Losses and Loss Adjustment Expenses Incurred and Paid - Schedule of Average Historical Annual Percentage Payout of Incurred Losses By Age, Net of Reinsurance (Unaudited) (Detail)	Dec. 31, 2016
Insurance [Abstract]
Average historical annual percentage payout of incurred losses by age, net of reinsurance, year 1	62.70%
Average historical annual percentage payout of incurred losses by age, net of reinsurance, year 2	25.20%
Average historical annual percentage payout of incurred losses by age, net of reinsurance, year 3	6.60%
Average historical annual percentage payout of incurred losses by age, net of reinsurance, year 4	2.70%
Average historical annual percentage payout of incurred losses by age, net of reinsurance, year 5	1.10%
Average historical annual percentage payout of incurred losses by age, net of reinsurance, year 6	0.70%
Average historical annual percentage payout of incurred losses by age, net of reinsurance, year 7	0.10%
Average historical annual percentage payout of incurred losses by age, net of reinsurance, year 8	0.20%
Average historical annual percentage payout of incurred losses by age, net of reinsurance, year 9	0.10%
Average historical annual percentage payout of incurred losses by age, net of reinsurance, year 10	0.00%

No definition available.

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- Definition

Percentage of average annual payout, after reinsurance, in the eighth year after a claim is incurred, beginning with the earliest accident year disclosed for short-duration insurance contracts.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 40
-Section 50
-Paragraph 4G
-URI http://asc.fasb.org/extlink&oid=65670685&loc=SL65671329-158438

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- Definition

Percentage of average annual payout, after reinsurance, in the fifth year after a claim is incurred, beginning with the earliest accident year disclosed for short-duration insurance contracts.

+ References

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Percentage of average annual payout, after reinsurance, in the fourth year after a claim is incurred, beginning with the earliest accident year disclosed for short-duration insurance contracts.

+ References

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- Definition

Percentage of average annual payout, after reinsurance, in the ninth year after a claim is incurred, beginning with the earliest accident year disclosed for short-duration insurance contracts.

+ References

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Percentage of average annual payout, after reinsurance, in the first year after a claim is incurred, beginning with the earliest accident year disclosed for short-duration insurance contracts.

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- Definition

Percentage of average annual payout, after reinsurance, in the seventh year after a claim is incurred, beginning with the earliest accident year disclosed for short-duration insurance contracts.

+ References

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Percentage of average annual payout, after reinsurance, in the sixth year after a claim is incurred, beginning with the earliest accident year disclosed for short-duration insurance contracts.

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- Definition

Percentage of average annual payout, after reinsurance, in the tenth year after a claim is incurred, beginning with the earliest accident year disclosed for short-duration insurance contracts.

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- Definition

Percentage of average annual payout, after reinsurance, in the third year after a claim is incurred, beginning with the earliest accident year disclosed for short-duration insurance contracts.

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Percentage of average annual payout, after reinsurance, in the second year after a claim is incurred, beginning with the earliest accident year disclosed for short-duration insurance contracts.

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