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Employee Benefits (Details) (USD $)
12 Months Ended
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2012
Employee Benefits [Abstract]      
Employer matching contribution percentage 50.00%us-gaap_DefinedContributionPlanEmployerMatchingContributionPercentOfMatch    
Maximum employer contribution amount of employee compensation $ 1,500ddd_MaximumEmployerContributionAmountOfEmployeeCompensation    
Employee benefit expenses $ 721,000us-gaap_DefinedBenefitPlanContributionsByEmployer $ 527,000us-gaap_DefinedBenefitPlanContributionsByEmployer $ 489,000us-gaap_DefinedBenefitPlanContributionsByEmployer