Armstrong World Industries (AWI) 10-Q 29 Apr 19 2019 Q1 Quarterly report Financial data

Document And Entity Information

Document And Entity Information - shares	3 Months Ended
	Mar. 31, 2019	Apr. 24, 2019
Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Mar. 31, 2019
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	Q1
Entity Registrant Name	ARMSTRONG WORLD INDUSTRIES INC
Trading Symbol	awi
Entity Central Index Key	0000007431
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Entity Emerging Growth Company	false
Entity Small Business	false
Entity Common Stock, Shares Outstanding		48,959,255

Condensed Consolidated Statemen

Condensed Consolidated Statements of Earnings and Comprehensive Income - USD ($) shares in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Income Statement [Abstract]
Net sales	$ 242.1	$ 227.3
Cost of goods sold	150.7	156.5
Gross profit	91.4	70.8
Selling, general and administrative expenses	55.6	37.5
Equity earnings from joint venture	(18.9)	(16.3)
Operating income	54.7	49.6
Interest expense	10.4	9.2
Other non-operating (income), net	(5.5)	(9)
Earnings from continuing operations before income taxes	49.8	49.4
Income tax expense	13.4	8.2
Earnings from continuing operations	36.4	41.2
Net earnings from discontinued operations, net of tax (benefit) expense of ($0.1) and $1.5	0.5	3.9
Gain (loss) from disposal of discontinued businesses, net of tax (benefit) of $- and ($0.4)	2.2	(17.3)
Net gain (loss) from discontinued operations	2.7	(13.4)
Net earnings	39.1	27.8
Other comprehensive income (loss), net of tax:
Foreign currency translation adjustments	5.3	5.9
Derivative (loss) gain, net	(5.1)	3.8
Pension and postretirement adjustments	2.8	1.8
Total other comprehensive income	3	11.5
Total comprehensive income	$ 42.1	$ 39.3
Earnings per share of common stock, continuing operations:
Basic	$ 0.75	$ 0.78
Diluted	0.73	0.76
Earnings (loss) per share of common stock, discontinued operations:
Basic	0.05	(0.25)
Diluted	0.05	(0.25)
Net earnings per share of common stock:
Basic	0.80	0.53
Diluted	$ 0.78	$ 0.51
Average number of common shares outstanding:
Basic	48.7	53
Diluted	49.5	53.8

Condensed Consolidated Statem_2

Condensed Consolidated Statements of Earnings and Comprehensive Income (Parenthetical) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Income Statement [Abstract]
Net earnings from discontinued operations, tax expense (benefit)	$ (0.1)	$ 1.5
Gain (Loss) from disposal of discontinued business, tax (benefit)		$ (0.4)

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets - USD ($) $ in Millions	Mar. 31, 2019	Dec. 31, 2018
Current assets:
Cash and cash equivalents	$ 273.8	$ 325.7
Accounts and notes receivable, net	85.3	79.9
Inventories, net	72.1	61.2
Assets of discontinued operations	308.9	279.5
Income tax receivable	0.7	1.7
Other current assets	8.2	4.8
Total current assets	749	752.8
Property, plant, and equipment, less accumulated depreciation and amortization of $421.8 and $412.9, respectively	510.5	501
Lease right-of-use assets	28.8
Prepaid pension costs	59.5	52.8
Investment in joint venture	38.7	40.8
Goodwill and intangible assets, net	472.3	442
Deferred income taxes	19	14.8
Income taxes receivable	0.8	0.8
Other non-current assets	64	68.5
Total assets	1,942.6	1,873.5
Current liabilities:
Current installments of long-term debt	62.5	55
Accounts payable and accrued expenses	390.9	383.3
Liabilities of discontinued operations	129.3	110.3
Income tax payable	7.2	0.9
Total current liabilities	589.9	549.5
Long-term debt, less current installments	749.7	764.8
Lease non-current liabilities	23.6
Postretirement benefit liabilities	57.6	58.8
Pension benefit liabilities	49.7	50.3
Other long-term liabilities	33	38
Income taxes payable	26.9	26.5
Deferred income taxes	131.9	124.4
Total non-current liabilities	1,072.4	1,062.8
Shareholders' equity:
Common stock, $0.01 par value per share, 200 million shares authorized, 61,717,806 shares issued and 48,640,635 shares outstanding as of March 31, 2019 and 61,553,724, shares issued and 48,808,239 shares outstanding as of December 31, 2018	0.6	0.6
Capital in excess of par value	553.3	547.4
Retained earnings	895.1	865
Treasury stock, at cost, 13,077,171 shares as of March 31, 2019 and 12,745,485 shares as of December 31, 2018	(712.2)	(692.2)
Accumulated other comprehensive (loss)	(456.5)	(459.6)
Total shareholders' equity	280.3	261.2
Total liabilities and shareholders' equity	$ 1,942.6	$ 1,873.5

Condensed Consolidated Balanc_2

Condensed Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Millions	Mar. 31, 2019	Dec. 31, 2018
Statement Of Financial Position [Abstract]
Property, plant and equipment, accumulated depreciation and amortization	$ 421.8	$ 412.9
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	200,000,000	200,000,000
Common stock, shares issued	61,717,806	61,553,724
Common stock, shares outstanding	48,640,635	48,808,239
Treasury stock, shares	13,077,171	12,745,485

Condensed Consolidated Statem_3

Condensed Consolidated Statements of Shareholders' Equity - USD ($) $ in Millions	Total	Common Stock	Additional Paid-in Capital	Retained Earnings	Treasury Stock	AOCI Attributable to Parent
Balance at Dec. 31, 2017	$ 419.3	$ 0.6	$ 516.8	$ 633.4	$ (385.6)	$ (345.9)
Balance at Dec. 31, 2017		52,772,139
Balance at Dec. 31, 2017					8,010,597
Cumulative effect impact of ASU adoption | ASU 2018-02 [Member]	(54.3)			54.3		(54.3)
Stock issuance, net		591,584
Share-based employee compensation	15.2		15.2
Net earnings	27.8			27.8
Other comprehensive income	11.5					11.5
Acquisition of treasury stock	(70)				$ (70)
Acquisition of treasury stock, shares		(1,165,247)			1,165,247
Balance at Mar. 31, 2018	403.8	$ 0.6	532	715.5	$ (455.6)	(388.7)
Balance at Mar. 31, 2018		52,198,476
Balance at Mar. 31, 2018					9,175,844
Balance at Dec. 31, 2018	$ 261.2	$ 0.6	547.4	865	$ (692.2)	(459.6)
Balance at Dec. 31, 2018	48,808,239	48,808,239
Balance at Dec. 31, 2018	12,745,485				12,745,485
Cumulative effect impact of ASU adoption | ASU 2017-12 [Member]	$ 0.1			(0.1)		0.1
Stock issuance, net		164,082
Cash dividends - $0.175 per common share	(8.9)			(8.9)
Share-based employee compensation	5.9		5.9
Net earnings	39.1			39.1
Other comprehensive income	3					3
Acquisition of treasury stock	(20)				$ (20)
Acquisition of treasury stock, shares		(331,686)			331,686
Balance at Mar. 31, 2019	$ 280.3	$ 0.6	$ 553.3	$ 895.1	$ (712.2)	$ (456.5)
Balance at Mar. 31, 2019	48,640,635	48,640,635
Balance at Mar. 31, 2019	13,077,171				13,077,171

Condensed Consolidated Statem_4

Condensed Consolidated Statements of Shareholders' Equity (Parenthetical)	3 Months Ended
	Mar. 31, 2019$ / shares
Statement Of Stockholders Equity [Abstract]
Dividends declared	$ 0.175

Condensed Consolidated Statem_5

Condensed Consolidated Statements of Cash Flows - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Cash flows from operating activities:
Net earnings	$ 39.1	$ 27.8
Adjustments to reconcile net earnings to net cash provided by operating activities:
Depreciation and amortization	15.1	22.8
(Gain) loss on disposal of discontinued operations	(2.2)	17.7
Deferred income taxes	5	1.5
Share-based compensation	1.8	2.6
Equity earnings from joint venture	(18.9)	(16.3)
U.S. pension (credit)	(1.9)	(6.6)
Other non-cash adjustments, net	0.2	(0.8)
Changes in operating assets and liabilities:
Receivables	3.5	22.5
Inventories	(11.4)	(17.3)
Other current assets	(1.1)	(0.9)
Lease right-of-use assets	3.2
Other non-current assets	(3)	(0.6)
Accounts payable and accrued expenses	(5)	(26.4)
Income taxes payable	5.3	5.9
Non-current lease liabilities	(3.6)
Other long-term liabilities	(11.7)	(4.6)
Other, net	0.3	(1.3)
Net cash provided by operating activities	14.7	26
Cash flows from investing activities:
Purchases of property, plant and equipment	(14.8)	(10.2)
Return of investment from joint venture	19.7	16
Cash paid for acquisitions	(43.1)
Other investing activities	0.2
Net cash (used for) provided by investing activities	(38)	5.8
Cash flows from financing activities:
Payments of long-term debt	(8.1)	(8.1)
Dividend paid	(8.5)
Proceeds from exercised stock options	4.8	13.9
Payment for treasury stock acquired	(20)	(70)
Other financing activities	1.9
Net cash (used for) financing activities	(29.9)	(64.2)
Effect of exchange rate changes on cash and cash equivalents	1.3	(0.3)
Net (decrease) in cash and cash equivalents	(51.9)	(32.7)
Cash and cash equivalents at beginning of year	335.7	159.6
Cash and cash equivalents at end of period	283.8	126.9
Cash and cash equivalents at end of period of discontinued operations	10	10
Cash and cash equivalents at end of period of continuing operations	273.8	116.9
Supplemental Cash Flow Disclosures:
Interest paid	10.8	7.7
Income tax payments, net	3	1.8
Amounts in accounts payable for capital expenditures	$ 0.9	$ 2.3

Business and Basis of Presentat

Business and Basis of Presentation	3 Months Ended
	Mar. 31, 2019
Accounting Policies [Abstract]
Business and Basis of Presentation	NOTE 1. BUSINESS AND BASIS OF PRESENTATION Armstrong World Industries, Inc. (“AWI”) is a Pennsylvania corporation incorporated in 1891. When we refer to “AWI,” the “Company,” “we,” “our” or “us” in these notes, we are referring to AWI and its subsidiaries. The accounting policies used in preparing the Condensed Consolidated Financial Statements in this Form 10-Q are the same as those used in preparing the Consolidated Financial Statements for the year ended December 31, 2018. These statements should therefore be read in conjunction with the Consolidated Financial Statements and notes that are included in the Form 10-K for the fiscal year ended December 31, 2018. In the opinion of management, all adjustments of a normal recurring nature have been included to provide a fair statement of the results for the reporting periods presented. Operating results for the first quarter of 2019 and 2018 included in this report are unaudited. Quarterly results are not necessarily indicative of annual earnings, primarily due to the different level of sales in each quarter of the year and the possibility of changes in general economic conditions. On March 4, 2019, we acquired the business and assets of Architectural Components Group, Inc. (“ACGI”), based in Marshfield, Missouri. ACGI is a manufacturer of custom wood ceilings and walls with one manufacturing facility. ACGI’s operations, and its assets and liabilities, are included as a component of our Architectural Specialties segment. See Note 4 for further information. On August 16, 2018, we acquired the business and assets of Steel Ceilings, Inc. (“Steel Ceilings”), based in Johnstown, Ohio. Steel Ceilings is a manufacturer of aluminum and stainless metal ceilings that include architectural, radiant and security solutions with one manufacturing facility. Steel Ceilings’ operations, and its assets and liabilities, are included as a component of our Architectural Specialties segment. See Note 4 for further information. On May 31, 2018, we acquired the business and assets of Plasterform, Inc. (“Plasterform”), based in Mississauga, Ontario, Canada. Plasterform is a manufacturer of architectural cast ceilings, walls, facades, columns and moldings with one manufacturing facility. Plasterform On November 17, 2017, we entered into a Share Purchase Agreement (the “Purchase Agreement”) with Knauf International GmbH (“Knauf”), to sell certain subsidiaries comprising our business in Europe, the Middle East and Africa (including Russia) (“EMEA”) and the Pacific Rim, including the corresponding businesses and operations conducted by Worthington Armstrong Venture (“WAVE”), our joint venture with Worthington Industries, Inc. (“Worthington”) in which AWI holds a 50% interest. The Purchase Agreement provides that the consideration to be paid by Knauf in connection with the sale is $330.0 million in cash, inclusive of amounts due to WAVE, subject to certain adjustments as provided in the Purchase Agreement, including adjustments based on the economic impact of any required regulatory remedies and a working capital adjustment. We received both the $250 million payment and the $80 million payment from Knauf in the third quarter of 2018. Upon or prior to closing, we expect to enter into (i) a Transition Services Agreement with Knauf for its benefit and the benefit of the buyer of the divestment business under which we will provide certain transition technology and information technology services for a limited period of time following closing, (ii) an intellectual property License Agreement with Knauf for its benefit and the benefit of the buyer of the divestment business under which we will license certain patents, trademarks and know-how for their use in certain licensed territories, and (iii) a Supply Agreement with each of Knauf and the buyer of the divestment business under which the parties may continue to purchase certain products from each other following closing. WAVE will enter into similar agreements with Knauf and/or the buyer of the divestment business for such purposes. These Condensed Consolidated Financial Statements are prepared in accordance with U.S. generally accepted accounting principles (“U.S. GAAP”). The statements include management estimates and judgments, where appropriate. Management utilizes estimates to record many items including certain asset values, allowances for bad debts, inventory obsolescence and lower of cost and net realizable value charges, warranty reserves, workers’ compensation, general liability and environmental claims, and income taxes. When preparing an estimate, management determines the amount based upon the consideration of relevant information. Management may confer with outside parties, including outside counsel. Actual results may differ from these estimates. Recently Adopted Accounting Standards In February 2016, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) 2016-02, “Leases,” In January 2018, FASB issued ASU 2018-01, “Land Easement Practical Expedient for Transition to Topic 842,” “Codification improvements to Topic 842, Leases,” “Targeted Improvements,” Effective January 1, 2019, we adopted these standards using the modified retrospective transition method and have applied all practical expedients related to leases existing at the date of initial application. Upon adoption, the most significant change was to the Condensed Consolidated Balance Sheet related to the recognition of new ROU assets and lease liabilities on a continuing operations basis. We have recognized ROU assets and lease liabilities of $28.8 million, based on the present value of the future minimum rental payments for existing operating leases. We have no leases that classify as financing arrangements. As required by the lease ASC updates, we have expanded our disclosure of leases. See Note 9 for additional information. In August 2017, the FASB issued ASU 2017-12, “Derivatives and Hedging (Topic 815): Targeted Improvements to Accounting for Hedging Activities,” In June 2018, the FASB issued ASU 2018-07, “Improvements to Nonemployee Share-Based Payment Accounting,” had no material impact on our financial condition, results of operations or cash flows. Recently Issued Accounting Standards In August 2018, the FASB issued ASU 2018-14, “ Disclosure Framework – Changes to the Disclosure Requirements for Defined Benefit Plans” In August 2018, the FASB issued ASU 2018-15, “Customer’s Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That is a Service Contract”

Segment Results

Segment Results	3 Months Ended
	Mar. 31, 2019
Segment Reporting [Abstract]
Segment Results	NOTE 2. SEGMENT RESULTS Three Months Ended March 31, 2019 2018 Net sales Mineral Fiber $ 196.7 $ 190.7 Architectural Specialties 45.4 36.6 Total net sales $ 242.1 $ 227.3 Three Months Ended March 31, 2019 2018 Segment operating income (loss) Mineral Fiber $ 47.6 $ 43.7 Architectural Specialties 9.2 8.3 Unallocated Corporate (2.1 ) (2.4 ) Total consolidated operating income $ 54.7 $ 49.6 Three Months Ended March 31, 2019 2018 Total consolidated operating income $ 54.7 $ 49.6 Interest expense 10.4 9.2 Other non-operating (income), net (5.5 ) (9.0 ) Earnings from continuing operations before income taxes $ 49.8 $ 49.4 March 31, 2019 December 31, 2018 Segment assets Mineral Fiber $ 1,118.0 $ 1,096.1 Architectural Specialties 147.2 84.7 Unallocated Corporate 368.5 413.2 Total consolidated assets $ 1,633.7 $ 1,594.0 In connection with the closing of our St. Helens, Oregon Mineral Fiber manufacturing facility in the second quarter of 2018, we recorded $7.7 million in cost of goods sold related to accelerated depreciation of property, plant and equipment in the first quarter of 2018.

Revenue

Revenue	3 Months Ended
	Mar. 31, 2019
Revenue From Contract With Customer [Abstract]
Revenue	NOTE 3. REVENUE Revenue Recognition We recognize revenue upon transfer of control of our products to the customer, which typically occurs upon shipment. Our main performance obligation to our customers is the delivery of products in accordance with purchase orders. Each purchase order defines the transaction price for the products purchased under the arrangement. Direct sales to building materials distributors, home centers, direct customers, and retailers represent the majority of our sales. Our standard sales terms are Free On Board (“FOB”) shipping point. We have some sales terms that are FOB destination. At the point of shipment, the customer is required to pay under normal sales terms. Our normal payment terms in most cases are Incremental costs to fulfill our customer arrangements are expensed as incurred, as the amortization period is less than one year. Our products are sold with normal and customary return provisions. We provide limited warranties for defects in materials or factory workmanship, sagging and warping, and certain other manufacturing defects. Warranties are not sold separately to customers. Our product warranties place certain requirements on the purchaser, including installation and maintenance in accordance with our written instructions. In addition to our warranty program, under certain limited circumstances, we will occasionally and at our sole discretion, provide a customer accommodation repair or replacement. Warranty repairs and replacements are most commonly made by professional installers employed by or affiliated with our independent distributors. Reimbursement for costs associated with warranty repairs are provided to our independent distributors through a credit against accounts receivable from the distributor to us. Sales returns and warranty claims have historically not been material and do not constitute separate performance obligations. We often enter into agreements with our customers to offer incentive programs, primarily volume rebates and promotions. The majority of our rebates are designated as a percentage of annual customer purchases. We estimate the amount of rebate based on actual sales for the period and accrue for the projected incentive programs costs. We record the costs of the rebate accruals as a reduction to our revenue. In addition, other sales discounts, including early pay promotions, are deducted immediately from the sales invoice. Shipping and Handling We account for product shipping and handling costs as fulfillment activities and present the associated costs in costs of goods sold in the period in which we sell our product. Disaggregation of Revenues Our Mineral Fiber and Architectural Specialties operating segments both manufacture and sell ceiling systems (primarily mineral fiber, fiberglass wool, metal, and wood) throughout the Americas. We disaggregate revenue based on our product based segments and major customer grouping as these categories represent the most appropriate depiction of how the nature, amount, and timing of revenues and cash flows are affected by economic factors. Net sales by major customer group are as follows: Distributors – represents net sales to building materials distributors, who re-sell our products to contractors, subcontractors’ alliances, large architect and design firms, and major facility owners. Geographically, this category includes sales throughout the U.S., Canada, and Latin America. Home centers – represents net sales to home centers such as Lowe’s Companies, Inc. and The Home Depot, Inc. Direct customers – represents net sales sold directly to contractors, subcontractors’ alliances, large architect and design firms, and major facility owners. Only sales to U.S. customers are reported within this customer group. Retailers and other – represents net sales to independent retailers and certain national account customers, including wholesalers who re-sell our products to dealers who service builders, contractors and consumers. Geographically, this category includes sales throughout the U.S., Canada, and Latin America. The following tables provide net sales by major customer group within the Mineral Fiber and Architectural Specialties segments for the three months ended March 31, 2019 and 2018: Three months ended March 31, Mineral Fiber 2019 2018 Distributors $ 144.6 $ 137.7 Home centers 23.1 24.0 Direct customers 14.1 13.7 Retailers and other 14.9 15.3 Total $ 196.7 $ 190.7 Three months ended March 31, Architectural Specialties 2019 2018 Distributors $ 31.5 $ 28.4 Direct customers 13.1 7.9 Retailers and other 0.8 0.3 Total $ 45.4 $ 36.6

Acquisition and Discontinued Op

Acquisition and Discontinued Operations	3 Months Ended
	Mar. 31, 2019
Discontinued Operations [Abstract]
Acquisition and Discontinued Operations	NOTE 4. ACQUISITION AND DISCONTINUED OPERATIONS ACQUISITION OF ACGI On March 4, 2019, we acquired the business and assets of ACGI. The $43.1 million purchase price, which is subject to customary working capital adjustments These amounts are subject to adjustment as our purchase accounting analysis is completed. ACQUISITION OF STEEL CEILINGS On August 16, 2018, we acquired the business and assets of Steel Ceilings. The $12.3 million purchase price was allocated to the assets acquired and the liabilities assumed based on their estimated fair values, with the remaining amount recorded as goodwill. In October 2018, we sold certain assets related to an acquired product line to WAVE for $2.0 million. The total fair value of tangible assets acquired, less liabilities assumed, was $4.4 million. The total fair value of identifiable intangible assets acquired was mostly comprised of amortizable customer relationships of $1.4 million and tradenames of $1.3 million, resulting in $3.2 million of goodwill. All of the acquired goodwill is deductible for tax purposes. ACQUISITION OF PLASTERFORM On May 31, 2018, we acquired the business and assets of Plasterform. The $11.9 million purchase price was allocated to the assets acquired and the liabilities assumed based on their estimated fair values, with the remaining amount recorded as goodwill. The total fair value of tangible assets acquired, less liabilities assumed, was $2.2 million. The total fair value of identifiable intangible assets acquired, comprised of amortizable customer relationships, was $4.8 million, resulting in $4.9 million of goodwill. All of the acquired goodwill is deductible for tax purposes. EMEA AND PACIFIC RIM BUSINESSES On November 17, 2017, we agreed to sell certain subsidiaries comprising our businesses in EMEA and the Pacific Rim to Knauf. Each quarter we compare the anticipated sales proceeds from Knauf to the carrying value of EMEA and Pacific Rim net assets. We record an estimated loss if the carrying value exceeds the anticipated sales proceeds. Net gains can only be recorded to the extent of previous estimated losses. In 2017, we recorded an estimated loss of $74.0 million, which included $51.4 million of unfavorable Accumulated Other Comprehensive Income (“AOCI”) adjustments. In 2018, we recorded an estimated loss of $19.3 million, which included $25.5 million of unfavorable AOCI adjustments. During the three months ended March 31, 2019, we recorded a net gain of $2.2 million, which included $9.1 million of favorable AOCI adjustments. These AOCI adjustments related primarily to accumulated foreign currency translation amounts that will be subsequently reclassified to earnings from discontinued operations upon sale of our EMEA and Pacific Rim businesses. See Note 1 for further discussion of the divestiture status. FLOORING BUSINESSES Separation and Distribution of AFI On April 1, 2016, we completed our separation of Armstrong Flooring, Inc. (“AFI”) by allocating the assets and liabilities related primarily to our Resilient and Wood Flooring segments to AFI and then distributing the common stock of AFI to our shareholders at a ratio of one share of AFI common stock for every two shares of AWI common stock. In connection with the separation and distribution of AFI, we entered into several agreements with AFI that, together with a plan of division, provide for the separation and allocation between AWI and AFI of the flooring assets, employees, liabilities and obligations of AWI and its subsidiaries attributable to periods prior to, at and after AFI’s separation from AWI, and govern the relationship between AWI and AFI subsequent to the completion of the separation and distribution. These agreements include a Tax Matters Agreement, an Employee Matters Agreement, a Trademark License Agreement, a Transition Trademark License Agreement and a Campus Lease Agreement. European Resilient Flooring On December 4, 2014, our Board of Directors approved the cessation of funding to our DLW subsidiary, which at that time was our European flooring business. Summarized Financial Information of Discontinued Operations The following tables detail the businesses and line items that comprise discontinued operations on the Condensed Consolidated Statements of Earnings and Comprehensive Income. EMEA and Pacific Rim Businesses Three months ended March 31, 2019: Net sales $ 96.9 Cost of goods sold 75.7 Gross profit 21.2 Selling, general and administrative expenses 20.8 Operating income 0.4 Earnings from discontinued operations before income tax 0.4 Income tax (benefit) (0.1 ) Net earnings from discontinued operations, net of tax $ 0.5 Gain from disposal of discontinued businesses, before income tax $ 2.2 Income tax expense - Gain from disposal of discontinued businesses, net of tax $ 2.2 Net earnings from discontinued operations $ 2.7 EMEA and Pacific Rim Businesses Flooring Businesses Total Three months ended March 31, 2018: Net sales $ 104.4 $ - $ 104.4 Cost of goods sold 77.8 - 77.8 Gross profit 26.6 - 26.6 Selling, general and administrative expenses 22.0 - 22.0 Operating income 4.6 - 4.6 Interest expense 0.4 - 0.4 Other non-operating (income), net (1.2 ) - (1.2 ) Earnings from discontinued operations before income tax 5.4 - 5.4 Income tax expense 1.5 - 1.5 Net earnings from discontinued operations, net of tax $ 3.9 $ - $ 3.9 Loss from disposal of discontinued businesses, before income tax $ (17.7 ) $ - $ (17.7 ) Income tax (benefit) - (0.4 ) (0.4 ) Loss from disposal of discontinued business, net of tax $ (17.7 ) $ 0.4 $ (17.3 ) Net loss from discontinued operations $ (13.8 ) $ 0.4 $ (13.4 ) The following is a summary of the carrying amount of major classes of assets and liabilities classified as assets and liabilities of discontinued operations as of March 31, 2019 and December 31, 2018 related to our EMEA and Pacific Rim businesses. March 31, 2019 December 31, 2018 Assets Current assets: Cash and cash equivalents $ 10.0 $ 10.0 Accounts and notes receivable, net 47.3 56.2 Inventories, net 65.3 59.8 Income tax receivable 4.2 1.8 Other current assets 10.3 8.2 Total current assets discontinued operations 137.1 136.0 Property, plant, and equipment, less accumulated depreciation and amortization (1) (2) 109.3 103.8 Prepaid pension costs (1) 29.9 28.9 Goodwill and intangible assets, net (1) 7.0 6.8 Deferred income taxes (1) 3.1 3.0 Lease ROU assets (1) 21.8 - Other non-current assets (1) 0.7 1.0 Total non-current assets of discontinued operations (1) 171.8 143.5 Total assets of discontinued operations (1) $ 308.9 $ 279.5 Liabilities Current liabilities: Accounts payable and accrued expenses $ 73.2 $ 67.1 Income tax payable 1.2 1.1 Total current liabilities 74.4 68.2 Pension benefit liabilities (3) 33.6 33.8 Lease non-current liabilities (3) 12.7 - Other long-term liabilities (3) 1.8 1.8 Income taxes payable (3) 0.2 - Deferred income taxes (3) 6.6 6.5 Total non-current liabilities of discontinued operations (3) 54.9 42.1 Total liabilities of discontinued operations (3) $ 129.3 $ 110.3 (1) Presented as Assets of discontinued operations on the Condensed Consolidated Balance Sheets. (2) Includes reversal of previous pre-tax estimated losses of $2.2 million recorded in the first three months of 2019. As of December 31, 2018, cumulative pre-tax estimated losses were $93.3 million. (3) Presented as Liabilities of discontinued operations on the Condensed Consolidated Balance Sheets . The following is a summary of total estimated gains and losses, capital expenditures, and operating lease information related to our EMEA and Pacific Rim businesses which are presented as discontinued operations and included as components of operating and investing cash flows on our Condensed Consolidated Statements of Cash Flows: Three Months Ended March 31, 2019 2018 Reversal of previous estimated loss on sale to Knauf (1) (2.2 ) - Estimated loss on sale to Knauf (1) - 17.7 Purchases of property, plant and equipment (0.4 ) (1.2 ) Operating lease cost (2) 2.3 - ROU assets obtained in exchange for lease obligations (2) 24.6 - (1) Represents comparison of the EMEA and Pacific Rim net assets to the expected sales proceeds to be received upon closure of the transaction. (2) Operating lease cost and non-cash activity relating to ASC Topic 842 – Leases. We do not believe the amount of cash paid for amounts included in the measurement of lease liabilities to be materially different from our operating lease cost for the three months ended March 31, 2019.

Accounts and Notes Receivable

Accounts and Notes Receivable	3 Months Ended
	Mar. 31, 2019
Receivables [Abstract]
Accounts and Notes Receivable	NOTE 5. ACCOUNTS AND NOTES RECEIVABLE March 31, 2019 December 31, 2018 Customer receivables $ 85.4 $ 70.4 Miscellaneous receivables 3.1 11.5 Less allowance for warranties, discounts and losses (3.2 ) (2.0 ) Accounts and notes receivable, net $ 85.3 $ 79.9 We sell our products to select, pre-approved customers whose businesses are affected by changes in economic and market conditions. We consider these factors and the financial condition of each customer when establishing our allowance for losses from doubtful accounts. Miscellaneous receivables as of March 31, 2019 included $1.7 million of insurance recoveries related to environmental matters that we expect to collect during the second quarter of 2019. Miscellaneous receivables as of December 31, 2018 included $6.5 million of insurance recoveries related to environmental matters, which were collected during the first quarter of 2019. See Note 20 for additional information.

Inventories

Inventories	3 Months Ended
	Mar. 31, 2019
Inventory Disclosure [Abstract]
Inventories	NOTE 6. INVENTORIES March 31, 2019 December 31, 2018 Finished goods $ 40.1 $ 38.8 Goods in process 4.9 4.4 Raw materials and supplies 37.2 27.8 Less LIFO reserves (10.1 ) (9.8 ) Total inventories, net $ 72.1 $ 61.2

Other Current Assets

Other Current Assets	3 Months Ended
	Mar. 31, 2019
Deferred Costs Capitalized Prepaid And Other Assets Disclosure [Abstract]
Other Current Assets	NOTE 7. OTHER CURRENT ASSETS March 31, 2019 December 31, 2018 Prepaid expenses $ 7.3 $ 4.1 Other 0.9 0.7 Total other current assets $ 8.2 $ 4.8

Equity Investment

Equity Investment	3 Months Ended
	Mar. 31, 2019
Equity Method Investments And Joint Ventures [Abstract]
Equity Investment	NOTE 8. EQUITY INVESTMENT Investment in joint venture reflects our 50% equity interest in WAVE. The WAVE joint venture is reflected within the Mineral Fiber segment in our consolidated financial statements using the equity method of accounting. On November 17, 2017, in connection with the Purchase Agreement we entered into with Knauf, the corresponding European and Pacific Rim businesses of WAVE will also be subject to sale to Knauf. Accordingly, WAVE’s European and Pacific Rim historical financial statement results have been reflected in WAVE’s consolidated financial statements as a discontinued operation for all periods presented. Condensed income statement data for WAVE is summarized below. Three Months Ended March 31, 2019 2018 Net sales $ 96.9 $ 87.7 Gross profit 52.6 47.8 Net earnings 40.2 35.6

Leases

Leases	3 Months Ended
	Mar. 31, 2019
Leases [Abstract]
Leases	NOTE 9. LEASES We enter into operating leases for certain real estate, equipment and automobiles. Our leases have remaining lease terms of 1 to 15 years, with several leases including options for us to purchase leased items at fair value or renew for up to 5 years, or multiple 5-year renewal periods, and some of which include options to terminate the lease within 1 year. We have lease agreements with lease and non-lease components, which are accounted for separately. For purposes of calculating operating lease liabilities, lease terms may be deemed to include options to extend or terminate the lease when it is reasonably certain that we will exercise that option. Short-term leases with an initial term of 12 months or less are not recorded on the balance sheet. We recognize lease expense for these leases on a straight line basis over the lease term. Short-term lease expense was not material for the three months ended March 31, 2019. As most of our leases do not provide an implicit rate, we use our incremental borrowing rate based on the information available at the lease commencement date in determining the present value of lease payments. We used the incremental borrowing rate on January 1, 2019 for operating leases that commenced prior to that date. Our lease agreements do not contain any residual value guarantees or material restrictive covenants. As of March 31, 2019, we do not have any financing leases and we have no additional operating leases that have not yet commenced. As noted in Note 1, effective January 1, 2019, we adopted ASC Topic 842 using the modified retrospective transition method. As such, we did not restate financial statement and lease disclosure data for all periods prior to January 1, 2019, which was prepared in accordance with ASC Topic 840 – Leases. The following table presents our operating lease cost and supplemental cash flow information related to our operating leases: Three Months Ended March 31, 2019 Operating lease cost $ 1.6 Non-cash activity: ROU assets obtained in exchange for lease obligations 29.2 We do not believe the amount of cash paid for amounts included in the measurement of lease liabilities to be materially different from our operating lease cost for the three months ended March 31, 2019. The following table presents weighted average assumptions used to compute our ROU assets and lease liabilities: March 31, 2019 Weighted average remaining lease term (in years) 7.9 Weighted average discount rate 5.0 % Undiscounted future minimum lease payments as of March 31, 2019, by year and in the aggregate, having non-cancelable lease terms in excess of one year are as follows: Maturities of Lease Liabilities 2019 (1) $ 4.9 2020 6.1 2021 5.0 2022 4.0 2023 3.5 Thereafter 12.0 Total lease payments 35.5 Less interest (6.7 ) Present value of lease liabilities $ 28.8 (1) Scheduled maturities of lease liabilities represents the time period of April 1, 2019 to December 31, 2019. Future minimum lease payments as of December 31, 2018, by year and in the aggregate, having non-cancelable lease terms in excess of one year were expected to be as follows: Total Minimum Lease payments 2019 5.3 2020 4.7 2021 4.2 2022 3.7 2023 2.2 Thereafter 4.7 Total 24.8 Rent expense was $6.1 million in 2018.

Goodwill and Intangible Assets

Goodwill and Intangible Assets	3 Months Ended
	Mar. 31, 2019
Goodwill And Intangible Assets Disclosure [Abstract]
Goodwill and Intangible Assets	NOTE 10. GOODWILL AND INTANGIBLE ASSETS The following table details amounts related to our goodwill and intangible assets as of March 31, 2019 and December 31, 2018. March 31, 2019 December 31, 2018 Estimated Useful Life Gross Carrying Amount Accumulated Amortization Gross Carrying Amount Accumulated Amortization Amortizing intangible assets Customer relationships 3-20 years $ 188.9 $ 105.5 $ 181.4 $ 103.0 Developed technology 15 years 84.6 67.9 84.3 66.5 Trademarks and brand names 5-20 years 3.9 0.1 1.1 0.2 Other Various 7.8 1.4 5.6 1.2 Total $ 285.2 $ 174.9 $ 272.4 $ 170.9 Goodwill and non-amortizing intangible assets Trademarks and brand names Indefinite 321.4 321.3 Goodwill Indefinite 40.6 19.2 Total goodwill and intangible assets $ 647.2 $ 612.9 Three Months Ended March 31, 2019 2018 Amortization expense $ 3.9 $ 3.6

Accounts Payable And Accrued Ex

Accounts Payable And Accrued Expenses	3 Months Ended
	Mar. 31, 2019
Payables And Accruals [Abstract]
Accounts Payable And Accrued Expenses	NOTE 11. ACCOUNTS PAYABLE AND ACCRUED EXPENSES March 31, 2019 December 31, 2018 Payables, trade and other $ 76.0 $ 82.2 Current portion of lease liabilities 5.2 - Employment costs 6.6 18.6 Current portion of pension and postretirement liabilities 11.1 10.9 Advance receipt of Knauf proceeds 237.6 237.6 Payable to WAVE for advance receipt of Knauf proceeds 22.4 22.4 Current portion of environmental liabilities 9.6 0.7 Other 22.4 10.9 Total accounts payable and accrued expenses $ 390.9 $ 383.3

Income Tax Expense

Income Tax Expense	3 Months Ended
	Mar. 31, 2019
Income Tax Disclosure [Abstract]
Income Tax Expense	NOTE 12. INCOME TAX EXPENSE Three Months Ended March 31, 2019 2018 Earnings from continuing operations before income taxes $ 49.8 $ 49.4 Income tax expense 13.4 8.2 Effective tax rate 26.8 % 16.6 % The effective tax rate for the first quarter was higher compared to the same period in 2018 primarily due to the favorable impact of share-based compensation deductions in the first quarter of 2018 that did not recur as extensively in the first quarter of 2019. It is reasonably possible that the amount of unrecognized tax benefits could significantly increase or decrease within the next twelve months. However, an estimate of the range of reasonably possible outcomes cannot be made. Changes to unrecognized tax benefits could result from the completion of ongoing examinations, the expiration of the statute of limitations or other unforeseen circumstances.

Debt

Debt	3 Months Ended
	Mar. 31, 2019
Debt Disclosure [Abstract]
Debt	NOTE 13. DEBT As of March 31, 2019 and December 31, 2018, our long-term debt included borrowings outstanding under our $1,050.0 million variable rate senior credit facility, which is comprised of a $200.0 million revolving credit facility (with a $150.0 million sublimit for letters of credit), a $600.0 million Term Loan A and a $250.0 million Term Loan B. As of March 31, 2019 and December 31, 2018, there were no borrowings outstanding on our revolving credit facility. As of March 31, 2019 and December 31, 2018, our outstanding long-term debt included a $35.0 million variable rate, tax-exempt industrial development bond that financed the construction of a U.S. plant in prior years. We also have a $25.0 We utilize lines of credit and other commercial commitments in order to ensure that adequate funds are available to meet operating requirements. Letters of credit are currently arranged through our revolving credit facility, our bi-lateral facility and our securitization facility. Letters of credit are issued to third party suppliers, insurance institutions and financial institutions and typically can only be drawn upon in the event of AWI’s failure to pay its obligations to the beneficiary. The following table presents details related to our letters of credit facilities: As of March 31, 2019 Financing Arrangements Limit Used Available Accounts receivable securitization facility $ 31.9 $ 36.2 $ (4.3 ) Bi-lateral facility 25.0 13.4 11.6 Revolving credit facility 150.0 - 150.0 Total $ 206.9 $ 49.6 $ 157.3 As of March 31, 2019 and December 31, 2018, $4.3 million and $6.0 million of letters of credit issued under our accounts receivable securitization facility in excess of our maximum limit were classified as restricted cash and reported as a component of Cash and cash equivalents on our Condensed Consolidated Balance Sheets. As of March 31, 2019, we had a $36.2 million Accounts Receivable Securitization Facility with the Bank of Nova Scotia (the “funding entity”) that matures in March 2020. Under our Accounts Receivable Securitization Facility we sell accounts receivables to Armstrong Receivables Company, LLC (“ARC”), a Delaware entity that is consolidated in these financial statements. ARC is a 100% wholly owned single member LLC special purpose entity created specifically for this transaction; therefore, any receivables sold to ARC are not available to the general creditors of AWI. ARC then sells an undivided interest in the purchased accounts receivables to the funding entity. This undivided interest acts as collateral for drawings on the facility. Any borrowings under this facility are obligations of ARC and not AWI. ARC contracts with and pays a servicing fee to AWI to manage, collect and service the purchased accounts receivables. All new receivables under the program are continuously purchased by ARC with the proceeds from collections of receivables previously purchased. As of March 31, 2019, we had no borrowings under this facility.

Pension and Other Benefit Progr

Pension and Other Benefit Programs	3 Months Ended
	Mar. 31, 2019
Compensation And Retirement Disclosure [Abstract]
Pensions and Other Benefit Programs	NOTE 14. PENSIONS AND OTHER BENEFIT PROGRAMS Following are the components of net periodic benefit costs (credits): Three Months Ended March 31, 2019 2018 U.S. defined benefit plans: Pension benefits Service cost of benefits earned during the period $ 1.2 $ 1.4 Interest cost on projected benefit obligation 12.6 11.5 Expected return on plan assets (20.1 ) (24.0 ) Amortization of net actuarial loss 4.8 5.0 Net periodic pension (credit) $ (1.5 ) $ (6.1 ) Retiree health and life insurance benefits Interest cost on projected benefit obligation $ 0.6 $ 0.6 Amortization of net actuarial gain (2.2 ) (1.4 ) Net periodic postretirement (credit) $ (1.6 ) $ (0.8 ) We also have an unfunded non-U.S. defined benefit pension plan in Germany, which will not be acquired by Knauf in connection with the announced sale of our EMEA and Pacific Rim segments that is reported as a component of our Unallocated Corporate segment. Net periodic pension cost for this plan was immaterial for the three months ended March 31, 2019 and 2018.

Financial Instruments

Financial Instruments	3 Months Ended
	Mar. 31, 2019
Fair Value Disclosures [Abstract]
Financial Instruments	NOTE 15. FINANCIAL INSTRUMENTS We do not hold or issue financial instruments for trading purposes. The estimated fair values of our financial instruments are as follows: March 31, 2019 December 31, 2018 Carrying amount Estimated fair value Carrying amount Estimated fair value Assets/(Liabilities), net: Total long-term debt, including current portion $ (812.2 ) $ (812.8 ) $ (819.8 ) $ (811.3 ) Interest rate swap contracts (3.3 ) (3.3 ) 3.5 3.5 The carrying amounts of cash and cash equivalents, receivables, accounts payable, and accrued expenses approximate fair value because of the short-term maturity of these instruments. The fair value estimates of long-term debt were primarily based on quotes from a major financial institution based on recently observed trading levels of our Term Loan A and Term Loan B debt. The fair value estimates for interest rate swap contracts are estimated by obtaining quotes from major financial institutions with verification by internal valuation models. Fair value is defined as the exchange price that would be received for an asset or paid to transfer a liability (an exit price) in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants at the measurement date. Three levels of inputs may be used to measure fair value: Level 1 — Quoted prices in active markets for identical assets or liabilities; Level 2 — Observable inputs other than quoted prices included in Level 1, such as quoted prices for similar assets and liabilities in active markets; quoted prices for identical or similar assets and liabilities in markets that are not active; or other inputs that are observable or can be corroborated by observable market data; or Level 3 — Unobservable inputs that are supported by little or no market activity and that are significant to the fair value of the assets or liabilities. This includes certain pricing models, discounted cash flow methodologies and similar techniques that use significant unobservable inputs. The fair value measurement of interest rate swap contracts measured at fair value on a recurring basis and reported on the Condensed Consolidated Balance Sheets were valued using Level 2 (other observable) inputs as of March 31, 2019 and December 31, 2018. We do not have any financial assets or liabilities that are valued using Level 1 (quoted, active market) or Level 3 (unobservable) inputs as of March 31, 2019 and December 31, 2018.

Derivative Financial Instrument

Derivative Financial Instruments	3 Months Ended
	Mar. 31, 2019
Derivative Instruments And Hedging Activities Disclosure [Abstract]
Derivative Financial Instruments	NOTE 16. DERIVATIVE FINANCIAL INSTRUMENTS We are exposed to market risk from changes in foreign exchange rates, interest rates and commodity prices that could impact our results of operations, cash flows and financial condition. We use swaps to hedge interest rate exposures. At inception, derivatives that we designate as hedging instruments are formally documented as either (1) a hedge of a forecasted transaction or “cash flow” hedge, or (2) a hedge of the fair value of a recognized liability or asset or “fair value” hedge. We also formally assess, both at inception and at least quarterly thereafter, whether the derivatives that are used in hedging transactions are highly effective in offsetting changes in either the fair value or cash flows of the hedged item. If it is determined that a derivative ceases to be a highly effective hedge, or if the anticipated transaction is no longer probable of occurring, we discontinue hedge accounting and any future mark-to-market adjustments are recognized in earnings. We use derivative financial instruments as risk management tools and not for speculative trading purposes. Counterparty Risk We only enter into derivative transactions with established financial institution counterparties having an investment-grade credit rating. We monitor counterparty credit default swap levels and credit ratings on a regular basis. All of our derivative transactions with counterparties are governed by master International Swap and Derivatives Association agreements (“ISDAs”) with netting arrangements. These agreements can limit our exposure in situations where we have gain and loss positions outstanding with a single counterparty. We do not post nor do we receive cash collateral with any counterparty for our derivative transactions. These ISDAs do not have any credit contingent features; however, a default under our bank credit facility would trigger a default under these agreements. Exposure to individual counterparties is controlled, and thus we consider the risk of counterparty default to be negligible. Commodity Price Risk We purchase natural gas and other various commodities for use in the manufacturing process. Although we are exposed to fluctuations in commodity pricing, we currently have no outstanding derivative hedge positions. Currency Rate Risk – Sales and Purchases Upon completion of the sale of our EMEA and Pacific Rim businesses, and on a continuing operations basis as of March 31, 2019, our only major foreign currency exposure is to the Canadian dollar. We manage our Canadian cash flow exposures on a net basis. We currently do not expect to enter into any foreign exchange derivative products. Interest Rate Risk We utilize interest rate swaps to minimize the fluctuations in earnings caused by interest rate volatility. These swaps are designated as cash flow hedges against changes in LIBOR for a portion of our variable rate debt. The following table summarizes our interest rate swaps as of March 31, 2019: Trade Date Notional Amount Coverage Period Risk Coverage November 13, 2016 $ 200.0 November 2016 to March 2021 USD-LIBOR April 1, 2016 $ 100.0 April 2016 to March 2023 USD-LIBOR November 28, 2018 $ 200.0 November 2018 to November 2023 USD-LIBOR November 28, 2018 $ 100.0 March 2021 to March 2025 USD-LIBOR Under the terms of the November 2016 swap maturing in 2021, we receive 3-month LIBOR and pay a fixed rate over the hedged period, in addition to a basis rate swap to convert the floating rate risk under our November 2016 Swap from 3-month LIBOR to 1-month LIBOR. As a result, we receive 1-month LIBOR and pay a fixed rate over the hedged period. Under the terms of the April 2016 swap maturing in 2023, we receive the greater of 3-month LIBOR or a 0.75% LIBOR Floor and pay a fixed rate over the hedged period. Under the terms of the November 2018 swap maturing in 2023, we pay a fixed rate over the hedged amount and receive 1-month LIBOR. This is inclusive of a 0% floor. Under the terms of the November 2018 swap maturing in 2025, we will pay a fixed rate monthly and receive 1-month LIBOR. This is inclusive of a 0% floor. Financial Statement Impacts The following tables detail amounts related to our derivatives as of March 31, 2019 and December 31, 2018. We had no derivative assets or liabilities not designated as hedging instruments as of March 31, 2019 or December 31, 2018. The derivative asset and liability amounts below are shown in gross amounts; we have not netted assets with liabilities. Derivative Assets Derivative Liabilities Fair Value Fair Value Balance Sheet Location March 31, 2019 December 31, 2018 Balance Sheet Location March 31, 2019 December 31, 2018 Derivatives designated as hedging instruments Interest rate swap contracts Other non-current assets $ 6.7 $ 9.6 Other long-term liabilities $ 10.0 $ 6.1 Amount of Gain (Loss) Recognized in AOCI Location of (Loss) Reclassified AOCI into Income (Loss) Reclassified from AOCI into Income Three Months Ended Three Months Ended March 31, March 31, 2019 2018 2019 2018 Derivatives in cash flow hedging relationships Natural gas commodity contracts $ - $ - Cost of goods sold $ - $ (0.4 ) Foreign exchange contracts – purchases - 0.1 Cost of goods sold - - Foreign exchange contracts – sales - 0.3 Net sales - (0.2 ) Interest rate swap contracts (7.4 ) 3.3 Interest expense (0.6 ) (0.5 ) Total $ (7.4 ) $ 3.7 Total (loss) from continuing operations $ (0.6 ) $ (1.1 ) Total (loss) from discontinued operations - (0.1 ) Total (loss) $ (0.6 ) $ (1.2 ) As of March 31, 2019, the amount of existing losses in AOCI expected to be recognized in earnings over the next twelve months is $0.8 million.

Other Long-Term Liabilities

Other Long-Term Liabilities	3 Months Ended
	Mar. 31, 2019
Other Liabilities Disclosure [Abstract]
Other Long-Term Liabilities	NOTE 17. OTHER LONG-TERM LIABILITIES March 31, 2019 December 31, 2018 Long-term deferred compensation arrangements $ 14.0 $ 14.0 Environmental liabilities 2.8 11.7 Fair value of derivative liabilities 10.0 6.1 Other 6.2 6.2 Total other long-term liabilities $ 33.0 $ 38.0

Shareholders' Equity

Shareholders' Equity	3 Months Ended
	Mar. 31, 2019
Stockholders Equity Note [Abstract]
Shareholders' Equity	NOTE 18. SHAREHOLDERS’ EQUITY 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. The ASR terminated on October 8, 2018, with an additional 389,825 shares returned on that day to complete the ASR During the three months ended March 31, 2019, we repurchased 0.3 million shares under the Program for a total cost of $20.0 million, or an average price of $60.30 per share. Since inception of the Program, through March 31, 2019, including the ASR, we have repurchased 8.0 million shares under the Program for a total cost of $450.6 million, or an average price of $56.19 per share. Dividends In February 2019, our Board of Directors declared a $0.175 per share quarterly dividend, which was paid to shareholders in March 2019.

Accumulated Other Comprehensive

Accumulated Other Comprehensive Income (Loss)	3 Months Ended
	Mar. 31, 2019
Equity [Abstract]
Accumulated Other Comprehensive Income (Loss)	NOTE 19. ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS) Foreign Currency Translation Adjustments Derivative Gain (Loss) (1) Pension and Postretirement Adjustments (1) Total Accumulated Other Comprehensive (Loss) (1) Balance, December 31, 2018 $ (74.7 ) $ 5.3 $ (390.2 ) $ (459.6 ) Impact of ASU 2017-12 adoption - 0.1 - 0.1 Other comprehensive income (loss) before reclassifications, net of tax expense (benefit) of $ -, $1.9, ($0.2) and $1.7 5.3 (5.6 ) 0.7 0.4 Amounts reclassified from accumulated other comprehensive (loss) - 0.5 2.1 2.6 Net current period other comprehensive income (loss) 5.3 (5.1 ) 2.8 3.0 Balance, March 31, 2019 $ (69.4 ) $ 0.3 $ (387.4 ) $ (456.5 ) Foreign Currency Translation Adjustments Derivative Gain (Loss) (1) Pension and Postretirement Adjustments (1) Total Accumulated Other Comprehensive (Loss) (1) Balance, December 31, 2017 $ (47.1 ) $ 3.5 $ (302.3 ) $ (345.9 ) Impact of ASU 2018-02 adoption - 0.7 (55.0 ) (54.3 ) Other comprehensive income (loss) before reclassifications, net of tax expense of $ -, $1.2, $0.6 and $1.8 5.9 2.9 (1.0 ) 7.8 Amounts reclassified from accumulated other comprehensive (loss) - 0.9 2.8 3.7 Net current period other comprehensive income 5.9 3.8 1.8 11.5 Balance, March 31, 2018 $ (41.2 ) $ 8.0 $ (355.5 ) $ (388.7 ) (1) Amounts are net of tax Amounts Reclassified from Accumulated Other Comprehensive (Loss) (1) Affected Condensed Consolidated Statement of Earnings and Comprehensive Income Three Months Ended March 31, 2019 2018 Derivative Adjustments: Natural gas commodity contracts $ - $ 0.4 Cost of goods sold Foreign exchange contracts - purchases - 0.1 Cost of goods sold Foreign exchange contracts - sales - 0.2 Net sales Interest rate swap contracts 0.6 0.5 Interest expense Total loss, before tax 0.6 1.2 Tax impact (0.1 ) (0.3 ) Income tax expense Total loss, net of tax 0.5 0.9 Pension and Postretirement Adjustments: Amortization of net actuarial loss 2.7 3.6 Other non-operating (income), net Total expense, before tax 2.7 3.6 Tax impact (0.6 ) (0.8 ) Income tax expense Total expense, net of tax 2.1 2.8 Total reclassifications for the period $ 2.6 $ 3.7 (1) Includes activity from discontinued operations.

Litigation and Related Matters

Litigation and Related Matters	3 Months Ended
	Mar. 31, 2019
Commitments And Contingencies Disclosure [Abstract]
Litigation and Related Matters	NOTE 20. LITIGATION AND RELATED MATTERS ENVIRONMENTAL MATTERS Environmental Compliance Our manufacturing and research facilities are affected by various federal, state and local requirements relating to the discharge of materials and the protection of the environment. We make expenditures necessary for compliance with applicable environmental requirements at each of our operating facilities. These regulatory requirements continually change, therefore we cannot predict with certainty future expenditures associated with compliance with environmental requirements. Environmental Sites Summary We are actively involved in the investigation, closure and/or remediation of existing or potential environmental contamination under the Comprehensive Environmental Response, Compensation and Liability Act (“CERCLA”) and state Superfund and similar environmental laws at three domestically owned locations allegedly resulting from past industrial activity. In each location, we are one of multiple potentially responsible parties and have agreed to jointly fund the required investigation and remediation, while preserving our defenses to the liability. We may also have rights of contribution or reimbursement from other parties or coverage under applicable insurance policies. We are currently pursuing coverage and recoveries under those policies with respect to certain of the sites, including the St. Helens, OR site, the Macon, GA site and the Elizabeth City, NC site, each of which is summarized below. These efforts include two active and independent litigation matters against legacy primary and excess policy insurance carriers for recovery of fees and costs incurred by us in connection with our investigation and remediation activities for such sites. Other than disclosed below, we are unable to predict the outcome of these matters or the timing of any recoveries, whether through settlement or otherwise. We are also unable to predict the extent to which any recoveries might cover our final share of investigation and remediation costs for these sites. Our final share of investigation and remediation costs may exceed any such recoveries, and such amounts net of insurance recoveries may be material. In 2017 and 2018, we entered settlement agreements totaling $37.5 million with certain legacy insurance carriers to resolve ongoing litigation and recover fees and costs previously incurred by us in connection with certain environmental sites. These settlements were recorded as a $9.2 million reduction to cost of goods sold and a $28.3 million reduction to SG&A expenses reflecting the same income statement categories where environmental expenditures were historically recorded. All of these cash settlements have been released to us from escrow, including $6.5 million received in the first quarter of 2019. In the first quarter of 2019, we entered into one new settlement agreement for $1.7 million and received an additional $0.2 million payment related to a previous settlement with a different carrier. These settlements were recorded as a $1.9 million reduction to SG&A expenses. We anticipate that we may enter into additional settlement agreements in the future, which may or may not be material, with other legacy insurers to obtain reimbursement or contribution for environmental site expenses. Estimates of our future liability at the environmental sites are based on evaluations of currently available facts regarding each individual site. We consider factors such as our activities associated with the site, existing technology, presently enacted laws and regulations and prior company experience in remediating contaminated sites. Although current law imposes joint and several liability on all parties at Superfund sites, our contribution to the remediation of these sites is expected to be limited by the number of other companies potentially liable for site remediation. As a result, our estimated liability reflects only our expected share. In determining the probability of contribution, we consider the solvency of other parties, the site activities of other parties, whether liability is being disputed, the terms of any existing agreements and experience with similar matters, and the effect of our October 2006 Chapter 11 reorganization upon the validity of the claim, if any. Specific Material Events St Helens, OR In August 2010, we entered into a Consent Order (the “Consent Order”) with the Oregon Department of Environmental Quality (“ODEQ”), along with Kaiser Gypsum Company, Inc. (“Kaiser”), and Owens Corning Sales LLC (“OC”), with respect to our St. Helens, OR facility, which was previously owned by Kaiser and then OC. The Consent Order required that we and Kaiser complete a remedial investigation and feasibility study (“RI/FS”) on the portion of the site owned by us (“Owned Property”), which is comprised of Upland and Lowland areas. The Consent Order further required us, Kaiser and OC to conduct an RI/FS in the in-water area of the adjacent Scappoose Bay. Costs and responsibilities for investigation, including the current RI/FS, for the Owned Property have been shared with Kaiser pursuant to a cost sharing agreement with Kaiser. Costs and responsibilities for the investigation with respect to the in-water area that we do not own have been shared with Kaiser and OC pursuant to a cost sharing agreement with Kaiser and OC. On September 14, 2016, the parties submitted a Feasibility Study to the ODEQ proposing remedial action options for the Upland area. We have participated in the investigation phase for the Lowland area of the Owned Property and the Scappoose Bay and worked with the ODEQ, Kaiser and OC to finalize the reports to move to the feasibility study phase. On September 30, 2016, Kaiser filed a voluntary petition for relief under Chapter 11 of the Bankruptcy Code in the U.S. Bankruptcy Court for the Western District of North Carolina (Case No. 16-31602) (the “Bankruptcy Court”). AWI, OC and the ODEQ have all been included on the master list of potential creditors filed with the Bankruptcy Court for notice purposes. By order dated October 14, 2016, the Bankruptcy Court formed a statutory committee of unsecured creditors, to which we were appointed to serve, along with OC and The Boeing Company. The Committee is charged with, among other things, maximizing recovery of all unsecured creditor claims, including claims of AWI and ODEQ. Noticed parties submitted claims to the Bankruptcy Court on September 13, 2017. The Chapter 11 case impacts Kaiser’s ongoing participation in the RI/FS process, as well as the ODEQ consent order and cost sharing agreements. In November 2017, we participated in voluntary mediation with ODEQ, OC and Kaiser to negotiate a resolution that would discharge Potentially Responsible Parties (“PRPs”) liability for the site. As a result of the mediation, on February 1, 2018, ODEQ issued a Public Notice and a proposed consent judgment (“Consent Judgment”) recommending that, in exchange for a release from ODEQ for all contamination claims against AWI, we would pay $8.6 million to the State of Oregon and perform a previously scoped remedial action for the Upland area. During the fourth quarter of 2017, we increased our reserve for environmental liabilities by $8.6 million as a result of this pending settlement with the State of Oregon. On April 5, 2018, ODEQ issued Public Notice of the Remedial Action for the Upland area and subsequently responded to public comments. On June 26, 2018 ODEQ published its Record of Decision confirming the selected remedial action required for the Upland area. AWI will be responsible for performing the remedial action upon ODEQ’s filing of the Consent Judgment with the court, pending appeal. The Consent Judgment remains subject to entry and approval by the Columbia County Circuit Court. Kaiser continues to assert that the Consent Judgment violates the stay imposed by its bankruptcy case. The Bankruptcy Court, however, ruled in favor of ODEQ’s position that the Consent Judgment does not violate the stay. In response to that ruling, on October 3, 2018, Kaiser filed a motion for stay pending appeal. A decision on that motion remains pending. Kaiser filed objections to the ODEQ proof of claim and AWI’s proof of claim and sought discovery related to the determination of costs incurred by the parties at the site. On November 26, 2018, Kaiser filed a complaint against AWI seeking monetary damages and declaratory relief including cost recovery and/or contributions from AWI in connection with the environmental costs incurred by Kaiser at St. Helens. On March 1, 2019, we entered into a settlement agreement with Kaiser resolving all claims between us. In exchange for a payment of $1.0 million, Kaiser agreed to withdraw its appeal of the automatic stay imposed by the bankruptcy as it applies to the Consent Judgment, dismiss its complaint against AWI, and refrain from filing any objections to the Consent Judgment once filed with the Columbia County Circuit Court. Our settlement with Kaiser is conditioned on the effectiveness of a pending settlement between ODEQ and Kaiser, which we expect to occur in the second quarter of 2019. The Bankruptcy Court approved our settlement with Kaiser on March 14, 2019. Macon, GA The U.S. Environmental Protection Agency (the “EPA”) has listed two landfills located on a portion of our facility in Macon, GA, along with the former Macon Naval Ordnance Plant landfill adjacent to our property, portions of Rocky Creek, and certain tributaries leading to Rocky Creek (collectively, the “Macon Site”) as a Superfund site on the National Priorities List due to the presence of contaminants, most notably polychlorinated biphenyls (“PCBs”). In September 2010, we entered into an Administrative Order on Consent for a Removal Action with the EPA to investigate PCB contamination in one of the landfills on our property, the Wastewater Treatment Plant Landfill (the “WWTP Landfill,” also known as “Operable Unit 1”). After completing an investigation of the WWTP Landfill and submitting our final Engineering Evaluation/Cost Analysis, the EPA issued an Action Memorandum in July 2013 selecting our recommended remedy for the Removal Action. The Operable Unit 1 response action for the WWTP Landfill is complete and the final report was submitted to the EPA on October 11, 2016. The EPA approved the final report on November 28, 2016, and a Post-Removal Control Plan (the “Plan”) was submitted to the EPA on March 28, 2017. That Plan will monitor the effectiveness of the WWTP Landfill response action and our estimate of future liabilities includes these tasks. It is probable that we will incur field investigation, engineering and oversight costs associated with a RI/FS with respect to the remainder of the Superfund site, which includes the other landfill on our property, as well as areas on and adjacent to AWI’s property and Rocky Creek (the “Remaining Site,” also known as “Operable Unit 2”). On September 25, 2015, AWI and other PRPs received a Special Notice Letter from the EPA under CERCLA inviting AWI and the PRPs to enter into the negotiation of an agreement to conduct an RI/FS of Operable Unit 2. We and the other PRPs entered into a settlement agreement with the EPA effective September 18, 2018, in response to the Special Notice Letter to conduct the RI/FS. The PRPs are required to submit a complete RI/FS work plan in April 2019. While the investigative work on this portion of the site has not yet commenced, we anticipate that the EPA will require significant investigative work for Operable Unit 2 and that we may ultimately incur costs in remediating any contamination discovered during the RI/FS. The current estimate of future liability at this site includes only our estimated share of the costs of the investigative work that, at this time, we anticipate the EPA will require the PRPs to perform. We are unable to reasonably estimate AWI’s final share of the costs or the total costs associated with the investigation work or any resulting remediation therefrom, although such amounts may be material. Elizabeth City, NC This site is a former cabinet manufacturing facility that was operated by Triangle Pacific Corporation, now known as Armstrong Wood Products, Inc. (“Triangle Pacific”), from 1977 until 1996. The site was formerly owned by the U.S. Navy (“Navy”) and Westinghouse, now CBS Corporation (“CBS”). We assumed ownership of the site when we acquired the stock of Triangle Pacific in 1998. Prior to our acquisition, the NC Department of Environment and Natural Resources listed the site as a hazardous waste site. In 1997, Triangle Pacific entered into a cost sharing agreement with Westinghouse whereby the parties agreed to share equally in costs associated with investigation and potential remediation. In 2000, Triangle Pacific and CBS entered into an Administrative Order on Consent to conduct an RI/FS with the EPA for the site. In 2007, we and CBS entered into an agreement with the Navy whereby the Navy agreed to pay one third of defined past and future investigative costs up to a certain amount, which has now been exhausted. The EPA approved the RI/FS work plan in August 2011. In January 2014, we submitted the draft Remedial Investigation and Risk Assessment reports and conducted supplemental investigative work based upon agency comments to those reports. The EPA published an Interim Action Proposed Plan for the site in April 2018 seeking public comment through June 7, 2018. The EPA has evaluated comments, including ours, and has published its Interim Record Of Decision selecting an interim cleanup approach. On September 25, 2018, AWI and CBS received a Special Notice Letter from the EPA under CERCLA inviting AWI and CBS to enter into the negotiation of a settlement agreement to conduct or finance the response action at the site. During the third quarter of 2018, we increased our reserve for the cost of the interim cleanup, which we expect to be shared with CBS and the Navy. Summary of Financial Position Total liabilities of $12.4 million as of March 31, 2019 and December 31, 2018 were recorded for environmental liabilities that we consider probable and for which a reasonable estimate of the probable liability could be made. As of March 31, 2019 and December 31, 2018, $9.6 million and $0.7 million were reflected within Accounts payable and accrued expenses with respect to environmental liabilities. During the three months ended March 31, 2019, we recorded $1.0 million of additional reserves. During the three months ended March 31, 2018, we did not record any additional reserves for environmental liabilities. Where existing data is sufficient to estimate the liability, that estimate has been used; where only a range of probable liabilities is available and no amount within that range is more likely than any other, the lower end of the range has been used. As assessments and remediation activities progress at each site, these liabilities are reviewed to reflect new information as it becomes available, and adjusted to reflect amounts actually incurred and paid. These liabilities are undiscounted. The estimated liabilities above do not take into account any claims for recoveries from insurance or third parties. It is our policy to record insurance recoveries when probable. For insurance recoveries that are reimbursements of prior environmental expenditures, the income statement impact is recorded within cost of goods sold and SG&A expenses, which are the same income statement categories where environmental expenditures were historically recorded. Insurance recoveries in excess of historical environmental spending, are recorded on the balance sheet as a part of other long-term liabilities and released as future environmental spending occurs or the liability is settled. The estimated liabilities above do not take into account any claims for recoveries from insurance or third parties. It is our policy to record recoveries as assets in the Condensed Consolidated Balance Sheets. As of March 31, 2019, we have $1.7 million of receivables for insurance recoveries reflected within Accounts and notes receivable, net. Actual costs to be incurred at identified sites may vary from our estimates. Based on our knowledge of the identified sites, it is not possible to reasonably estimate future costs in excess of amounts already recognized. OTHER CLAIMS On September 8, 2017, Roxul USA, Inc. (d/b/a Rockfon) (“Rockfon”) filed litigation against us in the United States District Court for the District of Delaware (the “Court”) alleging anticompetitive conduct seeking remedial measures and unspecified damages. Roxul USA, Inc. is a significant ceilings systems competitor with global headquarters in Europe and expanding operations in the Americas. On April 3, 2019, we entered into a confidential settlement agreement with Rockfon to fully resolve the litigation between us, and Rockfon filed a Stipulation of Dismissal with Prejudice (“Dismissal”) with the Court. Pursuant to the Dismissal, Rockfon formally dismissed all claims it had against AWI with prejudice. All claims in the litigation have been fully and finally dismissed and released with AWI making a payment to Rockfon for its costs, expenses and attorneys’ fees. Pursuant to the settlement, both parties acknowledged that (a) AWI denies all claims of wrongdoing and makes no admission of wrongdoing or of the truth of any of the claims or allegations contained in Rockfon’s complaint or otherwise alleged in the litigation; (b) all AWI exclusive distribution locations (i.e., any location where a reseller has agreed to sell only AWI ceiling system products) will remain exclusive to AWI under their respective distribution agreements, and (c) in all other non-exclusive or “open” distribution locations, resellers are free to purchase and resell ceiling systems products of any manufacturer at their discretion. During the first quarter of 2019, we incurred $19.7 million of expenses in connection with the matter, primarily relating to legal and professional fees incurred by us in connection with the litigation, including expenses and attorney’s fees paid under the settlement agreement. As a result of the settlement and Dismissal, we do not expect to incur additional future costs or expenses relating to the matter. We are involved in other various lawsuits, claims, investigations and other legal matters from time to time that arise in the ordinary course of business, including matters involving our products, intellectual property, relationships with suppliers, relationships with distributors, relationships with competitors, employees and other matters. From time to time, for example, we may be a party to litigation matters that involve product liability, tort liability and other claims under various allegations, including illness due to exposure to certain chemicals used in the workplace; or medical conditions arising from exposure to product ingredients or the presence of trace contaminants. Such allegations may involve multiple defendants and relate to legacy products that we and other defendants purportedly manufactured or sold. We believe that any current claims are without merit and intend to defend them vigorously. For these matters, we also may have rights of contribution or reimbursement from other parties or coverage under applicable insurance policies. When applicable and appropriate, we will pursue coverage and recoveries under those policies, but are unable to predict the outcome of those demands. While complete assurance cannot be given to the outcome of these proceedings, we do not believe that any current claims, individually or in the aggregate, will have a material adverse effect on our financial condition, liquidity or results of operations.

Earnings Per Share

Earnings Per Share	3 Months Ended
	Mar. 31, 2019
Earnings Per Share [Abstract]
Earnings Per Share	NOTE 21. EARNINGS PER SHARE Earnings per share (“EPS”) components may not add due to rounding. The following table is a reconciliation of earnings to earnings attributable to common shares used in our basic and diluted EPS calculations for the three months ended March 31, 2019 and 2018: Three Months Ended March 31, 2019 2018 Earnings from continuing operations $ 36.4 $ 41.2 Earnings allocated to participating non-vested share awards (0.1 ) (0.1 ) Earnings from continuing operations attributable to common shares $ 36.3 $ 41.1 The following table is a reconciliation of basic shares outstanding to diluted shares outstanding for the three months ended March 31, 2019 and 2018 (shares in millions): Three Months Ended March 31, 2019 2018 Basic shares outstanding 48.7 53.0 Dilutive effect of common stock equivalents 0.8 0.8 Diluted shares outstanding 49.5 53.8 Anti-dilutive stock awards excluded from the computation of diluted EPS for the three months ended March 31, 2019 were 30,371. There were no anti-dilutive stock awards excluded from the computation of diluted EPS for the three months ended March 31, 2018.

Business and Basis of Present_2

Business and Basis of Presentation (Policies)	3 Months Ended
	Mar. 31, 2019
Accounting Policies [Abstract]
Recently Adopted and Recently Issued Accounting Standards	Recently Adopted Accounting Standards In February 2016, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) 2016-02, “Leases,” In January 2018, FASB issued ASU 2018-01, “Land Easement Practical Expedient for Transition to Topic 842,” “Codification improvements to Topic 842, Leases,” “Targeted Improvements,” Effective January 1, 2019, we adopted these standards using the modified retrospective transition method and have applied all practical expedients related to leases existing at the date of initial application. Upon adoption, the most significant change was to the Condensed Consolidated Balance Sheet related to the recognition of new ROU assets and lease liabilities on a continuing operations basis. We have recognized ROU assets and lease liabilities of $28.8 million, based on the present value of the future minimum rental payments for existing operating leases. We have no leases that classify as financing arrangements. As required by the lease ASC updates, we have expanded our disclosure of leases. See Note 9 for additional information. In August 2017, the FASB issued ASU 2017-12, “Derivatives and Hedging (Topic 815): Targeted Improvements to Accounting for Hedging Activities,” In June 2018, the FASB issued ASU 2018-07, “Improvements to Nonemployee Share-Based Payment Accounting,” had no material impact on our financial condition, results of operations or cash flows. Recently Issued Accounting Standards In August 2018, the FASB issued ASU 2018-14, “ Disclosure Framework – Changes to the Disclosure Requirements for Defined Benefit Plans” In August 2018, the FASB issued ASU 2018-15, “Customer’s Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That is a Service Contract”
Revenue Recognition	Revenue Recognition We recognize revenue upon transfer of control of our products to the customer, which typically occurs upon shipment. Our main performance obligation to our customers is the delivery of products in accordance with purchase orders. Each purchase order defines the transaction price for the products purchased under the arrangement. Direct sales to building materials distributors, home centers, direct customers, and retailers represent the majority of our sales. Our standard sales terms are Free On Board (“FOB”) shipping point. We have some sales terms that are FOB destination. At the point of shipment, the customer is required to pay under normal sales terms. Our normal payment terms in most cases are Incremental costs to fulfill our customer arrangements are expensed as incurred, as the amortization period is less than one year. Our products are sold with normal and customary return provisions. We provide limited warranties for defects in materials or factory workmanship, sagging and warping, and certain other manufacturing defects. Warranties are not sold separately to customers. Our product warranties place certain requirements on the purchaser, including installation and maintenance in accordance with our written instructions. In addition to our warranty program, under certain limited circumstances, we will occasionally and at our sole discretion, provide a customer accommodation repair or replacement. Warranty repairs and replacements are most commonly made by professional installers employed by or affiliated with our independent distributors. Reimbursement for costs associated with warranty repairs are provided to our independent distributors through a credit against accounts receivable from the distributor to us. Sales returns and warranty claims have historically not been material and do not constitute separate performance obligations. We often enter into agreements with our customers to offer incentive programs, primarily volume rebates and promotions. The majority of our rebates are designated as a percentage of annual customer purchases. We estimate the amount of rebate based on actual sales for the period and accrue for the projected incentive programs costs. We record the costs of the rebate accruals as a reduction to our revenue. In addition, other sales discounts, including early pay promotions, are deducted immediately from the sales invoice.
Shipping and Handling	Shipping and Handling We account for product shipping and handling costs as fulfillment activities and present the associated costs in costs of goods sold in the period in which we sell our product.

Segment Results (Tables)

Segment Results (Tables)	3 Months Ended
	Mar. 31, 2019
Segment Reporting [Abstract]
Schedule of Net Sales	Three Months Ended March 31, 2019 2018 Net sales Mineral Fiber $ 196.7 $ 190.7 Architectural Specialties 45.4 36.6 Total net sales $ 242.1 $ 227.3
Schedule of Segment Operating Income (Loss)	Three Months Ended March 31, 2019 2018 Segment operating income (loss) Mineral Fiber $ 47.6 $ 43.7 Architectural Specialties 9.2 8.3 Unallocated Corporate (2.1 ) (2.4 ) Total consolidated operating income $ 54.7 $ 49.6
Reconciliation of Total Consolidated Operating Income to Earnings Before Income Taxes	Three Months Ended March 31, 2019 2018 Total consolidated operating income $ 54.7 $ 49.6 Interest expense 10.4 9.2 Other non-operating (income), net (5.5 ) (9.0 ) Earnings from continuing operations before income taxes $ 49.8 $ 49.4
Reconciliation of Total Segment Assets to Total Consolidated Assets	March 31, 2019 December 31, 2018 Segment assets Mineral Fiber $ 1,118.0 $ 1,096.1 Architectural Specialties 147.2 84.7 Unallocated Corporate 368.5 413.2 Total consolidated assets $ 1,633.7 $ 1,594.0

Revenue (Tables)

Revenue (Tables)	3 Months Ended
	Mar. 31, 2019
Mineral Fiber [Member]
Disaggregation Of Revenue [Line Items]
Schedule of Net Sales by Major Customer Group within Each Segment	The following tables provide net sales by major customer group within the Mineral Fiber and Architectural Specialties segments for the three months ended March 31, 2019 and 2018: Three months ended March 31, Mineral Fiber 2019 2018 Distributors $ 144.6 $ 137.7 Home centers 23.1 24.0 Direct customers 14.1 13.7 Retailers and other 14.9 15.3 Total $ 196.7 $ 190.7
Architectural Specialties [Member]
Disaggregation Of Revenue [Line Items]
Schedule of Net Sales by Major Customer Group within Each Segment	Three months ended March 31, Architectural Specialties 2019 2018 Distributors $ 31.5 $ 28.4 Direct customers 13.1 7.9 Retailers and other 0.8 0.3 Total $ 45.4 $ 36.6

Acquisition and Discontinued _2

Acquisition and Discontinued Operations (Tables)	3 Months Ended
	Mar. 31, 2019
Discontinued Operations [Abstract]
Summary of Results of Discontinued Operations	The following tables detail the businesses and line items that comprise discontinued operations on the Condensed Consolidated Statements of Earnings and Comprehensive Income. EMEA and Pacific Rim Businesses Three months ended March 31, 2019: Net sales $ 96.9 Cost of goods sold 75.7 Gross profit 21.2 Selling, general and administrative expenses 20.8 Operating income 0.4 Earnings from discontinued operations before income tax 0.4 Income tax (benefit) (0.1 ) Net earnings from discontinued operations, net of tax $ 0.5 Gain from disposal of discontinued businesses, before income tax $ 2.2 Income tax expense - Gain from disposal of discontinued businesses, net of tax $ 2.2 Net earnings from discontinued operations $ 2.7 EMEA and Pacific Rim Businesses Flooring Businesses Total Three months ended March 31, 2018: Net sales $ 104.4 $ - $ 104.4 Cost of goods sold 77.8 - 77.8 Gross profit 26.6 - 26.6 Selling, general and administrative expenses 22.0 - 22.0 Operating income 4.6 - 4.6 Interest expense 0.4 - 0.4 Other non-operating (income), net (1.2 ) - (1.2 ) Earnings from discontinued operations before income tax 5.4 - 5.4 Income tax expense 1.5 - 1.5 Net earnings from discontinued operations, net of tax $ 3.9 $ - $ 3.9 Loss from disposal of discontinued businesses, before income tax $ (17.7 ) $ - $ (17.7 ) Income tax (benefit) - (0.4 ) (0.4 ) Loss from disposal of discontinued business, net of tax $ (17.7 ) $ 0.4 $ (17.3 ) Net loss from discontinued operations $ (13.8 ) $ 0.4 $ (13.4 ) The following is a summary of the carrying amount of major classes of assets and liabilities classified as assets and liabilities of discontinued operations as of March 31, 2019 and December 31, 2018 related to our EMEA and Pacific Rim businesses. March 31, 2019 December 31, 2018 Assets Current assets: Cash and cash equivalents $ 10.0 $ 10.0 Accounts and notes receivable, net 47.3 56.2 Inventories, net 65.3 59.8 Income tax receivable 4.2 1.8 Other current assets 10.3 8.2 Total current assets discontinued operations 137.1 136.0 Property, plant, and equipment, less accumulated depreciation and amortization (1) (2) 109.3 103.8 Prepaid pension costs (1) 29.9 28.9 Goodwill and intangible assets, net (1) 7.0 6.8 Deferred income taxes (1) 3.1 3.0 Lease ROU assets (1) 21.8 - Other non-current assets (1) 0.7 1.0 Total non-current assets of discontinued operations (1) 171.8 143.5 Total assets of discontinued operations (1) $ 308.9 $ 279.5 Liabilities Current liabilities: Accounts payable and accrued expenses $ 73.2 $ 67.1 Income tax payable 1.2 1.1 Total current liabilities 74.4 68.2 Pension benefit liabilities (3) 33.6 33.8 Lease non-current liabilities (3) 12.7 - Other long-term liabilities (3) 1.8 1.8 Income taxes payable (3) 0.2 - Deferred income taxes (3) 6.6 6.5 Total non-current liabilities of discontinued operations (3) 54.9 42.1 Total liabilities of discontinued operations (3) $ 129.3 $ 110.3 (1) Presented as Assets of discontinued operations on the Condensed Consolidated Balance Sheets. (2) Includes reversal of previous pre-tax estimated losses of $2.2 million recorded in the first three months of 2019. As of December 31, 2018, cumulative pre-tax estimated losses were $93.3 million. (3) Presented as Liabilities of discontinued operations on the Condensed Consolidated Balance Sheets .
Summary of Total Estimated Gains and Losses, Capital Expenditures, and Operating Lease	The following is a summary of total estimated gains and losses, capital expenditures, and operating lease information related to our EMEA and Pacific Rim businesses which are presented as discontinued operations and included as components of operating and investing cash flows on our Condensed Consolidated Statements of Cash Flows: Three Months Ended March 31, 2019 2018 Reversal of previous estimated loss on sale to Knauf (1) (2.2 ) - Estimated loss on sale to Knauf (1) - 17.7 Purchases of property, plant and equipment (0.4 ) (1.2 ) Operating lease cost (2) 2.3 - ROU assets obtained in exchange for lease obligations (2) 24.6 - (1) Represents comparison of the EMEA and Pacific Rim net assets to the expected sales proceeds to be received upon closure of the transaction. (2) Operating lease cost and non-cash activity relating to ASC Topic 842 – Leases. We do not believe the amount of cash paid for amounts included in the measurement of lease liabilities to be materially different from our operating lease cost for the three months ended March 31, 2019.

Accounts and Notes Receivable (

Accounts and Notes Receivable (Tables)	3 Months Ended
	Mar. 31, 2019
Receivables [Abstract]
Schedule of Accounts and Notes Receivable	March 31, 2019 December 31, 2018 Customer receivables $ 85.4 $ 70.4 Miscellaneous receivables 3.1 11.5 Less allowance for warranties, discounts and losses (3.2 ) (2.0 ) Accounts and notes receivable, net $ 85.3 $ 79.9

Inventories (Tables)

Inventories (Tables)	3 Months Ended
	Mar. 31, 2019
Inventory Disclosure [Abstract]
Schedule of Inventories	March 31, 2019 December 31, 2018 Finished goods $ 40.1 $ 38.8 Goods in process 4.9 4.4 Raw materials and supplies 37.2 27.8 Less LIFO reserves (10.1 ) (9.8 ) Total inventories, net $ 72.1 $ 61.2

Other Current Assets (Tables)

Other Current Assets (Tables)	3 Months Ended
	Mar. 31, 2019
Deferred Costs Capitalized Prepaid And Other Assets Disclosure [Abstract]
Schedule of Other Current Assets	March 31, 2019 December 31, 2018 Prepaid expenses $ 7.3 $ 4.1 Other 0.9 0.7 Total other current assets $ 8.2 $ 4.8

Equity Investment (Tables)

Equity Investment (Tables)	3 Months Ended
	Mar. 31, 2019
WAVE [Member]
Schedule of Equity Method Investments [Line Items]
Summary of Investment in Joint Venture, Income Statement Data	Three Months Ended March 31, 2019 2018 Net sales $ 96.9 $ 87.7 Gross profit 52.6 47.8 Net earnings 40.2 35.6

Leases (Tables)

Leases (Tables)	3 Months Ended
	Mar. 31, 2019
Leases [Abstract]
Schedule of Operating Lease Cost and Supplemental Cash Flow Information Related to Operating Leases	The following table presents our operating lease cost and supplemental cash flow information related to our operating leases: Three Months Ended March 31, 2019 Operating lease cost $ 1.6 Non-cash activity: ROU assets obtained in exchange for lease obligations 29.2
Schedule of Weighted Average Assumptions Used To Compute Right To Use Assets	The following table presents weighted average assumptions used to compute our ROU assets and lease liabilities: March 31, 2019 Weighted average remaining lease term (in years) 7.9 Weighted average discount rate 5.0 %
Schedule of Undiscounted Future Minimum Payments	Undiscounted future minimum lease payments as of March 31, 2019, by year and in the aggregate, having non-cancelable lease terms in excess of one year are as follows: Maturities of Lease Liabilities 2019 (1) $ 4.9 2020 6.1 2021 5.0 2022 4.0 2023 3.5 Thereafter 12.0 Total lease payments 35.5 Less interest (6.7 ) Present value of lease liabilities $ 28.8 (1) Scheduled maturities of lease liabilities represents the time period of April 1, 2019 to December 31, 2019.
Schedule of Future Minimum Payments	Future minimum lease payments as of December 31, 2018, by year and in the aggregate, having non-cancelable lease terms in excess of one year were expected to be as follows: Total Minimum Lease payments 2019 5.3 2020 4.7 2021 4.2 2022 3.7 2023 2.2 Thereafter 4.7 Total 24.8

Goodwill and Intangible Assets

Goodwill and Intangible Assets (Tables)	3 Months Ended
	Mar. 31, 2019
Goodwill And Intangible Assets Disclosure [Abstract]
Schedule of Goodwill and Intangible Assets	The following table details amounts related to our goodwill and intangible assets as of March 31, 2019 and December 31, 2018. March 31, 2019 December 31, 2018 Estimated Useful Life Gross Carrying Amount Accumulated Amortization Gross Carrying Amount Accumulated Amortization Amortizing intangible assets Customer relationships 3-20 years $ 188.9 $ 105.5 $ 181.4 $ 103.0 Developed technology 15 years 84.6 67.9 84.3 66.5 Trademarks and brand names 5-20 years 3.9 0.1 1.1 0.2 Other Various 7.8 1.4 5.6 1.2 Total $ 285.2 $ 174.9 $ 272.4 $ 170.9 Goodwill and non-amortizing intangible assets Trademarks and brand names Indefinite 321.4 321.3 Goodwill Indefinite 40.6 19.2 Total goodwill and intangible assets $ 647.2 $ 612.9
Schedule of Amortization Expense	Three Months Ended March 31, 2019 2018 Amortization expense $ 3.9 $ 3.6

Accounts Payable And Accrued _2

Accounts Payable And Accrued Expenses (Tables)	3 Months Ended
	Mar. 31, 2019
Payables And Accruals [Abstract]
Schedule of Accounts Payable and Accrued Expenses	March 31, 2019 December 31, 2018 Payables, trade and other $ 76.0 $ 82.2 Current portion of lease liabilities 5.2 - Employment costs 6.6 18.6 Current portion of pension and postretirement liabilities 11.1 10.9 Advance receipt of Knauf proceeds 237.6 237.6 Payable to WAVE for advance receipt of Knauf proceeds 22.4 22.4 Current portion of environmental liabilities 9.6 0.7 Other 22.4 10.9 Total accounts payable and accrued expenses $ 390.9 $ 383.3

Income Tax Expense (Tables)

Income Tax Expense (Tables)	3 Months Ended
	Mar. 31, 2019
Income Tax Disclosure [Abstract]
Schedule of Income Tax Expense	Three Months Ended March 31, 2019 2018 Earnings from continuing operations before income taxes $ 49.8 $ 49.4 Income tax expense 13.4 8.2 Effective tax rate 26.8 % 16.6 %

Debt (Tables)

Debt (Tables)	3 Months Ended
	Mar. 31, 2019
Letter of Credit [Member]
Debt Instrument [Line Items]
Schedule of Letters of Credit Facilities	The following table presents details related to our letters of credit facilities: As of March 31, 2019 Financing Arrangements Limit Used Available Accounts receivable securitization facility $ 31.9 $ 36.2 $ (4.3 ) Bi-lateral facility 25.0 13.4 11.6 Revolving credit facility 150.0 - 150.0 Total $ 206.9 $ 49.6 $ 157.3

Pension and Other Benefit Pro_2

Pension and Other Benefit Programs (Tables)	3 Months Ended
	Mar. 31, 2019
Compensation And Retirement Disclosure [Abstract]
Schedule of Periodic Benefit Costs (Credits)	Following are the components of net periodic benefit costs (credits): Three Months Ended March 31, 2019 2018 U.S. defined benefit plans: Pension benefits Service cost of benefits earned during the period $ 1.2 $ 1.4 Interest cost on projected benefit obligation 12.6 11.5 Expected return on plan assets (20.1 ) (24.0 ) Amortization of net actuarial loss 4.8 5.0 Net periodic pension (credit) $ (1.5 ) $ (6.1 ) Retiree health and life insurance benefits Interest cost on projected benefit obligation $ 0.6 $ 0.6 Amortization of net actuarial gain (2.2 ) (1.4 ) Net periodic postretirement (credit) $ (1.6 ) $ (0.8 )

Financial Instruments (Tables)

Financial Instruments (Tables)	3 Months Ended
	Mar. 31, 2019
Fair Value Disclosures [Abstract]
Estimated Fair Value of Financial Instruments	The estimated fair values of our financial instruments are as follows: March 31, 2019 December 31, 2018 Carrying amount Estimated fair value Carrying amount Estimated fair value Assets/(Liabilities), net: Total long-term debt, including current portion $ (812.2 ) $ (812.8 ) $ (819.8 ) $ (811.3 ) Interest rate swap contracts (3.3 ) (3.3 ) 3.5 3.5

Derivative Financial Instrume_2

Derivative Financial Instruments (Tables)	3 Months Ended
	Mar. 31, 2019
Derivative Instruments And Hedging Activities Disclosure [Abstract]
Summary of Interest Rate Swaps	Trade Date Notional Amount Coverage Period Risk Coverage November 13, 2016 $ 200.0 November 2016 to March 2021 USD-LIBOR April 1, 2016 $ 100.0 April 2016 to March 2023 USD-LIBOR November 28, 2018 $ 200.0 November 2018 to November 2023 USD-LIBOR November 28, 2018 $ 100.0 March 2021 to March 2025 USD-LIBOR
Summary of Fair Value of Derivative Instruments on Consolidated Balance Sheet	Derivative Assets Derivative Liabilities Fair Value Fair Value Balance Sheet Location March 31, 2019 December 31, 2018 Balance Sheet Location March 31, 2019 December 31, 2018 Derivatives designated as hedging instruments Interest rate swap contracts Other non-current assets $ 6.7 $ 9.6 Other long-term liabilities $ 10.0 $ 6.1
Summary of Amount of Gain (Loss) Recognized in Accumulated Other Comprehensive Income	Amount of Gain (Loss) Recognized in AOCI Location of (Loss) Reclassified AOCI into Income (Loss) Reclassified from AOCI into Income Three Months Ended Three Months Ended March 31, March 31, 2019 2018 2019 2018 Derivatives in cash flow hedging relationships Natural gas commodity contracts $ - $ - Cost of goods sold $ - $ (0.4 ) Foreign exchange contracts – purchases - 0.1 Cost of goods sold - - Foreign exchange contracts – sales - 0.3 Net sales - (0.2 ) Interest rate swap contracts (7.4 ) 3.3 Interest expense (0.6 ) (0.5 ) Total $ (7.4 ) $ 3.7 Total (loss) from continuing operations $ (0.6 ) $ (1.1 ) Total (loss) from discontinued operations - (0.1 ) Total (loss) $ (0.6 ) $ (1.2 )

Other Long-Term Liabilities (Ta

Other Long-Term Liabilities (Tables)	3 Months Ended
	Mar. 31, 2019
Other Liabilities Disclosure [Abstract]
Schedule of Other Long-Term Liabilities	March 31, 2019 December 31, 2018 Long-term deferred compensation arrangements $ 14.0 $ 14.0 Environmental liabilities 2.8 11.7 Fair value of derivative liabilities 10.0 6.1 Other 6.2 6.2 Total other long-term liabilities $ 33.0 $ 38.0

Accumulated Other Comprehensi_2

Accumulated Other Comprehensive Income (Loss) (Tables)	3 Months Ended
	Mar. 31, 2019
Equity [Abstract]
Components of Accumulated Other Comprehensive Income (Loss)	Foreign Currency Translation Adjustments Derivative Gain (Loss) (1) Pension and Postretirement Adjustments (1) Total Accumulated Other Comprehensive (Loss) (1) Balance, December 31, 2018 $ (74.7 ) $ 5.3 $ (390.2 ) $ (459.6 ) Impact of ASU 2017-12 adoption - 0.1 - 0.1 Other comprehensive income (loss) before reclassifications, net of tax expense (benefit) of $ -, $1.9, ($0.2) and $1.7 5.3 (5.6 ) 0.7 0.4 Amounts reclassified from accumulated other comprehensive (loss) - 0.5 2.1 2.6 Net current period other comprehensive income (loss) 5.3 (5.1 ) 2.8 3.0 Balance, March 31, 2019 $ (69.4 ) $ 0.3 $ (387.4 ) $ (456.5 ) Foreign Currency Translation Adjustments Derivative Gain (Loss) (1) Pension and Postretirement Adjustments (1) Total Accumulated Other Comprehensive (Loss) (1) Balance, December 31, 2017 $ (47.1 ) $ 3.5 $ (302.3 ) $ (345.9 ) Impact of ASU 2018-02 adoption - 0.7 (55.0 ) (54.3 ) Other comprehensive income (loss) before reclassifications, net of tax expense of $ -, $1.2, $0.6 and $1.8 5.9 2.9 (1.0 ) 7.8 Amounts reclassified from accumulated other comprehensive (loss) - 0.9 2.8 3.7 Net current period other comprehensive income 5.9 3.8 1.8 11.5 Balance, March 31, 2018 $ (41.2 ) $ 8.0 $ (355.5 ) $ (388.7 ) (1) Amounts are net of tax
Reclassification out of Accumulated Other Comprehensive Income	Amounts Reclassified from Accumulated Other Comprehensive (Loss) (1) Affected Condensed Consolidated Statement of Earnings and Comprehensive Income Three Months Ended March 31, 2019 2018 Derivative Adjustments: Natural gas commodity contracts $ - $ 0.4 Cost of goods sold Foreign exchange contracts - purchases - 0.1 Cost of goods sold Foreign exchange contracts - sales - 0.2 Net sales Interest rate swap contracts 0.6 0.5 Interest expense Total loss, before tax 0.6 1.2 Tax impact (0.1 ) (0.3 ) Income tax expense Total loss, net of tax 0.5 0.9 Pension and Postretirement Adjustments: Amortization of net actuarial loss 2.7 3.6 Other non-operating (income), net Total expense, before tax 2.7 3.6 Tax impact (0.6 ) (0.8 ) Income tax expense Total expense, net of tax 2.1 2.8 Total reclassifications for the period $ 2.6 $ 3.7 (1) Includes activity from discontinued operations.

Earnings Per Share (Tables)

Earnings Per Share (Tables)	3 Months Ended
	Mar. 31, 2019
Earnings Per Share [Abstract]
Reconciliation of Earnings to Earnings Attributable to Common Shares Used in Basic and Diluted Calculation	The following table is a reconciliation of earnings to earnings attributable to common shares used in our basic and diluted EPS calculations for the three months ended March 31, 2019 and 2018: Three Months Ended March 31, 2019 2018 Earnings from continuing operations $ 36.4 $ 41.2 Earnings allocated to participating non-vested share awards (0.1 ) (0.1 ) Earnings from continuing operations attributable to common shares $ 36.3 $ 41.1
Reconciliation of Basic Shares Outstanding to Diluted Shares Outstanding	The following table is a reconciliation of basic shares outstanding to diluted shares outstanding for the three months ended March 31, 2019 and 2018 (shares in millions): Three Months Ended March 31, 2019 2018 Basic shares outstanding 48.7 53.0 Dilutive effect of common stock equivalents 0.8 0.8 Diluted shares outstanding 49.5 53.8

Business and Basis of Present_3

Business and Basis of Presentation (Narrative) (Details)	Mar. 04, 2019Facility	Aug. 16, 2018Facility	Jul. 18, 2018USD ($)	May 31, 2018Facility	Mar. 31, 2019USD ($)	Sep. 30, 2018USD ($)	Dec. 31, 2018USD ($)	Nov. 17, 2017USD ($)
Business And Basis Of Presentation [Line Items]
Potential adjustments to the purchase price consideration			$ 35,000,000
Potential adjustments to the purchase price consideration			20,000,000
Account payable and accrued expenses related to investment in joint venture					$ 390,900,000		$ 383,300,000
Lease right-of-use assets					28,800,000
Lease liabilities					28,800,000
Finance lease, liabilities					0
Accounting Standards Update 2016-02 [Member]
Business And Basis Of Presentation [Line Items]
Lease right-of-use assets					28,800,000
Lease liabilities					$ 28,800,000
August 1, 2018 [Member] | Knauf [Member]
Business And Basis Of Presentation [Line Items]
Receivable from sale of business			250,000,000
Proceeds from sale of business						$ 250,000,000
September 15, 2018 [Member] | Knauf [Member]
Business And Basis Of Presentation [Line Items]
Receivable from sale of business			$ 80,000,000
Proceeds from sale of business						80,000,000
EMEA and Pacific Rim Business [Member]
Business And Basis Of Presentation [Line Items]
Consideration to be received in connection with sale of businesses								$ 330,000,000
Architectural Components Group, Inc. [Member]
Business And Basis Of Presentation [Line Items]
Number of manufacturing facility | Facility	1
Steel Ceilings, Inc. [Member]
Business And Basis Of Presentation [Line Items]
Number of manufacturing facility | Facility		1
Plasterform, Inc. [Member]
Business And Basis Of Presentation [Line Items]
Number of manufacturing facility | Facility				1
WAVE [Member]
Business And Basis Of Presentation [Line Items]
Equity interest percentage					50.00%
Payment to WAVE from Knauf proceeds						$ 70,000,000
Account payable and accrued expenses related to investment in joint venture					$ 22,400,000
WAVE [Member] | Worthington [Member]
Business And Basis Of Presentation [Line Items]
Dividend received from joint venture					$ 35,000,000

Segment Results (Schedule of Ne

Segment Results (Schedule of Net Sales) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Segment Reporting Information [Line Items]
Total net sales	$ 242.1	$ 227.3
Mineral Fiber [Member]
Segment Reporting Information [Line Items]
Total net sales	196.7	190.7
Architectural Specialties [Member]
Segment Reporting Information [Line Items]
Total net sales	$ 45.4	$ 36.6

Segment Results (Schedule of Se

Segment Results (Schedule of Segment Operating Income (Loss)) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Segment Reporting Information [Line Items]
Total consolidated operating income	$ 54.7	$ 49.6
Mineral Fiber [Member]
Segment Reporting Information [Line Items]
Total consolidated operating income	47.6	43.7
Architectural Specialties [Member]
Segment Reporting Information [Line Items]
Total consolidated operating income	9.2	8.3
Unallocated Corporate [Member]
Segment Reporting Information [Line Items]
Total consolidated operating income	$ (2.1)	$ (2.4)

Segment Results (Reconciliation

Segment Results (Reconciliation of Total Consolidated Operating Income to Earnings Before Income Taxes) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Segment Reporting [Abstract]
Total consolidated operating income	$ 54.7	$ 49.6
Interest expense	10.4	9.2
Other non-operating (income), net	(5.5)	(9)
Earnings from continuing operations before income taxes	$ 49.8	$ 49.4

Segment Results (Reconciliati_2

Segment Results (Reconciliation of Total Segment Assets to Total Consolidated Assets) (Details) - USD ($) $ in Millions	Mar. 31, 2019	Dec. 31, 2018
Segment Reporting Information [Line Items]
Total consolidated assets	$ 1,633.7	$ 1,594
Mineral Fiber [Member]
Segment Reporting Information [Line Items]
Total consolidated assets	1,118	1,096.1
Architectural Specialties [Member]
Segment Reporting Information [Line Items]
Total consolidated assets	147.2	84.7
Unallocated Corporate [Member]
Segment Reporting Information [Line Items]
Total consolidated assets	$ 368.5	$ 413.2

Segment Results (Narrative) (De

Segment Results (Narrative) (Details) $ in Millions	3 Months Ended
	Mar. 31, 2018USD ($)
Mineral Fiber [Member]
Segment Reporting Information [Line Items]
Cost of goods sold for accelerated depreciation of property, plant and equipment	$ 7.7

Revenue (Narrative) (Details)

Revenue (Narrative) (Details) - Maximum [Member]	3 Months Ended
	Mar. 31, 2019
Disaggregation Of Revenue [Line Items]
Payment terms on sales	45 days
Incremental costs to fulfill customer arrangements amortization period	1 year

Revenue (Schedule of Net Sales

Revenue (Schedule of Net Sales by Major Customer Group within Each Segment) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Entity Wide Revenue Major Customer [Line Items]
Total net sales	$ 242.1	$ 227.3
Mineral Fiber [Member]
Entity Wide Revenue Major Customer [Line Items]
Total net sales	196.7	190.7
Mineral Fiber [Member] | Distributors [Member]
Entity Wide Revenue Major Customer [Line Items]
Total net sales	144.6	137.7
Mineral Fiber [Member] | Home Centers [Member]
Entity Wide Revenue Major Customer [Line Items]
Total net sales	23.1	24
Mineral Fiber [Member] | Direct Customers [Member]
Entity Wide Revenue Major Customer [Line Items]
Total net sales	14.1	13.7
Mineral Fiber [Member] | Retailers And Other
Entity Wide Revenue Major Customer [Line Items]
Total net sales	14.9	15.3
Architectural Specialties [Member]
Entity Wide Revenue Major Customer [Line Items]
Total net sales	45.4	36.6
Architectural Specialties [Member] | Distributors [Member]
Entity Wide Revenue Major Customer [Line Items]
Total net sales	31.5	28.4
Architectural Specialties [Member] | Direct Customers [Member]
Entity Wide Revenue Major Customer [Line Items]
Total net sales	13.1	7.9
Architectural Specialties [Member] | Retailers And Other
Entity Wide Revenue Major Customer [Line Items]
Total net sales	$ 0.8	$ 0.3

Acquisition and Discontinued _3

Acquisition and Discontinued Operations (Narrative) (Details) - USD ($) $ in Millions	Mar. 04, 2019	Aug. 16, 2018	May 31, 2018	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018	Dec. 31, 2017	Oct. 31, 2018
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Business acquisition, goodwill				$ 40.6		$ 19.2
(Loss) gain due to change in carrying value of discontinued operations net assets				2.2	$ (17.3)
EMEA and Pacific Rim Business [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
(Loss) gain due to change in carrying value of discontinued operations net assets				2.2	$ (17.7)	(19.3)	$ (74)
EMEA and Pacific Rim Business [Member] | Foreign Currency Translation Adjustments [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
(Loss) gain due to change in carrying value of discontinued operations net assets				$ 9.1		$ (25.5)	$ (51.4)
Architectural Components Group, Inc. [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Business acquisition, purchase price	$ 43.1
Business acquisition, total fair value of tangible assets acquired, less liabilities assumed	9.9
Business acquisition, total fair value of intangible assets acquired	12
Business acquisition, goodwill	21.2
Architectural Components Group, Inc. [Member] | Customer Relationships [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Business acquisition, total fair value of intangible assets acquired	7.4
Architectural Components Group, Inc. [Member] | TradeNames [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Business acquisition, total fair value of intangible assets acquired	$ 2.8
Steel Ceilings, Inc. [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Business acquisition, purchase price		$ 12.3
Business acquisition, total fair value of tangible assets acquired, less liabilities assumed		4.4
Business acquisition, goodwill		3.2
Assets Held-for-sale, Not Part of Disposal Group, Current, Other								$ 2
Steel Ceilings, Inc. [Member] | Customer Relationships [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Business acquisition, total fair value of intangible assets acquired		1.4
Steel Ceilings, Inc. [Member] | TradeNames [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Business acquisition, total fair value of intangible assets acquired		$ 1.3
Plasterform, Inc. [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Business acquisition, purchase price			$ 11.9
Business acquisition, total fair value of tangible assets acquired, less liabilities assumed			2.2
Business acquisition, total fair value of intangible assets acquired			4.8
Business acquisition, goodwill			$ 4.9

Acquisition and Discontinued _4

Acquisition and Discontinued Operations (Schedule of Business Details and Line Items Comprising Discontinued Operations on Statements of Earnings and Comprehensive Income) (Details) - USD ($) $ in Millions	3 Months Ended		12 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018	Dec. 31, 2017
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Net sales		$ 104.4
Cost of goods sold		77.8
Gross profit		26.6
Selling, general and administrative expenses		22
Operating income		4.6
Interest expense		0.4
Other non-operating (income) expense, net		(1.2)
Earnings from discontinued operations before income tax		5.4
Income tax (benefit) expense		1.5
Net earnings from discontinued operations, net of tax	$ 0.5	3.9
Gain (loss) from disposal of discontinued businesses, before income tax	2.2	(17.7)
Income tax expense (benefit)		(0.4)
Gain (loss) from disposal of discontinued businesses, net of tax	2.2	(17.3)
Net gain (loss) from discontinued operations	2.7	(13.4)
EMEA and Pacific Rim Business [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Net sales	96.9	104.4
Cost of goods sold	75.7	77.8
Gross profit	21.2	26.6
Selling, general and administrative expenses	20.8	22
Operating income	0.4	4.6
Interest expense		0.4
Other non-operating (income) expense, net		(1.2)
Earnings from discontinued operations before income tax	0.4	5.4
Income tax (benefit) expense	(0.1)	1.5
Net earnings from discontinued operations, net of tax	0.5	3.9
Gain (loss) from disposal of discontinued businesses, before income tax	2.2	(17.7)
Gain (loss) from disposal of discontinued businesses, net of tax	2.2	(17.7)	$ (19.3)	$ (74)
Net gain (loss) from discontinued operations	$ 2.7	(13.8)
Flooring Businesses [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Income tax expense (benefit)		(0.4)
Gain (loss) from disposal of discontinued businesses, net of tax		0.4
Net gain (loss) from discontinued operations		$ 0.4

Acquisition and Discontinued _5

Acquisition and Discontinued Operations (Summary of Carrying Amount of Major Classes of Assets and Liabilities Related to EMEA and Pacific Rim Businesses) (Details) - USD ($) $ in Millions	Mar. 31, 2019	Dec. 31, 2018
Current assets:
Total current assets discontinued operations	$ 308.9	$ 279.5
Total assets	1,942.6	1,873.5
Current liabilities:
Total current liabilities	129.3	110.3
EMEA and Pacific Rim Business [Member]
Current assets:
Cash and cash equivalents	10	10
Accounts and notes receivable, net	47.3	56.2
Inventories, net	65.3	59.8
Income tax receivable	4.2	1.8
Other current assets	10.3	8.2
Total current assets discontinued operations	137.1	136
Property, plant, and equipment, less accumulated depreciation and amortization	109.3	103.8
Prepaid pension costs	29.9	28.9
Goodwill and intangible assets, net	7	6.8
Deferred income taxes	3.1	3
Lease ROU assets	21.8
Other non-current assets	0.7	1
Total non-current assets of discontinued operations	171.8	143.5
Total assets	308.9	279.5
Current liabilities:
Accounts payable and accrued expenses	73.2	67.1
Income tax payable	1.2	1.1
Total current liabilities	74.4	68.2
Pension benefit liabilities	33.6	33.8
Lease non-current liabilities	12.7
Other long-term liabilities	1.8	1.8
Income taxes payable	0.2
Deferred income taxes	6.6	6.5
Total non-current liabilities of discontinued operations	54.9	42.1
Total liabilities of discontinued operations	$ 129.3	$ 110.3

Acquisition and Discontinued _6

Acquisition and Discontinued Operations (Summary of Carrying Amount of Major Classes of Assets and Liabilities Related to EMEA and Pacific Rim Businesses) (Parenthetical) (Details) - EMEA and Pacific Rim Business [Member] - USD ($) $ in Millions	Mar. 31, 2019	Dec. 31, 2018
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Adjustment of previously recorded cumulative estimated losses	$ 2.2
Accumulative pre-tax estimated losses		$ 93.3

Acquisition and Discontinued _7

Acquisition and Discontinued Operations (Summary of Total Depreciation and Amortization, Capital Expenditures and Estimated Losses) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Gain (loss) on disposal of discontinued business	$ 2.2	$ (17.7)
EMEA and Pacific Rim Business [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Gain (loss) on disposal of discontinued business	2.2	(17.7)
Purchases of property, plant and equipment	(0.4)	(1.2)
Operating lease cost	2.3
ROU assets obtained in exchange for lease obligations	24.6
EMEA and Pacific Rim Business [Member] | Knauf [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Gain (loss) on disposal of discontinued business	$ (2.2)	$ 17.7

Accounts and Notes Receivable_2

Accounts and Notes Receivable (Schedule of Accounts and Notes Receivable) (Details) - USD ($) $ in Millions	Mar. 31, 2019	Dec. 31, 2018
Receivables [Abstract]
Customer receivables	$ 85.4	$ 70.4
Miscellaneous receivables	3.1	11.5
Less allowance for warranties, discounts and losses	(3.2)	(2)
Accounts and notes receivable, net	$ 85.3	$ 79.9

Accounts and Notes Receivable_3

Accounts and Notes Receivable (Narrative) (Details) - USD ($) $ in Millions	Mar. 31, 2019	Dec. 31, 2018
Receivables [Abstract]
Insurance recoveries related to environmental matters	$ 1.7	$ 6.5

Inventories (Schedule of Invent

Inventories (Schedule of Inventories) (Details) - USD ($) $ in Millions	Mar. 31, 2019	Dec. 31, 2018
Inventory Disclosure [Abstract]
Finished goods	$ 40.1	$ 38.8
Goods in process	4.9	4.4
Raw materials and supplies	37.2	27.8
Less LIFO reserves	(10.1)	(9.8)
Total inventories, net	$ 72.1	$ 61.2

Other Current Assets (Schedule

Other Current Assets (Schedule of Other Current Assets) (Details) - USD ($) $ in Millions	Mar. 31, 2019	Dec. 31, 2018
Deferred Costs Capitalized Prepaid And Other Assets Disclosure [Abstract]
Prepaid expenses	$ 7.3	$ 4.1
Other	0.9	0.7
Total other current assets	$ 8.2	$ 4.8

Equity Investment (Narrative) (

Equity Investment (Narrative) (Details)	Mar. 31, 2019
WAVE [Member]
Schedule of Equity Method Investments [Line Items]
Equity interest percentage	50.00%

Equity Investment (Summary of I

Equity Investment (Summary of Investment in Joint Venture, Income Statement Data) (Details) - WAVE [Member] - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Schedule of Equity Method Investments [Line Items]
Net sales	$ 96.9	$ 87.7
Gross profit	52.6	47.8
Net earnings	$ 40.2	$ 35.6

Leases (Narrative) (Details)

Leases (Narrative) (Details) - USD ($)	3 Months Ended	12 Months Ended
	Mar. 31, 2019	Dec. 31, 2018
Lessee Lease Description [Line Items]
Operating lease option to terminate	within 1 year
Operating lease existence of option to terminate	true
Short-term leases term	12 months
Finance lease, liabilities	$ 0
Additional operating leases not yet commenced	no additional operating leases that have not yet commenced
Rent expense		$ 6,100,000
Minimum [Member]
Lessee Lease Description [Line Items]
Remaining lease term operating lease	1 year
Maximum [Member]
Lessee Lease Description [Line Items]
Remaining lease term operating lease	15 years
Lease renewal term operating lease	5 years

Leases (Schedule of Operating L

Leases (Schedule of Operating Lease Cost and Supplemental Cash Flow Information Related to Operating Leases) (Details) $ in Millions	3 Months Ended
	Mar. 31, 2019USD ($)
Lease Cost [Abstract]
Operating lease cost	$ 1.6
Non-cash activity:
ROU assets obtained in exchange for lease obligations	$ 29.2

Leases (Schedule of Weighted Av

Leases (Schedule of Weighted Average Assumptions Used To Compute ROU Assets and Lease Liabilities) (Details)	Mar. 31, 2019
Leases [Abstract]
Weighted average remaining lease term (in years)	7 years 10 months 24 days
Weighted average discount rate	5.00%

Leases (Schedule of Undiscounte

Leases (Schedule of Undiscounted Future Minimum Payments) (Details) $ in Millions	Mar. 31, 2019USD ($)
Leases [Abstract]
2019	$ 4.9
2020	6.1
2021	5
2022	4
2023	3.5
Thereafter	12
Total lease payments	35.5
Less interest	(6.7)
Lease liabilities	$ 28.8

Leases (Schedule of Future Mini

Leases (Schedule of Future Minimum Payments) (Details) $ in Millions	Dec. 31, 2018USD ($)
Leases [Abstract]
Total minimum lease payments, 2019	$ 5.3
Total minimum lease payments, 2020	4.7
Total minimum lease payments, 2021	4.2
Total minimum lease payments, 2022	3.7
Total minimum lease payments, 2023	2.2
Total minimum lease payments, Thereafter	4.7
Total minimum lease payments, Total	$ 24.8

Goodwill and Intangible Asset_2

Goodwill and Intangible Assets (Schedule of Goodwill and Intangible Assets) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Dec. 31, 2018
Schedule Of Intangible Assets And Goodwill [Line Items]
Goodwill, Estimated Useful Life	Indefinite
Amortizing intangible assets, Gross Carrying Amount	$ 285.2	$ 272.4
Amortizing intangible assets, Accumulated Amortization	174.9	170.9
Goodwill	40.6	19.2
Total goodwill and intangible assets	$ 647.2	612.9
Trademarks And Brand Names [Member]
Schedule Of Intangible Assets And Goodwill [Line Items]
Non-amortizing intangible assets, Estimated Useful Life	Indefinite
Non-amortizing intangible assets	$ 321.4	321.3
Customer Relationships [Member]
Schedule Of Intangible Assets And Goodwill [Line Items]
Amortizing intangible assets, Gross Carrying Amount	188.9	181.4
Amortizing intangible assets, Accumulated Amortization	$ 105.5	103
Customer Relationships [Member] | Minimum [Member]
Schedule Of Intangible Assets And Goodwill [Line Items]
Amortizing intangible assets, Estimated Useful Life	3 years
Customer Relationships [Member] | Maximum [Member]
Schedule Of Intangible Assets And Goodwill [Line Items]
Amortizing intangible assets, Estimated Useful Life	20 years
Developed Technology [Member]
Schedule Of Intangible Assets And Goodwill [Line Items]
Amortizing intangible assets, Estimated Useful Life	15 years
Amortizing intangible assets, Gross Carrying Amount	$ 84.6	84.3
Amortizing intangible assets, Accumulated Amortization	67.9	66.5
Trademarks And Brand Names [Member]
Schedule Of Intangible Assets And Goodwill [Line Items]
Amortizing intangible assets, Gross Carrying Amount	3.9	1.1
Amortizing intangible assets, Accumulated Amortization	$ 0.1	0.2
Trademarks And Brand Names [Member] | Minimum [Member]
Schedule Of Intangible Assets And Goodwill [Line Items]
Amortizing intangible assets, Estimated Useful Life	5 years
Trademarks And Brand Names [Member] | Maximum [Member]
Schedule Of Intangible Assets And Goodwill [Line Items]
Amortizing intangible assets, Estimated Useful Life	20 years
Other [Member]
Schedule Of Intangible Assets And Goodwill [Line Items]
Amortizing intangible assets, Estimated Useful Life	Various
Amortizing intangible assets, Gross Carrying Amount	$ 7.8	5.6
Amortizing intangible assets, Accumulated Amortization	$ 1.4	$ 1.2

Goodwill and Intangible Asset_3

Goodwill and Intangible Assets (Schedule of Amortization Expense) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Goodwill And Intangible Assets Disclosure [Abstract]
Amortization expense	$ 3.9	$ 3.6

Accounts Payable And Accrued _3

Accounts Payable And Accrued Expenses (Details) - USD ($) $ in Millions	Mar. 31, 2019	Dec. 31, 2018
Schedule Of Accounts Payble And Accrued Expenses [Line Items]
Payables, trade and other	$ 76	$ 82.2
Current portion of lease liabilities	5.2
Employment costs	6.6	18.6
Current portion of pension and postretirement liabilities	11.1	10.9
Current portion of environmental liabilities	9.6	0.7
Other	22.4	10.9
Total accounts payable and accrued expenses	390.9	383.3
Knauf [Member]
Schedule Of Accounts Payble And Accrued Expenses [Line Items]
Advance receipt of Knauf proceeds	237.6	237.6
Payable to WAVE for advance receipt of Knauf proceeds	$ 22.4	$ 22.4

Income Tax Expenses (Details)

Income Tax Expenses (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Income Tax Disclosure [Abstract]
Earnings from continuing operations before income taxes	$ 49.8	$ 49.4
Income tax expense	$ 13.4	$ 8.2
Effective tax rate	26.80%	16.60%

Debt (Narrative) (Details)

Debt (Narrative) (Details) - USD ($)	3 Months Ended
	Mar. 31, 2019	Dec. 31, 2018
Letter of Credit [Member]
Debt Instrument [Line Items]
Credit facility amount	$ 49,600,000
Line of credit availability	206,900,000
Term Loan A [Member]
Debt Instrument [Line Items]
Line of credit availability	600,000,000	$ 600,000,000
Term Loan B [Member]
Debt Instrument [Line Items]
Line of credit availability	250,000,000	250,000,000
Bi-lateral Facility [Member] | Letter of Credit [Member]
Debt Instrument [Line Items]
Credit facility amount	13,400,000
Line of credit availability	25,000,000	25,000,000
Tax-Exempt Industrial Development Bond [Member]
Debt Instrument [Line Items]
Long-term debt outstanding	35,000,000	35,000,000
Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Line of credit availability	200,000,000	200,000,000
Letter of credit maximum sublimit	150,000,000	150,000,000
Amount outstanding	0	0
Securitization Facility [Member]
Debt Instrument [Line Items]
Credit facility amount	36,200,000
Amount outstanding	$ 0
Maturity date	Mar. 31, 2020
Securitization Facility [Member] | ARC [Member]
Debt Instrument [Line Items]
Ownership interest	100.00%
Securitization Facility [Member] | Letter of Credit [Member]
Debt Instrument [Line Items]
Credit facility amount	$ 36,200,000
Line of credit availability	31,900,000
Letters of credit issued classified as restricted cash	4,300,000	6,000,000
Senior Credit Facility [Member]
Debt Instrument [Line Items]
Credit facility amount	$ 1,050,000,000	$ 1,050,000,000

Debt (Schedule of Letters of Cr

Debt (Schedule of Letters of Credit Facilities) (Details) - USD ($)	Mar. 31, 2019	Dec. 31, 2018
Letter of Credit [Member]
Debt Instrument [Line Items]
Letters of credit, Limit	$ 206,900,000
Letters of credit, Used	49,600,000
Letters of credit, Available	157,300,000
Letter of Credit [Member] | Bi-lateral Facility [Member]
Debt Instrument [Line Items]
Letters of credit, Limit	25,000,000	$ 25,000,000
Letters of credit, Used	13,400,000
Letters of credit, Available	11,600,000
Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Letter of credit maximum sublimit	150,000,000	150,000,000
Letters of credit, Limit	200,000,000	$ 200,000,000
Revolving Credit Facility [Member] | Letter of Credit [Member]
Debt Instrument [Line Items]
Letters of credit, Available	150,000,000
Accounts Receivable Securitization Facility [Member]
Debt Instrument [Line Items]
Letters of credit, Used	36,200,000
Accounts Receivable Securitization Facility [Member] | Letter of Credit [Member]
Debt Instrument [Line Items]
Letters of credit, Limit	31,900,000
Letters of credit, Used	36,200,000
Letters of credit, Available	$ (4,300,000)

Pension and Other Benefit Pro_3

Pension and Other Benefit Programs (Schedule of Periodic Benefit Costs (Credits) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
U.S. Defined-Benefit Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost of benefits earned during the period	$ 1.2	$ 1.4
Interest cost on projected benefit obligation	12.6	11.5
Expected return on plan assets	(20.1)	(24)
Amortization of net actuarial (gain) loss	4.8	5
Net periodic pension/postretirement (credit)	(1.5)	(6.1)
Retiree Health And Life Insurance Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Interest cost on projected benefit obligation	0.6	0.6
Amortization of net actuarial (gain) loss	(2.2)	(1.4)
Net periodic pension/postretirement (credit)	$ (1.6)	$ (0.8)

Financial Instruments (Estimate

Financial Instruments (Estimated Fair Value of Financial Instruments) (Details) - Level 2 [Member] - USD ($) $ in Millions	Mar. 31, 2019	Dec. 31, 2018
Carrying Amount [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total long-term debt, including current portion	$ (812.2)	$ (819.8)
Estimated Fair Value [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total long-term debt, including current portion	(812.8)	(811.3)
Interest Rate Swap Contracts [Member] | Carrying Amount [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets (liabilities), net	(3.3)	3.5
Interest Rate Swap Contracts [Member] | Estimated Fair Value [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets (liabilities), net	$ (3.3)	$ 3.5

Derivative Financial Instrume_3

Derivative Financial Instruments (Narrative) (Details)	Nov. 28, 2018	Nov. 13, 2016	Apr. 01, 2016	Mar. 31, 2019USD ($)item	Dec. 31, 2018USD ($)
Derivative [Line Items]
Loss in AOCI expected to be recognized in earnings over the next twelve months				$ (800,000)
Not Designated As Hedging Instrument [Member]
Derivative [Line Items]
Derivative assets				0	$ 0
Derivative liabilities				$ 0	$ 0
Commodity Price Risk [Member] | Open Natural Gas Contracts
Derivative [Line Items]
Number of Contract Designated Hedges | item				0
Currency Rate Risk – Sales and Purchases | Foreign Exchange
Derivative [Line Items]
Number of Contract Designated Hedges | item				0
Interest Rate Swap Mature 2021 [Member]
Derivative [Line Items]
Derivatives swap maturity year		2021
Interest Rate Swap Mature 2023 [Member]
Derivative [Line Items]
Derivatives swap maturity year	2023		2023
Interest Rate Swap Contracts [Member]
Derivative [Line Items]
LIBOR floor	0.00%
Interest Rate Swap Contracts [Member] | Minimum [Member]
Derivative [Line Items]
LIBOR floor			0.75%
Interest Rate Swap Mature 2025 [Member]
Derivative [Line Items]
Derivatives swap maturity year	2025

Derivative Financial Instrume_4

Derivative Financial Instruments (Summary of Interest Rate Swaps) (Details)	3 Months Ended
	Mar. 31, 2019USD ($)
November 2016 to March 2021 [Member]
Derivative [Line Items]
Trade Date	Nov. 13, 2016
Notional Amount	$ 200,000,000
Coverage Period	November 2016 to March 2021
Risk Coverage	USD-LIBOR
April 2016 to March 2023 [Member]
Derivative [Line Items]
Trade Date	Apr. 1, 2016
Notional Amount	$ 100,000,000
Coverage Period	April 2016 to March 2023
Risk Coverage	USD-LIBOR
November 2018 to November 2023 [Member]
Derivative [Line Items]
Trade Date	Nov. 28, 2018
Notional Amount	$ 200,000,000
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
Coverage Period	March 2021 to March 2025
Risk Coverage	USD-LIBOR

Derivative Financial Instrume_5

Derivative Financial Instruments (Summary of Fair Value of Derivative Instruments on Consolidated Balance Sheet) (Details) - Interest Rate Swap Contracts [Member] - USD ($) $ in Millions	Mar. 31, 2019	Dec. 31, 2018
Other Non-Current Assets [Member]
Derivatives, Fair Value [Line Items]
Derivative Assets, Fair Value	$ 6.7	$ 9.6
Other Long-Term Liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative Liabilities, Fair Value	$ 10	$ 6.1

Derivative Financial Instrume_6

Derivative Financial Instruments (Summary of Amount of Gain (Loss) Recognized in Accumulated Other Comprehensive Income) (Details) - Derivatives in Cash Flow Hedging Relationships [Member] - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain(Loss) Recognized in AOCI	$ (7.4)	$ 3.7
(Loss) Reclassified from AOCI into Income	(0.6)	(1.2)
Continuing Operations [Member]
Derivative Instruments, Gain (Loss) [Line Items]
(Loss) Reclassified from AOCI into Income	(0.6)	(1.1)
Discontinued Operations [Member]
Derivative Instruments, Gain (Loss) [Line Items]
(Loss) Reclassified from AOCI into Income		(0.1)
Natural Gas Commodity Contracts [Member] | Cost of goods sold [Member]
Derivative Instruments, Gain (Loss) [Line Items]
(Loss) Reclassified from AOCI into Income		(0.4)
Foreign Exchange Contracts - Purchases [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain(Loss) Recognized in AOCI		0.1
Foreign Exchange Contracts - Sales [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain(Loss) Recognized in AOCI		0.3
Foreign Exchange Contracts - Sales [Member] | Net Sales [Member]
Derivative Instruments, Gain (Loss) [Line Items]
(Loss) Reclassified from AOCI into Income		(0.2)
Interest Rate Swap Contracts [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain(Loss) Recognized in AOCI	(7.4)	3.3
Interest Rate Swap Contracts [Member] | Interest Expense [Member]
Derivative Instruments, Gain (Loss) [Line Items]
(Loss) Reclassified from AOCI into Income	$ (0.6)	$ (0.5)

Other Long-Term Liabilities (Sc

Other Long-Term Liabilities (Schedule of Other Long-Term Liabilities) (Details) - USD ($) $ in Millions	Mar. 31, 2019	Dec. 31, 2018
Other Liabilities Disclosure [Abstract]
Long-term deferred compensation arrangements	$ 14	$ 14
Environmental liabilities	2.8	11.7
Fair value of derivative liabilities	10	6.1
Other	6.2	6.2
Total other long-term liabilities	$ 33	$ 38

Shareholders' Equity (Narrative

Shareholders' Equity (Narrative) (Details) - USD ($)	Oct. 08, 2018	Aug. 02, 2018	Oct. 30, 2017	Jul. 29, 2016	Feb. 28, 2019	Mar. 31, 2019	Mar. 31, 2018	Mar. 31, 2019	Jul. 31, 2018
Equity Class Of Treasury Stock [Line Items]
Shares repurchase program, repurchased cost						$ 20,000,000	$ 70,000,000
Quarterly dividends declared					$ 0.175
Dividends declared						$ 0.175
Dividends payable, date to be paid, year and month						2019-03		2019-03
Accelerated Share Repurchase [Member] | Deutsche Bank AG [Member]
Equity Class Of Treasury Stock [Line Items]
Shares repurchase program, expiration date						Oct. 8, 2018
Pre payment of repurchase program		$ 150,000,000
Repurchase program, Shares		1,766,004
Accelerated share repurchase remaining shares returned	389,825
Common Stock
Equity Class Of Treasury Stock [Line Items]
Shares repurchase program, expiration date				Jul. 31, 2018
Stock repurchase program, additional authorized amount			$ 250,000,000						$ 300,000,000
Shares repurchase program, extended expiration date			Oct. 31, 2020
Shares repurchase program, shares repurchased						331,686	1,165,247
Common Stock | Share Repurchase Program Excluding ASR [Member]
Equity Class Of Treasury Stock [Line Items]
Shares repurchase program, shares repurchased						300,000		8,000,000
Shares repurchase program, repurchased cost						$ 20,000,000		$ 450,600,000
Shares repurchase program, average price per share						$ 60.30		$ 56.19
Common Stock | Maximum [Member]
Equity Class Of Treasury Stock [Line Items]
Shares repurchase program, authorized amount				$ 150,000,000					$ 700,000,000

Accumulated Other Comprehensi_3

Accumulated Other Comprehensive Income (Loss) (Components of Accumulated Other Comprehensive Income (Loss)) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Accumulated Other Comprehensive Income Loss [Line Items]
Balance	$ 261.2	$ 419.3
Other comprehensive income (loss) before reclassifications, net of tax expense (benefit)	0.4	7.8
Amounts reclassified from accumulated other comprehensive (loss)	2.6	3.7
Net current period other comprehensive income (loss)	3	11.5
Balance	280.3	403.8
ASU 2017-12 [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Impact of ASU adoption	0.1
ASU 2018-02 [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Impact of ASU adoption		(54.3)
Foreign Currency Translation Adjustments [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Balance	(74.7)	(47.1)
Other comprehensive income (loss) before reclassifications, net of tax expense (benefit)	5.3	5.9
Net current period other comprehensive income (loss)	5.3	5.9
Balance	(69.4)	(41.2)
Derivative Gain (Loss) [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Balance	5.3	3.5
Other comprehensive income (loss) before reclassifications, net of tax expense (benefit)	(5.6)	2.9
Amounts reclassified from accumulated other comprehensive (loss)	0.5	0.9
Net current period other comprehensive income (loss)	(5.1)	3.8
Balance	0.3	8
Derivative Gain (Loss) [Member] | ASU 2017-12 [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Impact of ASU adoption	0.1
Derivative Gain (Loss) [Member] | ASU 2018-02 [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Impact of ASU adoption		0.7
Pension And Postretirement Adjustments [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Balance	(390.2)	(302.3)
Other comprehensive income (loss) before reclassifications, net of tax expense (benefit)	0.7	(1)
Amounts reclassified from accumulated other comprehensive (loss)	2.1	2.8
Net current period other comprehensive income (loss)	2.8	1.8
Balance	(387.4)	(355.5)
Pension And Postretirement Adjustments [Member] | ASU 2018-02 [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Impact of ASU adoption		(55)
Accumulated Other Comprehensive (Loss) [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Balance	(459.6)	(345.9)
Balance	(456.5)	(388.7)
Accumulated Other Comprehensive (Loss) [Member] | ASU 2017-12 [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Impact of ASU adoption	$ 0.1
Accumulated Other Comprehensive (Loss) [Member] | ASU 2018-02 [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Impact of ASU adoption		$ (54.3)

Accumulated Other Comprehensi_4

Accumulated Other Comprehensive Income (Loss) (Components of Accumulated Other Comprehensive Income (Loss)) (Parenthetical) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Accumulated Other Comprehensive Income Loss [Line Items]
Other comprehensive income (loss) before reclassifications, tax expense (benefit)	$ 1.7	$ 1.8
Derivative Gain (Loss) [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Other comprehensive income (loss) before reclassifications, tax expense (benefit)	1.9	1.2
Pension And Postretirement Adjustments [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Other comprehensive income (loss) before reclassifications, tax expense (benefit)	$ (0.2)	$ 0.6

Accumulated Other Comprehensi_5

Accumulated Other Comprehensive Income (Loss) (Reclassification out of Accumulated Other Comprehensive Income) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Cost of goods sold	$ 150.7	$ 156.5
Net sales	242.1	227.3
Interest expense	10.4	9.2
Total loss, before tax	(49.8)	(49.4)
Tax impact	13.4	8.2
Total loss, net of tax	(39.1)	(27.8)
Total reclassifications for the period	2.6	3.7
Derivative Gain (Loss) [Member]
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Total reclassifications for the period	0.5	0.9
Derivative Gain (Loss) [Member] | Reclassified From Accumulated Other Comprehensive (Loss) [Member]
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Total loss, before tax	0.6	1.2
Tax impact	(0.1)	(0.3)
Total loss, net of tax	0.5	0.9
Derivative Gain (Loss) [Member] | Natural Gas Commodity Contracts [Member] | Reclassified From Accumulated Other Comprehensive (Loss) [Member]
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Cost of goods sold		0.4
Derivative Gain (Loss) [Member] | Foreign Exchange Contracts - Purchases [Member] | Reclassified From Accumulated Other Comprehensive (Loss) [Member]
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Cost of goods sold		0.1
Derivative Gain (Loss) [Member] | Foreign Exchange Contracts - Sales [Member] | Reclassified From Accumulated Other Comprehensive (Loss) [Member]
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Net sales		0.2
Derivative Gain (Loss) [Member] | Interest Rate Swap Contracts [Member] | Reclassified From Accumulated Other Comprehensive (Loss) [Member]
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Interest expense	0.6	0.5
Amortization Of Net Actuarial Loss [Member] | Reclassified From Accumulated Other Comprehensive (Loss) [Member]
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Amortization of net actuarial loss	2.7	3.6
Pension And Postretirement Adjustments [Member]
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Total reclassifications for the period	2.1	2.8
Pension And Postretirement Adjustments [Member] | Reclassified From Accumulated Other Comprehensive (Loss) [Member]
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Total expense, before tax	2.7	3.6
Tax impact	(0.6)	(0.8)
Total expense, net of tax	$ 2.1	$ 2.8

Litigation and Related Matters

Litigation and Related Matters (Narrative) (Details)	Mar. 01, 2019USD ($)	Sep. 30, 2010site	Mar. 31, 2019USD ($)Litigationsite	Mar. 31, 2018USD ($)	Dec. 31, 2017USD ($)	Dec. 31, 2007	Dec. 31, 2018USD ($)	Feb. 01, 2018USD ($)
Loss Contingencies [Line Items]
Number of active and independent litigation matters for which pursuing coverage and recoveries | Litigation			2
Settlement agreement amount of litigation agreement			$ 1,700,000				$ 37,500,000
Cash received from litigation settlements			6,500,000
Additional cash received from litigation settlements			200,000
Environmental liabilities			12,400,000				12,400,000
Reserves for potential environmental liabilities			1,000,000	$ 0
Settlement agreement amount paid for litigation agreement			19,700,000
Accounts Payable and Accrued Expenses [Member]
Loss Contingencies [Line Items]
Environmental liabilities			9,600,000				700,000
Accounts and Notes Receivable, Net [Member]
Loss Contingencies [Line Items]
Insurance recoveries related to environmental matters			$ 1,700,000
St. Helens [Member]
Loss Contingencies [Line Items]
Environmental liabilities								$ 8,600,000
Reserves for potential environmental liabilities					$ 8,600,000
Settlement agreement amount paid for litigation agreement	$ 1,000,000
Macon Site [Member]
Loss Contingencies [Line Items]
Number of landfills listed as Superfund site | site			2
Number of landfills AWI entered into an Administrative Order on Consent for a Removal Action | site		1
Submission date of final report to EPA		Oct. 11, 2016
Elizabeth City [Member]
Loss Contingencies [Line Items]
Percentage of site costs Navy agreed to pay						33.33%
Cost Of Goods Sold [Member]
Loss Contingencies [Line Items]
Settlement agreement amount of litigation agreement							9,200,000
SG&A Expenses [Member]
Loss Contingencies [Line Items]
Settlement agreement amount of litigation agreement			$ 1,900,000				$ 28,300,000

Earnings Per Share (Reconciliat

Earnings Per Share (Reconciliation of Earnings to Earnings Attributable to Common Shares Used in Basic and Diluted Calculation) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Earnings Per Share [Abstract]
Earnings from continuing operations	$ 36.4	$ 41.2
Earnings allocated to participating non-vested share awards	(0.1)	(0.1)
Earnings from continuing operations attributable to common shares	$ 36.3	$ 41.1

Earnings Per Share (Reconcili_2

Earnings Per Share (Reconciliation of Basic Shares Outstanding to Diluted Shares Outstanding) (Details) - shares shares in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Earnings Per Share [Abstract]
Basic shares outstanding	48.7	53
Dilutive effect of common stock equivalents	0.8	0.8
Diluted shares outstanding	49.5	53.8

Earnings Per Share (Narrative)

Earnings Per Share (Narrative) (Details) - shares	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Earnings Per Share [Abstract]
Awards to purchase common stock not included in the computation of diluted EPS	30,371	0