Income Taxes - Additional Information (Detail) - USD ($) $ in Millions	Sep. 30, 2017	Dec. 31, 2016
Income Tax Contingency [Line Items]
Gross unrecognized tax benefits	$ 17.1	$ 14.2
Unrecognized tax benefits that would impact effective tax rate	11.5
Minimum [Member]
Income Tax Contingency [Line Items]
Gross unrecognized tax benefits balance may decrease within the next twelve months	0.0
Maximum [Member]
Income Tax Contingency [Line Items]
Gross unrecognized tax benefits balance may decrease within the next twelve months	$ 0.7

Amount of decrease reasonably possible in the next twelve months for the unrecognized tax benefit.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 15
-Subparagraph (d)(3)
-URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32718-109319

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Amount of unrecognized tax benefits.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 15A
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=84230637&loc=SL6600010-109319

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The total amount of unrecognized tax benefits that, if recognized, would affect the effective tax rate.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 15A
-Subparagraph (b)
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