Income Taxes - Deferred Income Tax Balances (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Income Tax Disclosure [Abstract]
U.S. foreign tax credit	$ 5,516	$ 5,058
Stock and long-term compensation plans	1,693	1,318
Foreign NOL & other carryforwards	2,629vdsi_ForeignNolAndOtherCarryForwards	2,930vdsi_ForeignNolAndOtherCarryForwards
US state income taxes	263	574
US alternative minimum tax	395	395
Deferred revenue	752vdsi_DeferredTaxAssetsDeferredRevenue	965vdsi_DeferredTaxAssetsDeferredRevenue
Reserve for uncertain tax issues	(560)	(560)
Amortization and depreciation	434	195
US tax on unremitted foreign earnings	(955)	(380)
Accrued expenses and other	124	(128)
Total gross deferred tax assets	10,291us-gaap_DeferredTaxAssetsGross	10,367us-gaap_DeferredTaxAssetsGross
Less: Valuation allowance	(2,500)	(2,399)
Net deferred income tax assets	7,791us-gaap_DeferredTaxAssetsNet	7,968us-gaap_DeferredTaxAssetsNet
Swiss tax allowances	1,235	726
Intangible assets	213	321
Deferred tax liabilities	$ 1,448us-gaap_DeferredTaxLiabilities	$ 1,047us-gaap_DeferredTaxLiabilities

Amount before allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences and carryforwards.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 740

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=6907707&loc=d3e32537-109319

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Deferred Tax Asset

-URI http://asc.fasb.org/extlink&oid=6510090