
Provision for credit losses	31,854	0
Fair value option—change in fair value	583	(2,185)
Other investments	240	(156)
Realized gains (losses) from investments	(26,097)	1,329
Applicable tax	5,480	(279)
Realized gains (losses), net of tax	(20,617)	1,050
Exchanges of fixed maturities	5,900	68,900
Exchanges of fixed maturities, net realized gains	$ 0	$ 5,800

Debt Securities, Available-For-Sale, Noncash Sale, Exchange Of Securities

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Debt Securities, Available-For-Sale, Realized Gain (Loss) On Exchanges

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Realized gains (losses) from investments, Applicable tax

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Realized gains (losses) from investments, Net of tax

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Amount of realized gain (loss) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), excluding other-than-temporary impairment (OTTI).

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- Definition

For each line item in the statement of financial position, the amounts of gains and losses from fair value changes included in earnings.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 30
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=75031198&loc=d3e14172-108612

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Amount of gain (loss) included in earnings for investments classified as other.

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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=118932676&loc=d3e3602-108585

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Amount of other-than-temporary impairment (OTTI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), recognized in earnings.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 45
-Paragraph 8A
-URI http://asc.fasb.org/extlink&oid=118954083&loc=SL6284422-111562

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- Definition

The net realized gains or losses on investments during the period, not including gains or losses on securities separately or otherwise categorized as trading, available-for-sale, or held-to-maturity.

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 220
-Section S99
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