Annual report pursuant to Section 13 and 15(d)

Cash Equivalents And Investments (Schedule Of Estimated Fair Value Of Available-For-Sale Securities) (Details)

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Cash Equivalents And Investments (Schedule Of Estimated Fair Value Of Available-For-Sale Securities) (Details) (USD $)
In Thousands, unless otherwise specified
Dec. 31, 2014
Dec. 31, 2013
Schedule of Available-for-sale Securities [Line Items]    
Fair Value $ 17,216us-gaap_AvailableForSaleSecuritiesDebtSecurities $ 15,655us-gaap_AvailableForSaleSecuritiesDebtSecurities
Investments [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Due within one year, Amortized Cost 4,598us-gaap_AvailableForSaleSecuritiesDebtMaturitiesNextRollingTwelveMonthsAmortizedCostBasis
/ jcs_AdditionalInvestmentInformationAxis
= us-gaap_InvestmentsMember
 
Due after one year through five years, Amortized Cost 11,593us-gaap_AvailableForSaleSecuritiesDebtMaturitiesRollingYearTwoThroughFiveAmortizedCostBasis
/ jcs_AdditionalInvestmentInformationAxis
= us-gaap_InvestmentsMember
 
Amortized Cost 16,191us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAmortizedCost
/ jcs_AdditionalInvestmentInformationAxis
= us-gaap_InvestmentsMember
 
Due within one year, Fair Value 4,603us-gaap_AvailableForSaleSecuritiesDebtMaturitiesWithinOneYearFairValue
/ jcs_AdditionalInvestmentInformationAxis
= us-gaap_InvestmentsMember
 
Due after one year through five years, Fair Value 11,540us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterOneThroughFiveYearsFairValue
/ jcs_AdditionalInvestmentInformationAxis
= us-gaap_InvestmentsMember
 
Fair Value $ 16,143us-gaap_AvailableForSaleSecuritiesDebtSecurities
/ jcs_AdditionalInvestmentInformationAxis
= us-gaap_InvestmentsMember
$ 9,903us-gaap_AvailableForSaleSecuritiesDebtSecurities
/ jcs_AdditionalInvestmentInformationAxis
= us-gaap_InvestmentsMember