Common Stock Repurchase Plan	9 Months Ended
Sep. 30, 2018
Equity [Abstract]
Common Stock Repurchase Plan	NOTE 15. COMMON STOCK REPURCHASE PLAN On July 29, 2016, we announced that our Board of Directors had approved a share repurchase program pursuant to which we were authorized to repurchase up to $150.0 million of our outstanding shares of common stock through July 31, 2018 (the “Program”). On October 30, 2017, we announced that our Board of Directors had approved an additional $250.0 million authorization to repurchase shares under the Program. The Program was also extended through October 31, 2020. On July 31, 2018, we announced that our Board of Directors had approved an additional $300.0 million authorization to repurchase shares, increasing the total authorized amount under the Program to $700.0 million. Repurchases under the Program may be made through open market, block and privately-negotiated transactions, including Rule 10b5-1 plans, at such times and in such amounts as management deems appropriate, subject to market and business conditions, regulatory requirements and other factors. The Program does not obligate AWI to repurchase any particular amount of common stock and may be suspended or discontinued at any time without notice. On August 2, 2018, we entered into an accelerated share repurchase (“ASR”) agreement with Deutsche Bank AG under the Program. The ASR included a pre-payment of $150.0 million to Deutsche Bank, at which time we received 1,766,004 shares, or 80% of the share delivery. The total number of shares ultimately delivered and therefore the average repurchase price paid per share, was determined as of the end of the applicable purchase period based on the volume weighted-average price of our common stock during that period. Volume weighted-average pricing was calculated in accordance with Rule 10b-18 under the Securities Act. The ASR terminated on October 8, 2018, with approximately 389,825 shares returned on that day to complete the ASR. During the nine months ended September 30, 2018, including the ASR, we repurchased 3.6 million shares under the Program for a total cost of $226.0 million, or an average price of $63.35 per share. Since inception of the Program, through September 30, 2018, including the ASR, we have repurchased 6.5 million shares under the Program for a total cost of $350.2 million, or an average price of $53.68 per share.

NOTE 15. COMMON STOCK REPURCHASE PLAN

On July 29, 2016, we announced that our Board of Directors had approved a share repurchase program pursuant to which we were authorized to repurchase up to $150.0 million of our outstanding shares of common stock through July 31, 2018 (the “Program”). On October 30, 2017, we announced that our Board of Directors had approved an additional $250.0 million authorization to repurchase shares under the Program. The Program was also extended through October 31, 2020. On July 31, 2018, we announced that our Board of Directors had approved an additional $300.0 million authorization to repurchase shares, increasing the total authorized amount under the Program to $700.0 million. Repurchases under the Program may be made through open market, block and privately-negotiated transactions, including Rule 10b5-1 plans, at such times and in such amounts as management deems appropriate, subject to market and business conditions, regulatory requirements and other factors. The Program does not obligate AWI to repurchase any particular amount of common stock and may be suspended or discontinued at any time without notice.

On August 2, 2018, we entered into an accelerated share repurchase (“ASR”) agreement with Deutsche Bank AG under the Program. The ASR included a pre-payment of $150.0 million to Deutsche Bank, at which time we received 1,766,004 shares, or 80% of the share delivery. The total number of shares ultimately delivered and therefore the average repurchase price paid per share, was determined as of the end of the applicable purchase period based on the volume weighted-average price of our common stock during that period. Volume weighted-average pricing was calculated in accordance with Rule 10b-18 under the Securities Act. The ASR terminated on October 8, 2018, with approximately 389,825 shares returned on that day to complete the ASR.

During the nine months ended September 30, 2018, including the ASR, we repurchased 3.6 million shares under the Program for a total cost of $226.0 million, or an average price of $63.35 per share. Since inception of the Program, through September 30, 2018, including the ASR, we have repurchased 6.5 million shares under the Program for a total cost of $350.2 million, or an average price of $53.68 per share.