Income Taxes - Differences Between Income Taxes Using Federal Statutory Income Tax Rate and Effective Tax Rate (Detail)	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
U.S. federal statutory income tax rate	35.00%	35.00%	35.00%
State income taxes, net of federal tax benefit	1.40%	2.10%	1.50%
Impact of U.S. Tax Cuts and Jobs Act	23.10%	0.00%	0.00%
Impact of differences in foreign tax rates	(18.00%)	(6.30%)	(16.20%)
Valuation allowance release for Israel	0.00%	(12.90%)	0.00%
Stock-based compensation	(6.30%)	1.20%	1.60%
Other items not individually material	0.50%	2.00%	0.70%
Effective Income Tax Rate, Continuing Operations, Total	35.70%	21.10%	22.60%

Effective Income Tax Rate Reconciliation, Tax Cuts and Jobs Act of 2017

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Effective Income Tax Rate Reconciliation, Valuation Allowance Release For Foreign Country

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Percentage of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

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-Publisher FASB
-Name Accounting Standards Codification
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Percentage of domestic federal statutory tax rate applicable to pretax income (loss).

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Percentage 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 applicable to statutory income tax expense (benefit) outside of the country of domicile.

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Percentage 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 applicable to state and local income tax expense (benefit), net of federal tax expense (benefit).

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