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Investments Narrative (Details) (USD $)
In Thousands, unless otherwise specified
3 Months Ended 1 Months Ended
Mar. 31, 2015
Mar. 31, 2014
Jan. 31, 2015
Apr. 30, 2013
Oct. 31, 2009
Jun. 30, 2014
Dec. 31, 2014
Mar. 31, 2013
Schedule of Equity Method Investments [Line Items]                
Payments to Acquire Businesses and Interest in Affiliates $ 12,908us-gaap_PaymentsToAcquireBusinessesAndInterestInAffiliates $ 0us-gaap_PaymentsToAcquireBusinessesAndInterestInAffiliates            
J-Devices [Member]                
Schedule of Equity Method Investments [Line Items]                
Ownership interest 65.70%us-gaap_EquityMethodInvestmentOwnershipPercentage
/ us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis
= amkr_JDevicesMember
  65.70%us-gaap_EquityMethodInvestmentOwnershipPercentage
/ us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis
= amkr_JDevicesMember
60.00%us-gaap_EquityMethodInvestmentOwnershipPercentage
/ us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis
= amkr_JDevicesMember
    60.00%us-gaap_EquityMethodInvestmentOwnershipPercentage
/ us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis
= amkr_JDevicesMember
30.00%us-gaap_EquityMethodInvestmentOwnershipPercentage
/ us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis
= amkr_JDevicesMember
Payments to Acquire Businesses and Interest in Affiliates     $ 12,900us-gaap_PaymentsToAcquireBusinessesAndInterestInAffiliates
/ us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis
= amkr_JDevicesMember
$ 67,400us-gaap_PaymentsToAcquireBusinessesAndInterestInAffiliates
/ us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis
= amkr_JDevicesMember
$ 16,700us-gaap_PaymentsToAcquireBusinessesAndInterestInAffiliates
/ us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis
= amkr_JDevicesMember
     
Ownership Threshold 2015 [Member] | J-Devices [Member]                
Schedule of Equity Method Investments [Line Items]                
Maximum ownership ratio of call options 80.00%amkr_MaximumOwnershipRatioOfCallOptions
/ amkr_OptionOwnershipThresholdsAxis
= amkr_OwnershipThreshold2015Member
/ us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis
= amkr_JDevicesMember
             
Minimum ownership threshold, put option 80.00%amkr_MinimumOwnershipThresholdPutOption
/ amkr_OptionOwnershipThresholdsAxis
= amkr_OwnershipThreshold2015Member
/ us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis
= amkr_JDevicesMember
             
Former NMD Shareholders [Member] | J-Devices [Member]                
Schedule of Equity Method Investments [Line Items]                
Ownership interest 34.30%us-gaap_EquityMethodInvestmentOwnershipPercentage
/ amkr_MinorityShareholderinEquityMethodInvestmentAxis
= amkr_FormerNMDShareholdersMember
/ us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis
= amkr_JDevicesMember
             
Japanese Subsidiary [Member]                
Schedule of Equity Method Investments [Line Items]                
Sale of Stock, Percentage of Ownership before Transaction           100.00%us-gaap_SaleOfStockPercentageOfOwnershipBeforeTransaction
/ us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis
= amkr_JapaneseSubsidiaryMember