Losses and Loss Adjustment Reserve - Effects of Reinsurance on Premiums Written and Earned (Detail) $ in Thousands	9 Months Ended
Sep. 30, 2018 USD ($)
Written
Direct premiums	$ 469,078
Ceded premiums	(469,065)
Net premiums	13
Earned
Direct premiums	445,140
Ceded premiums	(445,127)
Net premiums	$ 13

Amount of earned premiums ceded to other entities.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 225
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-04.1)
-URI http://asc.fasb.org/extlink&oid=6879464&loc=d3e573970-122913

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-URI http://asc.fasb.org/extlink&oid=6486672&loc=d3e27261-158547

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+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
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Amount, after premiums ceded to other entities and premiums assumed by the entity, of premiums written.

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