Income Taxes - Additional Information (Detail) - USD ($) $ in Millions	6 Months Ended	12 Months Ended
Jun. 30, 2018	Dec. 31, 2017
Income Tax Contingency [Line Items]
Federal income tax rate	21.00%	35.00%
Increase in effective tax rate due to GILTI provisions	10.00%
Gross unrecognized tax benefits	$ 28.2	$ 26.9
Unrecognized tax benefits that would impact effective tax rate	$ 18.0
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	$ 4.7
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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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 unrecognized tax benefits.

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

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