Subsidiary Dividend Restrictions - Additional Information (Detail) - Wright Flood - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2017	Dec. 31, 2018
Dividend Restrictions [Line Items]
Dividend rate as a percentage of net income	100.00%
Statutory Dividend Payment Restrictions Disclosure	Under the insurance regulations of Texas, where WNFIC in incorporated, the maximum amount of ordinary dividends that WNFIC can pay to shareholders in a rolling twelve month period is limited to the greater of 10% of statutory adjusted capital and surplus as shown on WNFIC’s last annual statement on file with the superintendent of the Texas Department of Insurance or 100% of adjusted net income
Scenario, Forecast
Dividend Restrictions [Line Items]
Maximum dividend payout that may be made without prior approval		$ 4.8
Maximum
Dividend Restrictions [Line Items]
Dividend rate as a percentage of net income	10.00%

[Line Items] for Dividend Restrictions [Table]

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Expected dividends to be paid to holders of the underlying shares or financial instruments (expressed as a percentage of the share or instrument's price).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (bbb)
-URI http://asc.fasb.org/extlink&oid=66048111&loc=d3e19207-110258

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- Definition

Amount of dividends that can be declared or paid without approval of regulatory agency.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08.(e))
-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690

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- Definition

Disclosure of statutory restrictions on the payment of dividends as prescribed by the National Association of Insurance Commissioners or state regulatory authorities, amounts not available for future dividend payments, and amount of dividends paid.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 505
-Section 50
-Paragraph 1
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=6486098&loc=d3e24708-158529

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