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Commitments, Contingencies and Off-Balance Sheet Arrangements - Contingent Liabilities - Additional Information (Detail) - Errors and Omissions [Member]	6 Months Ended
	Jun. 30, 2018 USD ($)
Commitments Contingencies And Off Balance Sheet Arrangements [Line Items]
Insurance claims, amount retained	$ 5,000,000
Amount of losses in excess of retained amounts	175,000,000
Maximum [Member]
Commitments Contingencies And Off Balance Sheet Arrangements [Line Items]
Actuarial range value	7,100,000
Minimum [Member]
Commitments Contingencies And Off Balance Sheet Arrangements [Line Items]
Actuarial range value	$ 1,600,000

X

- Definition

Commitments Contingencies And Off Balance Sheet Arrangements [Line Items]

+ References

No definition available.

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- Definition

Present value of the accrual for product liability loss contingencies as of the balance sheet date (if the accrual qualifies for discounting).

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 450
-SubTopic 20
-Section S99
-Paragraph 1
-Subparagraph (SAB Topic 5.Y.Q1)
-URI http://asc.fasb.org/extlink&oid=27011672&loc=d3e149879-122751

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- Definition

Amount of insurance benefit, claim, loss and settlement expenses incurred, as disclosed in supplementary insurance information.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 235
-Section S99
-Paragraph 1
-Subparagraph (SX 210.12-16(Column H))
-URI http://asc.fasb.org/extlink&oid=34713774&loc=d3e574960-122915

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- Definition

Amount of claim and benefit payable classified as other, disclosed in supplementary insurance information.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 235
-Section S99
-Paragraph 1
-Subparagraph (SX 210.12-16(Column E))
-URI http://asc.fasb.org/extlink&oid=34713774&loc=d3e574960-122915

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