Derivative Financial Instruments (Summary of Interest Rate Swaps) (Details)	3 Months Ended
Mar. 31, 2020 USD ($)
November 2016 to March 2021 [Member]
Derivative [Line Items]
Trade Date	Nov. 13, 2016
Notional Amount	$ 200,000,000.0
Coverage Period	November 2016 to March 2021
Risk Coverage	USD-LIBOR
November 2018 to November 2023 [Member]
Derivative [Line Items]
Trade Date	Nov. 28, 2018
Notional Amount	$ 200,000,000.0
Coverage Period	November 2018 to November 2023
Risk Coverage	USD-LIBOR
March 2021 to March 2025 [Member]
Derivative [Line Items]
Trade Date	Nov. 28, 2018
Notional Amount	$ 100,000,000.0
Coverage Period	March 2021 to March 2025
Risk Coverage	USD-LIBOR
March 2020 to March 2022 [Member]
Derivative [Line Items]
Trade Date	Mar. 06, 2020
Notional Amount	$ 50,000,000.0
Coverage Period	March 2020 to March 2022
Risk Coverage	USD-LIBOR
March 2021 to March 2024 [Member]
Derivative [Line Items]
Trade Date	Mar. 10, 2020
Notional Amount	$ 50,000,000.0
Coverage Period	March 2021 to March 2024
Risk Coverage	USD-LIBOR
March 2021 to March 2024 [Member]
Derivative [Line Items]
Trade Date	Mar. 11, 2020
Notional Amount	$ 50,000,000.0
Coverage Period	March 2021 to March 2024
Risk Coverage	USD-LIBOR

Derivative maturity coverage.

No definition available.

Name:	awi_DerivativeMaturityCoverage
Namespace Prefix:	awi_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Date the entity entered into the derivative contract, in CCYY-MM-DD format.

+ References

No definition available.

+ Details

Name:	us-gaap_DerivativeInceptionDates
Namespace Prefix:	us-gaap_
Data Type:	xbrli:dateItemType
Balance Type:	na
Period Type:	duration

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

Name:	us-gaap_DerivativeLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Nominal or face amount used to calculate payment on derivative.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 1B
-URI http://asc.fasb.org/extlink&oid=109980867&loc=SL5580258-113959

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 1A
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=109980867&loc=SL5579245-113959

+ Details

Name:	us-gaap_DerivativeNotionalAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	na
Period Type:	instant

- Definition

Description of primary underlying risk exposure associated with the derivative, for example, but not limited to, interest rate risk, credit risk, foreign exchange rate risk, or price risk.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 1B
-URI http://asc.fasb.org/extlink&oid=109980867&loc=SL5580258-113959

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=109980867&loc=d3e41641-113959

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 1A
-URI http://asc.fasb.org/extlink&oid=109980867&loc=SL5579245-113959

Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=109980867&loc=SL5579240-113959

+ Details

Name:	us-gaap_DerivativeUnderlyingRisk
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=awi_InterestRateSwapsCoveragePeriodNovemberTwentySixteenToMarchTwentyTwentyOneMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=awi_InterestRateSwapsCoveragePeriodNovemberTwentyEighteenToNovemberTwentyTwentyThreeMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=awi_InterestRateSwapsCoveragePeriodMarchTwentyTwentyOneToMarchTwentyTwentyFiveMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=awi_InterestRateSwapsCoveragePeriodMarchTwentyTwentyToMarchTwentyTwentyTwoMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=awi_InterestRateSwapsCoveragePeriodMarchTenTwentyTwentyOneToMarchTwentyTwentyFourMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=awi_InterestRateSwapsCoveragePeriodMarchElevenTwentyTwentyOneToMarchTwentyTwentyFourMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: