Commitments and Contingencies - Additional Information (Detail) - USD ($) $ in Millions	1 Months Ended	3 Months Ended
Feb. 28, 2015	Mar. 31, 2017
Loss Contingencies [Line Items]
Retention amount		$ 5.0
AIIC [Member] \| Iowa [Member]
Loss Contingencies [Line Items]
Appeal bond		27.8
AIIC [Member] \| 2009 Workers' Compensation Claim [Member] \| Iowa [Member]
Loss Contingencies [Line Items]
Workers compensation claim, damages awarded	$ 25.3
Workers compensation claims contingency reserves		2.4
Total amount expensed on workers compensation claim		$ 5.4
AIIC [Member] \| Plaintiff Seeking Actual Damages [Member] \| Iowa [Member]
Loss Contingencies [Line Items]
Amount of damages	0.3
AIIC [Member] \| Plaintiff Seeking Punitive Damages [Member] \| Iowa [Member]
Loss Contingencies [Line Items]
Amount of damages	$ 25.0

Appeal bond.

No definition available.

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- Definition

Workers compensation claims contingency reserves.

+ References

No definition available.

+ Details

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- Definition

Workers compensation claims contingency reserves plus inception to date loss and loss adjustment expense paid.

+ References

No definition available.

+ Details

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- Definition

Amount of judgment or settlement awarded to (against) the entity in respect of litigation.

+ References

No definition available.

+ Details

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

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- Definition

Amount of damages awarded to the plaintiff in the legal matter.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 450
-SubTopic 20
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=25496072&loc=d3e14326-108349

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 450
-SubTopic 20
-Section 50
-Paragraph 4
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=25496072&loc=d3e14435-108349

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 450
-SubTopic 20
-Section 50
-Paragraph 9
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=25496072&loc=d3e14557-108349

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- Definition

Stated amount that is the upper retention limit per entity policy.

+ References

No definition available.

+ Details

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- Details

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- Details

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- Details

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