Income Taxes - Additional Information (Detail) - USD ($) $ in Millions	9 Months Ended	12 Months Ended
Sep. 30, 2018	Dec. 31, 2017
Income Tax Contingency [Line Items]
Federal income tax rate	21.00%	35.00%
Increase in provisional amount of repatriation transition tax	$ 0.4
Increase in effective tax rate due to GILTI provisions	11.00%
Valuation allowance	$ 5.7
Gross unrecognized tax benefits	28.7	$ 26.9
Unrecognized tax benefits that would impact effective tax rate	$ 18.6
Maximum [Member]
Income Tax Contingency [Line Items]
Percentage of deduction in GILTI Income	50.00%
Gross unrecognized tax benefits balance may decrease within the next twelve months	$ 6.9
Minimum [Member]
Income Tax Contingency [Line Items]
Gross unrecognized tax benefits balance may decrease within the next twelve months	$ 0.0

Tax cuts and jobs act of 2017 change in effective tax rate due to global intangible low-taxed income provisions.

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Tax cuts and jobs act of 2017, deduction in global intangible low taxed income, percentage.

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

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Amount of deferred tax assets for which it is more likely than not that a tax benefit will not be realized.

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Percentage of domestic federal statutory tax rate applicable to pretax income (loss).

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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.

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Amount of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations attributable to repatriation of foreign earnings.

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

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