Beacon Roofing Supply (BECN) 10-Q 9 Feb 21 2021 Q1 Quarterly report Financial data

Document And Entity Information

Document And Entity Information - shares	3 Months Ended
	Dec. 31, 2020	Jan. 31, 2021
Cover [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Dec. 31, 2020
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	Q1
Trading Symbol	BECN
Entity Registrant Name	BEACON ROOFING SUPPLY, INC.
Entity Central Index Key	0001124941
Current Fiscal Year End Date	--09-30
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Common Stock, Shares Outstanding		69,407,397
Entity Shell Company	false
Entity Current Reporting Status	Yes
Entity File Number	000-50924
Entity Tax Identification Number	36-4173371
Entity Address, Address Line One	505 Huntmar Park Drive
Entity Address, Address Line Two	Suite 300
Entity Address, City or Town	Herndon
Entity Address, State or Province	VA
Entity Address, Postal Zip Code	20170
City Area Code	571
Local Phone Number	323-3939
Entity Interactive Data Current	Yes
Entity Incorporation, State or Country Code	DE
Document Quarterly Report	true
Document Transition Report	false
Title of 12(b) Security	Common Stock, $0.01 par value
Security Exchange Name	NASDAQ

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Millions		Dec. 31, 2020	Sep. 30, 2020	Dec. 31, 2019
Current assets:
Cash and cash equivalents		$ 461.4	$ 624.6	$ 43.7
Accounts receivable, less allowance of $20.6, $17.9 and $13.8 as of December 31, 2020, September 30, 2020 and December 31, 2019, respectively		746.4	885.2	716.5
Inventories, net		952.9	871.4	946.7
Prepaid expenses and other current assets		330	351.8	279.1
Current assets held for sale		997	243.8	267.7
Total current assets		3,487.7	2,976.8	2,253.7
Property and equipment, net		209.5	207.8	210.4
Goodwill		1,757.5	1,756.1	1,756.9
Intangibles, net		492.6	518	747.9
Operating lease assets		371.8	376.2	395.9
Deferred income taxes, net		12.4
Other assets, net		2.1	2.1
Non-current assets held for sale			1,120.5	1,173.7
Total assets		6,333.6	6,957.5	6,538.5
Current liabilities:
Accounts payable		738.3	885.8	542.2
Accrued expenses		442.2	509.7	356.4
Current operating lease liabilities		84	84	83.1
Current portions of long-term debt/obligations		11.3	12.3	13.9
Current liabilities held for sale		175.1	139.4	123.1
Total current liabilities		1,450.9	1,631.2	1,118.7
Borrowings under revolving lines of credit, net		151.7	251.1	215.6
Long-term debt, net		2,494.1	2,494.2	2,495.1
Deferred income taxes, net			71.8	99.7
Non-current operating lease liabilities		286.6	290.5	308.5
Long-term obligations under equipment financing, net				1.6
Other long-term liabilities		6.3	5.2	0.4
Non-current liabilities held for sale			53.4	59
Total liabilities		4,389.6	4,797.4	4,298.6
Commitments and contingencies (Note 10)
Convertible Preferred Stock; $0.01 par value; aggregate liquidation preference $400.0; 0.4 shares authorized, issued and outstanding as of December 31, 2020, September 30, 2020 and December 31, 2019	[1]	399.2	399.2	399.2
Stockholders' equity:
Common stock (voting); $0.01 par value; 100.0 shares authorized; 69.4, 69.0 and 68.8 shares issued and outstanding as of December 31, 2020, September 30, 2020 and December 31, 2019, respectively		0.7	0.7	0.7
Undesignated preferred stock; 5.0 shares authorized, none issued or outstanding		0	0	0
Additional paid-in capital		1,109.8	1,100.6	1,087
Retained earnings		463.5	694.3	769.8
Accumulated other comprehensive income (loss)		(29.2)	(34.7)	(16.8)
Total stockholders' equity		1,544.8	1,760.9	1,840.7
Total liabilities and stockholders' equity		$ 6,333.6	$ 6,957.5	$ 6,538.5
[1]	See Note 5 for additional information.

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Millions	Dec. 31, 2020	Sep. 30, 2020	Dec. 31, 2019
Statement Of Financial Position [Abstract]
Accounts receivable, allowances	$ 20.6	$ 17.9	$ 13.8
Convertible preferred stock, par value	$ 0.01	$ 0.01	$ 0.01
Convertible preferred stock. aggregate liquidation preference	$ 400	$ 400	$ 400
Convertible preferred stock, shares authorized	400,000	400,000	400,000
Convertible preferred stock, shares issued	400,000	400,000	400,000
Convertible preferred stock, shares outstanding	400,000	400,000	400,000
Common stock (voting), par value	$ 0.01	$ 0.01	$ 0.01
Common stock (voting), shares authorized	100,000,000	100,000,000	100,000,000
Common Stock (voting), issued	69,400,000	69,000,000	68,800,000
Common Stock (voting), outstanding	69,400,000	69,000,000	68,800,000
Undesignated Preferred Stock, shares authorized	5,000,000	5,000,000	5,000,000
Undesignated Preferred Stock, issued	0	0	0
Undesignated Preferred Stock, outstanding	0	0	0

Consolidated Statements of Oper

Consolidated Statements of Operations - USD ($) $ in Millions		3 Months Ended
		Dec. 31, 2020	Dec. 31, 2019
Income Statement [Abstract]
Net sales		$ 1,576.5	$ 1,415.3
Cost of products sold		1,176.8	1,075.2
Gross profit		399.7	340.1
Operating expense:
Selling, general and administrative		265.2	273.2
Depreciation		13.9	15.8
Amortization		25.5	32.1
Total operating expense		304.6	321.1
Income (loss) from operations		95.1	19
Interest expense, financing costs, and other		30	38.4
Loss on debt extinguishment		0	14.7
Income (loss) from continuing operations before income taxes		65.1	(34.1)
Provision for (benefit from) income taxes		17.7	(10.1)
Net income (loss) from continuing operations		47.4	(24)
Net income (loss) from discontinued operations	[1]	(267.9)	0.6
Net income (loss)		(220.5)	(23.4)
Dividends on Preferred Stock		6	6
Net income (loss) attributable to common shareholders		$ (226.5)	$ (29.4)
Weighted-average common stock outstanding:
Basic		69,200,000	68,700,000
Diluted		70,000,000	68,700,000
Net income (loss) per share:
Basic - Continuing operations	[2]	$ 0.60	$ (0.44)
Basic - Discontinued operations	[2]	(3.87)	0.01
Basic net income (loss) per share	[2]	(3.27)	(0.43)
Diluted - Continuing operations	[2]	0.59	(0.44)
Diluted - Discontinued operations	[2]	(3.83)	0.01
Diluted net income (loss) per share	[2]	$ (3.24)	$ (0.43)
[1]	See Note 3 for additional information.
[2]	See Note 5 for detailed calculations and further discussion.

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Statement Of Income And Comprehensive Income [Abstract]
Net income (loss)	$ (220.5)	$ (23.4)
Other comprehensive income (loss):
Foreign currency translation adjustment	3.9	1.3
Unrealized gain (loss) due to change in fair value of derivatives, net of tax	1.6	2.5
Total other comprehensive income (loss)	5.5	3.8
Comprehensive income (loss)	$ (215)	$ (19.6)

Consolidated Statements of Stoc

Consolidated Statements of Stockholders' Equity - USD ($) $ in Millions	Total	Common Stock [Member]	APIC [Member]	[1]	Retained Earnings [Member]	AOCI [Member]	[2]
Balance at Sep. 30, 2019	$ 1,862.3	$ 0.7	$ 1,083		$ 799.2	$ (20.6)
Balance (in shares) at Sep. 30, 2019		68,600,000
Issuance of common stock, net of shares withheld for taxes	(1.2)		(1.2)
Issuance of common stock, net of shares withheld for taxes (Shares)		200,000
Stock-based compensation	5.2		5.2
Other comprehensive income (loss)	3.8					3.8
Net income (loss)	(23.4)				(23.4)
Dividends on Preferred Stock	(6)				(6)
Balance at Dec. 31, 2019	1,840.7	$ 0.7	1,087		769.8	(16.8)
Balance (in shares) at Dec. 31, 2019		68,800,000
Balance at Sep. 30, 2020	1,760.9	$ 0.7	1,100.6		694.3	(34.7)
Balance (in shares) at Sep. 30, 2020		69,000,000
Adoption of ASU 2016-13 | ASU 2016-13 [Member]	(4.3)				(4.3)
Issuance of common stock, net of shares withheld for taxes	4.3		4.3
Issuance of common stock, net of shares withheld for taxes (Shares)		400,000
Stock-based compensation	4.9		4.9
Other comprehensive income (loss)	5.5					5.5
Net income (loss)	(220.5)				(220.5)
Dividends on Preferred Stock	(6)				(6)
Balance at Dec. 31, 2020	$ 1,544.8	$ 0.7	$ 1,109.8		$ 463.5	$ (29.2)
Balance (in shares) at Dec. 31, 2020		69,400,000
[1]	Additional Paid-in Capital (“APIC”).
[2]	Accumulated Other Comprehensive Income (Loss) ("AOCI").

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Millions		3 Months Ended
		Dec. 31, 2020	Dec. 31, 2019
Operating Activities
Net income (loss)		$ (220.5)	$ (23.4)
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Depreciation and amortization		52.3	63.9
Stock-based compensation		4.9	5.2
Certain interest expense and other financing costs		2.9	2.8
Loss on debt extinguishment		0	14.7
Gain on sale of fixed assets and other		(0.6)	(0.3)
Deferred income taxes		(85.9)	2.4
Loss on classification as held for sale	[1]	355.4	0
Changes in operating assets and liabilities:
Accounts receivable		149.6	247.6
Inventories		(89.3)	(19.2)
Prepaid expenses and other current assets		18	(3.4)
Accounts payable and accrued expenses		(227.5)	(417.5)
Other assets and liabilities		1.6	1.9
Net cash provided by (used in) operating activities		(39.1)	(125.3)
Investing Activities
Purchases of property and equipment		(18)	(12.2)
Proceeds from the sale of assets		0.7	0.4
Net cash provided by (used in) investing activities		(17.3)	(11.8)
Financing Activities
Borrowings under revolving lines of credit		2.3	750.7
Payments under revolving lines of credit		(102.3)	(616.8)
Payments under term loan		(2.4)	(2.4)
Borrowings under senior notes		0	300
Payment under senior notes		0	(309.6)
Payment of debt issuance costs		0	(3.6)
Payments under equipment financing facilities and finance leases		(1.7)	(2.3)
Payment of dividends on Preferred Stock		(6)	(6)
Proceeds from issuance of common stock related to equity awards		7.1	0.9
Payment of taxes related to net share settlement of equity awards		(2.8)	(2.1)
Net cash provided by (used in) financing activities		(105.8)	108.8
Effect of exchange rate changes on cash and cash equivalents		(1)	(0.3)
Net increase (decrease) in cash and cash equivalents		(163.2)	(28.6)
Cash and cash equivalents, beginning of period		624.6	72.3
Cash and cash equivalents, end of period		461.4	43.7
Supplemental Cash Flow Information
Operating cash flows provided by (used in) discontinued operations		(6.4)	12.4
Investing cash flows provided by (used in) discontinued operations		(2.5)	(6.9)
Cash paid during the period for:
Interest		47.1	57.4
Income taxes paid (received), net of refunds		$ 2	$ 0.1
[1]	See Note 3 for additional information.

Company Overview

Company Overview	3 Months Ended
	Dec. 31, 2020
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Company Overview	1. Company Overview Beacon Roofing Supply, Inc. (“Beacon” or the “Company”) was incorporated in the state of Delaware on August 22, 1997 and is the largest publicly traded distributor of residential and non-residential roofing materials and complementary building products in the United States and Canada. On December 20, 2020, the Company entered into an Equity Purchase Agreement (the “Purchase Agreement”) with ASP Sailor Acquisition Corp. (the “Buyer”). Pursuant to the Purchase Agreement, Beacon has agreed to sell its interior products and insulation businesses (“Interior Products”) to the Buyer, an entity controlled by affiliates of American Securities LLC. Subject to the terms and conditions of the Purchase Agreement, the Buyer has agreed to purchase all of the outstanding equity interests in a limited liability company newly formed to hold Interior Products for a purchase price of $850 million in cash payable at closing, subject to certain customary adjustments set forth in the Purchase Agreement. The definitive agreement was publicly announced on December 21, 2020. The transaction is expected to close during the Company’s fiscal 2021 second quarter, subject to customary closing conditions as set forth in the Purchase Agreement. The Company has reflected Interior Products as discontinued operations for all periods presented. For additional information, see Notes 2 and 3. On January 15, 2020, the Company announced the rebranding of its exterior products branches with the trade name “Beacon Building Products” (the “Rebranding”). The new name, and a related logo, were adopted at over 450 Beacon one-step exterior products branches. The Company’s Interior Products, weatherproofing and two-step branches continue to operate under legacy brand names. The Company operates its business under regional and local trade names and services customers in all 50 states throughout the U.S. and 6 provinces in Canada. The Company’s material subsidiaries are Beacon Sales Acquisition, Inc. and Beacon Roofing Supply Canada Company.

Summary of Significant Accounti

Summary of Significant Accounting Policies	3 Months Ended
	Dec. 31, 2020
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	2. Summary of Significant Accounting Policies Basis of Presentation The Company prepared the condensed consolidated financial statements in accordance with U.S. generally accepted accounting principles (“GAAP”) for interim financial information and the requirements of the Securities and Exchange Commission (“SEC”). As permitted under those rules, certain footnotes or other financial information have been condensed or omitted. Additionally, beginning with the condensed consolidated financial statements for the three months ended December 31, 2020, the Company has reflected Interior Products as discontinued operations for all periods presented. Unless otherwise noted, amounts and disclosures throughout these Notes to Condensed Consolidated Financial Statements relate to the Company's continuing operations. Certain prior period amounts have been reclassified to conform to current period presentation. The balance sheet as of December 31, 2019 has been presented for a better understanding of the impact of seasonal fluctuations on the Company’s financial condition. In management’s opinion, the financial statements include all normal and recurring adjustments that are considered necessary for the fair presentation of the Company’s financial position and operating results. The results for the three months ended December 31, 2020 are not necessarily indicative of the results to be expected for the twelve months ending September 30, 2021. The three-month periods ended each These interim Condensed Consolidated Financial Statements should be read in conjunction with the audited Consolidated Financial Statements and Notes thereto contained in the Company’s fiscal year 2020 (“2020”) Annual Report on Form 10-K for the year ended September 30, 2020. Use of Estimates The preparation of consolidated financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the amounts reported in these consolidated financial statements and accompanying notes. Significant items subject to such estimates include accounts receivable, inventories, purchase price allocations, goodwill and intangibles, and income taxes. Assumptions made in the development of these estimates contemplate the impact of the novel coronavirus (“COVID‑19”) on the economy and the Company’s anticipated results; however, actual amounts could differ materially from these estimates. Recent Accounting Pronouncements—Adopted In June 2016, the FASB issued ASU 2016-13, “ Financial Instruments—Credit Losses: Measurement of Credit Losses on Financial Instruments In January 2017, the FASB issued ASU 2017-04, “ Simplifying the Accounting for Goodwill Impairment.” Recent Accounting Pronouncements—Not Yet Adopted In December 2019, the FASB issued ASU 2019-12, “Income Taxes – Simplifying the Accounting for Income Taxes.” In March 2020, the FASB issued ASU 2020-04, “ Reference Rate Reform (Topic 848), Facilitation of the Effects of Reference Rate Reform on Financial Reporting Reference Rate Reform (Topic 848), Scope

Discontinued Operations

Discontinued Operations	3 Months Ended
	Dec. 31, 2020
Discontinued Operations And Disposal Groups [Abstract]
Discontinued Operations	3. Discontinued Operations On December 20, 2020, the Company entered into the Purchase Agreement, pursuant to which it has agreed to sell Interior Products to the Buyer. Subject to the terms and conditions of the Purchase Agreement, the Buyer has agreed to purchase all of the outstanding equity interests in a limited liability company newly formed to hold Interior Products for a purchase price of $850 million in cash payable at closing, subject to certain customary adjustments set forth in the Purchase Agreement. The definitive agreement was publicly announced on December 21, 2020. The Company entered into this divestiture of net assets previously acquired as part of the Allied Acquisition in 2018 (see Note 5 for additional information) to reduce net leverage, strengthen its balance sheet, enhance leadership focus, and provide the financial flexibility to pursue strategic growth initiatives in its core exteriors business. The transaction is expected to close during the Company’s fiscal 2021 second quarter, subject to customary closing conditions as set forth in the Purchase Agreement. The following table reconciles major line items constituting pretax income (loss) from discontinued operations to net income (loss) from discontinued operations as presented in the condensed consolidated statements of operations (in millions): Three Months Ended December 31, 2020 2019 Net sales $ 248.8 $ 259.8 Cost of products sold (183.8 ) (189.2 ) Selling, general and administrative (56.9 ) (53.7 ) Depreciation and amortization (12.9 ) (16.0 ) Other income (loss) 0.1 0.2 Loss on classification as held for sale (355.4 ) — Pretax income (loss) from discontinued operations (360.1 ) 1.1 Provision for (benefit from) income taxes (92.2 ) 0.5 Net income (loss) from discontinued operations $ (267.9 ) $ 0.6 The estimated loss on classification as held for sale of $355.4 million for the three months ended December 31, 2020 is calculated by comparing the purchase price (as adjusted) to the carrying value of the net assets of Interior Products. As Interior Products represents a component of the Company’s single reporting unit, the carrying value of the net assets of Interior Products includes an allocation of $734.3 million of the Company’s consolidated goodwill balance. The Company allocated consolidated goodwill based on the relative fair value of the component, which was determined using the estimated purchase price (as adjusted) of Interior Products and the market capitalization of the Company as of December 31, 2020. The net result of this allocation attributed a higher amount of goodwill than that which was directly associated with the Interior Products portion of the Allied Acquisition, thereby having a significant influence on the estimated loss on the Interior Products divestiture transaction. Upon closing of the transaction, the estimated loss will be adjusted accordingly to reflect the final purchase price and carrying value of the net assets of Interior Products as of the close date, which will include an updated allocation of the Company’s goodwill to Interior Products. The following table reconciles the carrying amounts of major classes of assets and liabilities of discontinued operations to total assets and liabilities of discontinued operations that are classified as held for sale in the condensed consolidated balance sheets (in millions): December 31, September 30, December 31, 2020 2020 2019 Carrying amounts of major classes of assets held for sale: Accounts receivable, net $ 130.6 $ 144.1 $ 144.6 Inventories, net 82.4 73.2 91.1 Prepaid expenses and other current assets 30.7 26.5 32.0 Total current assets 243.8 267.7 Property and equipment, net 35.8 35.9 42.6 Goodwill 378.9 734.3 734.3 Intangibles, net 273.1 283.2 329.6 Operating lease assets 65.5 67.1 67.2 Total non-current assets 1,120.5 1,173.7 Total assets held for sale 1 $ 997.0 $ 1,364.3 $ 1,441.4 Carrying amounts of major classes of liabilities held for sale: Accounts payable $ 52.6 $ 68.8 $ 52.4 Accrued expenses 56.3 54.1 54.8 Current operating lease liabilities 16.2 16.5 15.9 Total current liabilities 139.4 123.1 Deferred income taxes, net — 2.2 7.4 Non-current operating lease liabilities 48.9 49.9 50.0 Other long-term liabilities 1.1 1.3 1.6 Total non-current liabilities 53.4 59.0 Total liabilities held for sale 1 $ 175.1 $ 192.8 $ 182.1 __________________________________________________ 1

Net Sales

Net Sales	3 Months Ended
	Dec. 31, 2020
Revenue From Contract With Customer [Abstract]
Net Sales	4. Net Sales The following table presents the Company’s net sales by product line and geography (in millions): U.S. Canada Total Three Months Ended December 31, 2020 Residential roofing products $ 831.3 $ 13.5 $ 844.8 Non-residential roofing products 366.1 32.2 398.3 Complementary building products 331.0 2.4 333.4 Total net sales $ 1,528.4 $ 48.1 $ 1,576.5 Three Months Ended December 31, 2019 Residential roofing products $ 685.9 $ 10.9 $ 696.8 Non-residential roofing products 379.6 32.4 412.0 Complementary building products 304.3 2.2 306.5 Total net sales $ 1,369.8 $ 45.5 $ 1,415.3

Net Income (Loss) Per Share

Net Income (Loss) Per Share	3 Months Ended
	Dec. 31, 2020
Earnings Per Share [Abstract]
Net Income (Loss) Per Share	5. Net Income (Loss) Per Share Basic net income (loss) per share is calculated by dividing net income (loss) attributable to common shareholders by the weighted-average number of common shares outstanding during the period, without consideration for common share equivalents or the conversion of Preferred Stock. Common share equivalents consist of the incremental common shares issuable upon the exercise of stock options and vesting of restricted stock unit awards. Diluted net income (loss) per common share is calculated by dividing net income (loss) attributable to common shareholders by the fully diluted weighted-average number of common shares outstanding during the period. In connection with the acquisition of Allied Building Products Corp. (“Allied”) on January 2, 2018 (the “Allied Acquisition”), the Company completed the sale of 400,000 shares of Series A Cumulative Convertible Participating Preferred Stock, par value $0.01 per share (the “Preferred Stock”), with an aggregate liquidation preference of $400.0 million, at a purchase price of $1,000 per share, to CD&R Boulder Holdings, L.P. The Preferred Stock is convertible perpetual participating preferred stock of the Company, and conversion of the Preferred Stock into $0.01 par value shares of the Company’s common stock will be at a conversion price of $41.26 per share (or 9,694,619 shares of common stock). The Preferred Stock accumulates dividends at a rate of 6.0% per annum (payable in cash or in-kind, subject to certain conditions). The Preferred Stock is not mandatorily redeemable; therefore, it is classified as mezzanine equity on the Company’s consolidated balance sheets. Holders of Preferred Stock participate in dividends on an as-converted basis when declared on common shares. As a result, Preferred Stock is classified as a participating security and thereby requires the allocation of income that would have otherwise been available to common shareholders when calculating net income (loss) per share. Diluted net income (loss) per share is calculated by utilizing the most dilutive result of the if-converted and two-class methods. In both methods, net income (loss) attributable to common shareholders and the weighted-average common shares outstanding are adjusted to account for the impact of the assumed issuance of potential common shares that are dilutive, subject to dilution sequencing rules. The following table presents the components and calculations of basic and diluted net income (loss) per share (in millions, except per share amounts): Three Months Ended December 31, 2020 2019 Net income (loss) $ (220.5 ) $ (23.4 ) Dividends on Preferred Stock 6.0 6.0 Net income (loss) attributable to common shareholders (226.5 ) (29.4 ) Undistributed income allocated to participating securities — — Net income (loss) attributable to common shareholders - basic and diluted (226.5 ) (29.4 ) Net income (loss) from discontinued operations attributable to common shareholders - basic and diluted (267.9 ) 0.6 Net income (loss) from continuing operations attributable to common shareholders - basic and diluted $ 41.4 $ (30.0 ) Weighted-average common shares outstanding - basic 69.2 68.7 Effect of common share equivalents 0.8 — Weighted-average common shares outstanding - diluted 70.0 68.7 Net income (loss) per share: Basic - Continuing operations $ 0.60 $ (0.44 ) Basic - Discontinued operations (3.87 ) 0.01 Basic net income (loss) per share $ (3.27 ) $ (0.43 ) Diluted - Continuing operations $ 0.59 $ (0.44 ) Diluted - Discontinued operations (3.83 ) 0.01 Diluted net income (loss) per share $ (3.24 ) $ (0.43 ) The following table includes the number of shares that may be dilutive common shares in the future. These shares were not included in the computation of diluted net income (loss) per share because the effect was either anti-dilutive or the requisite performance conditions were not met (in millions): Three Months Ended December 31, 2020 2019 Stock options 1.3 1.9 Restricted stock units — 0.4 Preferred Stock 9.7 9.7

Stock-based Compensation

Stock-based Compensation	3 Months Ended
	Dec. 31, 2020
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Stock-based Compensation	6. Stock-based Compensation On December 23, 2019, the Board of Directors of the Company approved the Beacon Roofing Supply, Inc. Second Amended and Restated 2014 Stock Plan (the “2014 Plan”). On February 11, 2020, the shareholders of the Company approved an additional 4,850,000 shares under the 2014 Plan. The 2014 Plan, which was originally approved by the shareholders on February 12, 2014, provides for discretionary awards of stock options, stock awards, restricted stock units, and stock appreciation rights to selected employees and non-employee directors. The 2014 Plan mandates that all forfeited, expired, and withheld shares, including those from the predecessor plan, be returned to the 2014 Plan and made available for issuance. As of December 31, 2020, there were 5,204,996 shares of common stock available for issuance. The 2014 Plan is the only plan maintained by the Company pursuant to which equity awards are granted. Equity awards granted in fiscal year 2015 and later contain a “double trigger” change in control mechanism. Unless an award is continued or assumed by a public company in an equitable manner, an award shall become fully vested immediately prior to a change in control (at 100% of the grant target in the case of a performance-based restricted stock unit award). If an award is so continued or assumed, vesting will continue in accordance with the terms of the award, unless there is a qualifying termination within one-year following the change in control, in which event the award shall immediately become fully vested (at 100% of the grant target in the case of a performance-based restricted stock unit award). Options granted prior to October 1, 2014 vest immediately upon a change in control of the Company. Stock Options Non-qualified stock options generally expire 10 years after the grant date and, except under certain conditions, the options are subject to continued employment and vest in three annual installments over the three-year The fair values of the options granted for the three months ended December 31, 2020 were estimated on the dates of grants using the Black-Scholes option-pricing model with the following weighted-average assumptions: Risk-free interest rate 0.44 % Expected volatility 48.15 % Expected life (in years) 5.36 Dividend yield — The following table summarizes all stock option activity for the three months ended December 31, 2020 (in millions, except per share and time period amounts): Options Outstanding Weighted- Average Exercise Price Weighted- Average Remaining Contractual Term (Years) Aggregate Intrinsic Value 1 Balance as of September 30, 2020 2.5 $ 33.09 5.9 $ 6.9 Granted 0.3 35.78 Exercised (0.3 ) 26.93 Canceled/Forfeited (0.0 ) 45.99 Expired (0.0 ) 15.47 Balance as of December 31, 2020 2.5 $ 33.98 6.4 $ 19.9 Vested and expected to vest after December 31, 2020 2.4 $ 34.00 6.3 $ 19.6 Exercisable as of December 31, 2020 1.7 $ 34.86 5.1 $ 13.4 ______________________________________________________ 1 During the three months ended December 31, 2020 and 2019, the Company recorded stock-based compensation expense related to stock options of $1.1 million and $1.1 million, respectively. As of December 31, 2020, there was $8.5 million of total unrecognized compensation cost related to unvested stock options, which is expected to be recognized over a weighted-average period of 2.0 years. The following table summarizes additional information on stock options (in millions, except per share amounts): Three Months Ended December 31, 2020 2019 Weighted-average fair value of stock options granted $ 15.62 $ 10.70 Total grant date fair value of stock options vested $ 4.1 $ 3.9 Total intrinsic value of stock options exercised $ 2.6 $ 0.7 Restricted Stock Units Restricted stock unit (“RSU”) awards granted to employees are subject to continued employment and generally vest on the third anniversary of the grant date. The Company also grants certain RSU awards to management that contain one or more additional vesting conditions tied directly to a defined performance metric for the Company. The actual number of RSUs that will vest can range from 0% to 200% of the original grant amount, depending upon actual Company performance below or above the established performance metric targets. The Company estimates performance in relation to the defined targets when determining the projected number of RSUs that are expected to vest and calculating the related stock-based compensation expense. RSUs granted to non-employee directors are subject to continued service and vest on the first anniversary of the grant date (except under certain conditions). Generally, the common shares underlying the RSUs are not eligible for distribution until the non-employee director’s service on the Board has terminated, and for non-employee director RSU grants made prior to fiscal year 2014, the share distribution date is six months after the director’s termination of service on the board. Beginning in fiscal year 2016, the Company enacted a policy that allows any non-employee directors who have Beacon equity holdings (defined as common stock and outstanding vested equity awards) with a total fair value that is greater than or equal to five times the annual Board cash retainer to elect to have any future RSU grants settle simultaneously with vesting. The following table summarizes all restricted stock unit activity for the three months ended December 31, 2020 (in millions, except per share amounts): RSUs Outstanding Weighted-Average Grant Date Fair Value Balance as of September 30, 2020 1.2 $ 33.55 Granted 0.3 36.07 Released (0.2 ) 45.02 Canceled/Forfeited (0.2 ) 28.67 Balance as of December 31, 2020 1.1 $ 32.93 Vested and expected to vest after December 31, 2020 1.0 $ 32.95 During the three months ended December 31, 2020 and 2019, the Company recorded stock-based compensation expense related to restricted stock units of $2.7 million and $3.7 million, respectively. As of December 31, 2020, there was $20.8 million of unrecognized compensation cost related to unvested restricted stock units, which is expected to be recognized over a weighted-average period of 2.0 years. The following table summarizes additional information on RSUs (in millions, except per share amounts): Three Months Ended December 31, 2020 2019 Weighted-average fair value of RSUs granted $ 36.07 $ 33.47 Total grant date fair value of RSUs vested $ 11.3 $ 8.1 Total intrinsic value of RSUs released $ 9.5 $ 6.8

Goodwill and Intangible Assets

Goodwill and Intangible Assets	3 Months Ended
	Dec. 31, 2020
Goodwill And Intangible Assets Disclosure [Abstract]
Goodwill and Intangible Assets	7. Goodwill and Intangible Assets Goodwill The following table sets forth the change in the carrying amount of goodwill during the three months ended December 31, 2020 and 2019, respectively (in millions): Balance as of September 30, 2020 $ 1,756.1 Translation and other adjustments 1.4 Balance as of December 31, 2020 $ 1,757.5 Balance as of September 30, 2019 $ 1,756.3 Translation and other adjustments 0.6 Balance as of December 31, 2019 $ 1,756.9 The changes in the carrying amount of goodwill for the three months ended December 31, 2020 and 2019 were driven primarily by foreign currency translation adjustments. Intangible Assets The following table summarizes intangible assets by category (in millions, except time period amounts): December 31, 2020 September 30, 2020 December 31, 2019 Weighted-Average Remaining Life 1 (Years) Amortizable intangible assets: Non-compete agreements $ 0.2 $ 0.2 $ 2.8 1.4 Customer relationships 1,085.9 1,085.5 1,135.5 16.1 Trademarks 3.7 3.7 7.0 6.3 Total amortizable intangible assets 1,089.8 1,089.4 1,145.3 Accumulated amortization (607.0 ) (581.2 ) (544.2 ) Total amortizable intangible assets, net 482.8 508.2 601.1 Indefinite-lived trademarks 9.8 9.8 146.8 Total intangibles, net $ 492.6 $ 518.0 $ 747.9 _________________________________________ 1 As of December 31, 2020. In the second quarter of fiscal year 2020, in connection with the Rebranding, the Company incurred non-cash accelerated intangible asset amortization of $142.6 million related to the write-off of certain trade names, primarily Allied (exterior products only), Roofing Supply Group and JGA. The Company used an income approach, specifically the relief from royalty method, to determine the fair value of remaining indefinite-lived trademarks. Various Level 3 fair value assumptions were used in the determination of the estimated fair value, including items such as sales growth rates, royalty rates, discount rates, and other prospective financial information. During the three months ended December 31, 2020 and 2019, the Company recorded $25.5 million and $32.1 million of amortization expense relating to the above-listed intangible assets, respectively. The intangible asset lives range from 5 to 20 years and have a weighted-average remaining life of 16.1 years as of December 31, 2020. The following table summarizes the estimated future amortization expense for intangible assets (in millions): Year Ending September 30, 2021 (Jan - Sept) $ 75.7 2022 82.4 2023 66.6 2024 53.4 2025 43.2 Thereafter 161.5 Total future amortization expense $ 482.8

Financing Arrangements

Financing Arrangements	3 Months Ended
	Dec. 31, 2020
Debt Disclosure [Abstract]
Financing Arrangements	8. Financing Arrangements The following table summarizes all outstanding debt (presented net of unamortized debt issuance costs) and other financing arrangements (in millions): December 31, 2020 September 30, 2020 December 31, 2019 Revolving Lines of Credit 2023 ABL: U.S. Revolver 1 $ 151.7 $ 251.1 $ 209.5 Canada Revolver 2 — — 6.1 Current portion — — — Borrowings under revolving lines of credit, net $ 151.7 $ 251.1 $ 215.6 Long-term Debt, net Term Loan: 2025 Term Loan 3 $ 921.3 $ 922.3 $ 925.5 Current portion (9.7 ) (9.7 ) (9.7 ) Long-term borrowings under term loan 911.6 912.6 915.8 Senior Notes: 2025 Senior Notes 4 1,286.4 1,285.7 1,283.6 2026 Senior Notes 5 296.1 295.9 295.7 Current portion — — — Long-term borrowings under senior notes 1,582.5 1,581.6 1,579.3 Long-term debt, net $ 2,494.1 $ 2,494.2 $ 2,495.1 Equipment Financing Facilities, net Equipment financing facilities 6 $ 1.6 $ 2.6 $ 5.8 Current portion (1.6 ) (2.6 ) (4.2 ) Long-term obligations under equipment financing, net $ — $ — $ 1.6 ____________________________________________________________ 1 2 3 4 5 6 Debt Refinancing 2026 Senior Notes On October 9, 2019, the Company, and certain subsidiaries of the Company as guarantors, executed a private offering of $300.0 million aggregate principal amount of 4.50% Senior Notes due 2026 (the “2026 Senior Notes”) at an issue price of 100%. The 2026 Senior Notes mature on November 15, 2026 and bear interest at a rate of 4.50% per annum, payable on May 15 and November 15 of each year, commencing on May 15, 2020. The 2026 Senior Notes and related subsidiary guarantees were offered and sold in a private transaction exempt from the registration requirements of the Securities Act of 1933, as amended (the “Securities Act”), to qualified institutional buyers in accordance with Rule 144A under the Securities Act and to non-U.S. persons outside of the United States pursuant to Regulation S under the Securities Act. The 2026 Senior Notes and related subsidiary guarantees have not been, and will not be, registered under the Securities Act or the securities laws of any state or other jurisdiction, and may not be offered or sold in the United States absent registration or an applicable exemption from the registration requirements of the Securities Act and other applicable securities laws. On October 28, 2019, the Company used the net proceeds from the offering, together with cash on hand and available borrowings under the 2023 ABL (as defined below), to redeem all $300.0 million aggregate principal amount outstanding of the 2023 Senior Notes (as defined below) at a redemption price of 103.188% and to pay all related accrued interest, fees and expenses. The intent of the transaction was to take advantage of lower market interest rates by refinancing the existing 2023 Senior Notes with the 2026 Senior Notes. The Company accounted for the refinance as a debt extinguishment of the 2023 Senior Notes and an issuance of the 2026 Senior Notes. As a result, the Company recorded a loss on debt extinguishment of $14.7 million in the three months ended December 31, 2019 . T he Company has capitalized debt issuance costs of $ million related to the 2026 Senior Notes , which are being amortized over the term of the financing arrangements. As of December 31, 2020, the outstanding balance on the 2026 Senior Notes, net of $3.9 million of unamortized debt issuance costs, was $296.1 million. Financing - Allied Acquisition In connection with the Allied Acquisition, the Company entered into various financing arrangements totaling $3.57 billion, including an asset-based revolving line of credit of $1.30 billion (“2023 ABL”), $525.0 million of which was drawn at closing, and a $970.0 million term loan (“2025 Term Loan”). The Company also raised an additional $1.30 billion through the issuance of senior notes (the “2025 Senior Notes”). The proceeds from these financing arrangements were used to finance the Allied Acquisition, to refinance or otherwise extinguish all third-party indebtedness, to pay fees and expenses associated with the acquisition, and to provide working capital and funds for other general corporate purposes. The Company capitalized new debt issuance costs totaling approximately $65.3 million related to the 2023 ABL, the 2025 Term Loan and the 2025 Senior Notes, which are being amortized over the term of the financing arrangements. 2023 ABL On January 2, 2018, the Company entered into a $1.30 billion asset-based revolving line of credit with Wells Fargo Bank, N.A. and a syndicate of other lenders. The 2023 ABL, as amended to date, provides for revolving loans in both the United States (“2023 U.S. Revolver”) in an amount up to $1.25 billion and Canada (“2023 Canada Revolver”) in an amount up to $50.0 million, in each case subject to a borrowing base. The 2023 ABL has a maturity date of January 2, 2023. The 2023 ABL has various borrowing tranches with an interest rate based, at the Company’s option, on a base rate, plus an applicable margin, or a reserve adjusted LIBOR rate, plus an applicable margin. The applicable margin ranges from 0.25% to 0.75% per annum with respect to base rate borrowings and from 1.25% to 1.75% per annum with respect to LIBOR borrowings. The current unused commitment fees on the 2023 ABL are 0.25% per annum. On July 28, 2020, the Company amended the 2023 ABL to provide for, among other things, a mechanism for replacing LIBOR with the secured overnight financing rate published by the Federal Reserve Bank of New York or other alternate benchmark rate selected by the administrative agent and the Company. There is one financial covenant under the 2023 ABL, which is the Fixed Charge Coverage Ratio (the “FCCR”). The FCCR is calculated by dividing Consolidated EBITDA, less Capital Expenditures, by Consolidated Fixed Charges (all terms as defined in the agreement). Per the covenant, the Company’s FCCR must be a minimum of 1.00 at the end of each fiscal quarter, calculated on a trailing four quarter basis (or under certain circumstances, at the end of each fiscal month, calculated on a trailing twelve-month basis). Compliance is only required at such times as borrowing availability (subject to certain adjustments) is less than the greater of (i) 10% of the lesser of the borrowing base or the aggregate commitments or (ii) $90.0 million, and for a period of thirty days thereafter. The Company was in compliance with this covenant as of December 31, 2020. The 2023 ABL is secured by a first priority lien over substantially all of the Company’s and each guarantor’s accounts, chattel paper, deposit accounts, books, records and inventory (as well as intangibles related thereto), subject to certain customary exceptions (the “ABL Priority Collateral”), and a second priority lien over substantially all of the Company’s and each guarantor’s other assets, including all of the equity interests of any subsidiary held by the Company or any guarantor, subject to certain customary exceptions (the “Term Priority Collateral”). The 2023 ABL is guaranteed jointly, severally, fully and unconditionally by the Company’s active United States subsidiaries. As of December 31, 2020, the total balance outstanding on the 2023 ABL, net of $5.3 million of unamortized debt issuance costs, was $151.7 million. The Company also has outstanding standby letters of credit related to the 2023 U.S. Revolver in the amount of $12.8 million as of December 31, 2020. 2025 Term Loan On January 2, 2018, the Company entered into a $970.0 million Term Loan with Citibank N.A., and a syndicate of other lenders. The 2025 Term Loan requires quarterly principal payments in the amount of $2.4 million, with the remaining outstanding principal to be paid on its January 2, 2025 maturity date. The interest rate is based, at the Company’s option, on a base rate, plus an applicable margin, or a reserve adjusted LIBOR rate, plus an applicable margin. The applicable margin is 1.25% per annum with respect to base rate borrowings and 2.25% per annum with respect to LIBOR borrowings. The Company has the option of selecting a LIBOR period that determines the rate at which interest can accrue on the Term Loan as well as the period in which interest payments are made. The 2025 Term Loan is secured by a first priority lien on the Term Priority Collateral and a second priority lien on the ABL Priority Collateral. Certain excluded assets will not be included in the Term Priority Collateral and the ABL Priority Collateral. The Term Loan is guaranteed jointly, severally, fully and unconditionally by the Company’s active United States subsidiaries. As of December 31, 2020 , the outstanding balance on the 2025 Term Loan, net of $22.0 million of unamortized debt issuance costs, was $921.3 million . 2025 Senior Notes On October 25, 2017, Beacon Escrow Corporation, a wholly owned subsidiary of the Company (the “Escrow Issuer”), completed a private offering of $1.30 billion aggregate principal amount of 4.875% Senior Notes due 2025 at an issue price of 100%. The 2025 Senior Notes bear interest at a rate of 4.875% per annum, payable semi-annually in arrears, beginning May 1, 2018. The Company anticipates repaying the 2025 Senior Notes at the maturity date of November 1, 2025. Per the terms of the Escrow Agreement, the net proceeds from the 2025 Senior Notes remained in escrow until they were used to fund a portion of the purchase price of the Allied Acquisition payable at closing on January 2, 2018. Upon closing of the Allied Acquisition on January 2, 2018, (i) the Escrow Issuer merged with and into the Company, and the Company assumed all obligations under the 2025 Senior Notes; and (ii) all existing domestic subsidiaries of the Company (including the entities acquired in the Allied Acquisition) became guarantors of the 2025 Senior Notes. As of December 31, 2020, the outstanding balance on the 2025 Senior Notes, net of $13.6 million of unamortized debt issuance costs, was $1.29 billion. Financing - RSG Acquisition 2023 Senior Notes On October 1, 2015, in connection with the acquisition of Roofing Supply Group, the Company raised $300.0 million by issuing 6.38% Senior Notes due 2023 (the “2023 Senior Notes”). The 2023 Senior Notes had a coupon rate of 6.38% per annum and were payable semi-annually in arrears, beginning April 1, 2016. There were early payment provisions in the indenture under which the Company would be subject to redemption premiums. On October 28, 2019, the Company redeemed all $300.0 million aggregate principal amount outstanding of the 2023 Senior Notes at a redemption price of 103.188% plus accrued interest and, as a result, wrote off $5.1 million of unamortized debt issuance costs. Equipment Financing Facilities As of December 31, 2020, the Company had $1.6 million outstanding under equipment financing facilities, with fixed interest rates ranging from 2.33% to 2.89% and payments due through September 2021

Leases

Leases	3 Months Ended
	Dec. 31, 2020
Leases [Abstract]
Leases	9. Leases The following table summarizes components of operating lease costs recognized within selling, general and administrative expenses (in millions): Three Months Ended December 31, 2020 2019 Operating lease costs $ 25.7 $ 26.5 Variable lease costs 2.3 2.2 Total operating lease costs $ 28.0 $ 28.7 The following table presents supplemental cash flow information related to operating leases (in millions): Three Months Ended December 31, 2020 Operating cash flows for operating lease liabilities $ 24.4 As of December 31, 2020, the Company’s operating leases had a weighted-average remaining lease term of 5.7 years and a weighted-average discount rate of 3.81% The following table summarizes future lease payments under operating leases as of December 31, 2020 (in millions): Year Ending September 30, 2021 (Jan - Sept) $ 72.7 2022 88.0 2023 73.3 2024 59.2 2025 37.2 Thereafter 81.4 Total future lease payments 411.8 Imputed interest (41.2 ) Total operating lease liabilities $ 370.6

Commitments and Contingencies

Commitments and Contingencies	3 Months Ended
	Dec. 31, 2020
Commitments And Contingencies Disclosure [Abstract]
Commitments and Contingencies	10. Commitments and Contingencies The Company is subject to loss contingencies pursuant to various federal, state and local environmental laws and regulations; however, the Company is not aware of any reasonably possible losses that would have a material impact on its results of operations, financial position, or liquidity. Potential loss contingencies include possible obligations to remove or mitigate the effects on the environment of the placement, storage, disposal or release of certain chemical or other substances by the Company or by other parties. In connection with its acquisitions, the Company’s practice is to request indemnification for any and all known material liabilities of significance as of the respective dates of acquisition. Historically, environmental liabilities have not had a material impact on the Company’s results of operations, financial position or liquidity. The Company is subject to litigation from time to time in the ordinary course of business; however, the Company does not expect the results, if any, to have a material adverse impact on its results of operations, financial position or liquidity.

Accumulated Other Comprehensive

Accumulated Other Comprehensive Income (Loss)	3 Months Ended
	Dec. 31, 2020
Equity [Abstract]
Accumulated Other Comprehensive Income (Loss)	11. Accumulated Other Comprehensive Income (Loss) Other comprehensive income (loss) is composed of certain gains and losses that are excluded from net income under GAAP and instead recorded as a separate element of stockholders’ equity. The following table summarizes the components of and changes in accumulated other comprehensive loss (in millions): Foreign Derivative Currency Translation Financial Instruments AOCI Balance as of September 30, 2020 $ (19.7 ) $ (15.0 ) $ (34.7 ) Other comprehensive income before reclassifications 3.9 1.6 5.5 Reclassifications out of other comprehensive loss — — — Balance as of December 31, 2020 $ (15.8 ) $ (13.4 ) $ (29.2 ) Gains (losses) on derivative instruments are recognized in the consolidated statements of operations in interest expense, financing costs, and other.

Geographic Data

Geographic Data	3 Months Ended
	Dec. 31, 2020
Segment Reporting [Abstract]
Geographic Data	12. Geographic Data The following table summarizes certain geographic information (in millions): December 31, 2020 September 30, 2020 December 31, 2019 Long-lived assets: U.S. $ 683.9 $ 708.2 $ 799.5 Canada 10.5 9.9 12.0 Total long-lived assets $ 694.4 $ 718.1 $ 811.5

Fair Value Measurement

Fair Value Measurement	3 Months Ended
	Dec. 31, 2020
Fair Value Disclosures [Abstract]
Fair Value Measurement	13. Fair Value Measurement As of December 31, 2020, the carrying amount of cash and cash equivalents, accounts receivable, prepaid and other current assets, accounts payable and accrued expenses approximated fair value because of the short-term nature of these instruments. The Company measures its cash equivalents at amortized cost, which approximates fair value based upon quoted market prices (Level 1). As of December 31, 2020, based upon recent trading prices (Level 2), the fair value of the Company’s $300.0 million Senior Notes due in 2026 was $314.3 million and the fair value of the $1.30 billion Senior Notes due 2025 was $1.33 billion. As of December 31, 2020, the fair value of the Company’s term loan and revolving lines of credit approximated the amount outstanding. The Company estimates the fair value of its term loan and revolving lines of credit by discounting the future cash flows of each instrument using estimated market rates of debt instruments with similar maturities and credit profiles (Level 3).

Financial Derivatives

Financial Derivatives	3 Months Ended
	Dec. 31, 2020
Derivative Instruments And Hedging Activities Disclosure [Abstract]
Financial Derivatives	14. Financial Derivatives The Company uses interest rate derivative instruments to manage the risk related to fluctuating cash flows from interest rate changes by converting a portion of its variable-rate borrowings into fixed-rate borrowings. On September 11, 2019, the Company entered into two interest rate swap agreements to manage the interest rate risk associated with the variable rate on the 2025 Term Loan. Each swap agreement has a notional amount of $250 million. One agreement (the “5-year swap”) will expire on August 30, 2024 and swaps the thirty-day LIBOR with a fixed-rate of 1.49%. The second agreement (the “3-year swap”) will expire on August 30, 2022 and swaps the thirty-day LIBOR with a fixed-rate of 1.50%. At the inception of the swap agreements, the Company determined that both swaps qualified for cash flow hedge accounting under ASC 815. Therefore, changes in the fair value of the effective portions of the swaps, net of taxes, will be recognized in other comprehensive income each period, then reclassified into the consolidated statements of operations as a component of interest expense, financing costs, and other in the period in which the hedged transaction affects earnings. Any ineffective portions of the hedges are immediately recognized in earnings as a component of interest expense, financing costs and other. The effectiveness of the swaps will be assessed qualitatively by the Company during the lives of the hedges by a) comparing the current terms of the hedges with the related hedged debt to assure they continue to coincide and b) through an evaluation of the ability of the counterparty to the hedges to honor their obligations under the hedges. The Company performed a qualitative analysis as of December 31, 2020 and concluded that the swap agreements continue to meet the requirements under ASC 815 to qualify for cash flow hedge accounting. As of December 31, 2020, the fair value of the 3‑year and 5‑year swaps, net of tax, were $4.4 million and $9.0 million, respectively, both in favor of the counterparty. These amounts are included in accrued expenses in the accompanying consolidated balance sheets. The Company records any differences paid or received on its interest rate hedges to interest expense, financing costs and other. The following table summarizes the combined fair values, net of tax, of the interest rate derivative instruments (in millions): Instrument Fair Value Hierarchy December 31, 2020 September 30, 2020 December 31, 2019 Designated interest rate swaps 1 Level 2 $ (13.4 ) $ (15.0 ) $ 0.9 _______________________ 1 Assets are included on the consolidated balance sheets in prepaid expenses and other current assets, while liabilities are included in accrued expenses. The fair value of the interest rate swaps is determined through the use of a pricing model, which utilizes verifiable inputs such as market interest rates that are observable at commonly quoted intervals (generally referred to as the “LIBOR Curve”) for the full terms of the hedge agreements. These values reflect a Level 2 measurement under the applicable fair value hierarchy. The following table summarizes the amounts of gain (loss) on the interest rate derivative instruments recognized in other comprehensive income (in millions): Three Months Ended December 31, Instrument 2020 2019 Designated interest rate swaps $ 1.6 $ 2.5

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	3 Months Ended
	Dec. 31, 2020
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The Company prepared the condensed consolidated financial statements in accordance with U.S. generally accepted accounting principles (“GAAP”) for interim financial information and the requirements of the Securities and Exchange Commission (“SEC”). As permitted under those rules, certain footnotes or other financial information have been condensed or omitted. Additionally, beginning with the condensed consolidated financial statements for the three months ended December 31, 2020, the Company has reflected Interior Products as discontinued operations for all periods presented. Unless otherwise noted, amounts and disclosures throughout these Notes to Condensed Consolidated Financial Statements relate to the Company's continuing operations. Certain prior period amounts have been reclassified to conform to current period presentation. The balance sheet as of December 31, 2019 has been presented for a better understanding of the impact of seasonal fluctuations on the Company’s financial condition. In management’s opinion, the financial statements include all normal and recurring adjustments that are considered necessary for the fair presentation of the Company’s financial position and operating results. The results for the three months ended December 31, 2020 are not necessarily indicative of the results to be expected for the twelve months ending September 30, 2021. The three-month periods ended each These interim Condensed Consolidated Financial Statements should be read in conjunction with the audited Consolidated Financial Statements and Notes thereto contained in the Company’s fiscal year 2020 (“2020”) Annual Report on Form 10-K for the year ended September 30, 2020.
Use of Estimates	Use of Estimates The preparation of consolidated financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the amounts reported in these consolidated financial statements and accompanying notes. Significant items subject to such estimates include accounts receivable, inventories, purchase price allocations, goodwill and intangibles, and income taxes. Assumptions made in the development of these estimates contemplate the impact of the novel coronavirus (“COVID‑19”) on the economy and the Company’s anticipated results; however, actual amounts could differ materially from these estimates.
Recent Accounting Pronouncements - Adopted and Not Yet Adopted	Recent Accounting Pronouncements—Adopted In June 2016, the FASB issued ASU 2016-13, “ Financial Instruments—Credit Losses: Measurement of Credit Losses on Financial Instruments In January 2017, the FASB issued ASU 2017-04, “ Simplifying the Accounting for Goodwill Impairment.” Recent Accounting Pronouncements—Not Yet Adopted In December 2019, the FASB issued ASU 2019-12, “Income Taxes – Simplifying the Accounting for Income Taxes.” In March 2020, the FASB issued ASU 2020-04, “ Reference Rate Reform (Topic 848), Facilitation of the Effects of Reference Rate Reform on Financial Reporting Reference Rate Reform (Topic 848), Scope

Discontinued Operations (Tables

Discontinued Operations (Tables)	3 Months Ended
	Dec. 31, 2020
Discontinued Operations And Disposal Groups [Abstract]
Schedule of Reconciliation of Major Line Items Constituting Pretax Income (Loss) from Discontinued Operations to Net Income (Loss) from Discontinued Operations	The following table reconciles major line items constituting pretax income (loss) from discontinued operations to net income (loss) from discontinued operations as presented in the condensed consolidated statements of operations (in millions): Three Months Ended December 31, 2020 2019 Net sales $ 248.8 $ 259.8 Cost of products sold (183.8 ) (189.2 ) Selling, general and administrative (56.9 ) (53.7 ) Depreciation and amortization (12.9 ) (16.0 ) Other income (loss) 0.1 0.2 Loss on classification as held for sale (355.4 ) — Pretax income (loss) from discontinued operations (360.1 ) 1.1 Provision for (benefit from) income taxes (92.2 ) 0.5 Net income (loss) from discontinued operations $ (267.9 ) $ 0.6
Schedule of Reconciliation of Carrying Amounts of Major Classes of Assets and Liabilities of Discontinued Operations to Total Assets	The following table reconciles the carrying amounts of major classes of assets and liabilities of discontinued operations to total assets and liabilities of discontinued operations that are classified as held for sale in the condensed consolidated balance sheets (in millions): December 31, September 30, December 31, 2020 2020 2019 Carrying amounts of major classes of assets held for sale: Accounts receivable, net $ 130.6 $ 144.1 $ 144.6 Inventories, net 82.4 73.2 91.1 Prepaid expenses and other current assets 30.7 26.5 32.0 Total current assets 243.8 267.7 Property and equipment, net 35.8 35.9 42.6 Goodwill 378.9 734.3 734.3 Intangibles, net 273.1 283.2 329.6 Operating lease assets 65.5 67.1 67.2 Total non-current assets 1,120.5 1,173.7 Total assets held for sale 1 $ 997.0 $ 1,364.3 $ 1,441.4 Carrying amounts of major classes of liabilities held for sale: Accounts payable $ 52.6 $ 68.8 $ 52.4 Accrued expenses 56.3 54.1 54.8 Current operating lease liabilities 16.2 16.5 15.9 Total current liabilities 139.4 123.1 Deferred income taxes, net — 2.2 7.4 Non-current operating lease liabilities 48.9 49.9 50.0 Other long-term liabilities 1.1 1.3 1.6 Total non-current liabilities 53.4 59.0 Total liabilities held for sale 1 $ 175.1 $ 192.8 $ 182.1 __________________________________________________ 1

Net Sales (Tables)

Net Sales (Tables)	3 Months Ended
	Dec. 31, 2020
Revenue From Contract With Customer [Abstract]
Summary of Net Sales by Product Line and Geography	The following table presents the Company’s net sales by product line and geography (in millions): U.S. Canada Total Three Months Ended December 31, 2020 Residential roofing products $ 831.3 $ 13.5 $ 844.8 Non-residential roofing products 366.1 32.2 398.3 Complementary building products 331.0 2.4 333.4 Total net sales $ 1,528.4 $ 48.1 $ 1,576.5 Three Months Ended December 31, 2019 Residential roofing products $ 685.9 $ 10.9 $ 696.8 Non-residential roofing products 379.6 32.4 412.0 Complementary building products 304.3 2.2 306.5 Total net sales $ 1,369.8 $ 45.5 $ 1,415.3

Net Income (Loss) Per Share (Ta

Net Income (Loss) Per Share (Tables)	3 Months Ended
	Dec. 31, 2020
Earnings Per Share [Abstract]
Components and Calculation of Basic and Diluted Net Income (Loss) Per Share	The following table presents the components and calculations of basic and diluted net income (loss) per share (in millions, except per share amounts): Three Months Ended December 31, 2020 2019 Net income (loss) $ (220.5 ) $ (23.4 ) Dividends on Preferred Stock 6.0 6.0 Net income (loss) attributable to common shareholders (226.5 ) (29.4 ) Undistributed income allocated to participating securities — — Net income (loss) attributable to common shareholders - basic and diluted (226.5 ) (29.4 ) Net income (loss) from discontinued operations attributable to common shareholders - basic and diluted (267.9 ) 0.6 Net income (loss) from continuing operations attributable to common shareholders - basic and diluted $ 41.4 $ (30.0 ) Weighted-average common shares outstanding - basic 69.2 68.7 Effect of common share equivalents 0.8 — Weighted-average common shares outstanding - diluted 70.0 68.7 Net income (loss) per share: Basic - Continuing operations $ 0.60 $ (0.44 ) Basic - Discontinued operations (3.87 ) 0.01 Basic net income (loss) per share $ (3.27 ) $ (0.43 ) Diluted - Continuing operations $ 0.59 $ (0.44 ) Diluted - Discontinued operations (3.83 ) 0.01 Diluted net income (loss) per share $ (3.24 ) $ (0.43 )
Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share	The following table includes the number of shares that may be dilutive common shares in the future. These shares were not included in the computation of diluted net income (loss) per share because the effect was either anti-dilutive or the requisite performance conditions were not met (in millions): Three Months Ended December 31, 2020 2019 Stock options 1.3 1.9 Restricted stock units — 0.4 Preferred Stock 9.7 9.7

Stock-based Compensation (Table

Stock-based Compensation (Tables)	3 Months Ended
	Dec. 31, 2020
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Fair Values of Options, Black-Scholes Option-Pricing Model, Weighted-Average Assumptions	The fair values of the options granted for the three months ended December 31, 2020 were estimated on the dates of grants using the Black-Scholes option-pricing model with the following weighted-average assumptions: Risk-free interest rate 0.44 % Expected volatility 48.15 % Expected life (in years) 5.36 Dividend yield —
Stock Options Outstanding and Activity During the Period	The following table summarizes all stock option activity for the three months ended December 31, 2020 (in millions, except per share and time period amounts): Options Outstanding Weighted- Average Exercise Price Weighted- Average Remaining Contractual Term (Years) Aggregate Intrinsic Value 1 Balance as of September 30, 2020 2.5 $ 33.09 5.9 $ 6.9 Granted 0.3 35.78 Exercised (0.3 ) 26.93 Canceled/Forfeited (0.0 ) 45.99 Expired (0.0 ) 15.47 Balance as of December 31, 2020 2.5 $ 33.98 6.4 $ 19.9 Vested and expected to vest after December 31, 2020 2.4 $ 34.00 6.3 $ 19.6 Exercisable as of December 31, 2020 1.7 $ 34.86 5.1 $ 13.4 ______________________________________________________ 1
Stock Option Grants, Vesting, and Exercises	The following table summarizes additional information on stock options (in millions, except per share amounts): Three Months Ended December 31, 2020 2019 Weighted-average fair value of stock options granted $ 15.62 $ 10.70 Total grant date fair value of stock options vested $ 4.1 $ 3.9 Total intrinsic value of stock options exercised $ 2.6 $ 0.7
Restricted Shares and Units Outstanding and Activity During the Period	The following table summarizes all restricted stock unit activity for the three months ended December 31, 2020 (in millions, except per share amounts): RSUs Outstanding Weighted-Average Grant Date Fair Value Balance as of September 30, 2020 1.2 $ 33.55 Granted 0.3 36.07 Released (0.2 ) 45.02 Canceled/Forfeited (0.2 ) 28.67 Balance as of December 31, 2020 1.1 $ 32.93 Vested and expected to vest after December 31, 2020 1.0 $ 32.95
Schedule Of Restricted Stock Units Additional Information	The following table summarizes additional information on RSUs (in millions, except per share amounts): Three Months Ended December 31, 2020 2019 Weighted-average fair value of RSUs granted $ 36.07 $ 33.47 Total grant date fair value of RSUs vested $ 11.3 $ 8.1 Total intrinsic value of RSUs released $ 9.5 $ 6.8

Goodwill and Intangible Assets

Goodwill and Intangible Assets (Tables)	3 Months Ended
	Dec. 31, 2020
Goodwill And Intangible Assets Disclosure [Abstract]
Summary of Changes in goodwill	The following table sets forth the change in the carrying amount of goodwill during the three months ended December 31, 2020 and 2019, respectively (in millions): Balance as of September 30, 2020 $ 1,756.1 Translation and other adjustments 1.4 Balance as of December 31, 2020 $ 1,757.5 Balance as of September 30, 2019 $ 1,756.3 Translation and other adjustments 0.6 Balance as of December 31, 2019 $ 1,756.9
Summary of Intangible Assets	The following table summarizes intangible assets by category (in millions, except time period amounts): December 31, 2020 September 30, 2020 December 31, 2019 Weighted-Average Remaining Life 1 (Years) Amortizable intangible assets: Non-compete agreements $ 0.2 $ 0.2 $ 2.8 1.4 Customer relationships 1,085.9 1,085.5 1,135.5 16.1 Trademarks 3.7 3.7 7.0 6.3 Total amortizable intangible assets 1,089.8 1,089.4 1,145.3 Accumulated amortization (607.0 ) (581.2 ) (544.2 ) Total amortizable intangible assets, net 482.8 508.2 601.1 Indefinite-lived trademarks 9.8 9.8 146.8 Total intangibles, net $ 492.6 $ 518.0 $ 747.9 _________________________________________ 1 As of December 31, 2020.
Summary of Estimated Future Amortization	The following table summarizes the estimated future amortization expense for intangible assets (in millions): Year Ending September 30, 2021 (Jan - Sept) $ 75.7 2022 82.4 2023 66.6 2024 53.4 2025 43.2 Thereafter 161.5 Total future amortization expense $ 482.8

Financing Arrangements (Tables)

Financing Arrangements (Tables)	3 Months Ended
	Dec. 31, 2020
Debt Disclosure [Abstract]
Schedule of Outstanding Debt Presented Net of Unamortized debt Issuance Costs and Other Financing Arrangements	The following table summarizes all outstanding debt (presented net of unamortized debt issuance costs) and other financing arrangements (in millions): December 31, 2020 September 30, 2020 December 31, 2019 Revolving Lines of Credit 2023 ABL: U.S. Revolver 1 $ 151.7 $ 251.1 $ 209.5 Canada Revolver 2 — — 6.1 Current portion — — — Borrowings under revolving lines of credit, net $ 151.7 $ 251.1 $ 215.6 Long-term Debt, net Term Loan: 2025 Term Loan 3 $ 921.3 $ 922.3 $ 925.5 Current portion (9.7 ) (9.7 ) (9.7 ) Long-term borrowings under term loan 911.6 912.6 915.8 Senior Notes: 2025 Senior Notes 4 1,286.4 1,285.7 1,283.6 2026 Senior Notes 5 296.1 295.9 295.7 Current portion — — — Long-term borrowings under senior notes 1,582.5 1,581.6 1,579.3 Long-term debt, net $ 2,494.1 $ 2,494.2 $ 2,495.1 Equipment Financing Facilities, net Equipment financing facilities 6 $ 1.6 $ 2.6 $ 5.8 Current portion (1.6 ) (2.6 ) (4.2 ) Long-term obligations under equipment financing, net $ — $ — $ 1.6 ____________________________________________________________ 1 2 3 4 5 6

Leases (Tables)

Leases (Tables)	3 Months Ended
	Dec. 31, 2020
Leases [Abstract]
Components of Operating Lease Costs Recognized Within Selling, General and Administrative Expenses	The following table summarizes components of operating lease costs recognized within selling, general and administrative expenses (in millions): Three Months Ended December 31, 2020 2019 Operating lease costs $ 25.7 $ 26.5 Variable lease costs 2.3 2.2 Total operating lease costs $ 28.0 $ 28.7
Summary of Supplemental Cash Flow Information Related to Operating Leases	The following table presents supplemental cash flow information related to operating leases (in millions): Three Months Ended December 31, 2020 Operating cash flows for operating lease liabilities $ 24.4
Summary of Future Lease Payments Under Operating Leases	The following table summarizes future lease payments under operating leases as of December 31, 2020 (in millions): Year Ending September 30, 2021 (Jan - Sept) $ 72.7 2022 88.0 2023 73.3 2024 59.2 2025 37.2 Thereafter 81.4 Total future lease payments 411.8 Imputed interest (41.2 ) Total operating lease liabilities $ 370.6

Accumulated Other Comprehensi_2

Accumulated Other Comprehensive Income (Loss) (Tables)	3 Months Ended
	Dec. 31, 2020
Equity [Abstract]
Reclassification out of Accumulated Other Comprehensive Income	The following table summarizes the components of and changes in accumulated other comprehensive loss (in millions): Foreign Derivative Currency Translation Financial Instruments AOCI Balance as of September 30, 2020 $ (19.7 ) $ (15.0 ) $ (34.7 ) Other comprehensive income before reclassifications 3.9 1.6 5.5 Reclassifications out of other comprehensive loss — — — Balance as of December 31, 2020 $ (15.8 ) $ (13.4 ) $ (29.2 )

Geographic Data (Tables)

Geographic Data (Tables)	3 Months Ended
	Dec. 31, 2020
Segment Reporting [Abstract]
Schedule of Geographic Information	The following table summarizes certain geographic information (in millions): December 31, 2020 September 30, 2020 December 31, 2019 Long-lived assets: U.S. $ 683.9 $ 708.2 $ 799.5 Canada 10.5 9.9 12.0 Total long-lived assets $ 694.4 $ 718.1 $ 811.5

Financial Derivatives (Tables)

Financial Derivatives (Tables)	3 Months Ended
	Dec. 31, 2020
Derivative Instruments And Hedging Activities Disclosure [Abstract]
Summary of Combined Fair Values, Net of Tax of Interest Rate Derivative Instruments	The Company records any differences paid or received on its interest rate hedges to interest expense, financing costs and other. The following table summarizes the combined fair values, net of tax, of the interest rate derivative instruments (in millions): Instrument Fair Value Hierarchy December 31, 2020 September 30, 2020 December 31, 2019 Designated interest rate swaps 1 Level 2 $ (13.4 ) $ (15.0 ) $ 0.9 _______________________ 1 Assets are included on the consolidated balance sheets in prepaid expenses and other current assets, while liabilities are included in accrued expenses.
Summary of Amounts of Gain (Loss) on Interest Rate Derivative Instruments Recognized in Other Comprehensive Income	The following table summarizes the amounts of gain (loss) on the interest rate derivative instruments recognized in other comprehensive income (in millions): Three Months Ended December 31, Instrument 2020 2019 Designated interest rate swaps $ 1.6 $ 2.5

Company Overview - Additional I

Company Overview - Additional Information (Detail) $ in Millions	Dec. 20, 2020USD ($)	Dec. 31, 2020StateProvince
Company Overview [Line Items]
Date of incorporation		Aug. 22, 1997
Stock Purchase Agreement [Member] | Interior Products [Member] | ASP Sailor Acquisition Corp [Member]
Company Overview [Line Items]
Purchase price of outstanding equity interests payable in cash | $	$ 850
U.S. [Member]
Company Overview [Line Items]
Number of states in which entity operates | State		50
Canada [Member]
Company Overview [Line Items]
Number of provinces in which entity operates | Province		6

Summary of Significant Accoun_3

Summary of Significant Accounting Policies - Additional Information (Detail) - Accounting Standards Update 2016-13 [Member] - Restatement Adjustment [Member] $ in Millions	Oct. 01, 2020USD ($)
Significant Accounting Policies [Line Items]
Accounts receivable reserve	$ 4.3
Retained earnings adjustment	$ 4.3

Discontinued Operations - Addit

Discontinued Operations - Additional Information (Detail) - Interior Products [Member] - USD ($) $ in Millions	Dec. 20, 2020	Dec. 31, 2020
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Loss on classification as held for sale		$ 355.4
Consolidated goodwill balance included in carrying value of net assets		$ 734.3
Stock Purchase Agreement [Member] | ASP Sailor Acquisition Corp [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Purchase price of outstanding equity interests payable in cash	$ 850

Discontinued Operations - Sched

Discontinued Operations - Schedule of Reconciliation of Major Line Items Constituting Pretax Income (Loss) from Discontinued Operations to Net Income (Loss) from Discontinued Operations (Detail) - Interior Products [Member] - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Disposal Group Including Discontinued Operation Income Statement Disclosures [Line Items]
Net sales	$ 248.8	$ 259.8
Cost of products sold	(183.8)	(189.2)
Selling, general and administrative	(56.9)	(53.7)
Depreciation and amortization	(12.9)	(16)
Other income (loss)	0.1	0.2
Loss on classification as held for sale	(355.4)
Pretax income (loss) from discontinued operations	(360.1)	1.1
Provision for (benefit from) income taxes	(92.2)	0.5
Net income (loss) from discontinued operations	$ (267.9)	$ 0.6

Discontinued Operations - Sch_2

Discontinued Operations - Schedule of Reconciliation of Carrying Amounts of Major Classes of Assets and Liabilities of Discontinued Operations to Total Assets (Detail) - USD ($) $ in Millions		Dec. 31, 2020	Sep. 30, 2020	Dec. 31, 2019
Carrying amounts of major classes of assets held for sale:
Total current assets		$ 997	$ 243.8	$ 267.7
Total non-current assets			1,120.5	1,173.7
Carrying amounts of major classes of liabilities held for sale:
Total current liabilities		175.1	139.4	123.1
Total non-current liabilities			53.4	59
Interior Products [Member] | Discontinued Operations, Held-for-sale [Member]
Carrying amounts of major classes of assets held for sale:
Accounts receivable, net		130.6	144.1	144.6
Inventories, net		82.4	73.2	91.1
Prepaid expenses and other current assets		30.7	26.5	32
Total current assets			243.8	267.7
Property and equipment, net		35.8	35.9	42.6
Goodwill		378.9	734.3	734.3
Intangibles, net		273.1	283.2	329.6
Operating lease assets		65.5	67.1	67.2
Total non-current assets			1,120.5	1,173.7
Total assets held for sale	[1]	997	1,364.3	1,441.4
Carrying amounts of major classes of liabilities held for sale:
Accounts payable		52.6	68.8	52.4
Accrued expenses		56.3	54.1	54.8
Current operating lease liabilities		16.2	16.5	15.9
Total current liabilities			139.4	123.1
Deferred income taxes, net			2.2	7.4
Non-current operating lease liabilities		48.9	49.9	50
Other long-term liabilities		1.1	1.3	1.6
Total non-current liabilities			53.4	59
Total liabilities held for sale	[1]	$ 175.1	$ 192.8	$ 182.1
[1]	All assets and liabilities held for sale as of December 31, 2020 were classified as current because the sale of Interior Products was probable to be completed within one year.

Net Sales - Summary of Net Sale

Net Sales - Summary of Net Sales by Product Line and Geography (Detail) - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Disaggregation Of Revenue [Line Items]
Net sales	$ 1,576.5	$ 1,415.3
Residential Roofing Products [Member]
Disaggregation Of Revenue [Line Items]
Net sales	844.8	696.8
Non-Residential Roofing Products [Member]
Disaggregation Of Revenue [Line Items]
Net sales	398.3	412
Complementary Building Products [Member]
Disaggregation Of Revenue [Line Items]
Net sales	333.4	306.5
U.S. [Member]
Disaggregation Of Revenue [Line Items]
Net sales	1,528.4	1,369.8
U.S. [Member] | Residential Roofing Products [Member]
Disaggregation Of Revenue [Line Items]
Net sales	831.3	685.9
U.S. [Member] | Non-Residential Roofing Products [Member]
Disaggregation Of Revenue [Line Items]
Net sales	366.1	379.6
U.S. [Member] | Complementary Building Products [Member]
Disaggregation Of Revenue [Line Items]
Net sales	331	304.3
Canada [Member]
Disaggregation Of Revenue [Line Items]
Net sales	48.1	45.5
Canada [Member] | Residential Roofing Products [Member]
Disaggregation Of Revenue [Line Items]
Net sales	13.5	10.9
Canada [Member] | Non-Residential Roofing Products [Member]
Disaggregation Of Revenue [Line Items]
Net sales	32.2	32.4
Canada [Member] | Complementary Building Products [Member]
Disaggregation Of Revenue [Line Items]
Net sales	$ 2.4	$ 2.2

Net Income (Loss) Per Share - A

Net Income (Loss) Per Share - Additional Information (Detail) - USD ($)	Jan. 02, 2018	Dec. 31, 2020	Sep. 30, 2020	Dec. 31, 2019
Preferred stock, issuance		0	0	0
Common stock, par value		$ 0.01	$ 0.01	$ 0.01
Allied Acquisition [Member] | Investment Agreement [Member] | Series A Cumulative Convertible Participating Preferred Stock [Member]
Preferred stock, issuance	400,000
Preferred stock, par value	$ 0.01
Preferred stock, liquidation preference value	$ 400,000,000
Preferred stock, liquidation purchase price per share	$ 1,000
Preferred stock conversion price per share	$ 41.26
Preferred stock dividend rate	6.00%
Common stock to be issued upon conversion of convertible preferred stock	9,694,619

Net Income (Loss) Per Share - C

Net Income (Loss) Per Share - Components and Calculation of Basic and Diluted Net Income (Loss) Per Share (Detail) - USD ($) $ / shares in Units, $ in Millions		3 Months Ended
		Dec. 31, 2020	Dec. 31, 2019
Earnings Per Share [Abstract]
Net income (loss)		$ (220.5)	$ (23.4)
Dividends on Preferred Stock		6	6
Net income (loss) attributable to common shareholders		(226.5)	(29.4)
Net income (loss) attributable to common shareholders - basic and diluted		(226.5)	(29.4)
Net income (loss) from discontinued operations attributable to common shareholders - basic and diluted		(267.9)	0.6
Net income (loss) from continuing operations attributable to common shareholders - basic and diluted		$ 41.4	$ (30)
Weighted-average common shares outstanding - basic		69,200,000	68,700,000
Effect of common share equivalents		800,000
Weighted-average common shares outstanding - diluted		70,000,000	68,700,000
Basic - Continuing operations	[1]	$ 0.60	$ (0.44)
Basic - Discontinued operations	[1]	(3.87)	0.01
Basic net income (loss) per share	[1]	(3.27)	(0.43)
Diluted - Continuing operations	[1]	0.59	(0.44)
Diluted - Discontinued operations	[1]	(3.83)	0.01
Diluted net income (loss) per share	[1]	$ (3.24)	$ (0.43)
[1]	See Note 5 for detailed calculations and further discussion.

Net Income (Loss) Per Share - S

Net Income (Loss) Per Share - Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share (Detail) - shares	3 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Preferred Stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from computation of diluted net income (loss) per share	9,700,000	9,700,000
Stock Options [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from computation of diluted net income (loss) per share	1,300,000	1,900,000
Restricted Stock Units [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from computation of diluted net income (loss) per share		400,000

Stock-based Compensation - Addi

Stock-based Compensation - Additional Information (Detail) - USD ($) $ in Millions	Feb. 11, 2020	Dec. 31, 2020	Dec. 31, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation number of additional shares authorized	4,850,000
Stock-based compensation number of shares authorized		5,204,996
Restricted Stock Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of shares that will vest		100.00%
Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Non-qualified options granted expiration period		10 years
Vesting period		3 years
Allocated stock-based compensation expense		$ 1.1	$ 1.1
Unrecognized compensation cost related to unvested stock		$ 8.5
Unrecognized compensation cost related to unvested stock, expected weighted-average period of recognition		2 years
Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Allocated stock-based compensation expense		$ 2.7	$ 3.7
Unrecognized compensation cost related to unvested stock		$ 20.8
Unrecognized compensation cost related to unvested stock, expected weighted-average period of recognition		2 years
Restricted Stock Units (RSUs) [Member] | Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of shares that will vest		0.00%
Restricted Stock Units (RSUs) [Member] | Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of shares that will vest		200.00%

Stock-based Compensation - Fair

Stock-based Compensation - Fair Values of Options, Black-Scholes Option-Pricing Model, Weighted-Average Assumptions (Detail)	3 Months Ended
	Dec. 31, 2020
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Risk-free interest rate	0.44%
Expected volatility	48.15%
Expected life (in years)	5 years 4 months 9 days
Dividend yield	0.00%

Stock-based compensation - Stoc

Stock-based compensation - Stock Options Outstanding and Activity During the Period (Detail) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended	12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020
Options Outstanding
Balance as of September 30, 2020	2,500,000
Granted	300,000
Exercised	(300,000)
Canceled/Forfeited	0
Expired	0
Balance as of December 31, 2020	2,500,000	2,500,000
Vested and expected to vest after December 31, 2020	2,400,000
Exercisable as of December 31, 2020	1,700,000
Weighted-Average Exercise Price
Beginning Balance	$ 33.09
Granted	35.78
Exercised	26.93
Canceled/Forfeited	45.99
Expired	15.47
Ending Balance	33.98	$ 33.09
Vested and expected to vest after December 31, 2020	34
Exercisable as of December 31, 2020	$ 34.86
Weighted-Average Remaining Contractual Life
Balance	6 years 4 months 24 days	5 years 10 months 24 days
Vested and expected to vest after December 31, 2020	6 years 3 months 18 days
Exercisable as of December 31, 2020	5 years 1 month 6 days
Aggregate Intrinsic Value
Balance	$ 19.9	$ 6.9
Vested and expected to vest after December 31, 2020	19.6
Exercisable as of December 31, 2020	$ 13.4

Stock-based compensation - St_2

Stock-based compensation - Stock Option Grants, Vesting, and Exercises (Detail) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Weighted-average fair value of stock options granted	$ 15.62	$ 10.70
Total grant date fair value of stock options vested	$ 4.1	$ 3.9
Total intrinsic value of stock options exercised	$ 2.6	$ 0.7

Stock-based Compensation - Rest

Stock-based Compensation - Restricted Shares and Units Outstanding and Activity During the Period (Detail) - $ / shares	3 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Weighted - Average Grant Date Fair Value
Granted	$ 36.07	$ 33.47
Restricted Stock Units (RSUs) [Member]
Outstanding
Balance as of September 30, 2020	1,200,000
Granted	300,000
Released	(200,000)
Canceled/Forfeited	(200,000)
Balance as of December 31, 2020	1,100,000
Vested and expected to vest after December 31, 2020	1,000,000
Weighted - Average Grant Date Fair Value
Balance as of September 30, 2020	$ 33.55
Granted	36.07
Released	45.02
Canceled/Forfeited	28.67
Balance as of December 31, 2020	32.93
Vested and expected to vest after December 31, 2020	$ 32.95

Stock-based Compensation - Sche

Stock-based Compensation - Schedule Of Restricted Stock Units Additional Information (Detail) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Weighted-average fair value of RSUs granted	$ 36.07	$ 33.47
Total grant date fair value of RSUs vested	$ 11.3	$ 8.1
Total intrinsic value of RSUs released	$ 9.5	$ 6.8

Goodwill and Intangible Asset_2

Goodwill and Intangible Assets - Summary of Changes in goodwill (Detail) - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Goodwill And Intangible Assets Disclosure [Abstract]
Beginning balance	$ 1,756.1	$ 1,756.3
Translation and other adjustments	1.4	0.6
Ending balance	$ 1,757.5	$ 1,756.9

Goodwill and Intangible Asset_3

Goodwill and Intangible Assets - Summary of Intangible Assets (Detail) - USD ($) $ in Millions		3 Months Ended
		Dec. 31, 2020	Sep. 30, 2020	Dec. 31, 2019
Finite Lived Intangible Assets [Line Items]
Amortizable intangible assets		$ 1,089.8	$ 1,089.4	$ 1,145.3
Accumulated amortization		(607)	(581.2)	(544.2)
Total amortizable intangible assets, net		482.8	508.2	601.1
Indefinite-lived trademarks		9.8	9.8	146.8
Total intangibles, net		$ 492.6	518	747.9
Weighted Average [Member]
Finite Lived Intangible Assets [Line Items]
Finite-Lived Intangible Asset, Useful Life		16 years 1 month 6 days
Minimum [Member]
Finite Lived Intangible Assets [Line Items]
Finite-Lived Intangible Asset, Useful Life		5 years
Maximum [Member]
Finite Lived Intangible Assets [Line Items]
Finite-Lived Intangible Asset, Useful Life		20 years
Noncompete Agreements [Member]
Finite Lived Intangible Assets [Line Items]
Amortizable intangible assets		$ 0.2	0.2	2.8
Noncompete Agreements [Member] | Weighted Average [Member]
Finite Lived Intangible Assets [Line Items]
Finite-Lived Intangible Asset, Useful Life	[1]	1 year 4 months 24 days
Customer Relationships [Member]
Finite Lived Intangible Assets [Line Items]
Amortizable intangible assets		$ 1,085.9	1,085.5	1,135.5
Customer Relationships [Member] | Weighted Average [Member]
Finite Lived Intangible Assets [Line Items]
Finite-Lived Intangible Asset, Useful Life	[1]	16 years 1 month 6 days
Trademarks [Member]
Finite Lived Intangible Assets [Line Items]
Amortizable intangible assets		$ 3.7	$ 3.7	$ 7
Trademarks [Member] | Weighted Average [Member]
Finite Lived Intangible Assets [Line Items]
Finite-Lived Intangible Asset, Useful Life	[1]	6 years 3 months 18 days
[1]	As of December 31, 2020.

Goodwill and Intangible Asset_4

Goodwill and Intangible Assets - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2020	Mar. 31, 2020	Dec. 31, 2019
Goodwill And Intangible Assets [Line Items]
Amortization	$ 25.5		$ 32.1
Minimum [Member]
Goodwill And Intangible Assets [Line Items]
Finite-Lived Intangible Asset, Useful Life	5 years
Maximum [Member]
Goodwill And Intangible Assets [Line Items]
Finite-Lived Intangible Asset, Useful Life	20 years
Weighted Average [Member]
Goodwill And Intangible Assets [Line Items]
Finite-Lived Intangible Asset, Useful Life	16 years 1 month 6 days
Allied Acquisition [Member] | Tradenames [Member]
Goodwill And Intangible Assets [Line Items]
Amortization		$ 142.6

Goodwill and Intangible Asset_5

Goodwill and Intangible Assets - Summary of Estimated Future Amortization (Detail) - USD ($) $ in Millions	Dec. 31, 2020	Sep. 30, 2020	Dec. 31, 2019
Goodwill And Intangible Assets Disclosure [Abstract]
2021 (Jan - Sept)	$ 75.7
2022	82.4
2023	66.6
2024	53.4
2025	43.2
Thereafter	161.5
Total amortizable intangible assets, net	$ 482.8	$ 508.2	$ 601.1

Financing Arrangements - Outsta

Financing Arrangements - Outstanding Debt Presented Net of Unamortized debt Issuance Costs and Other Financing Arrangements (Detail) - USD ($)		Dec. 31, 2020		Sep. 30, 2020		Dec. 31, 2019		Jan. 02, 2018
Debt Instrument [Line Items]
Borrowings under revolving lines of credit/term loans, net		$ 151,700,000		$ 251,100,000		$ 215,600,000
Current portion		0		0		0
Long-term borrowings under senior notes		1,582,500,000		1,581,600,000		1,579,300,000
Long-term debt, net		2,494,100,000		2,494,200,000		2,495,100,000
Equipment financing facilities	[1]	1,600,000		2,600,000		5,800,000
Long-term obligations under equipment financing, net						1,600,000
2025 Senior Notes [Member]
Debt Instrument [Line Items]
Senior Notes	[2]	1,286,400,000		1,285,700,000		1,283,600,000
2026 Senior Notes [Member]
Debt Instrument [Line Items]
Senior Notes	[3]	296,100,000		295,900,000		295,700,000
Equipment Financing Facilities [Member]
Debt Instrument [Line Items]
Current portion		(1,600,000)		(2,600,000)		(4,200,000)
Long-term obligations under equipment financing, net						1,600,000
Revolving Lines of Credit [Member]
Debt Instrument [Line Items]
Borrowings under revolving lines of credit/term loans, net		151,700,000		251,100,000		215,600,000
Revolving Lines of Credit [Member] | 2023 ABL [Member]
Debt Instrument [Line Items]
Borrowings under revolving lines of credit/term loans, net		151,700,000
Revolving Lines of Credit [Member] | 2023 ABL [Member] | U.S. [Member]
Debt Instrument [Line Items]
Total Borrowings under revolving lines of credit/term loans	[4]	151,700,000		251,100,000		209,500,000
Revolving Lines of Credit [Member] | 2023 ABL [Member] | Canada [Member]
Debt Instrument [Line Items]
Total Borrowings under revolving lines of credit/term loans	[5]					6,100,000
Term Loan [Member]
Debt Instrument [Line Items]
Current portion		(9,700,000)		(9,700,000)		(9,700,000)
Borrowings under revolving lines of credit/term loans, net		911,600,000		912,600,000		915,800,000
Term Loan [Member] | 2025 Term Loan [Member]
Debt Instrument [Line Items]
Total Borrowings under revolving lines of credit/term loans		$ 921,300,000	[6]	$ 922,300,000	[6]	$ 925,500,000	[6]	$ 970,000,000
[1]	Fixed interest rates ranging from 2.33% to 2.89% for all periods presented.
[2]	Interest rate of 4.88% for all periods presented.
[3]	Interest rate of 4.50% for all periods presented.
[4]	Effective rate on borrowings of 1.41%, 1.89% and 3.25% as of December 31, 2020, September 30, 2020 and December 31, 2019, respectively.
[5]	Effective rate on borrowings of 4.20% as of December 31, 2019.
[6]	Interest rate of 2.40%, 2.41% and 3.95% as of December 31, 2020, September 30, 2020 and December 31, 2019, respectively.

Financing Arrangements - Outs_2

Financing Arrangements - Outstanding Debt Presented Net of Unamortized debt Issuance Costs and Other Financing Arrangements (Parenthetical) (Detail)	Jan. 02, 2018	Dec. 31, 2020	Dec. 31, 2019	Sep. 30, 2020	Oct. 25, 2017
Equipment Financing Facilities [Member]
Debt Instrument [Line Items]
Debt instrument maturity date		Sep. 30, 2021	Sep. 30, 2021	Sep. 30, 2021
Equipment Financing Facilities [Member] | Minimum [Member]
Debt Instrument [Line Items]
Equipment financing facilities, fixed interest rate percentage		2.33%	2.33%	2.33%
Equipment Financing Facilities [Member] | Maximum [Member]
Debt Instrument [Line Items]
Equipment financing facilities, fixed interest rate percentage		2.89%	2.89%	2.89%
2025 Senior Notes [Member]
Debt Instrument [Line Items]
Debt interest rate at period end		4.88%	4.88%	4.88%	4.875%
Debt instrument maturity date		Nov. 1, 2025	Nov. 1, 2025	Nov. 1, 2025
2026 Senior Notes [Member]
Debt Instrument [Line Items]
Debt interest rate at period end		4.50%	4.50%	4.50%
Debt instrument maturity date		Nov. 15, 2026	Nov. 15, 2026	Nov. 15, 2026
Revolving Lines of Credit [Member] | 2023 ABL [Member]
Debt Instrument [Line Items]
Debt instrument maturity date	Jan. 2, 2023
Revolving Lines of Credit [Member] | 2023 ABL [Member] | U.S. [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Interest Rate at Period End		1.41%	3.25%	1.89%
Line of Credit Facility, Expiration Date		Jan. 2, 2023	Jan. 2, 2023	Jan. 2, 2023
Revolving Lines of Credit [Member] | 2023 ABL [Member] | Canada [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Interest Rate at Period End			4.20%
Line of Credit Facility, Expiration Date			Jan. 2, 2023
Term Loan [Member] | Term Loan, Matures January 2025 [Member]
Debt Instrument [Line Items]
Debt interest rate at period end		2.40%	3.95%	2.41%
Debt instrument maturity date	Jan. 2, 2025	Jan. 2, 2025	Jan. 2, 2025	Jan. 2, 2025

Financing Arrangements - 2026 S

Financing Arrangements - 2026 Senior Notes - Additional Information (Detail) - USD ($)		Oct. 28, 2019	Oct. 09, 2019	Jan. 02, 2018	Dec. 31, 2020	Dec. 31, 2019	Sep. 30, 2020	Oct. 01, 2015
Debt Instrument [Line Items]
Loss on debt extinguishment					$ 0	$ 14,700,000
Payments of debt issuance costs				$ 65,300,000	$ 0	$ 3,600,000
Senior Notes, Matures October 2023 [Member]
Debt Instrument [Line Items]
Debt instrument, aggregate principal amount			$ 300,000,000
Debt instrument interest rate			4.50%					6.38%
Debt instrument, issue price percentage			100.00%
Debt instrument maturity date			Nov. 15, 2026
Debt instrument, interest payable commencement date			May 15, 2020
Redemption of senior debt		$ 300,000,000
Debt redemption price percentage of principal amount		103.188%
Unamortized debt issuance costs		$ 5,100,000
Senior Notes, Matures October 2023 [Member]
Debt Instrument [Line Items]
Debt instrument interest rate					4.50%	4.50%	4.50%
Debt instrument maturity date					Nov. 15, 2026	Nov. 15, 2026	Nov. 15, 2026
Redemption of senior debt		$ 300,000,000
Debt redemption price percentage of principal amount		103.188%
Debt instrument, redemption description					On October 28, 2019, the Company used the net proceeds from the offering, together with cash on hand and available borrowings under the 2023 ABL (as defined below), to redeem all $300.0 million aggregate principal amount outstanding of the 2023 Senior Notes (as defined below) at a redemption price of 103.188%
Payments of debt issuance costs			$ 4,700,000
Unamortized debt issuance costs					$ 3,900,000
Senior Notes Payable	[1]				$ 296,100,000	$ 295,700,000	$ 295,900,000
Refinancing the Existing 2023 Senior Notes with Issuance of 2026 Senior Notes [Member]
Debt Instrument [Line Items]
Loss on debt extinguishment						$ 14,700,000
[1]	Interest rate of 4.50% for all periods presented.

Financing Arrangements - Financ

Financing Arrangements - Financing - Allied Acquisition - Additional Information (Detail) - USD ($)	Jan. 02, 2018	Dec. 31, 2020		Dec. 31, 2019		Sep. 30, 2020	[1]
Debt Instrument [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	$ 3,570,000,000
Borrowings under senior notes		$ 0		$ 300,000,000
Payments of debt issuance costs	65,300,000	0		3,600,000
Senior Notes, Matures November 2025 [Member]
Debt Instrument [Line Items]
Borrowings under senior notes	1,300,000,000
Revolving Lines of Credit [Member] | 2023 ABL [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	1,300,000,000
Proceeds from Lines of Credit	525,000,000
Term Loan [Member] | Term Loan, Matures January 2025 [Member]
Debt Instrument [Line Items]
Long-term line of credit	$ 970,000,000	$ 921,300,000	[1]	$ 925,500,000	[1]	$ 922,300,000
[1]	Interest rate of 2.40%, 2.41% and 3.95% as of December 31, 2020, September 30, 2020 and December 31, 2019, respectively.

Financing Arrangements - 2023 A

Financing Arrangements - 2023 ABL - Additional Information (Detail)	Jan. 02, 2018USD ($)	Dec. 31, 2020USD ($)Covenant	Sep. 30, 2020USD ($)	Dec. 31, 2019USD ($)
Debt Instrument [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	$ 3,570,000,000
Borrowings under revolving lines of credit/term loans, net		$ 151,700,000	$ 251,100,000	$ 215,600,000
Revolving Lines of Credit [Member]
Debt Instrument [Line Items]
Borrowings under revolving lines of credit/term loans, net		$ 151,700,000	$ 251,100,000	$ 215,600,000
Revolving Lines of Credit [Member] | 2023 ABL [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	$ 1,300,000,000
Debt instrument maturity date	Jan. 2, 2023
Line of credit facility, unused fees		0.25%
Number of financial covenants | Covenant		1
Debt instrument covenant compliance		Per the covenant, the Company’s FCCR must be a minimum of 1.00 at the end of each fiscal quarter, calculated on a trailing four quarter basis (or under certain circumstances, at the end of each fiscal month, calculated on a trailing twelve-month basis). Compliance is only required at such times as borrowing availability (subject to certain adjustments) is less than the greater of (i) 10% of the lesser of the borrowing base or the aggregate commitments or (ii) $90.0 million, and for a period of thirty days thereafter. The Company was in compliance with this covenant as of December 31, 2020.
Debt Instrument Covenant Required Borrowings Base Percentage		10.00%
Debt Instrument Covenant Required Borrowings Availability		$ 90,000,000
Fixed charge coverage ratio		100.00%
Borrowings under revolving lines of credit/term loans, net		$ 151,700,000
Unamortized debt issuance costs		5,300,000
Revolving Lines of Credit [Member] | U.S. [Member] | 2023 ABL [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	$ 1,250,000,000
Standby letters of credit outstanding		$ 12,800,000
Revolving Lines of Credit [Member] | Canada [Member] | 2023 ABL [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	$ 50,000,000
Revolving Lines of Credit [Member] | Base Rate [Member] | Minimum [Member] | 2023 ABL [Member]
Debt Instrument [Line Items]
Base rate borrowings	0.25%
Revolving Lines of Credit [Member] | Base Rate [Member] | Maximum [Member] | 2023 ABL [Member]
Debt Instrument [Line Items]
Base rate borrowings	0.75%
Revolving Lines of Credit [Member] | LIBOR [Member] | Minimum [Member] | 2023 ABL [Member]
Debt Instrument [Line Items]
Base rate borrowings	1.25%
Revolving Lines of Credit [Member] | LIBOR [Member] | Maximum [Member] | 2023 ABL [Member]
Debt Instrument [Line Items]
Base rate borrowings	1.75%

Financing Arrangements - 2025 T

Financing Arrangements - 2025 Term Loan - Additional Information (Detail) - Term Loan [Member] - Term Loan, Matures January 2025 [Member] - USD ($)	Jan. 02, 2018	Dec. 31, 2020		Dec. 31, 2019		Sep. 30, 2020
Debt Instrument [Line Items]
Long-term line of credit	$ 970,000,000	$ 921,300,000	[1]	$ 925,500,000	[1]	$ 922,300,000	[1]
Debt Instrument, Frequency of Periodic Payment		quarterly
Debt Instrument, Periodic Payment	$ 2,400,000
Debt instrument maturity date	Jan. 2, 2025	Jan. 2, 2025		Jan. 2, 2025		Jan. 2, 2025
Unamortized debt issuance costs		$ 22,000,000
Base Rate [Member]
Debt Instrument [Line Items]
Base rate borrowings	1.25%
LIBOR [Member]
Debt Instrument [Line Items]
Base rate borrowings	2.25%
[1]	Interest rate of 2.40%, 2.41% and 3.95% as of December 31, 2020, September 30, 2020 and December 31, 2019, respectively.

Financing Arrangements - 2025 S

Financing Arrangements - 2025 Senior Notes - Additional Information (Detail) - Senior Notes, Matures November 2025 [Member] - USD ($)		3 Months Ended		12 Months Ended
		Dec. 31, 2020	Dec. 31, 2019	Sep. 30, 2020	Oct. 25, 2017
Debt Instrument [Line Items]
Debt instrument, aggregate principal amount					$ 1,300,000,000
Debt instrument interest rate		4.88%	4.88%	4.88%	4.875%
Debt instrument, issue price percentage					100.00%
Debt instrument maturity date		Nov. 1, 2025	Nov. 1, 2025	Nov. 1, 2025
Unamortized debt issuance costs		$ 13,600,000
Senior Notes Payable	[1]	$ 1,286,400,000	$ 1,283,600,000	$ 1,285,700,000
[1]	Interest rate of 4.88% for all periods presented.

Financing Arrangements - 2023 S

Financing Arrangements - 2023 Senior Notes - Additional Information (Detail) - USD ($) $ in Millions	Oct. 28, 2019	Oct. 01, 2015	Dec. 31, 2020	Dec. 31, 2019	Oct. 09, 2019
Debt Instrument [Line Items]
Borrowings under senior notes			$ 0	$ 300
Senior Notes, Matures October 2023 [Member]
Debt Instrument [Line Items]
Borrowings under senior notes		$ 300
Debt instrument interest rate		6.38%			4.50%
Debt instrument, coupon rate		6.38%
Redemption of senior debt	$ 300
Debt redemption price percentage of principal amount	103.188%
Unamortized debt issuance costs	$ 5.1

Financing Arrangements - Equipm

Financing Arrangements - Equipment Financing Facilities - Additional Information (Detail) - USD ($)		3 Months Ended
		Dec. 31, 2020	Sep. 30, 2020	Dec. 31, 2019
Debt Instrument [Line Items]
Equipment financing facilities, various maturities through September 2021	[1]	$ 1,600,000	$ 2,600,000	$ 5,800,000
Equipment Financing Facilities [Member]
Debt Instrument [Line Items]
Equipment financing facilities, various maturities through September 2021		$ 1,600,000
Debt instrument maturity date		Sep. 30, 2021
Minimum [Member] | Equipment Financing Facilities [Member]
Debt Instrument [Line Items]
Percentage of fixed interest rate of equipment financing facilities		2.33%
Maximum [Member] | Equipment Financing Facilities [Member]
Debt Instrument [Line Items]
Percentage of fixed interest rate of equipment financing facilities		2.89%
[1]	Fixed interest rates ranging from 2.33% to 2.89% for all periods presented.

Leases - Components of Operatin

Leases - Components of Operating Lease Costs Recognized Within Selling, General and Administrative Expenses (Detail) - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Leases [Abstract]
Operating lease costs	$ 25.7	$ 26.5
Variable lease costs	2.3	2.2
Total operating lease costs	$ 28	$ 28.7

Leases - Summary of Supplementa

Leases - Summary of Supplemental Cash Flow Information Related to Operating Leases (Detail) $ in Millions	3 Months Ended
	Dec. 31, 2020USD ($)
Leases [Abstract]
Operating cash flows for operating lease liabilities	$ 24.4

Leases - Additional Information

Leases - Additional Information (Detail)	Dec. 31, 2020
Leases [Abstract]
Operating lease, weighted-average remaining lease term	5 years 8 months 12 days
Operating lease, weighted-average discount rate	3.81%

Leases - Summary of Future Leas

Leases - Summary of Future Lease Payments Under Operating Leases (Detail) $ in Millions	Dec. 31, 2020USD ($)
Leases [Abstract]
2021 (Jan - Sept)	$ 72.7
2022	88
2023	73.3
2024	59.2
2025	37.2
Thereafter	81.4
Total future lease payments	411.8
Imputed interest	(41.2)
Total operating lease liabilities	$ 370.6

Accumulated Other Comprehensi_3

Accumulated Other Comprehensive Income (Loss) - Reclassification out of Accumulated Other Comprehensive Income (Detail) - USD ($) $ in Millions		3 Months Ended
		Dec. 31, 2020	Dec. 31, 2019
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance		$ 1,760.9	$ 1,862.3
Other comprehensive income before reclassifications		5.5	3.8
Balance		1,544.8	1,840.7
Foreign Currency Translation
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance		(19.7)
Other comprehensive income before reclassifications		3.9
Balance		(15.8)
Derivative Financial Instruments
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance		(15)
Other comprehensive income before reclassifications		1.6
Balance		(13.4)
AOCI [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance	[1]	(34.7)	(20.6)
Other comprehensive income before reclassifications		5.5
Balance	[1]	$ (29.2)	$ (16.8)
[1]	Accumulated Other Comprehensive Income (Loss) ("AOCI").

Geographic Data - Schedule Of G

Geographic Data - Schedule Of Geographic Information (Detail) - USD ($) $ in Millions	Dec. 31, 2020	Sep. 30, 2020	Dec. 31, 2019
Segment Reporting Information [Line Items]
Long-lived assets	$ 694.4	$ 718.1	$ 811.5
U.S. [Member]
Segment Reporting Information [Line Items]
Long-lived assets	683.9	708.2	799.5
Canada [Member]
Segment Reporting Information [Line Items]
Long-lived assets	$ 10.5	$ 9.9	$ 12

Fair Value Measurement - Additi

Fair Value Measurement - Additional Information (Detail) - Fair Value, Inputs, Level 2 [Member] $ in Millions	3 Months Ended
	Dec. 31, 2020USD ($)
2026 Senior Notes [Member]
Fair Value, Concentration of Risk, Financial Statement Captions [Line Items]
Debt instrument maturity year	2026
2025 Senior Notes [Member]
Fair Value, Concentration of Risk, Financial Statement Captions [Line Items]
Debt instrument maturity year	2025
Carrying Value [Member] | 2026 Senior Notes [Member]
Fair Value, Concentration of Risk, Financial Statement Captions [Line Items]
Senior notes	$ 300
Carrying Value [Member] | 2025 Senior Notes [Member]
Fair Value, Concentration of Risk, Financial Statement Captions [Line Items]
Senior notes	1,300
Fair Value [Member] | 2026 Senior Notes [Member]
Fair Value, Concentration of Risk, Financial Statement Captions [Line Items]
Senior notes	314.3
Fair Value [Member] | 2025 Senior Notes [Member]
Fair Value, Concentration of Risk, Financial Statement Captions [Line Items]
Senior notes	$ 1,330

Financial Derivatives - Additio

Financial Derivatives - Additional Information (Detail)	Sep. 11, 2019USD ($)Agreement	Dec. 31, 2020USD ($)
Derivative [Line Items]
Number of interest rate swap agreements | Agreement	2
5-Year Swap [Member]
Derivative [Line Items]
Derivative, notional amount	$ 250,000,000
Term of derivative agreement	5 years
Derivative, maturity date	Aug. 30, 2024
Derivative, fixed interest rate	1.49%
Derivative fair value, net of tax		$ 9,000,000
3-Year Swap [Member]
Derivative [Line Items]
Derivative, notional amount	$ 250,000,000
Term of derivative agreement	3 years
Derivative, maturity date	Aug. 30, 2022
Derivative, fixed interest rate	1.50%
Derivative fair value, net of tax		$ 4,400,000

Financial Derivatives - Summary

Financial Derivatives - Summary of Combined Fair Values, Net of Tax of Interest Rate Derivative Instruments (Details) - USD ($) $ in Millions		Dec. 31, 2020	Sep. 30, 2020	Dec. 31, 2019
Designated as Hedging Instrument [Member] | Interest Rate Swaps [Member] | Fair Value, Inputs, Level 2 [Member]
Derivative [Line Items]
Derivative fair value, net of tax	[1]	$ (13.4)	$ (15)	$ 0.9
[1]	Assets are included on the consolidated balance sheets in prepaid expenses and other current assets, while liabilities are included in accrued expenses.

Financial Derivatives - Summa_2

Financial Derivatives - Summary of Amounts of Gain (Loss) on Interest Rate Derivative Instruments Recognized in Other Comprehensive Income (Detail) - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Derivative [Line Items]
Gain (loss) on interest rate derivative instruments recognized in other comprehensive income	$ 1.6	$ 2.5
Designated as Hedging Instrument [Member] | Interest Rate Swaps [Member]
Derivative [Line Items]
Gain (loss) on interest rate derivative instruments recognized in other comprehensive income	$ 1.6	$ 2.5