Schedule of Other Than Temporary Impairments on Investments (Detail) $ in Thousands	3 Months Ended
Mar. 31, 2019 USD ($)
Investments Debt And Equity Securities [Abstract]
OTTI losses, gross	$ (1,897)
Portion of loss recognized in other comprehensive income (pre-tax)	0
Net impairment losses on fixed maturities recognized in earnings	$ (1,897)

Amount, before tax, 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 other comprehensive income (OCI).

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 10A
-Subparagraph (g)
-URI http://asc.fasb.org/extlink&oid=118930883&loc=SL7669646-108580

Reference 2: 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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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration