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Derivative Financial Instruments (Summary Of The Amount Of (Loss) Recognized In Accumulated Other Comprehensive Income) (Details) (USD $)
In Millions, unless otherwise specified
 3 Months Ended
Mar. 31, 2015
Mar. 31, 2014
Derivative Instruments, Gain (Loss) [Line Items]    
Amount of Gain (Loss) Recognized in Accumulated Other Comprehensive Income ("AOCI") (Effective Portion) $ (7.6)us-gaap_DerivativeInstrumentsGainLossRecognizedInOtherComprehensiveIncomeEffectivePortionNet [1] $ (1.3)us-gaap_DerivativeInstrumentsGainLossRecognizedInOtherComprehensiveIncomeEffectivePortionNet [1]
Gain (Loss) Reclassified from AOCI into Income (Effective Portion) 0.9us-gaap_DerivativeInstrumentsGainLossReclassifiedFromAccumulatedOCIIntoIncomeEffectivePortionNet 2.7us-gaap_DerivativeInstrumentsGainLossReclassifiedFromAccumulatedOCIIntoIncomeEffectivePortionNet
(Loss) in Accumulated OCI expected to be recognized in earnings (0.6)us-gaap_DerivativeInstrumentsGainLossReclassificationFromAccumulatedOCIToIncomeEstimatedNetAmountToBeTransferred  
Natural Gas Commodity Contracts [Member]    
Derivative Instruments, Gain (Loss) [Line Items]    
Amount of Gain (Loss) Recognized in Accumulated Other Comprehensive Income ("AOCI") (Effective Portion) (2.7)us-gaap_DerivativeInstrumentsGainLossRecognizedInOtherComprehensiveIncomeEffectivePortionNet
/ us-gaap_DerivativeInstrumentRiskAxis
= us-gaap_CommodityContractMember		 [1] 0.6us-gaap_DerivativeInstrumentsGainLossRecognizedInOtherComprehensiveIncomeEffectivePortionNet
/ us-gaap_DerivativeInstrumentRiskAxis
= us-gaap_CommodityContractMember		 [1]
Foreign Exchange Contracts - Purchases [Member]    
Derivative Instruments, Gain (Loss) [Line Items]    
Amount of Gain (Loss) Recognized in Accumulated Other Comprehensive Income ("AOCI") (Effective Portion) 1.0us-gaap_DerivativeInstrumentsGainLossRecognizedInOtherComprehensiveIncomeEffectivePortionNet
/ us-gaap_DerivativeInstrumentRiskAxis
= awi_ForeignExchangeContractsPurchasesMember		 [1] 1.2us-gaap_DerivativeInstrumentsGainLossRecognizedInOtherComprehensiveIncomeEffectivePortionNet
/ us-gaap_DerivativeInstrumentRiskAxis
= awi_ForeignExchangeContractsPurchasesMember		 [1]
Foreign Exchange Contracts - Sales [Member]    
Derivative Instruments, Gain (Loss) [Line Items]    
Amount of Gain (Loss) Recognized in Accumulated Other Comprehensive Income ("AOCI") (Effective Portion) 7.4us-gaap_DerivativeInstrumentsGainLossRecognizedInOtherComprehensiveIncomeEffectivePortionNet
/ us-gaap_DerivativeInstrumentRiskAxis
= awi_ForeignExchangeContractsSalesMember		 [1] 4.8us-gaap_DerivativeInstrumentsGainLossRecognizedInOtherComprehensiveIncomeEffectivePortionNet
/ us-gaap_DerivativeInstrumentRiskAxis
= awi_ForeignExchangeContractsSalesMember		 [1]
Gain (Loss) Reclassified from AOCI into Income (Effective Portion) 2.3us-gaap_DerivativeInstrumentsGainLossReclassifiedFromAccumulatedOCIIntoIncomeEffectivePortionNet
/ us-gaap_DerivativeInstrumentRiskAxis
= awi_ForeignExchangeContractsSalesMember		 1.5us-gaap_DerivativeInstrumentsGainLossReclassifiedFromAccumulatedOCIIntoIncomeEffectivePortionNet
/ us-gaap_DerivativeInstrumentRiskAxis
= awi_ForeignExchangeContractsSalesMember
Interest Rate Swap Contracts [Member]    
Derivative Instruments, Gain (Loss) [Line Items]    
Amount of Gain (Loss) Recognized in Accumulated Other Comprehensive Income ("AOCI") (Effective Portion) (13.3)us-gaap_DerivativeInstrumentsGainLossRecognizedInOtherComprehensiveIncomeEffectivePortionNet
/ us-gaap_DerivativeInstrumentRiskAxis
= us-gaap_InterestRateSwapMember		 [1] (7.9)us-gaap_DerivativeInstrumentsGainLossRecognizedInOtherComprehensiveIncomeEffectivePortionNet
/ us-gaap_DerivativeInstrumentRiskAxis
= us-gaap_InterestRateSwapMember		 [1]
Cost Of Goods Sold [Member] | Natural Gas Commodity Contracts [Member]    
Derivative Instruments, Gain (Loss) [Line Items]    
Gain (Loss) Reclassified from AOCI into Income (Effective Portion) (1.5)us-gaap_DerivativeInstrumentsGainLossReclassifiedFromAccumulatedOCIIntoIncomeEffectivePortionNet
/ us-gaap_DerivativeInstrumentRiskAxis
= us-gaap_CommodityContractMember
/ us-gaap_IncomeStatementLocationAxis
= us-gaap_CostOfGoodsTotalMember		 0.7us-gaap_DerivativeInstrumentsGainLossReclassifiedFromAccumulatedOCIIntoIncomeEffectivePortionNet
/ us-gaap_DerivativeInstrumentRiskAxis
= us-gaap_CommodityContractMember
/ us-gaap_IncomeStatementLocationAxis
= us-gaap_CostOfGoodsTotalMember
Cost Of Goods Sold [Member] | Foreign Exchange Contracts - Purchases [Member]    
Derivative Instruments, Gain (Loss) [Line Items]    
Gain (Loss) Reclassified from AOCI into Income (Effective Portion) $ 0.1us-gaap_DerivativeInstrumentsGainLossReclassifiedFromAccumulatedOCIIntoIncomeEffectivePortionNet
/ us-gaap_DerivativeInstrumentRiskAxis
= awi_ForeignExchangeContractsPurchasesMember
/ us-gaap_IncomeStatementLocationAxis
= us-gaap_CostOfGoodsTotalMember		 $ 0.5us-gaap_DerivativeInstrumentsGainLossReclassifiedFromAccumulatedOCIIntoIncomeEffectivePortionNet
/ us-gaap_DerivativeInstrumentRiskAxis
= awi_ForeignExchangeContractsPurchasesMember
/ us-gaap_IncomeStatementLocationAxis
= us-gaap_CostOfGoodsTotalMember
[1] As of March 31, 2015 the amount of existing gains in AOCI expected to be recognized in earnings over the next twelve months is $0.6 million.