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Effective Income Tax Rate

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Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate Year One, Percent

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Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate Year Two, Percent

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Estimated Effective Income Tax Rate

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Income Taxes Benefit Expiring Year

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Income Taxes [Line Items]

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Operating Loss Carryforwards No Expiration

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- Definition

Percentage Tax Due On Dividend Distributions

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Period In Which Income Derived Is Tax Exempt

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Reduced income tax incentive period.

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Tax Payable Upon Dividend Distribution

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Term Of Tax Benefit Period

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Unrecognized tax benefits income tax penalties and interest expense (benefit).

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Amount of operating loss carryforward, before tax effects, available to reduce future taxable income under enacted tax laws.

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The portion of the valuation allowance pertaining to the deferred tax asset representing potential future taxable deductions from net operating loss carryforwards for which it is more likely than not that a tax benefit will not be realized.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
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- Definition

Amount accrued for interest on an underpayment of income taxes and penalties related to a tax position claimed or expected to be claimed in the tax return.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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-Section 50
-Paragraph 15
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-URI http://asc.fasb.org/extlink&oid=65882285&loc=d3e32718-109319

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Taxes on Income - Additional Information (Detail) - USD ($)				12 Months Ended
	Jan. 01, 2018	Jan. 01, 2016	Jan. 01, 2014	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income Taxes [Line Items]
Tax benefits under the Law for the Encouragement of Capital Investments period					10 years
Tax benefit expiration period					2023
Period of Income tax benefit - tax exempt					2 years
Tax rate of Approved enterprise, 2011-2012					15.00%
Tax rate of Approved enterprise, 2013					12.50%
Tax rate of Approved enterprise, thereafter					16.00%
Percentage of tax subject to dividends distributed from Preferred Income			20.00%
Additional tax liability related to distribution of dividends from preferred income					$ 0
Carryforward tax losses total					171,000,000
Carryforward tax losses without expiration date					$ 69,000,000
Federal operation loss carryforward expiration beginning year					2017
Federal operation loss carryforward expiration ending year					2027
Deferred tax assets valuation allowance					$ 32,900,000	$ 40,600,000
Carryforward capital losses for tax purposes totaled					43,400,000
Deferred income taxes					0
Tax payable upon dividend distribution					29,300,000
Net interest and penalties expenses					100,000	(100,000)	$ (100,000)
Net interest and penalties expenses related to unrecognized tax benefit					$ 900,000	$ 800,000
2017 Amendment [Member] \| Development Zonea [Member]
Income Taxes [Line Items]
Income tax rate range					7.50%
2017 Amendment [Member] \| Other than Development Zone A [Member]
Income Taxes [Line Items]
Income tax rate range					12.00%
United States Subsidiaries [Member]
Income Taxes [Line Items]
Carryforward tax losses total					$ 94,600,000
Special Preferred Enterprise [Member] \| Development Zonea [Member]
Income Taxes [Line Items]
Income tax rate range					5.00%
Special Preferred Enterprise [Member] \| Other than Development Zone A [Member]
Income Taxes [Line Items]
Income tax rate range					8.00%
Special Preferred Enterprise [Member] \| Development Zone A and Elsewhere [Member]
Income Taxes [Line Items]
Reduced income tax incentive period					10 years
Special Preferred Enterprise [Member] \| 2017 Amendment [Member]
Income Taxes [Line Items]
Income tax rate range					6.00%
Israel [Member]
Income Taxes [Line Items]
Corporate tax rate		25.00%				26.50%	26.50%
Israel [Member] \| Scenario, Forecast [Member]
Income Taxes [Line Items]
Corporate tax rate	23.00%			24.00%
Israel [Member] \| 2011 [Member] \| 2011 Amendment [Member] \| Development Zonea [Member]
Income Taxes [Line Items]
Income tax rate range					10.00%
Israel [Member] \| 2011 [Member] \| 2011 Amendment [Member] \| Other than Development Zone A [Member]
Income Taxes [Line Items]
Income tax rate range					15.00%
Israel [Member] \| 2012 [Member] \| 2011 Amendment [Member] \| Other than Development Zone A [Member]
Income Taxes [Line Items]
Income tax rate range					15.00%
Israel [Member] \| 2013 [Member] \| 2011 Amendment [Member] \| Development Zonea [Member]
Income Taxes [Line Items]
Income tax rate range					7.00%
Israel [Member] \| 2013 [Member] \| 2011 Amendment [Member] \| Other than Development Zone A [Member]
Income Taxes [Line Items]
Income tax rate range					12.50%
Israel [Member] \| 2016 Until [Member] \| 2011 Amendment [Member] \| Development Zonea [Member]
Income Taxes [Line Items]
Income tax rate range					9.00%
Israel [Member] \| 2016 Until [Member] \| 2011 Amendment [Member] \| Other than Development Zone A [Member]
Income Taxes [Line Items]
Income tax rate range					16.00%
Israel [Member] \| 2017 and Thereafter [Member] \| 2011 Amendment [Member] \| Development Zonea [Member]
Income Taxes [Line Items]
Income tax rate range					7.50%
Israel [Member] \| 2017 and Thereafter [Member] \| 2011 Amendment [Member] \| Other than Development Zone A [Member]
Income Taxes [Line Items]
Income tax rate range					16.00%
Israel [Member] \| Special Preferred Enterprise [Member] \| Individual Counterparty [Member]
Income Taxes [Line Items]
Income tax rate range					20.00%
Non-Israeli [Member] \| Individual Counterparty [Member]
Income Taxes [Line Items]
Income tax rate range					4.00%
Minimum [Member]
Income Taxes [Line Items]
Income tax rate range					15.00%
Federal operating loss carryforward expiration period					15 years
Minimum [Member] \| Israeli Subsidiaries [Member]
Income Taxes [Line Items]
Range of deferred taxes rate					8.60%
Minimum [Member] \| Non Israeli Subsidiaries [Member]
Income Taxes [Line Items]
Range of deferred taxes rate					9.00%
Maximum [Member]
Income Taxes [Line Items]
Income tax rate range					25.00%
Federal operating loss carryforward expiration period					20 years
Maximum [Member] \| Israeli Subsidiaries [Member]
Income Taxes [Line Items]
Range of deferred taxes rate					25.00%
Maximum [Member] \| Non Israeli Subsidiaries [Member]
Income Taxes [Line Items]
Range of deferred taxes rate					38.00%