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Commitments and Contingencies - Additional Information (Detail) (USD $)
12 Months Ended
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2012
Commitments and Contingencies Disclosure [Abstract]      
Aggregate rent expense under operating leases $ 3,061,000us-gaap_OperatingLeasesRentExpenseNet $ 3,400,000us-gaap_OperatingLeasesRentExpenseNet $ 3,340,000us-gaap_OperatingLeasesRentExpenseNet
Indemnification liability $ 0vdsi_IndemnificationLiability