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v2.4.1.9

Employee Benefit Plan - Additional Information (Detail) (USD $) In Thousands, unless otherwise specified | 12 Months Ended
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Dec. 31, 2014 | Dec. 31, 2013 | Dec. 31, 2012
United States [Member] |  |  |
Schedule Of Pension And Other Postretirement Benefits Expected Benefit Payments [Line Items] |  |  |
Contribution pension plan | $ 119 us-gaap_DefinedContributionPlanEmployerDiscretionaryContributionAmount / us-gaap_StatementGeographicalAxis = country_US | $ 116 us-gaap_DefinedContributionPlanEmployerDiscretionaryContributionAmount / us-gaap_StatementGeographicalAxis = country_US | $ 111 us-gaap_DefinedContributionPlanEmployerDiscretionaryContributionAmount / us-gaap_StatementGeographicalAxis = country_US
Belgium [Member] |  |  |
Schedule Of Pension And Other Postretirement Benefits Expected Benefit Payments [Line Items] |  |  |
Contribution pension plan | $ 697 us-gaap_DefinedContributionPlanEmployerDiscretionaryContributionAmount / us-gaap_StatementGeographicalAxis = country_BE | $ 655 us-gaap_DefinedContributionPlanEmployerDiscretionaryContributionAmount / us-gaap_StatementGeographicalAxis = country_BE | $ 542 us-gaap_DefinedContributionPlanEmployerDiscretionaryContributionAmount / us-gaap_StatementGeographicalAxis = country_BE

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- Definition Amount of discretionary contributions made by an employer to a defined contribution plan. + References No definition available. + Details
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Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

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- Details
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Namespace Prefix: | vdsi_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

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- Details
Name: | us-gaap_StatementGeographicalAxis=country_BE
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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- Details
Name: | us-gaap_StatementGeographicalAxis=country_US
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |