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Equity Investments (Details) (WAVE [Member], USD $)
In Millions, unless otherwise specified
 3 Months Ended
Mar. 31, 2015
Mar. 31, 2014
WAVE [Member]
    
Schedule of Equity Method Investments [Line Items]    
Net sales $ 86.6us-gaap_EquityMethodInvestmentSummarizedFinancialInformationRevenue
/ us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis
= awi_WorthingtonArmstrongVentureMember		 $ 92.3us-gaap_EquityMethodInvestmentSummarizedFinancialInformationRevenue
/ us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis
= awi_WorthingtonArmstrongVentureMember
Gross profit 40.8us-gaap_EquityMethodInvestmentSummarizedFinancialInformationGrossProfitLoss
/ us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis
= awi_WorthingtonArmstrongVentureMember		 43.5us-gaap_EquityMethodInvestmentSummarizedFinancialInformationGrossProfitLoss
/ us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis
= awi_WorthingtonArmstrongVentureMember
Net earnings $ 30.5us-gaap_EquityMethodInvestmentSummarizedFinancialInformationNetIncomeLoss
/ us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis
= awi_WorthingtonArmstrongVentureMember		 $ 32.2us-gaap_EquityMethodInvestmentSummarizedFinancialInformationNetIncomeLoss
/ us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis
= awi_WorthingtonArmstrongVentureMember
Equity interest percentage 50.00%us-gaap_EquityMethodInvestmentOwnershipPercentage
/ us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis
= awi_WorthingtonArmstrongVentureMember