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SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Narrative) (Details) (USD $)
12 Months Ended
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2012
Property, Plant and Equipment [Line Items]      
Research and development $ 274,568,000us-gaap_ResearchAndDevelopmentExpense $ 266,408,000us-gaap_ResearchAndDevelopmentExpense $ 251,519,000us-gaap_ResearchAndDevelopmentExpense
Foreign Currency Transaction Gain (Loss), before Tax 812,000us-gaap_ForeignCurrencyTransactionGainLossBeforeTax 2,256,000us-gaap_ForeignCurrencyTransactionGainLossBeforeTax 363,000us-gaap_ForeignCurrencyTransactionGainLossBeforeTax
Revenue from Grants 4,000,000us-gaap_RevenueFromGrants 5,000,000us-gaap_RevenueFromGrants 4,200,000us-gaap_RevenueFromGrants
Decrease in depreciation 18,000,000atml_Decreaseindepreciation    
Term of original or remaining maturity to classify available-for-sale securities as short-term (in days) 90 days    
Fair value of investment 1,066,000us-gaap_InvestmentOwnedAtFairValue 3,247,000us-gaap_InvestmentOwnedAtFairValue  
income impact from change of estimates 12,800,000atml_Incomeimpactfromchangeofestimates    
Credit from Reserved Economic Grant Income 0atml_CreditFromReservedEconomicGrantIncome 0atml_CreditFromReservedEconomicGrantIncome 10,689,000atml_CreditFromReservedEconomicGrantIncome
Grants to be repaid 571,000atml_GrantsPayableCurrent 579,000atml_GrantsPayableCurrent  
Maximum [Member]      
Property, Plant and Equipment [Line Items]      
Estimated Useful Life (in years)   5 years  
Percentage of likelihood of being sustained for uncertain tax position not to be recognized 50.00%atml_PercentageOfLikelihoodOfUncertainTaxPositionsNotRecognized
/ us-gaap_RangeAxis
= us-gaap_MaximumMember
   
Term of original or remaining maturity to classify investments as cash and cash equivalents (in days)   90 days  
Minimum [Member]      
Property, Plant and Equipment [Line Items]      
Estimated Useful Life (in years)   3 years  
Auction Rate Securities [Member]      
Property, Plant and Equipment [Line Items]      
Fair value of investment 1,066,000us-gaap_InvestmentOwnedAtFairValue
/ us-gaap_InvestmentTypeAxis
= us-gaap_AuctionRateSecuritiesMember
1,066,000us-gaap_InvestmentOwnedAtFairValue
/ us-gaap_InvestmentTypeAxis
= us-gaap_AuctionRateSecuritiesMember
 
Auction Rate Securities [Member] | Maximum [Member]      
Property, Plant and Equipment [Line Items]      
Short-term interest rate reset period (in days)   28 days  
Auction Rate Securities [Member] | Minimum [Member]      
Property, Plant and Equipment [Line Items]      
Short-term interest rate reset period (in days)   7 days  
Period of contractual maturities (in years)   10 years  
Allowance for doubtful accounts receivable:      
Property, Plant and Equipment [Line Items]      
Valuation Allowances and Reserves, Charged to Cost and Expense $ 4,054,000us-gaap_ValuationAllowancesAndReservesChargedToCostAndExpense
/ us-gaap_ValuationAllowancesAndReservesTypeAxis
= us-gaap_AllowanceForDoubtfulAccountsMember
$ (22,000)us-gaap_ValuationAllowancesAndReservesChargedToCostAndExpense
/ us-gaap_ValuationAllowancesAndReservesTypeAxis
= us-gaap_AllowanceForDoubtfulAccountsMember
$ (18,000)us-gaap_ValuationAllowancesAndReservesChargedToCostAndExpense
/ us-gaap_ValuationAllowancesAndReservesTypeAxis
= us-gaap_AllowanceForDoubtfulAccountsMember
Credit Concentration Risk [Member] | Accounts Receivable [Member]      
Property, Plant and Equipment [Line Items]      
Concentration Risk, Number of Major Distributor 2atml_ConcentrationRiskNumberofMajorDistributor
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= us-gaap_AccountsReceivableMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CreditConcentrationRiskMember
1atml_ConcentrationRiskNumberofMajorDistributor
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= us-gaap_AccountsReceivableMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CreditConcentrationRiskMember
 
Number of customers with concentration risk 0atml_ConcentrationRiskNumberofMajorCustomers
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= us-gaap_AccountsReceivableMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CreditConcentrationRiskMember
0atml_ConcentrationRiskNumberofMajorCustomers
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= us-gaap_AccountsReceivableMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CreditConcentrationRiskMember
 
Customer Concentration Risk [Member] | Sales Revenue, Goods, Net [Member]      
Property, Plant and Equipment [Line Items]      
Number of customers with concentration risk     1atml_ConcentrationRiskNumberofMajorCustomers
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= us-gaap_SalesRevenueGoodsNetMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CustomerConcentrationRiskMember
Major Distributor with Largest Balance [Member] | Sales Revenue, Goods, Net [Member]      
Property, Plant and Equipment [Line Items]      
Concentration Risk, Percentage     12.00%us-gaap_ConcentrationRiskPercentage1
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= us-gaap_SalesRevenueGoodsNetMember
/ us-gaap_MajorCustomersAxis
= atml_MajorDistributorWithLargestBalanceMember
Major Distributor with Largest Balance [Member] | Credit Concentration Risk [Member] | Accounts Receivable [Member]      
Property, Plant and Equipment [Line Items]      
Concentration Risk, Percentage 17.00%us-gaap_ConcentrationRiskPercentage1
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= us-gaap_AccountsReceivableMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CreditConcentrationRiskMember
/ us-gaap_MajorCustomersAxis
= atml_MajorDistributorWithLargestBalanceMember
   
Major Distributor with Largest Balance [Member] | Customer Concentration Risk [Member] | Sales Revenue, Goods, Net [Member]      
Property, Plant and Equipment [Line Items]      
Concentration Risk, Number of Major Distributor 2atml_ConcentrationRiskNumberofMajorDistributor
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= us-gaap_SalesRevenueGoodsNetMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CustomerConcentrationRiskMember
/ us-gaap_MajorCustomersAxis
= atml_MajorDistributorWithLargestBalanceMember
  1atml_ConcentrationRiskNumberofMajorDistributor
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= us-gaap_SalesRevenueGoodsNetMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CustomerConcentrationRiskMember
/ us-gaap_MajorCustomersAxis
= atml_MajorDistributorWithLargestBalanceMember
Number of customers with concentration risk     1atml_ConcentrationRiskNumberofMajorCustomers
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= us-gaap_SalesRevenueGoodsNetMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CustomerConcentrationRiskMember
/ us-gaap_MajorCustomersAxis
= atml_MajorDistributorWithLargestBalanceMember
Concentration Risk, Percentage 16.00%us-gaap_ConcentrationRiskPercentage1
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= us-gaap_SalesRevenueGoodsNetMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CustomerConcentrationRiskMember
/ us-gaap_MajorCustomersAxis
= atml_MajorDistributorWithLargestBalanceMember
   
Major Distributor with Second Largest Balance [Member] | Credit Concentration Risk [Member] | Accounts Receivable [Member]      
Property, Plant and Equipment [Line Items]      
Concentration Risk, Percentage 11.00%us-gaap_ConcentrationRiskPercentage1
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= us-gaap_AccountsReceivableMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CreditConcentrationRiskMember
/ us-gaap_MajorCustomersAxis
= atml_MajorDistributorWithSecondLargestBalanceMember
   
Major Distributor with Second Largest Balance [Member] | Customer Concentration Risk [Member] | Sales Revenue, Goods, Net [Member]      
Property, Plant and Equipment [Line Items]      
Concentration Risk, Percentage 10.00%us-gaap_ConcentrationRiskPercentage1
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= us-gaap_SalesRevenueGoodsNetMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CustomerConcentrationRiskMember
/ us-gaap_MajorCustomersAxis
= atml_MajorDistributorWithSecondLargestBalanceMember
   
Major Customer with Largest Balance [Member] | Sales Revenue, Goods, Net [Member]      
Property, Plant and Equipment [Line Items]      
Concentration Risk, Percentage 16.00%us-gaap_ConcentrationRiskPercentage1
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= us-gaap_SalesRevenueGoodsNetMember
/ us-gaap_MajorCustomersAxis
= atml_MajorCustomerWithLargestBalanceMember
14.00%us-gaap_ConcentrationRiskPercentage1
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= us-gaap_SalesRevenueGoodsNetMember
/ us-gaap_MajorCustomersAxis
= atml_MajorCustomerWithLargestBalanceMember
 
Major Customer with Largest Balance [Member] | Credit Concentration Risk [Member] | Accounts Receivable [Member]      
Property, Plant and Equipment [Line Items]      
Concentration Risk, Percentage   20.00%us-gaap_ConcentrationRiskPercentage1
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= us-gaap_AccountsReceivableMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CreditConcentrationRiskMember
/ us-gaap_MajorCustomersAxis
= atml_MajorCustomerWithLargestBalanceMember
 
Major Customer with Second Largest Balance [Member] | Sales Revenue, Goods, Net [Member]      
Property, Plant and Equipment [Line Items]      
Concentration Risk, Percentage 10.00%us-gaap_ConcentrationRiskPercentage1
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= us-gaap_SalesRevenueGoodsNetMember
/ us-gaap_MajorCustomersAxis
= atml_MajorCustomerWithSecondLargestBalanceMember
12.00%us-gaap_ConcentrationRiskPercentage1
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= us-gaap_SalesRevenueGoodsNetMember
/ us-gaap_MajorCustomersAxis
= atml_MajorCustomerWithSecondLargestBalanceMember
10.00%us-gaap_ConcentrationRiskPercentage1
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= us-gaap_SalesRevenueGoodsNetMember
/ us-gaap_MajorCustomersAxis
= atml_MajorCustomerWithSecondLargestBalanceMember
Major Customer with Second Largest Balance [Member] | Credit Concentration Risk [Member] | Accounts Receivable [Member]      
Property, Plant and Equipment [Line Items]      
Concentration Risk, Percentage 10.00%us-gaap_ConcentrationRiskPercentage1
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= us-gaap_AccountsReceivableMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CreditConcentrationRiskMember
/ us-gaap_MajorCustomersAxis
= atml_MajorCustomerWithSecondLargestBalanceMember