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Commitments and Contingencies - Additional Information (Detail) $ in Millions | 12 Months Ended
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Dec. 31, 2017 USD ($)
reinsurance contract obligation [Line Items] |
Minimum commitment under noncancelable purchase obligations | $ 546.3
unrecorded unconditional purchase obligations reinsurance [Member] | Lower Limit |
reinsurance contract obligation [Line Items] |
Reinsurance Contract Terms | 1 year
Other Commitment | $ 90.7
unrecorded unconditional purchase obligations reinsurance [Member] | Upper Limit |
reinsurance contract obligation [Line Items] |
Reinsurance Contract Terms | 3 years

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- Definition Period Terms of Multiple Layer Property Catastrophe excess of loss reinsurance claims with various reinsurers + References No definition available. + Details
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- Definition [Line Items] for reinsurance contract obligation [Table] + References No definition available. + Details
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- Definition Minimum amount of other commitment not otherwise specified in the taxonomy. Excludes commitments explicitly modeled in the taxonomy, including but not limited to, long-term and short-term purchase commitments, recorded and unrecorded purchase obligations, supply commitments, registration payment arrangements, leases, debt, product warranties, guarantees, environmental remediation obligations, and pensions. + References No definition available. + Details
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Period Type: | instant

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- Definition Amount of the unrecorded obligation to transfer funds in the future for fixed or minimum amounts or quantities of goods or services at fixed or minimum prices (for example, as in take-or-pay contracts or throughput contracts). + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 440 -SubTopic 10 -Section 50 -Paragraph 4 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=77896938&loc=d3e25336-109308 + Details
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- Details
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- Details
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- Details
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