Beacon Roofing Supply (BECN) 10-K 20 Nov 18 2018 FY Annual report Financial data

Document And Entity Information

Document And Entity Information - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2018	Oct. 31, 2018	Mar. 31, 2018
Document And Entity Information [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Sep. 30, 2018
Document Fiscal Year Focus	2,018
Document Fiscal Period Focus	FY
Trading Symbol	BECN
Entity Registrant Name	BEACON ROOFING SUPPLY INC
Entity Central Index Key	1,124,941
Current Fiscal Year End Date	--09-30
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Public Float			$ 3,600
Entity Common Stock, Shares Outstanding		68,156,582

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Sep. 30, 2018	Sep. 30, 2017
Current assets:
Cash and cash equivalents	$ 129,927	$ 138,250
Accounts receivable, less allowance of $17,584 and $11,829 as of September 30, 2018 and 2017, respectively	1,090,533	704,527
Inventories, net	936,047	551,924
Prepaid expenses and other current assets	244,360	209,138
Total current assets	2,400,867	1,603,839
Property and equipment, net	280,407	156,129
Goodwill	2,491,779	1,251,986
Intangibles, net	1,334,366	429,069
Other assets, net	1,243	8,534
Total Assets	6,508,662	3,449,557
Current liabilities:
Accounts payable	880,872	503,697
Accrued expenses	611,539	261,297
Current portions of long-term debt	19,661	14,141
Total current liabilities	1,512,072	779,135
Borrowings under revolving lines of credit, net	92,442	3,205
Long-term debt, net	2,494,725	721,268
Deferred income taxes, net	106,994	138,383
Long-term obligations under equipment financing and other, net	13,639	23,213
Other long-term liabilities	5,290	2,547
Total liabilities	4,225,162	1,667,751
Commitments and contingencies (Note 9)
Convertible preferred stock; $0.01 par value; aggregate liquidation preference $400,000; 400,000 shares authorized, issued and outstanding as of September 30, 2018; none authorized, issued and outstanding as of September 30, 2017	399,195
Stockholders' equity:
Common stock (voting); $.01 par value; 100,000,000 shares authorized; 68,135,790 issued and outstanding as of September 30, 2018 and 67,700,858 issued and outstanding as of September 30, 2017	681	677
Undesignated preferred stock; 5,000,000 shares authorized, none issued or outstanding	0	0
Additional paid-in capital	1,067,040	1,047,506
Retained earnings	833,834	748,186
Accumulated other comprehensive loss	(17,250)	(14,563)
Total stockholders' equity	1,884,305	1,781,806
Total Liabilities and Stockholders' Equity	$ 6,508,662	$ 3,449,557

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Sep. 30, 2018	Sep. 30, 2017
Statement Of Financial Position [Abstract]
Accounts receivable, allowances	$ 17,584	$ 11,829
Convertible preferred stock, par value	$ 0.01
Convertible preferred stock. aggregate liquidation preference	$ 400,000
Convertible preferred stock, shares authorized	400,000	0
Convertible preferred stock, shares issued	400,000	0
Convertible preferred stock, shares outstanding	400,000	0
Common stock (voting), par value	$ 0.01	$ 0.01
Common stock (voting), shares authorized	100,000,000	100,000,000
Common Stock (Voting), issued	68,135,790	67,700,858
Common Stock (voting), outstanding	68,135,790	67,700,858
Undesignated Preferred Stock, shares authorized	5,000,000	5,000,000
Undesignated Preferred Stock, issued	0	0
Undesignated Preferred Stock, outstanding	0	0

Consolidated Statements of Oper

Consolidated Statements of Operations - USD ($) $ in Thousands		12 Months Ended
		Sep. 30, 2018		Sep. 30, 2017	Sep. 30, 2016
Income Statement [Abstract]
Net sales		$ 6,418,311		$ 4,376,670	$ 4,127,109
Cost of products sold		4,824,990		3,300,731	3,114,040
Gross profit		1,593,321		1,075,939	1,013,069
Operating expense
Selling, general and administrative		1,187,192		743,376	707,893
Depreciation		60,318		34,002	31,876
Amortization		141,185		82,465	68,316
Total operating expense		1,388,695		859,843	808,085
Income (loss) from operations		204,626		216,096	204,984
Interest expense, financing costs, and other		136,544		52,751	58,452
Income (loss) before provision for income taxes		68,082		163,345	146,532
Provision for (benefit from) income taxes		(30,544)		62,481	56,615
Net income (loss)		98,626		100,864	89,917
Dividends on preferred shares		18,000	[1]	0	0
Net income (loss) attributable to common shareholders		$ 80,626		$ 100,864	$ 89,917
Weighted-average common stock outstanding:
Basic		68,012,879		60,315,648	59,424,372
Diluted		69,191,039		61,344,263	60,418,067
Net income (loss) per share:
Basic	[2]	$ 1.07		$ 1.67	$ 1.51
Diluted	[2]	$ 1.05		$ 1.64	$ 1.49
[1]	For the year ended September 30, 2018, $18.0 million is comprised of $5.0 million undeclared cumulative dividends as well as an additional $13.0 million of preferred share dividends that had been declared and paid as of period end.
[2]	See Note 4 for detailed calculations and further discussion.

Consolidated Statements of Op_2

Consolidated Statements of Operations (Parenthetical) $ in Thousands	12 Months Ended
	Sep. 30, 2018USD ($)
Income Statement [Abstract]
Dividends on preferred shares	$ 18,000	[1]
Cumulative preferred share dividends undeclared	5,000
Preferred share dividends declared and paid	$ 13,000
[1]	For the year ended September 30, 2018, $18.0 million is comprised of $5.0 million undeclared cumulative dividends as well as an additional $13.0 million of preferred share dividends that had been declared and paid as of period end.

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016
Statement Of Income And Comprehensive Income [Abstract]
Net income (loss)	$ 98,626	$ 100,864	$ 89,917
Other comprehensive income (loss):
Foreign currency translation adjustment	(2,687)	3,706	1,024
Total other comprehensive income (loss)	(2,687)	3,706	1,024
Comprehensive income (loss)	$ 95,939	$ 104,570	$ 90,941

Consolidated Statements of Stoc

Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands		Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income (Loss)
Balance at Sep. 30, 2015		$ 883,116	$ 497	$ 345,934	$ 557,405	$ (20,720)
Balance (in shares) at Sep. 30, 2015			49,790,743
Issuance of common stock, net of shares withheld for taxes		24,158	$ 11	24,147	0	0
Issuance of common stock, net of shares withheld for taxes (Shares)			1,061,134
Issuance of common stock in connection with RSG acquisition		306,824	$ 90	306,734	0	0
Issuance of common stock in connection with RSG acquisition (shares)			9,039,008
Stock-based compensation		17,749	$ 0	17,749	0	0
Other comprehensive income (loss)		2,063	0	0	0	2,063
Net income (loss)		89,917	0	0	89,917	0
Balance at Sep. 30, 2016		1,323,827	$ 598	694,564	647,322	(18,657)
Balance (in shares) at Sep. 30, 2016			59,890,885
Issuance of common stock, net of shares withheld for taxes		8,627	$ 6	8,621	0	0
Issuance of common stock, net of shares withheld for taxes (Shares)			536,223
Issuance of common stock from secondary offering, net of issuance costs		329,323	$ 73	329,250	0	0
Issuance of common stock from secondary offering, net of issuance costs (Shares)			7,273,750
Stock-based compensation		15,071	$ 0	15,071	0	0
Other comprehensive income (loss)		4,094	0	0	0	4,094
Net income (loss)		100,864	0	0	100,864	0
Balance at Sep. 30, 2017		1,781,806	$ 677	1,047,506	748,186	(14,563)
Balance (in shares) at Sep. 30, 2017			67,700,858
Issuance of common stock, net of shares withheld for taxes		3,539	$ 4	3,535	0	0
Issuance of common stock, net of shares withheld for taxes (Shares)			434,932
Issuance costs related to secondary offering of common stock		(474)	$ 0	(474)	0	0
Stock-based compensation		16,473	0	16,473	0	0
Other comprehensive income (loss)		(2,687)	0	0	0	(2,687)
Net income (loss)		98,626	0	0	98,626	0
Dividends on preferred shares	[1]	(12,978)	0	0	(12,978)	0
Balance at Sep. 30, 2018		$ 1,884,305	$ 681	$ 1,067,040	$ 833,834	$ (17,250)
Balance (in shares) at Sep. 30, 2018			68,135,790
[1]	Amount represents only dividends that have been declared and paid as of September 30, 2018.

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands		12 Months Ended
		Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016
Operating Activities
Net income (loss)		$ 98,626	$ 100,864	$ 89,917
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization		201,503	116,467	100,191
Stock-based compensation		16,473	15,071	17,749
Certain interest expense and other financing costs		17,338	10,497	8,329
Loss on debt extinguishment		1,248	0	0
Gain on sale of fixed assets		(1,294)	(839)	(1,882)
Deferred income taxes	[1]	(30,118)	393	25,200
Changes in operating assets and liabilities, net of the effects of businesses acquired:
Accounts receivable		(45,093)	(60,185)	(30,408)
Inventories		(65,069)	(51,768)	43,489
Prepaid expenses and other assets		57,554	(44,208)	(12,841)
Accounts payable and accrued expenses		287,428	228,908	(119,096)
Other liabilities		785	0	0
Net cash provided by (used in) operating activities		539,381	315,200	120,648
Investing Activities
Purchases of property and equipment		(46,010)	(39,828)	(26,315)
Acquisition of businesses, net		(2,740,480)	(129,390)	(1,018,188)
Proceeds from the sale of assets		2,149	2,233	1,882
Net cash provided by (used in) investing activities		(2,784,341)	(166,985)	(1,042,621)
Financing Activities
Borrowings under revolving lines of credit		2,807,741	2,464,128	1,892,459
Repayments under revolving lines of credit		(2,707,741)	(2,833,230)	(1,541,532)
Borrowings under term loan		970,000	0	490,793
Repayments under term loan		(445,850)	(4,500)	(230,918)
Borrowings under senior notes		1,300,000	0	300,000
Payment of debt issuance costs		(65,788)	(1,669)	(28,325)
Repayments under equipment financing facilities and other		(11,593)	(10,034)	(4,724)
Proceeds from issuance of convertible preferred stock		400,000	0	0
Proceeds from secondary offering of common stock		0	345,503	0
Payment of stock issuance costs		(1,279)	(14,684)	0
Payment of dividends on preferred stock		(12,978)	0	0
Proceeds from issuance of common stock related to equity awards		7,514	11,341	24,160
Taxes paid related to net share settlement of equity awards		(3,975)	(392)	(2)
Excess tax benefit from stock-based compensation		0	2,937	4,956
Net cash provided by (used in) financing activities		2,236,051	(40,600)	906,867
Effect of exchange rate changes on cash and cash equivalents		586	(751)	831
Net increase (decrease) in cash and cash equivalents		(8,323)	106,864	(14,275)
Cash and cash equivalents, beginning of period		138,250	31,386	45,661
Cash and cash equivalents, end of period		129,927	138,250	31,386
Cash paid during the period for:
Interest		111,283	49,067	57,934
Income taxes, net of tax refunds		$ 35,105	$ 56,158	$ 14,425
[1]	Includes impact of provisional amounts recognized relating to estimated impact of Tax Cuts and Jobs Act of 2017 – see Note 12 for further discussion.

Company Overview

Company Overview	12 Months Ended
	Sep. 30, 2018
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Company Overview	1. Company Overview Beacon Roofing Supply, Inc. (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 January 2, 2018 the Company finalized its acquisition of Allied Building Products Corp. (“Allied”), a New Jersey corporation, for $2.625 billion, subject to certain working capital and other adjustments. As of September 30, 2018, the adjusted purchase price for Allied was $2.88 billion, and purchase accounting entries had not yet been finalized (see Note 3 for further discussion). Allied was one of the largest exterior and interior building products distributors in the United States and was a wholly-owned subsidiary of Oldcastle Distribution, Inc. 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., Allied Building Products LLC and Beacon Roofing Supply Canada Company.

Summary of Significant Accounti

Summary of Significant Accounting Policies	12 Months Ended
	Sep. 30, 2018
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	2. Summary of Significant Accounting Policies Basis of Presentation The consolidated financial statements include the accounts of the Company and its wholly-owned subsidiaries. All inter-company transactions have been eliminated. Certain prior period amounts have been reclassified to conform to current period presentation. Use of Estimates The preparation of consolidated financial statements in conformity with United States generally accepted accounting principles (“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 inventories, purchase price allocations, recoverability of goodwill and intangibles, and income taxes. Actual amounts could differ from those estimates. Fiscal Year The fiscal years presented are the years ended September 30, 2018 (“2018”), September 30, 2017 (“2017”), and September 30, 2016 (“2016”). Each of the Company’s first three quarters ends on the last day of the calendar month. Segment Information Operating segments are defined as components of a business that can earn revenue and incur expenses for which discrete financial information is evaluated on a regular basis by the chief operating decision maker (“CODM”) in order to decide how to allocate resources and assess performance. The Company’s CODM, the Chief Executive Officer, reviews consolidated results of operations to make decisions, therefore the Company views its operations and manages its business as one operating segment. Cash and Cash Equivalents The Company considers all highly liquid investments with maturities of three months or less when purchased to be cash equivalents. Cash and cash equivalents also include unsettled credit card transactions. Cash equivalents are comprised of money market funds which invest primarily in commercial paper or bonds with a rating of A-1 or better, and bank certificates of deposit. Accounts Receivable Accounts receivables are derived from unpaid invoiced amounts and are recorded at their net realizable value. Each month the Company reviews its receivables on a customer-by-customer basis and evaluates whether an allowance for doubtful accounts is necessary based on any known or perceived collection issues. The allowance for doubtful accounts represents the Company’s estimate of credit exposure for each customer. Any balances that are eventually deemed uncollectible are written off against the allowance after all means of collection have been exhausted and the potential for recovery is considered remote. The Company’s accounts receivable are primarily from customers in the building industry located in the United States and Canada, and no single customer represented at least 10% of the Company’s revenue during the year ended September 30, 2018, or accounts receivable as of September 30, 2018. Concentrations of Risk Financial instruments that potentially subject the Company to significant concentration of credit risk consist primarily of cash, cash equivalents and accounts receivable. The Company maintains the majority of its cash and cash equivalents with one financial institution, which management believes to be financially sound and with minimal credit risk. The Company’s deposits periodically exceed amounts guaranteed by the Federal Deposit Insurance Corporation. Inventories Inventories, consisting substantially of finished goods, are valued at the lower of cost or market (net realizable value). Cost is determined using the moving weighted-average cost method. The Company’s arrangements with vendors typically provide for rebates after it makes a special purchase and/or monthly, quarterly and/or annual rebates of a specified amount of consideration payable when a number of measures have been achieved. Annual rebates are generally related to a specified cumulative level of purchases on a calendar-year basis. The Company accounts for such rebates as a reduction of the inventory value until the product is sold, at which time such rebates reduce cost of sales in the consolidated statements of operations. Throughout the year, the Company estimates the amount of the periodic rebates based upon the expected level of purchases. The Company continually revises these estimates to reflect actual rebates earned based on actual purchase levels. Amounts due from vendors under these arrangements are included in “prepaid expenses and other current assets” in the accompanying consolidated balance sheets. Property and Equipment Property and equipment acquired in connection with acquisitions are recorded at fair value as of the date of the acquisition and depreciated utilizing the straight-line method over the estimated remaining lives. All other additions are recorded at cost, and depreciation is computed using the straight-line method. The Company reviews the estimated useful lives of its fixed assets on an ongoing basis and the following table summarizes the estimates currently used: Asset Class Estimated Useful Life Buildings and improvements 40 years Equipment 3 to 7 years Furniture and fixtures 7 years Leasehold improvements Shorter of the estimated useful life or the term of the lease, considering renewal options expected to be exercised. Business Combinations The Company records acquisitions resulting in the consolidation of a business using the acquisition method of accounting. Under this method, the acquiring Company records the assets acquired, including intangible assets that can be identified and named, and liabilities assumed based on their estimated fair values at the date of acquisition. The Company uses an income approach to determine the fair value of acquired intangible assets, specifically the multi-period excess earnings method for customer relationships and the relief from royalty method for trade names. Various Level 3 fair value assumptions are used in the determination of these estimated fair values, including items such sales growth rates, cost synergies, customer attrition rates, discount rates, and other prospective financial information. The purchase price in excess of the fair value of the assets acquired and liabilities assumed is recorded as goodwill. Estimates associated with the accounting for acquisitions may change as additional information becomes available regarding the assets acquired and liabilities assumed. Transaction costs associated with acquisitions are expensed as incurred. Goodwill and Intangibles On an annual basis and at interim periods when circumstances require, the Company tests the recoverability of its goodwill and indefinite-lived intangible assets. Examples of such indicators include a significant change in the business climate, unexpected competition, loss of key personnel or a decline in the Company’s market capitalization below the Company’s net book value. The Company performs impairment assessments at the reporting unit level, which is defined as an operating segment or one level below an operating segment, also known as a component. The Company currently has five components which it evaluates for aggregation by examining the distribution methods, sales mix, and operating results of each component to determine if these characteristics will be sustained over a long-term basis. For purposes of this evaluation, the Company expects its components to exhibit similar economic characteristics 3-5 years after events such as an acquisition within the Company’s core roofing business or management/business restructuring. Components that exhibit similar economic characteristics are subsequently aggregated into a single reporting unit. Based on the Company’s most recent impairment assessment performed as of August 31, 2018, it was determined that all of the Company’s components exhibited similar economic characteristics, and therefore should be aggregated into a single reporting unit (collectively the “Reporting Unit”). To test for the recoverability of goodwill and indefinite-lived intangible assets, the Company first performs a qualitative assessment based on economic, industry and company-specific factors for all or selected reporting units to determine whether the existence of events and circumstances indicates that it is more likely than not that the goodwill or indefinite-lived intangible asset is impaired. Based on the results of the qualitative assessment, two additional steps in the impairment assessment may be required. The first step would require a comparison of each reporting unit’s fair value to the respective carrying value. If the carrying value exceeds the fair value, a second step is performed to measure the amount of impairment loss on a relative fair value basis, if any. Based on the Company’s most recent qualitative impairment assessment performed as of August 31, 2018, the Company concluded that there were no indicators of impairment, and that therefore it was more likely than not that the fair value of the goodwill and indefinite-lived intangible assets exceeded their net carrying amount, therefore the quantitative two-step impairment test was not required. The Company amortizes certain identifiable intangible assets that have finite lives, currently consisting of non-compete agreements, customer relationships and trade names. Non-compete agreements are amortized on a straight-line basis over the terms of the associated contractual agreements; customer relationship assets are amortized on an accelerated basis based on the expected cash flows generated by the existing customers; and trade names are amortized on an accelerated basis over a five or ten year period. Amortizable intangible assets are tested for impairment, when deemed necessary, based on undiscounted cash flows and, if impaired, are written down to fair value based on either discounted cash flows or appraised values. In connection with certain financing arrangements, the Company has debt issuance costs that are amortized over the lives of the associated financings. Evaluation of Long-Lived Assets The Company evaluates the recoverability of its long-lived assets for impairment whenever events or circumstances indicate that the carrying amount of the assets may not be recoverable. Recoverability is measured by comparing the carrying amount of the asset to the future undiscounted cash flows the asset is expected to generate. If the asset is considered to be impaired, the amount of any impairment is measured as the difference between the carrying value and the fair value of the impaired asset. Fair Value Measurement The Company applies fair value accounting for all financial assets and liabilities that are reported at fair value in the financial statements on a recurring basis. Fair value is defined as the price that would be received from selling an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date. The accounting guidance establishes a defined three-tier hierarchy to classify and disclose the fair value of assets and liabilities on both the date of their initial measurement as well as all subsequent periods. The hierarchy prioritizes the inputs used to measure fair value by the lowest level of input that is available and significant to the fair value measurement. The three levels are described as follows: • Level 1 : Observable inputs. Quoted prices in active markets for identical assets and liabilities; • Level 2 : Observable inputs other than the quoted price. Includes quoted prices for similar instruments, quoted prices for identical or similar instruments in inactive markets and amounts derived from valuation models where all significant inputs are observable in active markets; and • Level 3 : Unobservable inputs. Includes amounts derived from valuation models where one or more significant inputs are unobservable and require the Company to develop relevant assumptions. The Company evaluates its financial assets and liabilities subject to fair value measurements on a recurring basis to determine the appropriate level of classification as of each reporting period. Financial Derivatives The Company has entered into interest rate swaps to minimize the risks and costs associated with financing activities, as well as to maintain an appropriate mix of fixed-rate and floating-rate debt. The swap agreements are contracts to exchange variable-rate for fixed-interest rate payments over the life of the agreements. The Company's derivative instruments are designated as cash flow hedges, for which the Company records the effective portions of changes in their fair value, net of tax, in other comprehensive income. The Company recognizes any ineffective portion of the hedges in the consolidated statement of operations through interest expense, financing costs and other. Net Sales The Company recognizes revenue (net sales on the consolidated statement of operations) when the following four basic criteria are met: • persuasive evidence of an arrangement exists; • delivery has occurred or services have been rendered; • the price to the buyer is fixed and determinable; and • collectability is reasonability assured. Based on these criteria, the Company generally recognizes revenue at the point of sale or upon delivery to the customer site. For goods shipped by third party carriers, the Company recognizes revenue upon shipment since the terms are generally FOB shipping point. The Company also arranges for certain products to be shipped directly from the manufacturer to the customer. The Company recognizes the gross revenue for these sales upon shipment as the terms are FOB shipping point. Leases The Company leases the majority of its facilities and enters into various other operating lease agreements in conducting its business. At the inception of each lease, the Company evaluates the lease agreement to determine whether the lease is an operating or capital lease. Operating lease expenses are recognized in the statements of operations on a straight-line basis over the term of the related lease. Some of the Company’s lease agreements may contain renewal options, tenant improvement allowances, rent holidays or rent escalation clauses. When such items are included in a lease agreement, the Company records a deferred rent asset or liability on the consolidated balance sheets equal to the difference between the rent expense and cash rent payments. The cost of property and equipment acquired under capital lease arrangements represents the lesser of the present value of the minimum lease payments or the fair value of the leased asset as of the inception of the lease. Stock-Based Compensation The Company applies the fair value method to recognize compensation expense for stock-based awards. Using this method, the estimated grant-date fair value of the award is recognized on a straight-line basis over the requisite service period based on the portion of the award that is expected to vest. The Company estimates forfeitures at the time of grant and revises the estimates, if necessary, in subsequent periods if actual forfeitures differ from those estimates. For awards with a performance-based vesting condition, the Company accrues stock-based compensation expense if it is probable that the performance condition will be achieved. Stock-based compensation expense for restricted stock units is measured based on the fair value of the Company’s common stock on the grant date. The Company utilizes the Black-Scholes option pricing model to estimate the grant-date fair value of option awards. The exercise price of option awards is set to equal the estimated fair value of the common stock at the date of the grant. The following weighted-average assumptions are also used to calculate the estimated fair value of option awards: • Expected volatility : The expected volatility of the Company’s shares is estimated using the historical stock price volatility over the most recent period commensurate with the estimated expected term of the awards. • Expected term : For employee stock option awards, the Company determines the weighted average expected term equal to the weighted period between the vesting period and the contract life of all outstanding options. • Dividend yield : The Company has not paid dividends and does not anticipate paying a cash dividend in the foreseeable future and, accordingly, uses an expected dividend yield of zero. • Risk-free interest rate : The Company bases the risk-free interest rate on the implied yield available on a U.S. Treasury note with a term equal to the estimated expected term of the awards. Foreign Currency Translation The Company’s operations located outside of the United States where the local currency is the functional currency are translated into U.S. dollars using the current rate method. Results of operations are translated at the average rate of exchange for the period. Assets and liabilities are translated at the closing rates on the period end date. Gains and losses on translation of these accounts are accumulated and reported as a separate component of equity and other comprehensive income (loss). Gains and losses on foreign currency transactions are recognized in the consolidated statements of operations as a component of interest expense, financing costs, and other. Income Taxes The Company accounts for income taxes using the liability method, which requires it to recognize a current tax liability or asset for current taxes payable or refundable and a deferred tax liability or asset for the estimated future tax effects of temporary differences between the financial statement and tax reporting bases of assets and liabilities to the extent that they are realizable. Deferred tax expense (benefit) results from the net change in deferred tax assets and liabilities during the year. FASB ASC Topic 740 prescribes a recognition threshold and measurement attribute for the financial statement recognition and measurement of a tax position taken or expected to be taken in a tax return. Based on this guidance, the Company analyzes its filing positions in all of the federal and state jurisdictions where it is required to file income tax returns, as well as all open tax years in these jurisdictions. Tax benefits from uncertain tax positions are recognized if it is more likely than not that the position is sustainable based solely on its technical merits. 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. 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 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. Recent Accounting Pronouncements—Adopted In March 2016, the FASB issued ASU 2016-09, “ Compensation—Stock Compensation: Improvements to Employee Share-Based Payment Accounting.” In November 2016, the FASB issued ASU 2016-18, “ Restricted Cash.” Recent Accounting Pronouncements—Not Yet Adopted In May 2014, the FASB issued ASU 2014-09, “ Revenue from Contracts with Customers In February 2016, the FASB issued ASU 2016-02, “ Leases 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 2017-01, “ Business Combinations: Clarifying the Definition of a Business.” In January 2017, the FASB issued ASU 2017-04, “ Simplifying the Accounting for Goodwill Impairment.” In May 2017, the FASB issued ASU 2017-09, “Scope of Modification Accounting.” In February 2018, the FASB issued ASU 2018-02, “Income Statement – Reporting Comprehensive Income.”

Acquisitions

Acquisitions	12 Months Ended
	Sep. 30, 2018
Business Combinations [Abstract]
Acquisitions	3. Acquisitions Allied Building Products Corp. On January 2, 2018 (the “Closing Date”), the Company completed its previously announced acquisition (the “Allied Acquisition”) of all the outstanding capital stock of Allied Building Products Corp. and an affiliated entity (together, “Allied”), pursuant to that certain Stock Purchase Agreement, dated August 24, 2017 (the “Stock Purchase Agreement”), among the Company, Oldcastle, Inc., as parent, and Oldcastle Distribution, Inc., as seller, for approximately $2.625 billion in cash, subject to a working capital and certain other adjustments as set forth in the Stock Purchase Agreement (the “Purchase Price”). As of September 30, 2018, the adjusted purchase price for Allied was $2.88 billion (including a recorded a net working capital adjustment that increased the purchase price by $88.1 million) and purchase accounting entries had not yet been finalized. In connection with the Allied Acquisition, on the Closing Date the Company entered into (i) a new term loan agreement with Citibank, N.A., providing for a term loan B facility with an initial commitment of $970.0 million and (ii) an amended and restated credit agreement with Wells Fargo Bank, N.A., providing for a senior secured asset-based revolving credit facility with an initial commitment of $1.30 billion. Base borrowing rates on these facilities are at LIBOR plus 1.25% and LIBOR plus 2.25%, respectively. In connection with the Allied Acquisition, on the Closing Date, 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., pursuant to that certain Investment Agreement, dated as of August 24, 2017, with CD&R Boulder Holdings, L.P. and Clayton, Dubilier & Rice Fund IX, L.P. (solely for the purpose of limited provisions therein) (the “Convertible Preferred Stock Purchase”). The $400.0 million in proceeds from the Convertible Preferred Stock Purchase were used to finance, in part, the Purchase Price. 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. 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 on the Company’s consolidated balance sheets as mezzanine equity and recognized at $399.2 million (the $400.0 million proceeds received on the Closing Date, net of $0.8 million of issuance costs). Allied’s results of operations have been included with Company’s consolidated results beginning January 2, 2018. Allied distributed products in 208 locations across 31 states as of the date of the acquisition. The Allied Acquisition has been accounted for as a business combination in accordance with the requirements of ASC 805 Business Combinations January 2, 2018 January 2, 2018 (as reported at March 31, 2018) Adjustments (as adjusted at September 30, 2018) Cash $ 19,322 $ (19,153 ) $ 169 Accounts receivable 315,485 22,063 337,548 Inventory 322,705 (7,920 ) 314,785 Prepaid and other current assets 59,279 16,161 75,440 Property, plant, and equipment 139,528 (168 ) 139,360 Goodwill 1,130,635 102,145 1,232,780 Intangible assets 1,037,000 - 1,037,000 Current liabilities (271,252 ) 11,963 (259,289 ) Non-current liabilities (6,820 ) 6,097 (723 ) Total purchase price $ 2,745,882 $ 131,188 $ 2,877,070 The purchase accounting entries above include the impact of the Section 338(h)(10) election under the current U.S. tax code. The Company made this election on October 15, 2018 and has reflected the $164.0 million impact of this election in the purchase price and its fiscal year 2018 tax provision accordingly. The Company determined that $1.18 billion of goodwill related to the acquisition of Allied will become tax deductible. All of the Company’s goodwill plus the indefinite-lived trade name are tested for impairment annually, and all acquired goodwill and intangible assets are subject to review for impairment should future indicators of impairment develop. There were no material contingencies assumed as part of the Allied acquisition. Net sales from the Allied Acquisition included in the Company’s statements of operations for the year ended September 30, 2018 were $2.15 billion. Net income from the Allied Acquisition included in the Company’s statements of operations for the year ended September 30, 2018 was $62.0 million. The following table represents the unaudited pro forma consolidated net sales and net income (loss) for the Company for the periods indicated (in thousands): Twelve Months Ended September 30, 2018 2017 (unaudited) Net sales $ 7,083,960 $ 6,989,658 Net income (loss) 62,081 70,701 The above pro forma results have been calculated by combining the historical results of the Company and Allied as if the Allied Acquisition had occurred on the first day of the fiscal year (October 1) for each of the periods presented. The income tax provision used to calculate net income (loss) for the respective periods presented has been adjusted to reflect the effective tax rate for the annual periods as if it had been based on the resulting, combined results. The pro forma results include estimates for intangible asset amortization, depreciation, interest expense and debt issuance costs and are subject to change once final asset values have been determined. No other material pro forma adjustments were deemed necessary to conform to the Company’s accounting policies or for any other situation. The pro forma information is not necessarily indicative of the results that would have been achieved had the transactions occurred on the first day of the fiscal years presented or that may be achieved in the future. Additional Acquisitions – Fiscal Year 2018 During fiscal year 2018, the Company acquired 7 branches from the following acquisitions: • On May 1, 2018, the Company acquired Tri-State Builder’s Supply, a wholesale supplier of roofing, siding, windows, doors and related building products with 1 branch located in Duluth, Minnesota and annual sales of approximately $6 million. • On July 16, 2018, the Company acquired Atlas Supply, Inc., the Pacific Northwest’s leading distributor of sealants, coatings, adhesives and related waterproofing products, with 6 branches operating in Seattle, Tacoma, Spokane, and Mountlake Terrace in Washington, as well as locations in Portland, Oregon and Boise, Idaho, and annual sales of approximately $37 million. The Company has recorded purchase accounting entries on a preliminary basis for these transactions that recognized the acquired assets and liabilities at their estimated fair values as of the respective acquisition dates. These transactions resulted in goodwill of $8.1 million ($8.0 million of which is deductible for tax purposes) and $10.8 million in intangible assets. For those acquisitions where the acquisition accounting entries have yet to be finalized, the Company’s allocation of the purchase price is subject to change on receipt of additional information, including, but not limited to, the finalization of asset valuations (intangible and fixed) and income tax accounting as well as the Company’s continued review of the assumed liabilities that may result in the recognition of changes to the carrying amounts on the opening balance sheet and a related adjustment to goodwill. Additional Acquisitions – Fiscal Year 2017 During fiscal year 2017, the Company acquired 23 branches from the following five acquisitions: • On December 16, 2016, the Company purchased certain assets of BJ Supply Company, a distributor of roofing and related building products with 1 branch serving Pennsylvania and New Jersey and annual sales of approximately $4 million. The Company has finalized the acquisition accounting entries for this transaction. • On January 3, 2017, the Company acquired American Building & Roofing, Inc., a distributor of mainly residential roofing and related building products with 7 branches around Washington State and annual sales of approximately $36 million. The Company has finalized the acquisition accounting entries for this transaction. • On January 9, 2017, the Company acquired Eco Insulation Supply, a distributor of insulation and related accessories with 1 branch serving Connecticut, Southern New England and the New York City metropolitan area and annual sales of approximately $8 million. The Company has finalized the acquisition accounting entries for this transaction. • On March 1, 2017, the Company acquired Acme Building Materials, Inc., a distributor of residential roofing and related building products with 3 branches in Eastern Michigan and annual sales of approximately $13 million. The Company has finalized the acquisition accounting entries for this transaction. • On May 1, 2017, the Company purchased certain assets of Lowry’s Inc., a distributor of waterproofing and concrete restoration materials with 11 branches operating in California, Arizona, Utah and Hawaii and annual sales of approximately $76 million. The Company has finalized the acquisition accounting entries for this transaction. The Company recorded the acquired assets and liabilities related to these transactions at their estimated fair values as of the respective acquisition dates, with resulting goodwill of $53.0 million (all of which is deductible for tax purposes) and $47.4 million in intangible assets associated with these other acquisitions.

Net Income (Loss) Per Share

Net Income (Loss) Per Share	12 Months Ended
	Sep. 30, 2018
Earnings Per Share [Abstract]
Net Income (Loss) Per Share	4. Net Income (Loss) Per Share The following table presents the components and calculations of basic and diluted net income (loss) per share for each period presented (in thousands, except share and per share amounts): Year Ended September 30, 2018 2017 2016 Net income (loss) $ 98,626 $ 100,864 $ 89,917 Dividends on preferred shares (18,000 ) - - Net income (loss) attributable to common shareholders $ 80,626 $ 100,864 $ 89,917 Undistributed income allocated to participating securities (7,742 ) - - Net income (loss) attributable to common shareholders - basic and diluted $ 72,884 $ 100,864 $ 89,917 Weighted-average common shares outstanding - basic 68,012,879 60,315,648 59,424,372 Effect of common share equivalents 1,178,160 1,028,615 993,695 Weighted-average common shares outstanding - diluted 69,191,039 61,344,263 60,418,067 Net income (loss) per share - basic $ 1.07 $ 1.67 $ 1.51 Net income (loss) per share - diluted $ 1.05 $ 1.64 $ 1.49 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: Year Ended September 30, 2018 2017 2016 Stock options 388,731 331,681 502,294 Restricted stock units 192,151 61,890 45,220 Preferred Stock 7,224,483 - -

Prepaid Expenses and Other Curr

Prepaid Expenses and Other Current Assets	12 Months Ended
	Sep. 30, 2018
Prepaid Expenses And Other Current Assets [Abstract]
Prepaid Expenses and Other Current Assets	5. Prepaid Expenses and Other Current Assets The following table summarizes the significant components of prepaid expenses and other current assets (in thousands): September 30, 2018 2017 Vendor rebates $ 199,725 $ 193,071 Other 44,635 16,067 $ 244,360 $ 209,138

Property and Equipment

Property and Equipment	12 Months Ended
	Sep. 30, 2018
Property Plant And Equipment [Abstract]
Property and Equipment	6. Property and Equipment The following table provides a detailed breakout of property and equipment, by type (in thousands): September 30, 2018 2017 Land and buildings $ 82,991 $ 41,791 Equipment 419,385 293,489 Furniture and fixtures 34,901 23,140 Total property and equipment 537,277 358,420 Accumulated depreciation (256,870 ) (202,291 ) Total property and equipment, net $ 280,407 $ 156,129 Depreciation expense for the years ending September 30, 2018, 2017, and 2016 was $60.3 million, $34.0 million, and $31.9 million, respectively.

Goodwill and Intangible Assets

Goodwill and Intangible Assets	12 Months Ended
	Sep. 30, 2018
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 years ended September 30, 2018 and 2017, respectively (in thousands): Balance at September 30, 2016 $ 1,197,565 Acquisitions 53,012 Translation and other adjustments 1,409 Balance at September 30, 2017 $ 1,251,986 Balance at September 30, 2017 $ 1,251,986 Acquisitions 1,240,913 Translation and other adjustments (1,120 ) Balance at September 30, 2018 $ 2,491,779 The change in the carrying amount of goodwill for the year ended September 30, 2018 and 2017 is primarily attributable to the Company’s acquisitions finalized during the respective periods presented (see Note 3 for further discussion). The Company has recognized no goodwill impairments for any of the periods presented. Intangible Assets In connection with transactions finalized for the year ended September 30, 2018, the Company recorded intangible assets of $1.05 billion ($920.8 million of customer relationships, $7.0 million of beneficial lease arrangements, and $120.0 million of indefinite-lived trademarks). In connection with transactions finalized for the year ended September 30, 2017, the Company recorded intangible assets of $47.4 million ($42.7 million of customer relationships, $4.6 million of amortizable trademarks and $0.1 million of beneficial lease arrangements). The following table summarizes intangible assets by category (in thousands, except time period amounts): September 30, Weighted- Average Remaining Life 1 2018 2017 (Years) Amortizable intangible assets: Non-compete agreements $ 2,824 $ 2,824 2.60 Customer relationships 1,530,565 610,026 18.62 Trademarks 10,500 10,500 7.60 Beneficial lease arrangements 8,060 1,060 4.48 Total amortizable intangible assets 1,551,949 624,410 Accumulated amortization (410,633 ) (268,391 ) Total amortizable intangible assets, net $ 1,141,316 $ 356,019 Indefinite lived trademarks 193,050 73,050 Total intangibles, net $ 1,334,366 $ 429,069 1 For the years ended September 30, 2018, 2017, and 2016, the Company recorded $141.2 million, $82.5 million, and $68.3 million of amortization expense relating to the above-listed intangible assets, respectively. The intangible asset lives range from 5 to 20 years and the weighted-average remaining life was 18.5 years as of September 30, 2018. The following table summarizes the estimated future amortization expense for intangible assets (in thousands): Year Ending September 30, 2019 $ 208,404 2020 179,571 2021 149,888 2022 121,396 2023 97,474 Thereafter 384,583 $ 1,141,316

Financing Arrangements

Financing Arrangements	12 Months Ended
	Sep. 30, 2018
Debt Disclosure [Abstract]
Financing Arrangements	8. Financing Arrangements The following table summarizes all financing arrangements from the respective periods presented (in thousands): September 30, September 30, 2018 2017 Revolving Lines of Credit: 2020 ABL U.S. Revolver, expires October 1, 2020 1 $ - $ - Canada Revolver, expires October 1, 2020 2 - 3,205 2023 ABL U.S. Revolver, expires January 2, 2023 3 89,352 - Canada Revolver, expires January 2, 2023 4 3,090 - Current portion - - Borrowings under revolving lines of credit, net $ 92,442 $ 3,205 Term Loans: Term Loan, matures October 1, 2022 5 $ - $ 433,440 Term Loan, matures January 2, 2025 6 930,726 - Current portion (9,700 ) (4,500 ) Total long-term borrowings under term loans $ 921,026 $ 428,940 Senior Notes: Senior Notes, mature October 2023 7 293,607 292,328 Senior Notes, mature November 2025 8 1,280,092 - Current portion - - Total long-term borrowings under Senior Notes $ 1,573,699 $ 292,328 Long-term debt, net $ 2,494,725 $ 721,268 Equipment Financing Facilities and Other: Equipment financing facilities, various maturities through September 2021 9 $ 11,222 $ 12,898 Capital lease obligations, various maturities through November 2021 10 12,378 19,956 Current portion (9,961 ) (9,641 ) Long-term obligations under equipment financing and other, net $ 13,639 $ 23,213 1 Extinguished on January 2, 2018; Effective rate on borrowings of 2.00% as of September 30, 2017 2 Extinguished on January 2, 2018; Effective rate on borrowings of 3.70% as of September 30, 2017 3 Effective rate on borrowings of 3.36% as of 4 Effective rate on borrowings of 3.95% as of 5 Extinguished on January 2, 2018; 6 Interest rate of 4.53% as of 7 Interest rate of 6.38% as of 8 Interest rate of 4.88% as of September 30, 2018 9 Fixed interest rates ranging from 2.33% to 3.25% as of September 30, 2018 and September 30, 2017 10 Fixed interest rates ranging from 2.72% to 10.39% as of September 30, 2018 and September 30, 2017 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 $65.8 million related to the 2023 ABL, the 2025 Term Loan and the 2025 Senior Notes. Since the financing arrangements entered into in connection with the Allied Acquisition had certain lenders who also participated in previous financing arrangements entered into by the Company, portions of the transactions were accounted for as either a debt modification or a debt extinguishment. In accordance with the accounting for debt modification, the Company expensed $1.5 million of debt issuance costs related to the Allied financing arrangements and recognized a loss on debt extinguishment of $1.2 million. The remainder of the debt issuance costs will be amortized over the term of the Allied 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 consists of revolving loans in both the United States (“2023 U.S. Revolver”) in the amount of $1.20 billion and Canada (“2023 Canada Revolver”) in the amount of $100.0 million. The 2023 ABL has a maturity date of January 2, 2023. The 2023 ABL has various borrowing tranches with an interest rate based on a LIBOR rate (with a floor) plus a fixed spread. The current unused commitment fees on the 2023 ABL are 0.25% per annum. There is one financial covenant under the 2023 ABL, which is a Consolidated Fixed Charge Ratio. The Consolidated Fixed Charge Ratio is calculated by dividing consolidated earnings before interest, taxes, depreciation and amortization (EBITDA) by Consolidated Fixed Charges (both as defined in the agreement). Per the covenant, the Company’s Consolidated Fixed Charge Ratio has to be a minimum of 1.00 at the end of each fiscal quarter, calculated on a trailing four quarter basis. 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 September 30, 2018, the total balance outstanding on the 2023 ABL, net of $10.6 million of unamortized debt issuance costs, was $92.4 million. The Company also has outstanding standby letters of credit related to the 2023 U.S. Revolver in the amount of $13.4 million as of September 30, 2018. 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 on a LIBOR rate (with a floor) plus a fixed spread. 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 September 30, 2018, the outstanding balance on the 2025 Term Loan, net of $34.4 million of unamortized debt issuance costs, was $930.7 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 September 30, 2018, the outstanding balance on the 2025 Senior Notes, net of $19.9 million of unamortized debt issuance costs, was $1.28 billion. Financing - RSG Acquisition In connection with the RSG Acquisition, the Company entered into various financing arrangements totaling $1.45 billion, including an asset-based revolving line of credit (“2020 ABL”) of $700.0 million ($350.0 million of which was drawn at closing) and a $450.0 million term loan (“2022 Term Loan”). The Company also raised an additional $300.0 million through the issuance of senior notes (the “2023 Senior Notes”). The proceeds from these financing arrangements were used to provide working capital and funds for other general corporate purposes, to refinance or otherwise extinguish all third-party indebtedness for borrowed money under Company’s and RSG’s existing senior secured credit facilities and RSG’s unsecured senior notes due 2020, to finance the acquisition, and to pay fees and expenses associated with the RSG acquisition. The Company incurred debt issuance costs totaling approximately $31.3 million related to the 2020 ABL, 2022 Term Loan and 2023 Senior Notes. 2020 ABL On October 1, 2015, the Company entered into a $700.0 million asset-based revolving line of credit with Wells Fargo Bank, N.A. and a syndicate of other lenders. The 2020 ABL had an original maturity date of October 1, 2020 and consisted of revolving loans in both the United States (“2020 U.S. Revolver”) in the amount of $670.0 million and Canada (“Canada Revolver”) in the amount of $30.0 million. The 2020 ABL had various borrowing tranches with an interest rate based on a LIBOR rate (with a floor) plus a fixed spread. The full balance of the 2020 ABL was paid on January 2, 2018 in conjunction with the Allied Acquisition. 2022 Term Loan On October 1, 2015, the Company entered into a $450.0 million Term Loan with Citibank N.A., and a syndicate of other lenders. The 2022 Term Loan required quarterly principal payments in the amount of $1.1 million, with the remaining outstanding principal to be paid on its original maturity date of October 1, 2022. The interest rate was based on a LIBOR rate (with a floor) plus a fixed spread. The Company had the option of selecting a LIBOR period that determined the rate at which interest would accrue, as well as the period in which interest payments are made. The full balance of the 2022 Term Loan was paid on January 2, 2018 in conjunction with the Allied Acquisition, including the write-off of $0.7 million in debt issuance costs. 2023 Senior Notes On October 1, 2015, the Company raised $300.0 million by issuing senior notes due 2023. The 2023 Senior Notes have a coupon rate of 6.38% per annum and are payable semi-annually in arrears, beginning April 1, 2016. There are early payment provisions in the indenture in which the Company would be subject to “make whole” provisions. The Company anticipates repaying the notes at the maturity date of October 1, 2023. The 2023 Senior Notes are guaranteed jointly, severally, fully and unconditionally by the Company’s active United States subsidiaries. As of September 30, 2018, the outstanding balance on the 2023 Senior Notes, net of $6.4 million of unamortized debt issuance costs, was $293.6 million. Other Information Annual principal payments for all outstanding financing arrangements for each of the next five years and thereafter are as follows (in thousands): Year Ending September 30, 2023 ABL 2025 Term Loan Senior Notes Equipment Financing Facilities Total 2019 $ - $ 9,700 $ - $ 9,929 $ 19,629 2020 - 9,700 - 9,014 18,714 2021 - 9,700 - 4,327 14,027 2022 - 9,700 - 330 10,030 2023 103,090 9,700 300,000 - 412,790 Thereafter - 916,650 1,300,000 - 2,216,650 Total debt 103,090 965,150 1,600,000 23,600 2,691,840 Unamortized debt issuance costs (10,648 ) (34,424 ) (26,301 ) - (71,373 ) Total long-term debt $ 92,442 $ 930,726 $ 1,573,699 $ 23,600 $ 2,620,467 Under the terms of the 2023 ABL, the 2025 Term Loan, the 2025 Senior Notes and the 2023 Senior Notes, the Company is limited in making certain restricted payments, including dividends on its common stock. Based on the provisions in the respective debt agreements and given the Company’s intention to not pay common stock dividends in the foreseeable future, the Company does not believe that the restrictions are significant.

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Sep. 30, 2018
Commitments And Contingencies Disclosure [Abstract]
Commitments and Contingencies	9. Commitments and Contingencies Operating Leases The Company mostly operates in leased facilities, which are accounted for as operating leases. The leases typically provide for a base rent plus real estate taxes. Certain of the leases provide for escalating rents over the lives of the leases and rent expense is recognized over the terms of those leases on a straight-line basis. At September 30, 2018, the minimum rental commitments under all non-cancelable operating leases with initial or remaining terms of more than one year were as follows (in thousands): Year Ending September 30, 2019 $ 105,425 2020 94,348 2021 82,827 2022 62,863 2023 46,274 Thereafter 120,291 Total minimum lease payments $ 512,028 Rent expense was $99.1 million, $60.1 million, and $59.3 million for the years ending September 30, 2018, 2017, and 2016, respectively. Sublet income was immaterial for each of these periods. 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.

Stockholders' Equity

Stockholders' Equity	12 Months Ended
	Sep. 30, 2018
Equity [Abstract]
Stockholders' Equity	10. Stockholders’ Equity Common Stock The Company is authorized to issue 100 million shares of common stock. As of September 30, 2018 and 2017 there were 68,135,790 and 67,700,858 shares of common stock issued and outstanding, respectively. Accumulated Other Comprehensive Income (Loss ) Other comprehensive income (loss) is comprised 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 thousands): Foreign Currency Translation Derivative Financial Instruments Accumulated Other Comprehensive Loss Balance as of September 30, 2015 $ (19,293 ) $ (1,427 ) $ (20,720 ) Other comprehensive loss before reclassifications 1,024 - 1,024 Reclassifications out of other comprehensive loss - 1,039 1,039 Balance as of September 30, 2016 $ (18,269 ) $ (388 ) $ (18,657 ) Other comprehensive income before reclassifications 3,706 - 3,706 Reclassifications out of other comprehensive loss - 388 388 Balance as of September 30, 2017 $ (14,563 ) $ - $ (14,563 ) Other comprehensive income before reclassifications (2,687 ) - (2,687 ) Reclassifications out of other comprehensive loss - - - Balance as of September 30, 2018 $ (17,250 ) $ - $ (17,250 ) Gains (losses) on derivative instruments are recognized in the consolidated statements of operations in interest expense, financing costs, and other.

Stock-based Compensation

Stock-based Compensation	12 Months Ended
	Sep. 30, 2018
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Stock-based Compensation	11. Stock-based Compensation On February 9, 2016, the shareholders of the Company approved the Amended and Restated Beacon Roofing Supply, Inc. 2014 Stock Plan (the “2014 Plan”). The 2014 Plan provides for discretionary awards of stock options, stock awards, restricted stock units, and stock appreciation rights (“SARs”) for up to 5,000,000 shares of common stock to selected employees and non-employee directors. The 2014 Plan mandates that all forfeited, expired, and withheld shares, including those from the predecessor plans, be returned to the 2014 Plan and made available for issuance. As of September 30, 2018, there were 3,334,750 shares of common stock available for issuance. Prior to the 2014 Plan, the Company maintained the amended and restated Beacon Roofing Supply, Inc. 2004 Stock Plan (the “2004 Plan”). Upon shareholder approval of the 2014 Plan, the Company ceased issuing equity awards from the 2004 Plan and mandated that all future equity awards will be issued from the 2014 Plan. For all equity awards granted prior to October 1, 2014, in the event of a change in control of the Company, all awards are immediately vested. Beginning in fiscal 2015, equity awards contained 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). 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 period following the grant dates. The fair values of the options granted for the year ended September 30, 2018 were estimated on the dates of grants using the Black-Scholes option-pricing model with the following weighted-average assumptions: Year Ended September 30, 2018 2017 2016 Risk-free interest rate 2.10 % 1.97 % 1.87 % Expected volatility 26.43 % 28.83 % 30.96 % Expected life (in years) 5.46 5.30 5.60 Dividend yield - - - The following table summarizes all stock option activity for the periods presented (in thousands, except share, 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, 2017 2,084,228 $ 28.84 6.1 $ 46,714 Granted 276,370 55.17 Exercised (308,266 ) 24.38 Canceled/Forfeited (81,304 ) 32.92 Expired (1,991 ) 15.28 Balance as of September 30, 2018 1,969,037 $ 33.08 5.7 $ 14,088 Vested and expected to vest after September 30, 2018 1,956,534 $ 32.96 5.7 $ 14,078 Exercisable as of September 30, 2018 1,439,187 $ 27.48 4.7 $ 13,668 1 Aggregate intrinsic value as represents the difference between the closing fair value of the underlying common stock and the exercise price of outstanding, in-the-money options on the date of measurement. During the years ended September 30, 2018 and 2017, the Company recorded stock-based compensation expense related to stock options of $3.9 million and $4.8 million, respectively. As of September 30, 2018, there was $4.4 million of total unrecognized compensation cost related to unvested stock options, which is expected to be recognized over a weighted-average period of 1.7 years. The following table summarizes additional information on stock options for the periods presented (in thousands, except per share amounts): Year Ended September 30, 2018 2017 2016 Weighted-average fair value of stock options granted $ 15.86 $ 14.21 $ 12.89 Total fair value of stock options vested 4,208 5,541 12,347 Total intrinsic value of stock options exercised 9,645 10,941 22,693 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 periods presented: RSUs Outstanding Weighted- Average Grant Date Fair Value Balance at September 30, 2017 770,973 $ 38.95 Granted 370,190 57.40 Performance awards 1 41,440 39.56 Released (191,703 ) 31.91 Canceled/Forfeited (56,877 ) 51.10 Balance at September 30, 2018 934,023 $ 47.00 Vested and expected to vest after September 30, 2018 888,337 $ 46.87 _____________________________ 1 Additional restricted stock units outstanding as a result of the satisfaction of a performance vesting condition prior to the ascribed time-based vesting condition (release date). During the years ended September 30, 2018 and 2017, the Company recorded stock-based compensation expense related to restricted stock units of $12.6 million and $10.3 million, respectively. As of September 30, 2018, there was $17.1 million of total unrecognized compensation cost related to unvested restricted stock units, which is expected to be recognized over a weighted-average period of 1.7 years. The following table summarizes additional information on RSUs for the period presented (in thousands, except share and per share amounts): Year Ended September 30, 2018 2017 2016 Weighted-average fair value of RSUs granted $ 57.40 $ 47.31 $ 38.92 Total fair value of RSUs vested 6,656 4,562 743 Total intrinsic value of RSUs released 11,041 6,079 1,375

Income Taxes

Income Taxes	12 Months Ended
	Sep. 30, 2018
Income Tax Disclosure [Abstract]
Income Taxes	12. Income Taxes On December 22, 2017, the U.S. federal government officially signed into law the Tax Cut and Jobs Act of 2017 (“TCJA”). ASC 740, Accounting for Income Taxes, requires companies to recognize the effect of tax law changes in the period of enactment even though the effective date for most provisions is for tax years beginning after December 31, 2017, or in the case of certain other provisions, January 1, 2018. Though certain key aspects of the new law are effective January 1, 2018 and have an immediate accounting effect, other significant provisions are not effective or may not result in accounting effects for September 30 fiscal year-end companies until October 1, 2018. Given the significance of the legislation, the SEC staff issued Staff Accounting Bulletin No. 118 (“SAB 118”), which allows registrants to record provisional amounts during a one year “measurement period” similar to that used when accounting for business combinations. Per SAB 118, the measurement period is deemed to have an earlier end date when the registrant has obtained, prepared and analyzed the information necessary to finalize its accounting. During the measurement period, impacts of the updated tax law are expected to be recorded at the time a reasonable estimate for all, or a portion, of the effects can be made, and provisional amounts can be recognized and adjusted as information becomes available, prepared or analyzed. SAB 118 states, that at each reporting period, companies must disclose the effects of the TCJA for areas where accounting is complete, disclose provisional amounts (or adjustments to provisional amounts) for the effects of the TCJA areas where accounting is not complete but a reasonable estimate has been determined, and confirm areas where a reasonable estimate of the effects cannot yet be made, and therefore taxes are reflected in accordance with law prior to the enactment of the TCJA. As of September 30, 2018, the Company was able to make the following reasonable estimates regarding the impact of the TCJA on corporate taxation: • The Company has a blended federal corporate income tax rate for fiscal year 2018 of 24.5%. This transitional tax rate stems from Section 15 of the Internal Revenue Code that states if the tax rate changes in during a tax year, the tax rate for the full year is calculated using the prior and revised tax rates on a proportional basis using the number of days under each legislated rate. For the 2019 fiscal year, the Company will have a federal corporate income tax rate of 21%. • The Company remeasured all its deferred tax assets and liabilities based on the revised corporate income tax rate. Due to the Company’s status as a non-calendar year-end filer, it was required to perform additional analysis to distinguish those deferred taxes that will be realized during fiscal year 2018 at the blended federal corporate income tax rate of 24.5% from those that will be realized in future years at the revised rate. As a result, the Company decreased its deferred tax liabilities and recorded an income tax benefit of $50.0 million in its consolidated statement of operations for the year ended September 30, 2018. • The Company also calculated the impact of the mandatory repatriation transition tax the Company’s non-domestic subsidiary, Beacon Roofing Supply Canada Company (“BRSCC”). BRSCC is treated as a controlled foreign corporation and would generally be taxed in the United States only upon an actual or deemed distribution. As of September 30, 2018, BRSCC had $15.7 million of net accumulated earnings. Based on this amount, the Company recognized an expense of $1.2 million for the one-time repatriation transition tax liability in its consolidated statement of operations for the year ended September 30, 2018. This additional tax will be offset by the Company’s net operating loss for federal income tax purposes (see further discussion below). State conformity to the TCJA law changes have started to be communicated by the state and local jurisdictions at this time; therefore, the Company has not made adjustments related to the potential impact in its financial statements. The following table summarizes the components of the income tax provision (benefit) (in thousands): Year Ended September 30, 2018 2017 2016 Current: Federal 1 $ (4,435 ) $ 52,718 $ 23,403 Foreign 492 1,366 1,183 State 3,516 8,975 2,426 Total current taxes $ (427 ) $ 63,059 $ 27,012 Deferred: Federal $ (35,249 ) $ (656 ) $ 25,935 Foreign (173 ) - 321 State 5,305 78 3,347 Total deferred taxes $ (30,117 ) $ (578 ) $ 29,603 Provision for (benefit from) income taxes $ (30,544 ) $ 62,481 $ 56,615 _____________________________ 1 2018 tax benefit due to changes in the treatment of acquired fixed assets stemming from the Tax Cut and Jobs Act of 2017 The following table is a reconciliation of the statutory federal income tax rate to the Company’s effective income tax rate for the periods presented: Year Ended September 30, 2018 2017 2016 U.S. federal income taxes at statutory rate 24.5 % 35.0 % 35.0 % State income taxes, net of federal benefit 5.2 % 3.9 % 4.2 % Share-based payments (3.9 %) 0.0 % 0.0 % Deferred tax asset/liability remeasurement 1 (73.5 %) 0.0 % (1.0 %) Repatriation transition tax 1 1.8 % 0.0 % 0.0 % Non-deductible professional fees 0.0 % 0.0 % 0.4 % Other 1.0 % (0.6 %) 0.0 % Effective tax rate (44.9 %) 38.3 % 38.6 % 1 Deferred income taxes reflect the tax consequences of temporary differences between the amounts of assets and liabilities for financial reporting purposes and such amounts as measured by tax law. These temporary differences are determined according to ASC 740 Income Taxes. Temporary differences that give rise to deferred tax assets and liabilities are as follows (in thousands): September 30, 2018 2017 Deferred tax assets: Deferred compensation $ 11,346 $ 14,237 Allowance for doubtful accounts 663 1,318 Accrued vacation and other 5,079 6,602 Inventory valuation 12,900 10,564 Tax loss carryforwards 1 17,271 20,575 Other 1,517 958 Total deferred tax assets $ 48,776 $ 54,254 Deferred tax liabilities: Excess tax over book depreciation and amortization $ (155,770 ) $ (192,637 ) Total deferred tax liabilities (155,770 ) (192,637 ) Net deferred income tax liabilities $ (106,994 ) $ (138,383 ) 1 The Company acquired $135.3 million of federal and state net operating loss (“NOL”) carryforwards as part of its acquisition of Roofing Supply Group (“RSG”) in fiscal year 2016. For the year ended September 30, 2018, the Company utilized $15.7 million of federal NOLs and generated $2.6 million in foreign tax credits in connection with the repatriation tax from the TCJA. As of September 30, 2018, the Company had a total federal NOL carryforward balance of $59.3 million, portions of which is set to expire at various dates through 2035. The Company’s non-domestic subsidiary, BRSCC, is treated as a controlled foreign corporation. BRSCC’s taxable income, which reflects all of the Company’s Canadian operations, is being taxed only in Canada and would generally be taxed in the United States only upon an actual or deemed distribution. The Company expects that BRSCC’s earnings will be indefinitely reinvested for the foreseeable future; therefore, no United States deferred tax asset or liability for the differences between the book basis and the tax basis of BRSCC has been recorded as of September 30, 2018. As of September 30, 2018, the Company’s goodwill balance on its consolidated balance sheet was $2.49 billion, of which there remains an amortizable tax basis of $1.45 billion for income tax purposes. As of September 30, 2018, there were no uncertain tax positions which, if recognized, would affect the Company’s effective tax rate. The Company’s accounting policy is to recognize any interest and penalties related to income tax matters in income tax expense in the consolidated statements of operations. The Company has operations in 50 U.S. states and 6 provinces in Canada. The Company is currently under audit in certain state and local jurisdictions for various years. These audits may involve complex issues, which may require an extended period of time to resolve. Additional taxes are reasonably possible; however the amounts cannot be estimated at this time or would be significant. The Company is no longer subject to U.S. federal income tax examinations for any fiscal years ended on or before September 30, 2014. For the majority of states, the Company is also no longer subject to tax examinations for any fiscal years ended on or before September 30, 2014. In Canada, the Company is no longer subject to tax examinations for any fiscal years ended on or before September 30, 2014. For the Canadian provinces, the Company is no longer subject to tax examinations for any fiscal years ended on or before September 30, 2014.

Geographic and Product Data

Geographic and Product Data	12 Months Ended
	Sep. 30, 2018
Segment Reporting [Abstract]
Geographic and Product Data	13. Geographic and Product Data The following tables summarize certain geographic information for the periods presented (in thousands): Year Ended September 30, 2018 2017 2016 Net sales U.S. $ 6,239,332 $ 4,198,935 $ 3,949,067 Canada 178,979 177,735 178,042 Total net sales $ 6,418,311 $ 4,376,670 $ 4,127,109 September 30, 2018 2017 Long-lived assets U.S. $ 1,409,742 $ 507,236 Canada 13,224 13,446 Total long-lived assets $ 1,422,966 $ 520,682 The following table summarizes net sales from external customers by product group (in thousands): Year Ended September 30, 2018 2017 2016 Residential roofing products $ 2,798,756 $ 2,380,435 $ 2,190,762 Non-residential roofing products 1,635,963 1,273,153 1,331,319 Complementary building products 1,983,592 723,082 605,028 Total net sales $ 6,418,311 $ 4,376,670 $ 4,127,109

Supplemental Guarantor Informat

Supplemental Guarantor Information	12 Months Ended
	Sep. 30, 2018
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Supplemental Guarantor Information	14. The 2023 Senior Notes and 2025 Senior Notes are guaranteed jointly and severally by all of the United States subsidiaries of the Company (collectively, the “Guarantor”), and not by the Canadian subsidiaries of the Company. Such guarantees are full and unconditional. Supplemental condensed consolidating financial information of the Company, including such information for the Guarantor, is presented below. The information is presented in accordance with the requirements of Rule 3-10 under the SEC’s Regulation S-X. The financial information may not necessarily be indicative of results of operations, cash flows or financial position had the non-guarantor subsidiaries operated as independent entities. Investments in subsidiaries are presented using the equity method of accounting. The principal elimination entries eliminate investments in subsidiaries and intercompany balances and transactions. Separate financial statements of the Guarantor are not provided as the consolidating financial information contained herein provides a more meaningful disclosure to allow investors to determine the nature of the assets held by, and the operations of, the combined groups. BEACON ROOFING SUPPLY, INC. (Unaudited; In thousands) September 30, 2018 Parent Guarantor Subsidiaries Non-Guarantor Subsidiaries Eliminations and Other Consolidated Assets Current assets: Cash and cash equivalents $ - $ 136,499 $ 1,959 $ (8,531 ) $ 129,927 Accounts receivable, net - 1,051,410 40,262 (1,139 ) 1,090,533 Inventories, net - 907,605 28,442 - 936,047 Prepaid expenses and other current assets 23,711 214,011 6,638 - 244,360 Total current assets 23,711 2,309,525 77,301 (9,670 ) 2,400,867 Intercompany receivable, net - 1,361,615 - (1,361,615 ) - Investments in consolidated subsidiaries 6,109,325 - - (6,109,325 ) - Deferred income taxes, net 22,475 - - (22,475 ) - Property and equipment, net 18,929 250,517 10,961 - 280,407 Goodwill - 2,461,725 30,054 - 2,491,779 Intangibles, net - 1,332,104 2,262 - 1,334,366 Other assets, net 1,243 - - - 1,243 Total Assets $ 6,175,683 $ 7,715,486 $ 120,578 $ (7,503,085 ) $ 6,508,662 Liabilities and Stockholders' Equity Current liabilities: Accounts payable $ 24,154 $ 843,907 $ 22,482 $ (9,671 ) $ 880,872 Accrued expenses 41,448 564,331 5,760 - 611,539 Current portions of long-term debt 9,700 9,961 - - 19,661 Total current liabilities 75,302 1,418,199 28,242 (9,671 ) 1,512,072 Intercompany payable, net 1,322,156 - 39,459 (1,361,615 ) - Borrowings under revolving lines of credit, net - 89,352 3,090 - 92,442 Long-term debt, net 2,494,725 - - - 2,494,725 Deferred income taxes, net - 128,846 622 (22,474 ) 106,994 Long-term obligations under equipment financing and other, net - 13,639 - - 13,639 Other long-term liabilities - 5,207 83 - 5,290 Total liabilities 3,892,183 1,655,243 71,496 (1,393,760 ) 4,225,162 Convertible preferred stock 399,195 - - - 399,195 Total stockholders' equity 1,884,305 6,060,243 49,082 (6,109,325 ) 1,884,305 Total Liabilities and Stockholders' Equity $ 6,175,683 $ 7,715,486 $ 120,578 $ (7,503,085 ) $ 6,508,662 BEACON ROOFING SUPPLY, INC. Condensed Consolidating Balance Sheets (Unaudited; In thousands) September 30, 2017 Parent Guarantor Subsidiaries Non-Guarantor Subsidiaries Eliminations and Other Consolidated Assets Current assets: Cash and cash equivalents $ - $ 149,799 $ 1,582 $ (13,131 ) $ 138,250 Accounts receivable, net - 663,034 42,633 (1,140 ) 704,527 Inventories, net - 527,226 24,698 - 551,924 Prepaid expenses and other current assets 4,195 198,817 6,126 - 209,138 Total current assets 4,195 1,538,876 75,039 (14,271 ) 1,603,839 Intercompany receivable, net - 655,372 - (655,372 ) - Investments in consolidated subsidiaries 3,160,273 - - (3,160,273 ) - Deferred income taxes, net 30,822 - - (30,822 ) - Property and equipment, net 6,610 138,955 10,564 - 156,129 Goodwill - 1,220,812 31,174 - 1,251,986 Intangibles, net - 426,187 2,882 - 429,069 Other assets, net 2,912 5,622 - - 8,534 Total Assets $ 3,204,812 $ 3,985,824 $ 119,659 $ (3,860,738 ) $ 3,449,557 Liabilities and Stockholders' Equity Current liabilities: Accounts payable $ 27,174 $ 468,891 $ 21,903 $ (14,271 ) $ 503,697 Accrued expenses 51,183 204,173 5,941 - 261,297 Current portions of long-term obligations 4,500 9,641 - - 14,141 Total current liabilities 82,857 682,705 27,844 (14,271 ) 779,135 Intercompany payable, net 618,881 - 36,491 (655,372 ) - Borrowings under revolving lines of credit, net - - 3,205 - 3,205 Long-term debt, net 721,268 - - - 721,268 Deferred income taxes, net - 168,209 996 (30,822 ) 138,383 Long-term obligations under equipment financing and other, net - 23,147 66 - 23,213 Other long-term liabilities - 2,547 - - 2,547 Total liabilities 1,423,006 876,608 68,602 (700,465 ) 1,667,751 Total stockholders' equity 1,781,806 3,109,216 51,057 (3,160,273 ) 1,781,806 Total Liabilities and Stockholders' Equity $ 3,204,812 $ 3,985,824 $ 119,659 $ (3,860,738 ) $ 3,449,557 BEACON ROOFING SUPPLY, INC. Condensed Consolidating Statements of Operations (Unaudited; In thousands, except share and per share amounts) Year Ended September 30, 2018 Parent Guarantor Subsidiaries Non-Guarantor Subsidiaries Eliminations and Other Consolidated Net sales $ - $ 6,239,332 $ 178,979 $ - $ 6,418,311 Cost of products sold - 4,685,616 139,374 - 4,824,990 Gross profit - 1,553,716 39,605 - 1,593,321 Operating expense - - Selling, general and administrative 5,909 1,147,390 33,893 - 1,187,192 Depreciation 1,989 56,598 1,731 - 60,318 Amortization - 140,664 521 - 141,185 Total operating expense 7,898 1,344,652 36,145 - 1,388,695 Intercompany charges (income) (6,734 ) 6,565 169 - - Income (loss) from operations (1,164 ) 202,499 3,291 - 204,626 Interest expense, financing costs, and other 124,169 11,648 727 - 136,544 Intercompany interest expense (income) (24,270 ) 22,738 1,532 - - Income (loss) before provision for income taxes (101,063 ) 168,113 1,032 - 68,082 Provision for (benefit from) income taxes 11,398 (42,261 ) 319 - (30,544 ) Income (loss) before equity in net income of subsidiaries (112,461 ) 210,374 713 - 98,626 Equity in net income of subsidiaries 211,087 - - (211,087 ) - Net income (loss) $ 98,626 $ 210,374 $ 713 $ (211,087 ) $ 98,626 BEACON ROOFING SUPPLY, INC. Condensed Consolidating Statements of Operations (Unaudited; In thousands, except share and per share amounts) Year Ended September 30, 2017 Parent Guarantor Subsidiaries Non-Guarantor Subsidiaries Eliminations and Other Consolidated Net sales $ - $ 4,198,935 $ 177,735 $ - $ 4,376,670 Cost of products sold - 3,162,896 137,835 - 3,300,731 Gross profit - 1,036,039 39,900 - 1,075,939 Operating expense Selling, general and administrative 26,962 685,690 30,724 - 743,376 Depreciation 1,534 30,758 1,710 - 34,002 Amortization - 81,880 585 - 82,465 Total operating expense 28,496 798,328 33,019 - 859,843 Intercompany charges (income) (4,664 ) 4,342 322 - - Income (loss) from operations (23,832 ) 233,369 6,559 - 216,096 Interest expense, financing costs, and other 38,660 14,033 58 - 52,751 Intercompany interest expense (income) (24,458 ) 22,927 1,531 - - Income (loss) before provision for income taxes (38,034 ) 196,409 4,970 - 163,345 Provision for (benefit from) income taxes (3,284 ) 64,399 1,366 - 62,481 Income (loss) before equity in net income of subsidiaries (34,750 ) 132,010 3,604 - 100,864 Equity in net income of subsidiaries 135,614 - - (135,614 ) - Net income (loss) $ 100,864 $ 132,010 $ 3,604 $ (135,614 ) $ 100,864 BEACON ROOFING SUPPLY, INC. Condensed Consolidating Statements of Operations (Unaudited; In thousands, except share and per share amounts) Year Ended September 30, 2016 Parent Guarantor Subsidiaries Non-Guarantor Subsidiaries Eliminations and Other Consolidated Net sales $ - $ 3,949,313 $ 178,042 $ (246 ) $ 4,127,109 Cost of products sold - 2,977,174 137,112 (246 ) 3,114,040 Gross profit - 972,139 40,930 - 1,013,069 Operating expense Selling, general and administrative 58,592 619,045 30,256 - 707,893 Depreciation 1,357 28,975 1,544 - 31,876 Amortization - 67,649 667 - 68,316 Total operating expense 59,949 715,669 32,467 - 808,085 Intercompany charges (income) (51,942 ) 49,285 2,657 - - Income (loss) from operations (8,007 ) 207,185 5,806 - 204,984 Interest expense, financing costs, and other 42,835 14,965 652 - 58,452 Intercompany interest expense (income) (21,536 ) 19,928 1,608 - - Income (loss) before provision for income taxes (29,306 ) 172,292 3,546 - 146,532 Provision for (benefit from) income taxes (472 ) 55,613 1,474 - 56,615 Income (loss) before equity in net income of subsidiaries (28,834 ) 116,679 2,072 - 89,917 Equity in net income of subsidiaries 118,751 - - (118,751 ) - Net income (loss) $ 89,917 $ 116,679 $ 2,072 $ (118,751 ) $ 89,917 BEACON ROOFING SUPPLY, INC. Condensed Consolidating Statements of Comprehensive Income (Unaudited; In thousands) Year Ended September 30, 2018 Parent Guarantor Subsidiaries Non-Guarantor Subsidiaries Eliminations and Other Consolidated Net income (loss) $ 98,626 $ 210,374 $ 713 $ (211,087 ) $ 98,626 Other comprehensive income (loss): Foreign currency translation adjustment (2,687 ) - (2,687 ) 2,687 (2,687 ) Total other comprehensive income (loss) (2,687 ) - (2,687 ) 2,687 (2,687 ) Comprehensive income (loss) $ 95,939 $ 210,374 $ (1,974 ) $ (208,400 ) $ 95,939 Year Ended September 30, 2017 Parent Guarantor Subsidiaries Non-Guarantor Subsidiaries Eliminations and Other Consolidated Net income (loss) $ 100,864 $ 132,010 $ 3,604 $ (135,614 ) $ 100,864 Other comprehensive income (loss): Foreign currency translation adjustment 3,706 - 3,706 (3,706 ) 3,706 Total other comprehensive income (loss) 3,706 - 3,706 (3,706 ) 3,706 Comprehensive income (loss) $ 104,570 $ 132,010 $ 7,310 $ (139,320 ) $ 104,570 Year Ended September 30, 2016 Parent Guarantor Subsidiaries Non-Guarantor Subsidiaries Eliminations and Other Consolidated Net income (loss) $ 89,917 $ 116,679 $ 2,072 $ (118,751 ) $ 89,917 Other comprehensive income (loss): Foreign currency translation adjustment 1,024 - 1,024 (1,024 ) 1,024 Total other comprehensive income (loss) 1,024 - 1,024 (1,024 ) 1,024 Comprehensive income (loss) $ 90,941 $ 116,679 $ 3,096 $ (119,775 ) $ 90,941 BEACON ROOFING SUPPLY, INC. Condensed Consolidating Statements of Cash Flows (Unaudited; In thousands) Year Ended September 30, 2018 Parent Guarantor Subsidiaries Non-Guarantor Subsidiaries Eliminations and Other Consolidated Net cash provided by (used in) operating activities $ (100,302 ) $ 638,451 $ (680 ) $ 1,912 $ 539,381 Investing Activities Purchases of property and equipment (14,354 ) (29,132 ) (2,524 ) - (46,010 ) Acquisition of businesses (2,740,480 ) - - - (2,740,480 ) Proceeds from the sale of assets - 2,121 28 - 2,149 Intercompany activity 699,970 - - (699,970 ) - Net cash provided by (used in) investing activities (2,054,864 ) (27,011 ) (2,496 ) (699,970 ) (2,784,341 ) Financing Activities Borrowings under revolving lines of credit - 2,766,447 41,294 - 2,807,741 Repayments under revolving lines of credit - (2,666,447 ) (41,294 ) - (2,707,741 ) Borrowings under term loan 970,000 - - - 970,000 Repayments under term loan (445,850 ) - - - (445,850 ) Repayments under equipment financing facilities and other - (11,593 ) - - (11,593 ) Borrowings under senior notes 1,300,000 - - - 1,300,000 Payment of debt issuance costs (58,266 ) (7,522 ) - - (65,788 ) Proceeds from issuance of convertible preferred stock 400,000 - - - 400,000 Payment of stock issuance costs (1,279 ) - - - (1,279 ) Payment of dividends on preferred stock (12,978 ) - - - (12,978 ) Proceeds from issuance of common stock related to equity awards 7,514 - - - 7,514 Taxes paid related to net share settlement of equity awards (3,975 ) - - - (3,975 ) Intercompany activity - (705,625 ) 2,967 702,658 - Net cash provided by (used in) financing activities 2,155,166 (624,740 ) 2,967 702,658 2,236,051 Effect of exchange rate changes on cash and cash equivalents - - 586 - 586 Net increase (decrease) in cash and cash equivalents - (13,300 ) 377 4,600 (8,323 ) Cash and cash equivalents, beginning of period - 149,799 1,582 (13,131 ) 138,250 Cash and cash equivalents, end of period $ - $ 136,499 $ 1,959 $ (8,531 ) $ 129,927 BEACON ROOFING SUPPLY, INC. Condensed Consolidating Statements of Cash Flows (Unaudited; In thousands) Year Ended September 30, 2017 Parent Guarantor Subsidiaries Non-Guarantor Subsidiaries Eliminations and Other Consolidated Net cash provided by (used in) operating activities $ (2,466 ) $ 313,396 $ 4,888 $ (618 ) $ 315,200 Investing Activities Purchases of property and equipment (3,517 ) (34,584 ) (1,727 ) - (39,828 ) Acquisition of businesses (129,390 ) - - - (129,390 ) Proceeds from the sale of assets - 2,150 83 - 2,233 Intercompany activity (203,163 ) - - 203,163 - Net cash used in investing activities (336,070 ) (32,434 ) (1,644 ) 203,163 (166,985 ) Financing Activities Borrowings under revolving lines of credit - 2,445,084 19,044 - 2,464,128 Repayments under revolving lines of credit - (2,812,663 ) (20,567 ) - (2,833,230 ) Repayments under term loan (4,500 ) - - - (4,500 ) Repayments under equipment financing facilities and other - (10,049 ) 15 - (10,034 ) Payment of debt issuance costs (1,669 ) - - - (1,669 ) Proceeds from secondary offering of common stock 345,503 - - - 345,503 Payment of issuance costs from secondary offering of common stock (14,684 ) - - - (14,684 ) Proceeds from issue of common stock related to equity awards 11,341 - - - 11,341 Taxes paid related to net share settlement of equity awards (392 ) - - - (392 ) Excess tax benefit from stock-based compensation 2,937 - - - 2,937 Intercompany activity - 209,018 (2,279 ) (206,739 ) - Net cash provided by (used in) financing activities 338,536 (168,610 ) (3,787 ) (206,739 ) (40,600 ) Effect of exchange rate changes on cash and cash equivalents - - (751 ) - (751 ) Net decrease in cash and cash equivalents - 112,352 (1,294 ) (4,194 ) 106,864 Cash and cash equivalents, beginning of period - 37,447 2,876 (8,937 ) 31,386 Cash and cash equivalents, end of period $ - $ 149,799 $ 1,582 $ (13,131 ) $ 138,250 BEACON ROOFING SUPPLY, INC. Condensed Consolidating Statements of Cash Flows (Unaudited; In thousands) Year Ended September 30, 2016 Parent Guarantor Subsidiaries Non-Guarantor Subsidiaries Eliminations and Other Consolidated Net cash provided by operating activities $ (22,799 ) $ 143,427 $ 4,751 $ (4,731 ) $ 120,648 Investing Activities Purchases of property and equipment (3,654 ) (20,008 ) (2,653 ) - (26,315 ) Acquisition of businesses (1,018,188 ) - - - (1,018,188 ) Proceeds from the sale of assets - 1,882 - - 1,882 Intercompany activity 475,099 - - (475,099 ) - Net cash provided by (used in) investing activities (546,743 ) (18,126 ) (2,653 ) (475,099 ) (1,042,621 ) Financing Activities Borrowings under revolving lines of credit - 1,877,729 14,730 - 1,892,459 Repayments under revolving lines of credit - (1,520,003 ) (21,529 ) - (1,541,532 ) Borrowings under term loan 490,793 - - - 490,793 Repayments under term loan (230,918 ) - - - (230,918 ) Repayments under equipment financing facilities and other (45 ) (4,659 ) (20 ) - (4,724 ) Borrowings under senior notes 300,000 - - - 300,000 Payment of debt issuance costs (19,402 ) (8,923 ) - - (28,325 ) Proceeds from issuance of common stock 24,160 - - - 24,160 Taxes paid related to net share settlement of equity awards (2 ) - - - (2 ) Excess tax benefit from stock-based compensation 4,956 - - - 4,956 Intercompany activity - (474,814 ) (285 ) 475,099 - Net cash provided by (used in) financing activities 569,542 (130,670 ) (7,104 ) 475,099 906,867 Effect of exchange rate changes on cash and cash equivalents - - 831 - 831 Net increase (decrease) in cash and cash equivalents - (5,369 ) (4,175 ) (4,731 ) (14,275 ) Cash and cash equivalents, beginning of period - 42,816 7,051 (4,206 ) 45,661 Cash and cash equivalents, end of period $ - $ 37,447 $ 2,876 $ (8,937 ) $ 31,386

Allowance for Doubtful Accounts

Allowance for Doubtful Accounts	12 Months Ended
	Sep. 30, 2018
Allowance For Doubtful Accounts [Abstract]
Allowance for Doubtful Accounts	15. Allowance for Doubtful Accounts The following table summarizes changes in the valuation of the allowance for doubtful accounts (in thousands): Year Ended September 30, Beginning Balance Charged to Operations Write-offs Ending Balance 2018 $ 11,829 $ 10,948 $ (5,193 ) $ 17,584 2017 14,812 2,914 (5,897 ) 11,829 2016 6,298 13,681 (5,167 ) 14,812

Fair Value Measurement

Fair Value Measurement	12 Months Ended
	Sep. 30, 2018
Fair Value Disclosures [Abstract]
Fair Value Measurement	16. Fair Value Measurement As of September 30, 2018, 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 September 30, 2018, based upon recent trading prices (Level 2 — market approach), the fair value of the Company’s $300.0 million Senior Notes due in 2023 was $311.0 million and the fair value of the $1.30 billion Senior Notes due in 2025 was $1.20 billion. As of September 30, 2018, the fair value of the Company’s term loan and revolving asset-based line of credit approximated the amount outstanding. The Company estimates the fair value of these financing arrangements by discounting the future cash flows of each instrument using estimated market rates of debt instruments with similar maturities and credit profiles (Level 3).

Employee Benefit Plans

Employee Benefit Plans	12 Months Ended
	Sep. 30, 2018
Compensation And Retirement Disclosure [Abstract]
Employee Benefit Plans	17. Employee Benefit Plans The Company maintains defined contribution plans covering all full-time employees of the Company who have 90 days of service and are at least 21 years old. An eligible employee may elect to make a before-tax contribution of between 1% and 100% of his or her compensation through payroll deductions, not to exceed the annual limit set by law. The Company currently matches the first 50% of participant contributions limited to 6% of a participant’s gross compensation (maximum Company match is 3%). The combined total expense for this plan and a similar plan for Canadian employees was $11.8 million, $8.2 million, and $7.3 million for the years ended September 30, 2018, 2017, and 2016, respectively. The Company sponsors an external pension fund for certain of its foreign employees who belong to a local union. Pension contributions are made to government-sponsored social security pension plans in accordance with local legal requirements. Annual contributions were $0.2 million, $0.1 million, and $0.1 million for the years ended September 30, 2018, 2017, and 2016, respectively. The Company also participates in multi-employer defined benefit plans for which it is not the sponsor. The aggregated expense for these plans for the fiscal year ended September 30, 2018 was $1.8 million. In the event that the Company withdraws from participation in one of these plans, applicable law could require the Company to make a lump-sum contribution to the plan. The Company’s withdrawal liability depends on the extent of the plan’s funding of vested benefits. As of September 30, 2018, the Company’s multi-employer defined benefit plans are reported to have underfunded liabilities.

Financial Derivatives

Financial Derivatives	12 Months Ended
	Sep. 30, 2018
Derivative Instruments And Hedging Activities Disclosure [Abstract]
Derivative Instruments and Hedging Activities Disclosure	18. Financial Derivatives The Company has historically used 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 March 28, 2013, the Company entered into an interest rate swap agreement with a notional amount of $213.8 million which expired on March 31, 2017. This agreement swapped the thirty-day LIBOR to a fixed-rate of 1.38% and had scheduled reductions of the notional amount equal to $2.8 million per quarter, effectively matching the repayment schedule under the Term Loan outstanding at that time. The Company determined this swap agreement qualified for cash flow hedge accounting under ASC 815, therefore changes in the fair value of the swap were recognized through other comprehensive income each period. On October 1, 2015, the Company terminated the swap agreement and settled the $2.4 million unrealized loss with the counterparty. This $2.4 million unrealized loss was recognized on a straight-line basis as interest expense from the termination date through March 31, 2017, the original expiration date of the swap agreement.

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Sep. 30, 2018
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The consolidated financial statements include the accounts of the Company and its wholly-owned subsidiaries. All inter-company transactions have been eliminated. Certain prior period amounts have been reclassified to conform to current period presentation.
Use of Estimates	Use of Estimates The preparation of consolidated financial statements in conformity with United States generally accepted accounting principles (“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 inventories, purchase price allocations, recoverability of goodwill and intangibles, and income taxes. Actual amounts could differ from those estimates.
Fiscal Year	Fiscal Year The fiscal years presented are the years ended September 30, 2018 (“2018”), September 30, 2017 (“2017”), and September 30, 2016 (“2016”). Each of the Company’s first three quarters ends on the last day of the calendar month.
Segment Information	Segment Information Operating segments are defined as components of a business that can earn revenue and incur expenses for which discrete financial information is evaluated on a regular basis by the chief operating decision maker (“CODM”) in order to decide how to allocate resources and assess performance. The Company’s CODM, the Chief Executive Officer, reviews consolidated results of operations to make decisions, therefore the Company views its operations and manages its business as one operating segment.
Cash and Cash Equivalents	Cash and Cash Equivalents The Company considers all highly liquid investments with maturities of three months or less when purchased to be cash equivalents. Cash and cash equivalents also include unsettled credit card transactions. Cash equivalents are comprised of money market funds which invest primarily in commercial paper or bonds with a rating of A-1 or better, and bank certificates of deposit.
Accounts Receivable	Accounts Receivable Accounts receivables are derived from unpaid invoiced amounts and are recorded at their net realizable value. Each month the Company reviews its receivables on a customer-by-customer basis and evaluates whether an allowance for doubtful accounts is necessary based on any known or perceived collection issues. The allowance for doubtful accounts represents the Company’s estimate of credit exposure for each customer. Any balances that are eventually deemed uncollectible are written off against the allowance after all means of collection have been exhausted and the potential for recovery is considered remote. The Company’s accounts receivable are primarily from customers in the building industry located in the United States and Canada, and no single customer represented at least 10% of the Company’s revenue during the year ended September 30, 2018, or accounts receivable as of September 30, 2018.
Concentrations of Risk	Concentrations of Risk Financial instruments that potentially subject the Company to significant concentration of credit risk consist primarily of cash, cash equivalents and accounts receivable. The Company maintains the majority of its cash and cash equivalents with one financial institution, which management believes to be financially sound and with minimal credit risk. The Company’s deposits periodically exceed amounts guaranteed by the Federal Deposit Insurance Corporation.
Inventories	Inventories Inventories, consisting substantially of finished goods, are valued at the lower of cost or market (net realizable value). Cost is determined using the moving weighted-average cost method. The Company’s arrangements with vendors typically provide for rebates after it makes a special purchase and/or monthly, quarterly and/or annual rebates of a specified amount of consideration payable when a number of measures have been achieved. Annual rebates are generally related to a specified cumulative level of purchases on a calendar-year basis. The Company accounts for such rebates as a reduction of the inventory value until the product is sold, at which time such rebates reduce cost of sales in the consolidated statements of operations. Throughout the year, the Company estimates the amount of the periodic rebates based upon the expected level of purchases. The Company continually revises these estimates to reflect actual rebates earned based on actual purchase levels. Amounts due from vendors under these arrangements are included in “prepaid expenses and other current assets” in the accompanying consolidated balance sheets.
Property and Equipment	Property and Equipment Property and equipment acquired in connection with acquisitions are recorded at fair value as of the date of the acquisition and depreciated utilizing the straight-line method over the estimated remaining lives. All other additions are recorded at cost, and depreciation is computed using the straight-line method. The Company reviews the estimated useful lives of its fixed assets on an ongoing basis and the following table summarizes the estimates currently used: Asset Class Estimated Useful Life Buildings and improvements 40 years Equipment 3 to 7 years Furniture and fixtures 7 years Leasehold improvements Shorter of the estimated useful life or the term of the lease, considering renewal options expected to be exercised.
Business Combinations	Business Combinations The Company records acquisitions resulting in the consolidation of a business using the acquisition method of accounting. Under this method, the acquiring Company records the assets acquired, including intangible assets that can be identified and named, and liabilities assumed based on their estimated fair values at the date of acquisition. The Company uses an income approach to determine the fair value of acquired intangible assets, specifically the multi-period excess earnings method for customer relationships and the relief from royalty method for trade names. Various Level 3 fair value assumptions are used in the determination of these estimated fair values, including items such sales growth rates, cost synergies, customer attrition rates, discount rates, and other prospective financial information. The purchase price in excess of the fair value of the assets acquired and liabilities assumed is recorded as goodwill. Estimates associated with the accounting for acquisitions may change as additional information becomes available regarding the assets acquired and liabilities assumed. Transaction costs associated with acquisitions are expensed as incurred.
Goodwill and Intangibles	Goodwill and Intangibles On an annual basis and at interim periods when circumstances require, the Company tests the recoverability of its goodwill and indefinite-lived intangible assets. Examples of such indicators include a significant change in the business climate, unexpected competition, loss of key personnel or a decline in the Company’s market capitalization below the Company’s net book value. The Company performs impairment assessments at the reporting unit level, which is defined as an operating segment or one level below an operating segment, also known as a component. The Company currently has five components which it evaluates for aggregation by examining the distribution methods, sales mix, and operating results of each component to determine if these characteristics will be sustained over a long-term basis. For purposes of this evaluation, the Company expects its components to exhibit similar economic characteristics 3-5 years after events such as an acquisition within the Company’s core roofing business or management/business restructuring. Components that exhibit similar economic characteristics are subsequently aggregated into a single reporting unit. Based on the Company’s most recent impairment assessment performed as of August 31, 2018, it was determined that all of the Company’s components exhibited similar economic characteristics, and therefore should be aggregated into a single reporting unit (collectively the “Reporting Unit”). To test for the recoverability of goodwill and indefinite-lived intangible assets, the Company first performs a qualitative assessment based on economic, industry and company-specific factors for all or selected reporting units to determine whether the existence of events and circumstances indicates that it is more likely than not that the goodwill or indefinite-lived intangible asset is impaired. Based on the results of the qualitative assessment, two additional steps in the impairment assessment may be required. The first step would require a comparison of each reporting unit’s fair value to the respective carrying value. If the carrying value exceeds the fair value, a second step is performed to measure the amount of impairment loss on a relative fair value basis, if any. Based on the Company’s most recent qualitative impairment assessment performed as of August 31, 2018, the Company concluded that there were no indicators of impairment, and that therefore it was more likely than not that the fair value of the goodwill and indefinite-lived intangible assets exceeded their net carrying amount, therefore the quantitative two-step impairment test was not required. The Company amortizes certain identifiable intangible assets that have finite lives, currently consisting of non-compete agreements, customer relationships and trade names. Non-compete agreements are amortized on a straight-line basis over the terms of the associated contractual agreements; customer relationship assets are amortized on an accelerated basis based on the expected cash flows generated by the existing customers; and trade names are amortized on an accelerated basis over a five or ten year period. Amortizable intangible assets are tested for impairment, when deemed necessary, based on undiscounted cash flows and, if impaired, are written down to fair value based on either discounted cash flows or appraised values. In connection with certain financing arrangements, the Company has debt issuance costs that are amortized over the lives of the associated financings.
Evaluation of Long-Lived Assets	Evaluation of Long-Lived Assets The Company evaluates the recoverability of its long-lived assets for impairment whenever events or circumstances indicate that the carrying amount of the assets may not be recoverable. Recoverability is measured by comparing the carrying amount of the asset to the future undiscounted cash flows the asset is expected to generate. If the asset is considered to be impaired, the amount of any impairment is measured as the difference between the carrying value and the fair value of the impaired asset.
Fair Value Measurement	Fair Value Measurement The Company applies fair value accounting for all financial assets and liabilities that are reported at fair value in the financial statements on a recurring basis. Fair value is defined as the price that would be received from selling an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date. The accounting guidance establishes a defined three-tier hierarchy to classify and disclose the fair value of assets and liabilities on both the date of their initial measurement as well as all subsequent periods. The hierarchy prioritizes the inputs used to measure fair value by the lowest level of input that is available and significant to the fair value measurement. The three levels are described as follows: • Level 1 : Observable inputs. Quoted prices in active markets for identical assets and liabilities; • Level 2 : Observable inputs other than the quoted price. Includes quoted prices for similar instruments, quoted prices for identical or similar instruments in inactive markets and amounts derived from valuation models where all significant inputs are observable in active markets; and • Level 3 : Unobservable inputs. Includes amounts derived from valuation models where one or more significant inputs are unobservable and require the Company to develop relevant assumptions. The Company evaluates its financial assets and liabilities subject to fair value measurements on a recurring basis to determine the appropriate level of classification as of each reporting period.
Financial Derivatives	Financial Derivatives The Company has entered into interest rate swaps to minimize the risks and costs associated with financing activities, as well as to maintain an appropriate mix of fixed-rate and floating-rate debt. The swap agreements are contracts to exchange variable-rate for fixed-interest rate payments over the life of the agreements. The Company's derivative instruments are designated as cash flow hedges, for which the Company records the effective portions of changes in their fair value, net of tax, in other comprehensive income. The Company recognizes any ineffective portion of the hedges in the consolidated statement of operations through interest expense, financing costs and other.
Net Sales	Net Sales The Company recognizes revenue (net sales on the consolidated statement of operations) when the following four basic criteria are met: • persuasive evidence of an arrangement exists; • delivery has occurred or services have been rendered; • the price to the buyer is fixed and determinable; and • collectability is reasonability assured. Based on these criteria, the Company generally recognizes revenue at the point of sale or upon delivery to the customer site. For goods shipped by third party carriers, the Company recognizes revenue upon shipment since the terms are generally FOB shipping point. The Company also arranges for certain products to be shipped directly from the manufacturer to the customer. The Company recognizes the gross revenue for these sales upon shipment as the terms are FOB shipping point.
Leases	Leases The Company leases the majority of its facilities and enters into various other operating lease agreements in conducting its business. At the inception of each lease, the Company evaluates the lease agreement to determine whether the lease is an operating or capital lease. Operating lease expenses are recognized in the statements of operations on a straight-line basis over the term of the related lease. Some of the Company’s lease agreements may contain renewal options, tenant improvement allowances, rent holidays or rent escalation clauses. When such items are included in a lease agreement, the Company records a deferred rent asset or liability on the consolidated balance sheets equal to the difference between the rent expense and cash rent payments. The cost of property and equipment acquired under capital lease arrangements represents the lesser of the present value of the minimum lease payments or the fair value of the leased asset as of the inception of the lease.
Stock-Based Compensation	Stock-Based Compensation The Company applies the fair value method to recognize compensation expense for stock-based awards. Using this method, the estimated grant-date fair value of the award is recognized on a straight-line basis over the requisite service period based on the portion of the award that is expected to vest. The Company estimates forfeitures at the time of grant and revises the estimates, if necessary, in subsequent periods if actual forfeitures differ from those estimates. For awards with a performance-based vesting condition, the Company accrues stock-based compensation expense if it is probable that the performance condition will be achieved. Stock-based compensation expense for restricted stock units is measured based on the fair value of the Company’s common stock on the grant date. The Company utilizes the Black-Scholes option pricing model to estimate the grant-date fair value of option awards. The exercise price of option awards is set to equal the estimated fair value of the common stock at the date of the grant. The following weighted-average assumptions are also used to calculate the estimated fair value of option awards: • Expected volatility : The expected volatility of the Company’s shares is estimated using the historical stock price volatility over the most recent period commensurate with the estimated expected term of the awards. • Expected term : For employee stock option awards, the Company determines the weighted average expected term equal to the weighted period between the vesting period and the contract life of all outstanding options. • Dividend yield : The Company has not paid dividends and does not anticipate paying a cash dividend in the foreseeable future and, accordingly, uses an expected dividend yield of zero. • Risk-free interest rate : The Company bases the risk-free interest rate on the implied yield available on a U.S. Treasury note with a term equal to the estimated expected term of the awards.
Foreign Currency Translation	Foreign Currency Translation The Company’s operations located outside of the United States where the local currency is the functional currency are translated into U.S. dollars using the current rate method. Results of operations are translated at the average rate of exchange for the period. Assets and liabilities are translated at the closing rates on the period end date. Gains and losses on translation of these accounts are accumulated and reported as a separate component of equity and other comprehensive income (loss). Gains and losses on foreign currency transactions are recognized in the consolidated statements of operations as a component of interest expense, financing costs, and other.
Income Taxes	Income Taxes The Company accounts for income taxes using the liability method, which requires it to recognize a current tax liability or asset for current taxes payable or refundable and a deferred tax liability or asset for the estimated future tax effects of temporary differences between the financial statement and tax reporting bases of assets and liabilities to the extent that they are realizable. Deferred tax expense (benefit) results from the net change in deferred tax assets and liabilities during the year. FASB ASC Topic 740 prescribes a recognition threshold and measurement attribute for the financial statement recognition and measurement of a tax position taken or expected to be taken in a tax return. Based on this guidance, the Company analyzes its filing positions in all of the federal and state jurisdictions where it is required to file income tax returns, as well as all open tax years in these jurisdictions. Tax benefits from uncertain tax positions are recognized if it is more likely than not that the position is sustainable based solely on its technical merits.
Net Income (Loss) per Share	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. 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 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.
Recent Accounting Pronouncements - Adopted and Not Yet Adopted	Recent Accounting Pronouncements—Adopted In March 2016, the FASB issued ASU 2016-09, “ Compensation—Stock Compensation: Improvements to Employee Share-Based Payment Accounting.” In November 2016, the FASB issued ASU 2016-18, “ Restricted Cash.” Recent Accounting Pronouncements—Not Yet Adopted In May 2014, the FASB issued ASU 2014-09, “ Revenue from Contracts with Customers In February 2016, the FASB issued ASU 2016-02, “ Leases 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 2017-01, “ Business Combinations: Clarifying the Definition of a Business.” In January 2017, the FASB issued ASU 2017-04, “ Simplifying the Accounting for Goodwill Impairment.” In May 2017, the FASB issued ASU 2017-09, “Scope of Modification Accounting.” In February 2018, the FASB issued ASU 2018-02, “Income Statement – Reporting Comprehensive Income.”

Summary of Significant Accoun_3

Summary of Significant Accounting Policies (Tables)	12 Months Ended
	Sep. 30, 2018
Accounting Policies [Abstract]
Summary of Property and Equipment Estimated Useful Life	All other additions are recorded at cost, and depreciation is computed using the straight-line method. The Company reviews the estimated useful lives of its fixed assets on an ongoing basis and the following table summarizes the estimates currently used: Asset Class Estimated Useful Life Buildings and improvements 40 years Equipment 3 to 7 years Furniture and fixtures 7 years Leasehold improvements Shorter of the estimated useful life or the term of the lease, considering renewal options expected to be exercised.

Acquisitions (Tables)

Acquisitions (Tables)	12 Months Ended
	Sep. 30, 2018
Business Combinations [Abstract]
Schedule of Recognized Identified Assets Acquired and Liabilities Assumed	The Company has recorded purchase accounting entries on a preliminary basis for the Allied Acquisition, detailed as follows (in thousands): January 2, 2018 January 2, 2018 (as reported at March 31, 2018) Adjustments (as adjusted at September 30, 2018) Cash $ 19,322 $ (19,153 ) $ 169 Accounts receivable 315,485 22,063 337,548 Inventory 322,705 (7,920 ) 314,785 Prepaid and other current assets 59,279 16,161 75,440 Property, plant, and equipment 139,528 (168 ) 139,360 Goodwill 1,130,635 102,145 1,232,780 Intangible assets 1,037,000 - 1,037,000 Current liabilities (271,252 ) 11,963 (259,289 ) Non-current liabilities (6,820 ) 6,097 (723 ) Total purchase price $ 2,745,882 $ 131,188 $ 2,877,070
Business Acquisition, Pro Forma Information	The following table represents the unaudited pro forma consolidated net sales and net income (loss) for the Company for the periods indicated (in thousands): Twelve Months Ended September 30, 2018 2017 (unaudited) Net sales $ 7,083,960 $ 6,989,658 Net income (loss) 62,081 70,701

Net Income (Loss) Per Share (Ta

Net Income (Loss) Per Share (Tables)	12 Months Ended
	Sep. 30, 2018
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 for each period presented (in thousands, except share and per share amounts): Year Ended September 30, 2018 2017 2016 Net income (loss) $ 98,626 $ 100,864 $ 89,917 Dividends on preferred shares (18,000 ) - - Net income (loss) attributable to common shareholders $ 80,626 $ 100,864 $ 89,917 Undistributed income allocated to participating securities (7,742 ) - - Net income (loss) attributable to common shareholders - basic and diluted $ 72,884 $ 100,864 $ 89,917 Weighted-average common shares outstanding - basic 68,012,879 60,315,648 59,424,372 Effect of common share equivalents 1,178,160 1,028,615 993,695 Weighted-average common shares outstanding - diluted 69,191,039 61,344,263 60,418,067 Net income (loss) per share - basic $ 1.07 $ 1.67 $ 1.51 Net income (loss) per share - diluted $ 1.05 $ 1.64 $ 1.49
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: Year Ended September 30, 2018 2017 2016 Stock options 388,731 331,681 502,294 Restricted stock units 192,151 61,890 45,220 Preferred Stock 7,224,483 - -

Prepaid Expenses and Other Cu_2

Prepaid Expenses and Other Current Assets (Tables)	12 Months Ended
	Sep. 30, 2018
Prepaid Expenses And Other Current Assets [Abstract]
Schedule of Prepaid Expenses and Other Current Assets	The following table summarizes the significant components of prepaid expenses and other current assets (in thousands): September 30, 2018 2017 Vendor rebates $ 199,725 $ 193,071 Other 44,635 16,067 $ 244,360 $ 209,138

Property and Equipment (Tables)

Property and Equipment (Tables)	12 Months Ended
	Sep. 30, 2018
Property Plant And Equipment [Abstract]
Property and Equipment, net	The following table provides a detailed breakout of property and equipment, by type (in thousands): September 30, 2018 2017 Land and buildings $ 82,991 $ 41,791 Equipment 419,385 293,489 Furniture and fixtures 34,901 23,140 Total property and equipment 537,277 358,420 Accumulated depreciation (256,870 ) (202,291 ) Total property and equipment, net $ 280,407 $ 156,129

Goodwill and Intangible Assets

Goodwill and Intangible Assets (Tables)	12 Months Ended
	Sep. 30, 2018
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 years ended September 30, 2018 and 2017, respectively (in thousands): Balance at September 30, 2016 $ 1,197,565 Acquisitions 53,012 Translation and other adjustments 1,409 Balance at September 30, 2017 $ 1,251,986 Balance at September 30, 2017 $ 1,251,986 Acquisitions 1,240,913 Translation and other adjustments (1,120 ) Balance at September 30, 2018 $ 2,491,779
Summary of Intangible Assets	The following table summarizes intangible assets by category (in thousands, except time period amounts): September 30, Weighted- Average Remaining Life 1 2018 2017 (Years) Amortizable intangible assets: Non-compete agreements $ 2,824 $ 2,824 2.60 Customer relationships 1,530,565 610,026 18.62 Trademarks 10,500 10,500 7.60 Beneficial lease arrangements 8,060 1,060 4.48 Total amortizable intangible assets 1,551,949 624,410 Accumulated amortization (410,633 ) (268,391 ) Total amortizable intangible assets, net $ 1,141,316 $ 356,019 Indefinite lived trademarks 193,050 73,050 Total intangibles, net $ 1,334,366 $ 429,069 1
Summary of Estimated Future Amortization	The following table summarizes the estimated future amortization expense for intangible assets (in thousands): Year Ending September 30, 2019 $ 208,404 2020 179,571 2021 149,888 2022 121,396 2023 97,474 Thereafter 384,583 $ 1,141,316

Financing Arrangements (Tables)

Financing Arrangements (Tables)	12 Months Ended
	Sep. 30, 2018
Debt Disclosure [Abstract]
Schedule of Long-term Debt Instruments	The following table summarizes all financing arrangements from the respective periods presented (in thousands): September 30, September 30, 2018 2017 Revolving Lines of Credit: 2020 ABL U.S. Revolver, expires October 1, 2020 1 $ - $ - Canada Revolver, expires October 1, 2020 2 - 3,205 2023 ABL U.S. Revolver, expires January 2, 2023 3 89,352 - Canada Revolver, expires January 2, 2023 4 3,090 - Current portion - - Borrowings under revolving lines of credit, net $ 92,442 $ 3,205 Term Loans: Term Loan, matures October 1, 2022 5 $ - $ 433,440 Term Loan, matures January 2, 2025 6 930,726 - Current portion (9,700 ) (4,500 ) Total long-term borrowings under term loans $ 921,026 $ 428,940 Senior Notes: Senior Notes, mature October 2023 7 293,607 292,328 Senior Notes, mature November 2025 8 1,280,092 - Current portion - - Total long-term borrowings under Senior Notes $ 1,573,699 $ 292,328 Long-term debt, net $ 2,494,725 $ 721,268 Equipment Financing Facilities and Other: Equipment financing facilities, various maturities through September 2021 9 $ 11,222 $ 12,898 Capital lease obligations, various maturities through November 2021 10 12,378 19,956 Current portion (9,961 ) (9,641 ) Long-term obligations under equipment financing and other, net $ 13,639 $ 23,213 1 Extinguished on January 2, 2018; Effective rate on borrowings of 2.00% as of September 30, 2017 2 Extinguished on January 2, 2018; Effective rate on borrowings of 3.70% as of September 30, 2017 3 Effective rate on borrowings of 3.36% as of 4 Effective rate on borrowings of 3.95% as of 5 Extinguished on January 2, 2018; 6 Interest rate of 4.53% as of 7 Interest rate of 6.38% as of 8 Interest rate of 4.88% as of September 30, 2018 9 Fixed interest rates ranging from 2.33% to 3.25% as of September 30, 2018 and September 30, 2017 10 Fixed interest rates ranging from 2.72% to 10.39% as of September 30, 2018 and September 30, 2017
Schedule of Maturities of Long-term Debt	Annual principal payments for all outstanding financing arrangements for each of the next five years and thereafter are as follows (in thousands): Year Ending September 30, 2023 ABL 2025 Term Loan Senior Notes Equipment Financing Facilities Total 2019 $ - $ 9,700 $ - $ 9,929 $ 19,629 2020 - 9,700 - 9,014 18,714 2021 - 9,700 - 4,327 14,027 2022 - 9,700 - 330 10,030 2023 103,090 9,700 300,000 - 412,790 Thereafter - 916,650 1,300,000 - 2,216,650 Total debt 103,090 965,150 1,600,000 23,600 2,691,840 Unamortized debt issuance costs (10,648 ) (34,424 ) (26,301 ) - (71,373 ) Total long-term debt $ 92,442 $ 930,726 $ 1,573,699 $ 23,600 $ 2,620,467

Commitments and Contingencies (

Commitments and Contingencies (Tables)	12 Months Ended
	Sep. 30, 2018
Commitments And Contingencies Disclosure [Abstract]
Schedule of Minimum Rental Commitments under Non-cancelable Operating Leases	At September 30, 2018, the minimum rental commitments under all non-cancelable operating leases with initial or remaining terms of more than one year were as follows (in thousands): Year Ending September 30, 2019 $ 105,425 2020 94,348 2021 82,827 2022 62,863 2023 46,274 Thereafter 120,291 Total minimum lease payments $ 512,028

Stockholders' Equity (Tables)

Stockholders' Equity (Tables)	12 Months Ended
	Sep. 30, 2018
Equity [Abstract]
Reclassification out of Accumulated Other Comprehensive Income	The following table summarizes the components of and changes in accumulated other comprehensive loss (in thousands): Foreign Currency Translation Derivative Financial Instruments Accumulated Other Comprehensive Loss Balance as of September 30, 2015 $ (19,293 ) $ (1,427 ) $ (20,720 ) Other comprehensive loss before reclassifications 1,024 - 1,024 Reclassifications out of other comprehensive loss - 1,039 1,039 Balance as of September 30, 2016 $ (18,269 ) $ (388 ) $ (18,657 ) Other comprehensive income before reclassifications 3,706 - 3,706 Reclassifications out of other comprehensive loss - 388 388 Balance as of September 30, 2017 $ (14,563 ) $ - $ (14,563 ) Other comprehensive income before reclassifications (2,687 ) - (2,687 ) Reclassifications out of other comprehensive loss - - - Balance as of September 30, 2018 $ (17,250 ) $ - $ (17,250 )

Stock-based Compensation (Table

Stock-based Compensation (Tables)	12 Months Ended
	Sep. 30, 2018
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 year ended September 30, 2018 were estimated on the dates of grants using the Black-Scholes option-pricing model with the following weighted-average assumptions: Year Ended September 30, 2018 2017 2016 Risk-free interest rate 2.10 % 1.97 % 1.87 % Expected volatility 26.43 % 28.83 % 30.96 % Expected life (in years) 5.46 5.30 5.60 Dividend yield - - -
Stock Options Outstanding and Activity During the Period	The following table summarizes all stock option activity for the periods presented (in thousands, except share, 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, 2017 2,084,228 $ 28.84 6.1 $ 46,714 Granted 276,370 55.17 Exercised (308,266 ) 24.38 Canceled/Forfeited (81,304 ) 32.92 Expired (1,991 ) 15.28 Balance as of September 30, 2018 1,969,037 $ 33.08 5.7 $ 14,088 Vested and expected to vest after September 30, 2018 1,956,534 $ 32.96 5.7 $ 14,078 Exercisable as of September 30, 2018 1,439,187 $ 27.48 4.7 $ 13,668 1 Aggregate intrinsic value as represents the difference between the closing fair value of the underlying common stock and the exercise price of outstanding, in-the-money options on the date of measurement.
Stock Option Grants, Vesting, and Exercises	The following table summarizes additional information on stock options for the periods presented (in thousands, except per share amounts): Year Ended September 30, 2018 2017 2016 Weighted-average fair value of stock options granted $ 15.86 $ 14.21 $ 12.89 Total fair value of stock options vested 4,208 5,541 12,347 Total intrinsic value of stock options exercised 9,645 10,941 22,693
Restricted Shares and Units Outstanding and Activity During the Period	The following table summarizes all restricted stock unit activity for the periods presented: RSUs Outstanding Weighted- Average Grant Date Fair Value Balance at September 30, 2017 770,973 $ 38.95 Granted 370,190 57.40 Performance awards 1 41,440 39.56 Released (191,703 ) 31.91 Canceled/Forfeited (56,877 ) 51.10 Balance at September 30, 2018 934,023 $ 47.00 Vested and expected to vest after September 30, 2018 888,337 $ 46.87 _____________________________ 1 Additional restricted stock units outstanding as a result of the satisfaction of a performance vesting condition prior to the ascribed time-based vesting condition (release date).
Schedule Of Restricted Stock Units Additional Information	The following table summarizes additional information on RSUs for the period presented (in thousands, except share and per share amounts): Year Ended September 30, 2018 2017 2016 Weighted-average fair value of RSUs granted $ 57.40 $ 47.31 $ 38.92 Total fair value of RSUs vested 6,656 4,562 743 Total intrinsic value of RSUs released 11,041 6,079 1,375

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Sep. 30, 2018
Income Tax Disclosure [Abstract]
Schedule Of Income Tax Provision (Benefit)	The following table summarizes the components of the income tax provision (benefit) (in thousands): Year Ended September 30, 2018 2017 2016 Current: Federal 1 $ (4,435 ) $ 52,718 $ 23,403 Foreign 492 1,366 1,183 State 3,516 8,975 2,426 Total current taxes $ (427 ) $ 63,059 $ 27,012 Deferred: Federal $ (35,249 ) $ (656 ) $ 25,935 Foreign (173 ) - 321 State 5,305 78 3,347 Total deferred taxes $ (30,117 ) $ (578 ) $ 29,603 Provision for (benefit from) income taxes $ (30,544 ) $ 62,481 $ 56,615 _____________________________ 1 2018 tax benefit due to changes in the treatment of acquired fixed assets stemming from the Tax Cut and Jobs Act of 2017
Principal Reason for the Difference Between Effective Income Tax Rate and the Statutory Federal Income	The following table is a reconciliation of the statutory federal income tax rate to the Company’s effective income tax rate for the periods presented: Year Ended September 30, 2018 2017 2016 U.S. federal income taxes at statutory rate 24.5 % 35.0 % 35.0 % State income taxes, net of federal benefit 5.2 % 3.9 % 4.2 % Share-based payments (3.9 %) 0.0 % 0.0 % Deferred tax asset/liability remeasurement 1 (73.5 %) 0.0 % (1.0 %) Repatriation transition tax 1 1.8 % 0.0 % 0.0 % Non-deductible professional fees 0.0 % 0.0 % 0.4 % Other 1.0 % (0.6 %) 0.0 % Effective tax rate (44.9 %) 38.3 % 38.6 % 1
Components of the Company's Deferred Taxes	temporary differences are determined according to ASC 740 Income Taxes. Temporary differences that give rise to deferred tax assets and liabilities are as follows (in thousands): September 30, 2018 2017 Deferred tax assets: Deferred compensation $ 11,346 $ 14,237 Allowance for doubtful accounts 663 1,318 Accrued vacation and other 5,079 6,602 Inventory valuation 12,900 10,564 Tax loss carryforwards 1 17,271 20,575 Other 1,517 958 Total deferred tax assets $ 48,776 $ 54,254 Deferred tax liabilities: Excess tax over book depreciation and amortization $ (155,770 ) $ (192,637 ) Total deferred tax liabilities (155,770 ) (192,637 ) Net deferred income tax liabilities $ (106,994 ) $ (138,383 ) 1

Geographic and Product Data (Ta

Geographic and Product Data (Tables)	12 Months Ended
	Sep. 30, 2018
Segment Reporting [Abstract]
Schedule of Geographic Information	The following tables summarize certain geographic information for the periods presented (in thousands): Year Ended September 30, 2018 2017 2016 Net sales U.S. $ 6,239,332 $ 4,198,935 $ 3,949,067 Canada 178,979 177,735 178,042 Total net sales $ 6,418,311 $ 4,376,670 $ 4,127,109 September 30, 2018 2017 Long-lived assets U.S. $ 1,409,742 $ 507,236 Canada 13,224 13,446 Total long-lived assets $ 1,422,966 $ 520,682
Schedule Of Net Sales From External Customers By Product Group	The following table summarizes net sales from external customers by product group (in thousands): Year Ended September 30, 2018 2017 2016 Residential roofing products $ 2,798,756 $ 2,380,435 $ 2,190,762 Non-residential roofing products 1,635,963 1,273,153 1,331,319 Complementary building products 1,983,592 723,082 605,028 Total net sales $ 6,418,311 $ 4,376,670 $ 4,127,109

Supplemental Guarantor Inform_2

Supplemental Guarantor Information (Tables)	12 Months Ended
	Sep. 30, 2018
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Condensed Consolidating Balance Sheets	BEACON ROOFING SUPPLY, INC. (Unaudited; In thousands) September 30, 2018 Parent Guarantor Subsidiaries Non-Guarantor Subsidiaries Eliminations and Other Consolidated Assets Current assets: Cash and cash equivalents $ - $ 136,499 $ 1,959 $ (8,531 ) $ 129,927 Accounts receivable, net - 1,051,410 40,262 (1,139 ) 1,090,533 Inventories, net - 907,605 28,442 - 936,047 Prepaid expenses and other current assets 23,711 214,011 6,638 - 244,360 Total current assets 23,711 2,309,525 77,301 (9,670 ) 2,400,867 Intercompany receivable, net - 1,361,615 - (1,361,615 ) - Investments in consolidated subsidiaries 6,109,325 - - (6,109,325 ) - Deferred income taxes, net 22,475 - - (22,475 ) - Property and equipment, net 18,929 250,517 10,961 - 280,407 Goodwill - 2,461,725 30,054 - 2,491,779 Intangibles, net - 1,332,104 2,262 - 1,334,366 Other assets, net 1,243 - - - 1,243 Total Assets $ 6,175,683 $ 7,715,486 $ 120,578 $ (7,503,085 ) $ 6,508,662 Liabilities and Stockholders' Equity Current liabilities: Accounts payable $ 24,154 $ 843,907 $ 22,482 $ (9,671 ) $ 880,872 Accrued expenses 41,448 564,331 5,760 - 611,539 Current portions of long-term debt 9,700 9,961 - - 19,661 Total current liabilities 75,302 1,418,199 28,242 (9,671 ) 1,512,072 Intercompany payable, net 1,322,156 - 39,459 (1,361,615 ) - Borrowings under revolving lines of credit, net - 89,352 3,090 - 92,442 Long-term debt, net 2,494,725 - - - 2,494,725 Deferred income taxes, net - 128,846 622 (22,474 ) 106,994 Long-term obligations under equipment financing and other, net - 13,639 - - 13,639 Other long-term liabilities - 5,207 83 - 5,290 Total liabilities 3,892,183 1,655,243 71,496 (1,393,760 ) 4,225,162 Convertible preferred stock 399,195 - - - 399,195 Total stockholders' equity 1,884,305 6,060,243 49,082 (6,109,325 ) 1,884,305 Total Liabilities and Stockholders' Equity $ 6,175,683 $ 7,715,486 $ 120,578 $ (7,503,085 ) $ 6,508,662 BEACON ROOFING SUPPLY, INC. Condensed Consolidating Balance Sheets (Unaudited; In thousands) September 30, 2017 Parent Guarantor Subsidiaries Non-Guarantor Subsidiaries Eliminations and Other Consolidated Assets Current assets: Cash and cash equivalents $ - $ 149,799 $ 1,582 $ (13,131 ) $ 138,250 Accounts receivable, net - 663,034 42,633 (1,140 ) 704,527 Inventories, net - 527,226 24,698 - 551,924 Prepaid expenses and other current assets 4,195 198,817 6,126 - 209,138 Total current assets 4,195 1,538,876 75,039 (14,271 ) 1,603,839 Intercompany receivable, net - 655,372 - (655,372 ) - Investments in consolidated subsidiaries 3,160,273 - - (3,160,273 ) - Deferred income taxes, net 30,822 - - (30,822 ) - Property and equipment, net 6,610 138,955 10,564 - 156,129 Goodwill - 1,220,812 31,174 - 1,251,986 Intangibles, net - 426,187 2,882 - 429,069 Other assets, net 2,912 5,622 - - 8,534 Total Assets $ 3,204,812 $ 3,985,824 $ 119,659 $ (3,860,738 ) $ 3,449,557 Liabilities and Stockholders' Equity Current liabilities: Accounts payable $ 27,174 $ 468,891 $ 21,903 $ (14,271 ) $ 503,697 Accrued expenses 51,183 204,173 5,941 - 261,297 Current portions of long-term obligations 4,500 9,641 - - 14,141 Total current liabilities 82,857 682,705 27,844 (14,271 ) 779,135 Intercompany payable, net 618,881 - 36,491 (655,372 ) - Borrowings under revolving lines of credit, net - - 3,205 - 3,205 Long-term debt, net 721,268 - - - 721,268 Deferred income taxes, net - 168,209 996 (30,822 ) 138,383 Long-term obligations under equipment financing and other, net - 23,147 66 - 23,213 Other long-term liabilities - 2,547 - - 2,547 Total liabilities 1,423,006 876,608 68,602 (700,465 ) 1,667,751 Total stockholders' equity 1,781,806 3,109,216 51,057 (3,160,273 ) 1,781,806 Total Liabilities and Stockholders' Equity $ 3,204,812 $ 3,985,824 $ 119,659 $ (3,860,738 ) $ 3,449,557
Condensed Consolidating Statements of Operations	BEACON ROOFING SUPPLY, INC. Condensed Consolidating Statements of Operations (Unaudited; In thousands, except share and per share amounts) Year Ended September 30, 2018 Parent Guarantor Subsidiaries Non-Guarantor Subsidiaries Eliminations and Other Consolidated Net sales $ - $ 6,239,332 $ 178,979 $ - $ 6,418,311 Cost of products sold - 4,685,616 139,374 - 4,824,990 Gross profit - 1,553,716 39,605 - 1,593,321 Operating expense - - Selling, general and administrative 5,909 1,147,390 33,893 - 1,187,192 Depreciation 1,989 56,598 1,731 - 60,318 Amortization - 140,664 521 - 141,185 Total operating expense 7,898 1,344,652 36,145 - 1,388,695 Intercompany charges (income) (6,734 ) 6,565 169 - - Income (loss) from operations (1,164 ) 202,499 3,291 - 204,626 Interest expense, financing costs, and other 124,169 11,648 727 - 136,544 Intercompany interest expense (income) (24,270 ) 22,738 1,532 - - Income (loss) before provision for income taxes (101,063 ) 168,113 1,032 - 68,082 Provision for (benefit from) income taxes 11,398 (42,261 ) 319 - (30,544 ) Income (loss) before equity in net income of subsidiaries (112,461 ) 210,374 713 - 98,626 Equity in net income of subsidiaries 211,087 - - (211,087 ) - Net income (loss) $ 98,626 $ 210,374 $ 713 $ (211,087 ) $ 98,626 BEACON ROOFING SUPPLY, INC. Condensed Consolidating Statements of Operations (Unaudited; In thousands, except share and per share amounts) Year Ended September 30, 2017 Parent Guarantor Subsidiaries Non-Guarantor Subsidiaries Eliminations and Other Consolidated Net sales $ - $ 4,198,935 $ 177,735 $ - $ 4,376,670 Cost of products sold - 3,162,896 137,835 - 3,300,731 Gross profit - 1,036,039 39,900 - 1,075,939 Operating expense Selling, general and administrative 26,962 685,690 30,724 - 743,376 Depreciation 1,534 30,758 1,710 - 34,002 Amortization - 81,880 585 - 82,465 Total operating expense 28,496 798,328 33,019 - 859,843 Intercompany charges (income) (4,664 ) 4,342 322 - - Income (loss) from operations (23,832 ) 233,369 6,559 - 216,096 Interest expense, financing costs, and other 38,660 14,033 58 - 52,751 Intercompany interest expense (income) (24,458 ) 22,927 1,531 - - Income (loss) before provision for income taxes (38,034 ) 196,409 4,970 - 163,345 Provision for (benefit from) income taxes (3,284 ) 64,399 1,366 - 62,481 Income (loss) before equity in net income of subsidiaries (34,750 ) 132,010 3,604 - 100,864 Equity in net income of subsidiaries 135,614 - - (135,614 ) - Net income (loss) $ 100,864 $ 132,010 $ 3,604 $ (135,614 ) $ 100,864 BEACON ROOFING SUPPLY, INC. Condensed Consolidating Statements of Operations (Unaudited; In thousands, except share and per share amounts) Year Ended September 30, 2016 Parent Guarantor Subsidiaries Non-Guarantor Subsidiaries Eliminations and Other Consolidated Net sales $ - $ 3,949,313 $ 178,042 $ (246 ) $ 4,127,109 Cost of products sold - 2,977,174 137,112 (246 ) 3,114,040 Gross profit - 972,139 40,930 - 1,013,069 Operating expense Selling, general and administrative 58,592 619,045 30,256 - 707,893 Depreciation 1,357 28,975 1,544 - 31,876 Amortization - 67,649 667 - 68,316 Total operating expense 59,949 715,669 32,467 - 808,085 Intercompany charges (income) (51,942 ) 49,285 2,657 - - Income (loss) from operations (8,007 ) 207,185 5,806 - 204,984 Interest expense, financing costs, and other 42,835 14,965 652 - 58,452 Intercompany interest expense (income) (21,536 ) 19,928 1,608 - - Income (loss) before provision for income taxes (29,306 ) 172,292 3,546 - 146,532 Provision for (benefit from) income taxes (472 ) 55,613 1,474 - 56,615 Income (loss) before equity in net income of subsidiaries (28,834 ) 116,679 2,072 - 89,917 Equity in net income of subsidiaries 118,751 - - (118,751 ) - Net income (loss) $ 89,917 $ 116,679 $ 2,072 $ (118,751 ) $ 89,917
Condensed Consolidating Statements of Comprehensive Income	BEACON ROOFING SUPPLY, INC. Condensed Consolidating Statements of Comprehensive Income (Unaudited; In thousands) Year Ended September 30, 2018 Parent Guarantor Subsidiaries Non-Guarantor Subsidiaries Eliminations and Other Consolidated Net income (loss) $ 98,626 $ 210,374 $ 713 $ (211,087 ) $ 98,626 Other comprehensive income (loss): Foreign currency translation adjustment (2,687 ) - (2,687 ) 2,687 (2,687 ) Total other comprehensive income (loss) (2,687 ) - (2,687 ) 2,687 (2,687 ) Comprehensive income (loss) $ 95,939 $ 210,374 $ (1,974 ) $ (208,400 ) $ 95,939 Year Ended September 30, 2017 Parent Guarantor Subsidiaries Non-Guarantor Subsidiaries Eliminations and Other Consolidated Net income (loss) $ 100,864 $ 132,010 $ 3,604 $ (135,614 ) $ 100,864 Other comprehensive income (loss): Foreign currency translation adjustment 3,706 - 3,706 (3,706 ) 3,706 Total other comprehensive income (loss) 3,706 - 3,706 (3,706 ) 3,706 Comprehensive income (loss) $ 104,570 $ 132,010 $ 7,310 $ (139,320 ) $ 104,570 Year Ended September 30, 2016 Parent Guarantor Subsidiaries Non-Guarantor Subsidiaries Eliminations and Other Consolidated Net income (loss) $ 89,917 $ 116,679 $ 2,072 $ (118,751 ) $ 89,917 Other comprehensive income (loss): Foreign currency translation adjustment 1,024 - 1,024 (1,024 ) 1,024 Total other comprehensive income (loss) 1,024 - 1,024 (1,024 ) 1,024 Comprehensive income (loss) $ 90,941 $ 116,679 $ 3,096 $ (119,775 ) $ 90,941
Condensed Consolidating Statements of Cash Flows	BEACON ROOFING SUPPLY, INC. Condensed Consolidating Statements of Cash Flows (Unaudited; In thousands) Year Ended September 30, 2018 Parent Guarantor Subsidiaries Non-Guarantor Subsidiaries Eliminations and Other Consolidated Net cash provided by (used in) operating activities $ (100,302 ) $ 638,451 $ (680 ) $ 1,912 $ 539,381 Investing Activities Purchases of property and equipment (14,354 ) (29,132 ) (2,524 ) - (46,010 ) Acquisition of businesses (2,740,480 ) - - - (2,740,480 ) Proceeds from the sale of assets - 2,121 28 - 2,149 Intercompany activity 699,970 - - (699,970 ) - Net cash provided by (used in) investing activities (2,054,864 ) (27,011 ) (2,496 ) (699,970 ) (2,784,341 ) Financing Activities Borrowings under revolving lines of credit - 2,766,447 41,294 - 2,807,741 Repayments under revolving lines of credit - (2,666,447 ) (41,294 ) - (2,707,741 ) Borrowings under term loan 970,000 - - - 970,000 Repayments under term loan (445,850 ) - - - (445,850 ) Repayments under equipment financing facilities and other - (11,593 ) - - (11,593 ) Borrowings under senior notes 1,300,000 - - - 1,300,000 Payment of debt issuance costs (58,266 ) (7,522 ) - - (65,788 ) Proceeds from issuance of convertible preferred stock 400,000 - - - 400,000 Payment of stock issuance costs (1,279 ) - - - (1,279 ) Payment of dividends on preferred stock (12,978 ) - - - (12,978 ) Proceeds from issuance of common stock related to equity awards 7,514 - - - 7,514 Taxes paid related to net share settlement of equity awards (3,975 ) - - - (3,975 ) Intercompany activity - (705,625 ) 2,967 702,658 - Net cash provided by (used in) financing activities 2,155,166 (624,740 ) 2,967 702,658 2,236,051 Effect of exchange rate changes on cash and cash equivalents - - 586 - 586 Net increase (decrease) in cash and cash equivalents - (13,300 ) 377 4,600 (8,323 ) Cash and cash equivalents, beginning of period - 149,799 1,582 (13,131 ) 138,250 Cash and cash equivalents, end of period $ - $ 136,499 $ 1,959 $ (8,531 ) $ 129,927 BEACON ROOFING SUPPLY, INC. Condensed Consolidating Statements of Cash Flows (Unaudited; In thousands) Year Ended September 30, 2017 Parent Guarantor Subsidiaries Non-Guarantor Subsidiaries Eliminations and Other Consolidated Net cash provided by (used in) operating activities $ (2,466 ) $ 313,396 $ 4,888 $ (618 ) $ 315,200 Investing Activities Purchases of property and equipment (3,517 ) (34,584 ) (1,727 ) - (39,828 ) Acquisition of businesses (129,390 ) - - - (129,390 ) Proceeds from the sale of assets - 2,150 83 - 2,233 Intercompany activity (203,163 ) - - 203,163 - Net cash used in investing activities (336,070 ) (32,434 ) (1,644 ) 203,163 (166,985 ) Financing Activities Borrowings under revolving lines of credit - 2,445,084 19,044 - 2,464,128 Repayments under revolving lines of credit - (2,812,663 ) (20,567 ) - (2,833,230 ) Repayments under term loan (4,500 ) - - - (4,500 ) Repayments under equipment financing facilities and other - (10,049 ) 15 - (10,034 ) Payment of debt issuance costs (1,669 ) - - - (1,669 ) Proceeds from secondary offering of common stock 345,503 - - - 345,503 Payment of issuance costs from secondary offering of common stock (14,684 ) - - - (14,684 ) Proceeds from issue of common stock related to equity awards 11,341 - - - 11,341 Taxes paid related to net share settlement of equity awards (392 ) - - - (392 ) Excess tax benefit from stock-based compensation 2,937 - - - 2,937 Intercompany activity - 209,018 (2,279 ) (206,739 ) - Net cash provided by (used in) financing activities 338,536 (168,610 ) (3,787 ) (206,739 ) (40,600 ) Effect of exchange rate changes on cash and cash equivalents - - (751 ) - (751 ) Net decrease in cash and cash equivalents - 112,352 (1,294 ) (4,194 ) 106,864 Cash and cash equivalents, beginning of period - 37,447 2,876 (8,937 ) 31,386 Cash and cash equivalents, end of period $ - $ 149,799 $ 1,582 $ (13,131 ) $ 138,250 BEACON ROOFING SUPPLY, INC. Condensed Consolidating Statements of Cash Flows (Unaudited; In thousands) Year Ended September 30, 2016 Parent Guarantor Subsidiaries Non-Guarantor Subsidiaries Eliminations and Other Consolidated Net cash provided by operating activities $ (22,799 ) $ 143,427 $ 4,751 $ (4,731 ) $ 120,648 Investing Activities Purchases of property and equipment (3,654 ) (20,008 ) (2,653 ) - (26,315 ) Acquisition of businesses (1,018,188 ) - - - (1,018,188 ) Proceeds from the sale of assets - 1,882 - - 1,882 Intercompany activity 475,099 - - (475,099 ) - Net cash provided by (used in) investing activities (546,743 ) (18,126 ) (2,653 ) (475,099 ) (1,042,621 ) Financing Activities Borrowings under revolving lines of credit - 1,877,729 14,730 - 1,892,459 Repayments under revolving lines of credit - (1,520,003 ) (21,529 ) - (1,541,532 ) Borrowings under term loan 490,793 - - - 490,793 Repayments under term loan (230,918 ) - - - (230,918 ) Repayments under equipment financing facilities and other (45 ) (4,659 ) (20 ) - (4,724 ) Borrowings under senior notes 300,000 - - - 300,000 Payment of debt issuance costs (19,402 ) (8,923 ) - - (28,325 ) Proceeds from issuance of common stock 24,160 - - - 24,160 Taxes paid related to net share settlement of equity awards (2 ) - - - (2 ) Excess tax benefit from stock-based compensation 4,956 - - - 4,956 Intercompany activity - (474,814 ) (285 ) 475,099 - Net cash provided by (used in) financing activities 569,542 (130,670 ) (7,104 ) 475,099 906,867 Effect of exchange rate changes on cash and cash equivalents - - 831 - 831 Net increase (decrease) in cash and cash equivalents - (5,369 ) (4,175 ) (4,731 ) (14,275 ) Cash and cash equivalents, beginning of period - 42,816 7,051 (4,206 ) 45,661 Cash and cash equivalents, end of period $ - $ 37,447 $ 2,876 $ (8,937 ) $ 31,386

Allowance for Doubtful Accoun_2

Allowance for Doubtful Accounts (Tables)	12 Months Ended
	Sep. 30, 2018
Allowance For Doubtful Accounts [Abstract]
Allowance for Doubtful Accounts	The following table summarizes changes in the valuation of the allowance for doubtful accounts (in thousands): Year Ended September 30, Beginning Balance Charged to Operations Write-offs Ending Balance 2018 $ 11,829 $ 10,948 $ (5,193 ) $ 17,584 2017 14,812 2,914 (5,897 ) 11,829 2016 6,298 13,681 (5,167 ) 14,812

Company Overview - Additional I

Company Overview - Additional Information (Detail) $ in Thousands	Jan. 02, 2018USD ($)	Sep. 30, 2018USD ($)StateProvince	Mar. 31, 2018USD ($)
Company Overview [Line Items]
Date of incorporation		Aug. 22, 1997
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
Allied Acquisition [Member]
Company Overview [Line Items]
Acquisition purchase price in cash	$ 2,625,000
Adjusted purchase price		$ 2,877,070	$ 2,745,882

Summary of Significant Accoun_4

Summary of Significant Accounting Policies - Additional Information (Detail) $ in Millions	12 Months Ended
	Sep. 30, 2018USD ($)SegmentCustomer	Sep. 30, 2017	Sep. 30, 2016
Significant Accounting Policies [Line Items]
Number of operating segments | Segment	1
Number of customers, with at least 10% of revenue	0
Number of customers, with at least 10% of accounts receivable	0
Expected dividend yield	0.00%	0.00%	0.00%
Accounting Standards Update 2016-09
Significant Accounting Policies [Line Items]
Excess tax benefits recognized | $	$ 3.1
Trade Names [Member]
Significant Accounting Policies [Line Items]
Finite-lived intangible assets, amortization method	accelerated basis over a five or ten year period
Minimum [Member]
Significant Accounting Policies [Line Items]
Amortization period	5 years
Minimum [Member] | Trade Names [Member]
Significant Accounting Policies [Line Items]
Amortization period	5 years
Maximum [Member]
Significant Accounting Policies [Line Items]
Amortization period	20 years
Maximum [Member] | Trade Names [Member]
Significant Accounting Policies [Line Items]
Amortization period	10 years
Major Supplier Concentration Risk [Member] | Minimum [Member] | Cost of Goods, Total [Member]
Significant Accounting Policies [Line Items]
Goodwill impairment test period	3 years
Major Supplier Concentration Risk [Member] | Maximum [Member] | Cost of Goods, Total [Member]
Significant Accounting Policies [Line Items]
Goodwill impairment test period	5 years

Summary of Significant Accoun_5

Summary of Significant Accounting Policies - Summary of Property and Equipment Estimated Useful Life (Detail)	12 Months Ended
	Sep. 30, 2018
Building and Building Improvements [Member]
Property, Plant and Equipment [Line Items]
Estimated Useful Life	40 years
Furniture and Fixtures [Member]
Property, Plant and Equipment [Line Items]
Estimated Useful Life	7 years
Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Estimated Useful Life	Shorter of the estimated useful life or the term of the lease, considering renewal options expected to be exercised.
Minimum [Member] | Equipment [Member]
Property, Plant and Equipment [Line Items]
Estimated Useful Life	3 years
Maximum [Member] | Equipment [Member]
Property, Plant and Equipment [Line Items]
Estimated Useful Life	7 years

Acquisitions - Additional Infor

Acquisitions - Additional Information (Detail)	Jul. 16, 2018USD ($)Location	May 01, 2018USD ($)Location	Jan. 02, 2018USD ($)StateLocation$ / sharesshares	May 01, 2017USD ($)Location	Mar. 01, 2017USD ($)Location	Jan. 09, 2017USD ($)Location	Jan. 03, 2017USD ($)Location	Dec. 16, 2016USD ($)Location	Sep. 30, 2018USD ($)Branch$ / sharesshares	Sep. 30, 2017USD ($)BranchBusiness$ / sharesshares	Sep. 30, 2016USD ($)	Mar. 31, 2018USD ($)	Oct. 25, 2017USD ($)
Business Acquisition [Line Items]
Preferred stock, issuance | shares									0	0
Mezzanine equity									$ 399,195,000
Stock issuance costs									$ 1,279,000	$ 14,684,000	$ 0
Common stock, par value | $ / shares									$ 0.01	$ 0.01
Number of business locations acquired | Branch									7	23
Net sales									$ 6,418,311,000	$ 4,376,670,000	4,127,109,000
Net income (loss)									98,626,000	100,864,000	89,917,000
Business acquisition, sales reported by acquired entity for last annual period									7,083,960,000	6,989,658,000
Business acquisitions purchase price allocation goodwill amount									2,491,779,000	$ 1,251,986,000	$ 1,197,565,000
Number of business locations acquired | Business										5
Senior Notes, Matures November 2025 [Member]
Business Acquisition [Line Items]
Debt instrument, aggregate principal amount													$ 1,300,000,000
Allied Acquisition [Member]
Business Acquisition [Line Items]
Acquisition purchase price in cash			$ 2,625,000,000
Net working capital adjustment									88,100,000
Adjusted purchase price									2,877,070,000			$ 2,745,882,000
Number of business locations acquired | Location			208
Number of states business location acquired | State			31
Business acquisition, goodwill, tax deductible amount									1,180,000,000
Business acquisition purchase price and tax position									164,000,000
Net sales									2,150,000,000
Net income (loss)									62,000,000
Business acquisitions purchase price allocation goodwill amount									1,232,780,000			1,130,635,000
Business acquisitions purchase price allocation intangible assets other than goodwill									1,037,000,000			$ 1,037,000,000
Allied Acquisition [Member] | Investment Agreement [Member] | Series A Cumulative Convertible Participating Preferred Stock [Member]
Business Acquisition [Line Items]
Preferred stock, issuance | shares			400,000
Preferred stock, par value | $ / shares			$ 0.01
Preferred stock, liquidation preference value			$ 400,000,000
Preferred stock, liquidation purchase price per share | $ / shares			$ 1,000
Proceeds from convertible preferred stock			$ 400,000,000
Preferred stock conversion price per share | $ / shares			$ 41.26
Preferred stock dividend rate			6.00%
Mezzanine equity			$ 399,200,000
Stock issuance costs			800,000
Allied Acquisition [Member] | Secured Term Loan B Facility [Member]
Business Acquisition [Line Items]
Long-term line of credit			$ 970,000,000
Allied Acquisition [Member] | Secured Term Loan B Facility [Member] | LIBOR [Member]
Business Acquisition [Line Items]
Base borrowing rates			1.25%
Allied Acquisition [Member] | Senior Notes, Matures November 2025 [Member]
Business Acquisition [Line Items]
Debt instrument, aggregate principal amount			$ 1,300,000,000
Allied Acquisition [Member] | Senior-secured Asset-based Revolving Line Of Credit [Member] | LIBOR [Member]
Business Acquisition [Line Items]
Base borrowing rates			2.25%
Allied Acquisition [Member] | Stock Purchase Agreement [Member]
Business Acquisition [Line Items]
Acquisition purchase price in cash			$ 2,625,000,000
Tri-State Builder Supply [Member]
Business Acquisition [Line Items]
Number of business locations acquired | Location		1
Business acquisition, sales reported by acquired entity for last annual period		$ 6,000,000
Atlas Supply, Inc. [Member]
Business Acquisition [Line Items]
Number of business locations acquired | Location	6
Business acquisition, sales reported by acquired entity for last annual period	$ 37,000,000
Series of Individually Immaterial Business Acquisitions [Member]
Business Acquisition [Line Items]
Business acquisition, goodwill, tax deductible amount									8,000,000
Business acquisitions purchase price allocation goodwill amount									8,100,000	$ 53,000,000
Business acquisitions purchase price allocation intangible assets other than goodwill									$ 10,800,000	$ 47,400,000
BJ Supply Company [Member]
Business Acquisition [Line Items]
Number of business locations acquired | Location								1
Business acquisition, sales reported by acquired entity for last annual period								$ 4,000,000
American Building and Roofing, Inc. [Member]
Business Acquisition [Line Items]
Number of business locations acquired | Location							7
Business acquisition, sales reported by acquired entity for last annual period							$ 36,000,000
Eco Insulation Supply [Member]
Business Acquisition [Line Items]
Number of business locations acquired | Location						1
Business acquisition, sales reported by acquired entity for last annual period						$ 8,000,000
Acme Building Materials, Inc. [Member]
Business Acquisition [Line Items]
Number of business locations acquired | Location					3
Business acquisition, sales reported by acquired entity for last annual period					$ 13,000,000
Lowry's Inc. [Member]
Business Acquisition [Line Items]
Number of business locations acquired | Location				11
Business acquisition, sales reported by acquired entity for last annual period				$ 76,000,000

Acquisitions - Schedule of Reco

Acquisitions - Schedule of Recognized Identified Assets Acquired and Liabilities Assumed (Detail) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2018	Mar. 31, 2018	Sep. 30, 2017	Sep. 30, 2016
Business Combination Separately Recognized Transactions [Line Items]
Goodwill	$ 2,491,779		$ 1,251,986	$ 1,197,565
Allied Acquisition [Member]
Business Combination Separately Recognized Transactions [Line Items]
Cash	169	$ 19,322
Accounts receivable	337,548	315,485
Inventory	314,785	322,705
Prepaid and other current assets	75,440	59,279
Property, plant, and equipment	139,360	139,528
Goodwill	1,232,780	1,130,635
Intangible assets	1,037,000	1,037,000
Current liabilities	(259,289)	(271,252)
Non-current liabilities	(723)	(6,820)
Total purchase price	2,877,070	$ 2,745,882
Cash	(19,153)
Accounts receivable	22,063
Inventory	(7,920)
Prepaid and other current assets	16,161
Property, plant, and equipment	(168)
Goodwill	102,145
Current liabilities	11,963
Non-current liabilities	6,097
Total purchase price	$ 131,188

Acquisitions - Business Acquisi

Acquisitions - Business Acquisition, Pro Forma Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Business Acquisition Pro Forma Information [Abstract]
Net sales	$ 7,083,960	$ 6,989,658
Net income (loss)	$ 62,081	$ 70,701

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 Thousands		12 Months Ended
		Sep. 30, 2018		Sep. 30, 2017	Sep. 30, 2016
Earnings Per Share [Abstract]
Net income (loss)		$ 98,626		$ 100,864	$ 89,917
Dividends on preferred shares		(18,000)	[1]	0	0
Net income (loss) attributable to common shareholders		80,626		100,864	89,917
Undistributed income allocated to participating securities		(7,742)
Net income (loss) attributable to common shareholders - basic and diluted		$ 72,884		$ 100,864	$ 89,917
Weighted-average common shares outstanding - basic		68,012,879		60,315,648	59,424,372
Effect of common share equivalents		1,178,160		1,028,615	993,695
Weighted-average common shares outstanding - diluted		69,191,039		61,344,263	60,418,067
Net income (loss) per share - basic	[2]	$ 1.07		$ 1.67	$ 1.51
Net income (loss) per share - diluted	[2]	$ 1.05		$ 1.64	$ 1.49
[1]	For the year ended September 30, 2018, $18.0 million is comprised of $5.0 million undeclared cumulative dividends as well as an additional $13.0 million of preferred share dividends that had been declared and paid as of period end.
[2]	See Note 4 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	12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016
Preferred Stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from computation of diluted net income (loss) per share	7,224,483
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	388,731	331,681	502,294
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	192,151	61,890	45,220

Prepaid Expenses and Other Cu_3

Prepaid Expenses and Other Current Assets - Schedule of Prepaid Expenses and Other Current Assets (Detail) - USD ($) $ in Thousands	Sep. 30, 2018	Sep. 30, 2017
Prepaid Expenses And Other Current Assets [Abstract]
Vendor rebates	$ 199,725	$ 193,071
Other	44,635	16,067
Prepaid Expense and Other Assets, Current	$ 244,360	$ 209,138

Property and Equipment - Proper

Property and Equipment - Property and Equipment, net (Detail) - USD ($) $ in Thousands	Sep. 30, 2018	Sep. 30, 2017
Property, Plant and Equipment [Line Items]
Total property and equipment	$ 537,277	$ 358,420
Accumulated depreciation	(256,870)	(202,291)
Total property and equipment, net	280,407	156,129
Land and Buildings [Member]
Property, Plant and Equipment [Line Items]
Total property and equipment	82,991	41,791
Equipment [Member]
Property, Plant and Equipment [Line Items]
Total property and equipment	419,385	293,489
Furniture and Fixtures [Member]
Property, Plant and Equipment [Line Items]
Total property and equipment	$ 34,901	$ 23,140

Property and Equipment - Additi

Property and Equipment - Additional Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016
Property Plant And Equipment [Abstract]
Depreciation	$ 60,318	$ 34,002	$ 31,876

Goodwill and Intangible Asset_2

Goodwill and Intangible Assets - Summary of Changes in goodwill (Detail) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Goodwill And Intangible Assets Disclosure [Abstract]
Beginning balance	$ 1,251,986	$ 1,197,565
Acquisitions	1,240,913	53,012
Translation and other adjustments	(1,120)	1,409
Ending balance	$ 2,491,779	$ 1,251,986

Goodwill and Intangible Asset_3

Goodwill and Intangible Assets - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016
Goodwill And Intangible Assets [Line Items]
Finite-lived Intangible Assets Acquired	$ 1,050,000	$ 47,400
Amortization of Intangible Assets	$ 141,185	82,465	$ 68,316
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	18 years 6 months
Trademarks [Member]
Goodwill And Intangible Assets [Line Items]
Indefinite-lived Intangible Assets Acquired	$ 120,000
Customer Relationships [Member]
Goodwill And Intangible Assets [Line Items]
Finite-lived Intangible Assets Acquired	$ 920,800	42,700
Customer Relationships [Member] | Weighted Average [Member]
Goodwill And Intangible Assets [Line Items]
Finite-Lived Intangible Asset, Useful Life	18 years 7 months 13 days
Trademarks [Member]
Goodwill And Intangible Assets [Line Items]
Finite-lived Intangible Assets Acquired		4,600
Trademarks [Member] | Weighted Average [Member]
Goodwill And Intangible Assets [Line Items]
Finite-Lived Intangible Asset, Useful Life	7 years 7 months 6 days
Beneficial Lease Arrangements [Member]
Goodwill And Intangible Assets [Line Items]
Finite-lived Intangible Assets Acquired	$ 7,000	$ 100
Beneficial Lease Arrangements [Member] | Weighted Average [Member]
Goodwill And Intangible Assets [Line Items]
Finite-Lived Intangible Asset, Useful Life	4 years 5 months 23 days

Goodwill and Intangible Asset_4

Goodwill and Intangible Assets - Summary of Intangible Assets (Detail) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Finite Lived Intangible Assets [Line Items]
Amortizable intangible assets	$ 1,551,949	$ 624,410
Accumulated amortization	(410,633)	(268,391)
Total amortizable intangible assets, net	1,141,316	356,019
Indefinite lived trademarks	193,050	73,050
Total intangibles, net	$ 1,334,366	429,069
Weighted Average [Member]
Finite Lived Intangible Assets [Line Items]
Finite-Lived Intangible Asset, Useful Life	18 years 6 months
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	$ 2,824	2,824
Noncompete Agreements [Member] | Weighted Average [Member]
Finite Lived Intangible Assets [Line Items]
Finite-Lived Intangible Asset, Useful Life	2 years 7 months 6 days
Customer Relationships [Member]
Finite Lived Intangible Assets [Line Items]
Amortizable intangible assets	$ 1,530,565	610,026
Customer Relationships [Member] | Weighted Average [Member]
Finite Lived Intangible Assets [Line Items]
Finite-Lived Intangible Asset, Useful Life	18 years 7 months 13 days
Trademarks [Member]
Finite Lived Intangible Assets [Line Items]
Amortizable intangible assets	$ 10,500	10,500
Trademarks [Member] | Weighted Average [Member]
Finite Lived Intangible Assets [Line Items]
Finite-Lived Intangible Asset, Useful Life	7 years 7 months 6 days
Beneficial Lease Arrangements [Member]
Finite Lived Intangible Assets [Line Items]
Amortizable intangible assets	$ 8,060	$ 1,060
Beneficial Lease Arrangements [Member] | Weighted Average [Member]
Finite Lived Intangible Assets [Line Items]
Finite-Lived Intangible Asset, Useful Life	4 years 5 months 23 days

Goodwill and Intangible Asset_5

Goodwill and Intangible Assets - Summary of Estimated Future Amortization (Detail) - USD ($) $ in Thousands	Sep. 30, 2018	Sep. 30, 2017
Goodwill And Intangible Assets Disclosure [Abstract]
2,019	$ 208,404
2,020	179,571
2,021	149,888
2,022	121,396
2,023	97,474
Thereafter	384,583
Total amortizable intangible assets, net	$ 1,141,316	$ 356,019

Financing Arrangements - Long-t

Financing Arrangements - Long-term Debt Instruments (Detail) - USD ($)		Sep. 30, 2018		Jan. 02, 2018	Sep. 30, 2017	Oct. 02, 2015
Debt Instrument [Line Items]
Borrowings under revolving lines of credit/term loans, net		$ 92,442,000			$ 3,205,000
Current portion		0			0
Total long-term borrowings under Senior Notes		1,573,699,000			292,328,000
Long-term debt, net		2,494,725,000			721,268,000
Equipment financing facilities, various maturities through September 2021	[1]	11,222,000			12,898,000
Capital lease obligations, various maturities through November 2021	[2]	12,378,000			19,956,000
Long-term obligations under equipment financing and other, net		13,639,000			23,213,000
Senior Notes, Matures October 2023 [Member]
Debt Instrument [Line Items]
Senior Notes	[3]	293,607,000			292,328,000
Senior Notes, Matures November 2025 [Member]
Debt Instrument [Line Items]
Senior Notes	[4]	1,280,092,000
Equipment Financing Facilities and Other [Member]
Debt Instrument [Line Items]
Current portion		(9,961,000)			(9,641,000)
Long-term obligations under equipment financing and other, net		13,639,000			23,213,000
Revolving Lines of Credit [Member]
Debt Instrument [Line Items]
Borrowings under revolving lines of credit/term loans, net		92,442,000			3,205,000
Revolving Lines of Credit [Member] | 2020 ABL [Member] | U.S. [Member]
Debt Instrument [Line Items]
Total Borrowings under revolving lines of credit/term loans						$ 670,000,000
Revolving Lines of Credit [Member] | 2020 ABL [Member] | Canada [Member]
Debt Instrument [Line Items]
Total Borrowings under revolving lines of credit/term loans	[5]				3,205,000
Revolving Lines of Credit [Member] | 2023 ABL [Member]
Debt Instrument [Line Items]
Borrowings under revolving lines of credit/term loans, net		92,400,000
Revolving Lines of Credit [Member] | 2023 ABL [Member] | U.S. [Member]
Debt Instrument [Line Items]
Total Borrowings under revolving lines of credit/term loans	[6]	89,352,000
Revolving Lines of Credit [Member] | 2023 ABL [Member] | Canada [Member]
Debt Instrument [Line Items]
Total Borrowings under revolving lines of credit/term loans	[7]	3,090,000
Term Loan [Member]
Debt Instrument [Line Items]
Current portion		(9,700,000)			(4,500,000)
Borrowings under revolving lines of credit/term loans, net		921,026,000			428,940,000
Term Loan [Member] | Term Loan, Matures October 1, 2022 [Member]
Debt Instrument [Line Items]
Total Borrowings under revolving lines of credit/term loans	[8]				$ 433,440,000
Term Loan [Member] | Term Loan, Matures January 2, 2025 [Member]
Debt Instrument [Line Items]
Total Borrowings under revolving lines of credit/term loans		$ 930,726,000	[9]	$ 970,000,000
[1]	Fixed interest rates ranging from 2.33% to 3.25% as of September 30, 2018 and September 30, 2017
[2]	Fixed interest rates ranging from 2.72% to 10.39% as of September 30, 2018 and September 30, 2017
[3]	Interest rate of 6.38% as of September 30, 2018 and September 30, 2017
[4]	Interest rate of 4.88% as of September 30, 2018
[5]	Extinguished on January 2, 2018; Effective rate on borrowings of 3.70% as of September 30, 2017
[6]	Effective rate on borrowings of 3.36% as of September 30, 2018
[7]	Effective rate on borrowings of 3.95% as of September 30, 2018
[8]	Extinguished on January 2, 2018; Interest rate of 3.50% as of September 30, 2017
[9]	Interest rate of 4.53% as of September 30, 2018

Financing Arrangements - Long_2

Financing Arrangements - Long-term Debt Instruments (Parenthetical) (Detail)	Jan. 02, 2018	Oct. 02, 2015	Sep. 30, 2018	Sep. 30, 2017
Equipment Financing Facilities [Member]
Debt Instrument [Line Items]
Debt instrument maturity date			Sep. 30, 2021
Equipment Financing Facilities [Member] | Minimum [Member]
Debt Instrument [Line Items]
Equipment financing facilities, fixed interest rate percentage			2.33%	2.33%
Equipment Financing Facilities [Member] | Maximum [Member]
Debt Instrument [Line Items]
Equipment financing facilities, fixed interest rate percentage			3.25%	3.25%
Capital Lease Obligations [Member]
Debt Instrument [Line Items]
Debt instrument maturity date			Nov. 30, 2021
Capital Lease Obligations [Member] | Minimum [Member]
Debt Instrument [Line Items]
Capital lease obligations, fixed interest rate percentage			2.72%	2.72%
Capital Lease Obligations [Member] | Maximum [Member]
Debt Instrument [Line Items]
Capital lease obligations, fixed interest rate percentage			10.39%	10.39%
Senior Notes, Matures October 2023 [Member]
Debt Instrument [Line Items]
Debt interest rate at period end			6.38%	6.38%
Debt instrument maturity date		Oct. 1, 2023	Oct. 31, 2023
Senior Notes, Matures November 2025 [Member]
Debt Instrument [Line Items]
Debt interest rate at period end			4.88%
Debt instrument maturity date			Nov. 1, 2025
Revolving Lines of Credit [Member] | 2020 ABL [Member]
Debt Instrument [Line Items]
Debt instrument maturity date		Oct. 1, 2020
Revolving Lines of Credit [Member] | 2020 ABL [Member] | U.S. [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Interest Rate at Period End				2.00%
Line of Credit Facility, Expiration Date			Oct. 1, 2020
Debt extinguishment date			Jan. 2, 2018
Revolving Lines of Credit [Member] | 2020 ABL [Member] | Canada [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Interest Rate at Period End				3.70%
Line of Credit Facility, Expiration Date			Oct. 1, 2020
Debt extinguishment date			Jan. 2, 2018
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			3.36%
Line of Credit Facility, Expiration Date			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			3.95%
Line of Credit Facility, Expiration Date			Jan. 2, 2023
Term Loan [Member] | Term Loan, Matures October 1, 2022 [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Interest Rate at Period End				3.50%
Line of Credit Facility, Expiration Date			Oct. 1, 2022
Debt extinguishment date			Jan. 2, 2018
Term Loan [Member] | Term Loan, Matures January 2, 2025 [Member]
Debt Instrument [Line Items]
Debt interest rate at period end			4.53%
Debt instrument maturity date	Jan. 2, 2025		Jan. 2, 2025

Financing Arrangements - Additi

Financing Arrangements - Additional Information (Detail)		Jan. 02, 2018USD ($)	Oct. 02, 2015USD ($)	Sep. 30, 2018USD ($)Covenant		Sep. 30, 2017USD ($)	Sep. 30, 2016USD ($)	Oct. 25, 2017USD ($)
Debt Instrument [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity		$ 3,570,000,000	$ 1,450,000,000
Borrowings under senior notes				$ 1,300,000,000		$ 0	$ 300,000,000
Payments of debt issuance costs		65,800,000		65,788,000		1,669,000	28,325,000
Gains (Losses) on Extinguishment of Debt				(1,248,000)		0	$ 0
Unamortized debt issuance costs				71,373,000
Borrowings under revolving lines of credit/term loans, net				92,442,000		$ 3,205,000
Roofing Supply Group [Member]
Debt Instrument [Line Items]
Payments of debt issuance costs				$ 31,300,000
Roofing Supply Group [Member] | Unsecured Senior Notes [Member]
Debt Instrument [Line Items]
Debt instrument maturity year				2,020
Allied Financing Arrangements [Member]
Debt Instrument [Line Items]
Payments of debt issuance costs		1,500,000
Gains (Losses) on Extinguishment of Debt		(1,200,000)
2023 ABL [Member]
Debt Instrument [Line Items]
Unamortized debt issuance costs				$ 10,648,000
Term Loan, Matures January 2, 2025 [Member]
Debt Instrument [Line Items]
Unamortized debt issuance costs				$ 34,424,000
Senior Notes, Matures November 2025 [Member]
Debt Instrument [Line Items]
Borrowings under senior notes		1,300,000,000
Debt instrument maturity date				Nov. 1, 2025
Unamortized debt issuance costs				$ 19,900,000
Debt instrument, aggregate principal amount								$ 1,300,000,000
Debt instrument interest rate				4.88%
Debt instrument, issue price percentage								100.00%
Senior Notes Payable	[1]			$ 1,280,092,000
Senior Notes, Matures October 2023 [Member]
Debt Instrument [Line Items]
Borrowings under senior notes			$ 300,000,000
Debt instrument maturity date			Oct. 1, 2023	Oct. 31, 2023
Unamortized debt issuance costs				$ 6,400,000
Debt instrument interest rate				6.38%		6.38%
Senior Notes Payable	[2]			$ 293,607,000		$ 292,328,000
Debt instrument, coupon rate			6.38%
Revolving Lines of Credit [Member]
Debt Instrument [Line Items]
Borrowings under revolving lines of credit/term loans, net				$ 92,442,000		3,205,000
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
Debt instrument maturity date		Jan. 2, 2023
Line of credit facility, unused fees				0.25%
Number of financial covenants | Covenant				1
Fixed charge coverage ratio				100.00%
Unamortized debt issuance costs				$ 10,600,000
Borrowings under revolving lines of credit/term loans, net				92,400,000
Revolving Lines of Credit [Member] | 2023 ABL [Member] | U.S. [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity		$ 1,200,000,000
Long-term line of credit	[3]			89,352,000
Standby letters of credit outstanding				13,400,000
Revolving Lines of Credit [Member] | 2023 ABL [Member] | Canada [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity		100,000,000
Long-term line of credit	[4]			3,090,000
Revolving Lines of Credit [Member] | 2020 ABL [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity			$ 700,000,000
Proceeds from Lines of Credit			$ 350,000,000
Debt instrument maturity date			Oct. 1, 2020
Debt instrument paid off date			Jan. 2, 2018
Revolving Lines of Credit [Member] | 2020 ABL [Member] | U.S. [Member]
Debt Instrument [Line Items]
Long-term line of credit			$ 670,000,000
Revolving Lines of Credit [Member] | 2020 ABL [Member] | Canada [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity			30,000,000
Long-term line of credit	[5]					3,205,000
Term Loan [Member]
Debt Instrument [Line Items]
Borrowings under revolving lines of credit/term loans, net				921,026,000		$ 428,940,000
Term Loan [Member] | Term Loan, Matures January 2, 2025 [Member]
Debt Instrument [Line Items]
Long-term line of credit		$ 970,000,000		$ 930,726,000	[6]
Debt instrument maturity date		Jan. 2, 2025		Jan. 2, 2025
Unamortized debt issuance costs				$ 34,400,000
Debt Instrument, Frequency of Periodic Payment				quarterly
Debt Instrument, Periodic Payment		$ 2,400,000
Debt instrument interest rate				4.53%
Term Loan [Member] | 2022 Term Loan [Member]
Debt Instrument [Line Items]
Long-term line of credit			$ 450,000,000
Debt instrument maturity date			Oct. 1, 2022
Debt Instrument, Frequency of Periodic Payment				quarterly
Debt Instrument, Periodic Payment			$ 1,100,000
Debt instrument paid off date			Jan. 2, 2018
Write off of debt issuance costs			$ 700,000
[1]	Interest rate of 4.88% as of September 30, 2018
[2]	Interest rate of 6.38% as of September 30, 2018 and September 30, 2017
[3]	Effective rate on borrowings of 3.36% as of September 30, 2018
[4]	Effective rate on borrowings of 3.95% as of September 30, 2018
[5]	Extinguished on January 2, 2018; Effective rate on borrowings of 3.70% as of September 30, 2017
[6]	Interest rate of 4.53% as of September 30, 2018

Financing Arrangements - Schedu

Financing Arrangements - Schedule of Maturities of Long-term Debt (Detail) $ in Thousands	Sep. 30, 2018USD ($)
Debt Instrument [Line Items]
2,019	$ 19,629
2,020	18,714
2,021	14,027
2,022	10,030
2,023	412,790
Thereafter	2,216,650
Total debt	2,691,840
Unamortized debt issuance costs	(71,373)
Total long-term debt	2,620,467
2023 ABL [Member]
Debt Instrument [Line Items]
2,019	0
2,020	0
2,021	0
2,022	0
2,023	103,090
Thereafter	0
Total debt	103,090
Unamortized debt issuance costs	(10,648)
Total long-term debt	92,442
2025 Term Loan [Member]
Debt Instrument [Line Items]
2,019	9,700
2,020	9,700
2,021	9,700
2,022	9,700
2,023	9,700
Thereafter	916,650
Total debt	965,150
Unamortized debt issuance costs	(34,424)
Total long-term debt	930,726
Equipment Financing Facilities [Member]
Debt Instrument [Line Items]
2,019	9,929
2,020	9,014
2,021	4,327
2,022	330
2,023	0
Thereafter	0
Total debt	23,600
Unamortized debt issuance costs	0
Total long-term debt	23,600
Senior Notes [Member]
Debt Instrument [Line Items]
2,019	0
2,020	0
2,021	0
2,022	0
2,023	300,000
Thereafter	1,300,000
Total debt	1,600,000
Unamortized debt issuance costs	(26,301)
Total long-term debt	$ 1,573,699

Commitments and Contingencies -

Commitments and Contingencies - Schedule of Minimum Rental Commitments under Non-cancelable Operating Leases (Detail) $ in Thousands	Sep. 30, 2018USD ($)
Commitments And Contingencies Disclosure [Abstract]
2,019	$ 105,425
2,020	94,348
2,021	82,827
2,022	62,863
2,023	46,274
Thereafter	120,291
Total minimum lease payments	$ 512,028

Commitments and Contingencies_2

Commitments and Contingencies - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016
Commitments And Contingencies Disclosure [Abstract]
Operating Leases, Rent Expense, Net, Total	$ 99.1	$ 60.1	$ 59.3

Stockholders' Equity - Addition

Stockholders' Equity - Additional Information (Detail) - shares	Sep. 30, 2018	Sep. 30, 2017
Equity [Abstract]
Common stock (voting), shares authorized	100,000,000	100,000,000
Common Stock (Voting), issued	68,135,790	67,700,858
Common Stock (voting), outstanding	68,135,790	67,700,858

Stockholders' Equity - Reclassi

Stockholders' Equity - Reclassification out of Accumulated Other Comprehensive Income (Detail) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance	$ 1,781,806	$ 1,323,827	$ 883,116
Other comprehensive income (loss) before reclassifications	(2,687)	3,706	1,024
Reclassifications out of other comprehensive loss		388	1,039
Balance	1,884,305	1,781,806	1,323,827
Foreign Currency Translation
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance	(14,563)	(18,269)	(19,293)
Other comprehensive income (loss) before reclassifications	(2,687)	3,706	1,024
Balance	(17,250)	(14,563)	(18,269)
Derivative Financial Instruments
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance		(388)	(1,427)
Reclassifications out of other comprehensive loss		388	1,039
Balance			(388)
Accumulated Other Comprehensive Loss [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance	(14,563)	(18,657)	(20,720)
Balance	$ (17,250)	$ (14,563)	$ (18,657)

Stock-based Compensation - Addi

Stock-based Compensation - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Feb. 09, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation number of shares authorized			5,000,000
Stock-based compensation number of shares available for awards	3,334,750
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 Expire	10 years
Allocated stock-based compensation expense	$ 3.9	$ 4.8
Unrecognized compensation cost related to unvested stock	$ 4.4
Unrecognized compensation cost related to unvested stock, expected weighted-average period of recognition	1 year 8 months 12 days
Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Allocated stock-based compensation expense	$ 12.6	$ 10.3
Unrecognized compensation cost related to unvested stock	$ 17.1
Unrecognized compensation cost related to unvested stock, expected weighted-average period of recognition	1 year 8 months 12 days
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)	12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Risk-free interest rate	2.10%	1.97%	1.87%
Expected volatility	26.43%	28.83%	30.96%
Expected life (in years)	5 years 5 months 16 days	5 years 3 months 18 days	5 years 7 months 6 days
Dividend yield	0.00%	0.00%	0.00%

Stock-based compensation - Stoc

Stock-based compensation - Stock Options Outstanding and Activity During the Period (Detail) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Options Outstanding
Balance as of September 30, 2017	2,084,228
Granted	276,370
Exercised	(308,266)
Canceled/Forfeited	(81,304)
Expired	(1,991)
Balance as of September 30, 2018	1,969,037	2,084,228
Vested and expected to vest after September 30, 2018	1,956,534
Exercisable as of September 30, 2018	1,439,187
Weighted-Average Exercise Price
Beginning Balance	$ 28.84
Granted	55.17
Exercised	24.38
Canceled/Forfeited	32.92
Expired	15.28
Ending Balance	33.08	$ 28.84
Vested and expected to vest after September 30, 2018	32.96
Exercisable as of September 30, 2018	$ 27.48
Weighted-Average Remaining Contractual Life
Balance	5 years 8 months 12 days	6 years 1 month 6 days
Vested and expected to vest after September 30, 2018	5 years 8 months 12 days
Exercisable as of September 30, 2018	4 years 8 months 12 days
Aggregate Intrinsic Value
Balance	$ 14,088	$ 46,714
Vested and expected to vest after September 30, 2018	14,078
Exercisable as of September 30, 2018	$ 13,668

Stock-based compensation - St_2

Stock-based compensation - Stock Option Grants, Vesting, and Exercises (Detail) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Weighted-average fair value of stock options granted	$ 15.86	$ 14.21	$ 12.89
Total fair value of stock options vested	$ 4,208	$ 5,541	$ 12,347
Total intrinsic value of stock options exercised	$ 9,645	$ 10,941	$ 22,693

Stock-based Compensation - Rest

Stock-based Compensation - Restricted Shares and Units Outstanding and Activity During the Period (Detail) - $ / shares	12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016
Weighted - Average Grant Date Fair Value
Granted	$ 57.40	$ 47.31	$ 38.92
Restricted Stock Units (RSUs) [Member]
Outstanding
Balance at September 30, 2017	770,973
Granted	370,190
Performance awards	41,440
Released	(191,703)
Canceled/Forfeited	(56,877)
Balance at September 30, 2018	934,023	770,973
Vested and expected to vest after September 30, 2018	888,337
Weighted - Average Grant Date Fair Value
Balance at September 30, 2017	$ 38.95
Granted	57.40
Performance awards	39.56
Released	31.91
Canceled/Forfeited	51.10
Balance at September 30, 2018	47	$ 38.95
Vested and expected to vest after September 30, 2018	$ 46.87

Stock-based Compensation - Sche

Stock-based Compensation - Schedule Of Restricted Stock Units Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Weighted-average fair value of RSUs granted	$ 57.40	$ 47.31	$ 38.92
Total fair value of RSUs vested	$ 6,656	$ 4,562	$ 743
Total intrinsic value of RSUs released	$ 11,041	$ 6,079	$ 1,375

Income Taxes - Additional Infor

Income Taxes - Additional Information (Detail)	12 Months Ended
	Sep. 30, 2019	Sep. 30, 2018USD ($)StateProvince	Sep. 30, 2017USD ($)	Sep. 30, 2016USD ($)
Blended federal corporate income tax rate		24.50%
Federal corporate income tax rate		24.50%	35.00%	35.00%
Income tax benefit		$ 50,000,000
Accumulated earnings		833,834,000	$ 748,186,000
Expense for one-time repatriation transition tax liability		1,200,000
Operating Loss Carryforwards		59,300,000		$ 135,300,000
Net Operating Loss Carryforward Utilized		15,700,000
Foreign tax credits in connection with repatriation tax from TCJA		2,600,000
Goodwill		2,491,779,000	$ 1,251,986,000	$ 1,197,565,000
Goodwill amortizable for income tax		1,450,000,000
Uncertain tax positions		$ 0
U.S. [Member]
Number of States in which Entity Operates | State		50
Canada [Member]
Number of provinces in which entity operates | Province		6
BRSCC [Member]
Accumulated earnings		$ 15,700,000
Scenario, Forecast [Member]
Federal corporate income tax rate	21.00%

Income Taxes - Summary of Compo

Income Taxes - Summary of Components of Income Tax Provision (Benefit) (Detail) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016
Current:
Federal	$ (4,435)	$ 52,718	$ 23,403
Foreign	492	1,366	1,183
State	3,516	8,975	2,426
Total current taxes	(427)	63,059	27,012
Deferred:
Federal	(35,249)	(656)	25,935
Foreign	(173)	0	321
State	5,305	78	3,347
Total deferred taxes	(30,117)	(578)	29,603
Provision for (benefit from) income taxes	$ (30,544)	$ 62,481	$ 56,615

Income Taxes - Reconciliation o

Income Taxes - Reconciliation of Statutory Federal Income Tax Rate (Detail)	12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016
Income Tax Disclosure [Abstract]
U.S. federal income taxes at statutory rate	24.50%	35.00%	35.00%
State income taxes, net of federal benefit	5.20%	3.90%	4.20%
Share-based payments	(3.90%)	0.00%	0.00%
Deferred tax asset/liability remeasurement	(73.50%)	0.00%	(1.00%)
Repatriation transition tax	1.80%	0.00%	0.00%
Non-deductible professional fees	0.00%	0.00%	0.40%
Other	1.00%	(0.60%)	0.00%
Effective tax rate	(44.90%)	38.30%	38.60%

Income Taxes - Schedule of Temp

Income Taxes - Schedule of Temporary Differences That Give Rise to Deferred Tax Assets and Liabilities (Detail) - USD ($) $ in Thousands	Sep. 30, 2018	Sep. 30, 2017
Deferred tax assets:
Deferred compensation	$ 11,346	$ 14,237
Allowance for doubtful accounts	663	1,318
Accrued vacation and other	5,079	6,602
Inventory valuation	12,900	10,564
Tax loss carryforwards	17,271	20,575
Other	1,517	958
Total deferred tax assets	48,776	54,254
Deferred tax liabilities:
Excess tax over book depreciation and amortization	(155,770)	(192,637)
Total deferred tax liabilities	(155,770)	(192,637)
Net deferred income tax liabilities	$ (106,994)	$ (138,383)

Geographic and Product Data - S

Geographic and Product Data - Schedule Of Geographic Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016
Segment Reporting Information [Line Items]
Net sales	$ 6,418,311	$ 4,376,670	$ 4,127,109
Long-lived assets	1,422,966	520,682
U.S. [Member]
Segment Reporting Information [Line Items]
Net sales	6,239,332	4,198,935	3,949,067
Long-lived assets	1,409,742	507,236
Canada [Member]
Segment Reporting Information [Line Items]
Net sales	178,979	177,735	$ 178,042
Long-lived assets	$ 13,224	$ 13,446

Geographic and Product Data -_2

Geographic and Product Data - Schedule Of Net Sales From External Customers By Product Group (Detail) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016
Revenue from External Customer [Line Items]
Net sales	$ 6,418,311	$ 4,376,670	$ 4,127,109
Residential Roofing Products [Member]
Revenue from External Customer [Line Items]
Net sales	2,798,756	2,380,435	2,190,762
Non-Residential Roofing Products [Member]
Revenue from External Customer [Line Items]
Net sales	1,635,963	1,273,153	1,331,319
Complementary Building Products [Member]
Revenue from External Customer [Line Items]
Net sales	$ 1,983,592	$ 723,082	$ 605,028

Supplemental Guarantor Inform_3

Supplemental Guarantor Information - Condensed Consolidating Balance Sheets (Detail) - USD ($) $ in Thousands	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
Current assets:
Cash and cash equivalents	$ 129,927	$ 138,250
Accounts receivable, net	1,090,533	704,527
Inventories, net	936,047	551,924
Prepaid expenses and other current assets	244,360	209,138
Total current assets	2,400,867	1,603,839
Intercompany receivable, net	0	0
Investments in consolidated subsidiaries	0	0
Deferred income taxes, net	0	0
Property and equipment, net	280,407	156,129
Goodwill	2,491,779	1,251,986	$ 1,197,565
Intangibles, net	1,334,366	429,069
Other assets, net	1,243	8,534
Total Assets	6,508,662	3,449,557
Current liabilities:
Accounts payable	880,872	503,697
Accrued expenses	611,539	261,297
Current portions of long-term debt	19,661	14,141
Total current liabilities	1,512,072	779,135
Intercompany payable, net	0	0
Borrowings under revolving lines of credit, net	92,442	3,205
Long-term debt, net	2,494,725	721,268
Deferred income taxes, net	106,994	138,383
Long-term obligations under equipment financing and other, net	13,639	23,213
Other long-term liabilities	5,290	2,547
Total liabilities	4,225,162	1,667,751
Convertible preferred stock	399,195
Total stockholders' equity	1,884,305	1,781,806	$ 1,323,827	$ 883,116
Total Liabilities and Stockholders' Equity	6,508,662	3,449,557
Parent Company [Member]
Current assets:
Cash and cash equivalents	0	0
Accounts receivable, net	0	0
Inventories, net	0	0
Prepaid expenses and other current assets	23,711	4,195
Total current assets	23,711	4,195
Intercompany receivable, net	0	0
Investments in consolidated subsidiaries	6,109,325	3,160,273
Deferred income taxes, net	22,475	30,822
Property and equipment, net	18,929	6,610
Goodwill	0	0
Intangibles, net	0	0
Other assets, net	1,243	2,912
Total Assets	6,175,683	3,204,812
Current liabilities:
Accounts payable	24,154	27,174
Accrued expenses	41,448	51,183
Current portions of long-term debt	9,700	4,500
Total current liabilities	75,302	82,857
Intercompany payable, net	1,322,156	618,881
Borrowings under revolving lines of credit, net	0	0
Long-term debt, net	2,494,725	721,268
Deferred income taxes, net	0	0
Long-term obligations under equipment financing and other, net	0	0
Other long-term liabilities	0	0
Total liabilities	3,892,183	1,423,006
Convertible preferred stock	399,195
Total stockholders' equity	1,884,305	1,781,806
Total Liabilities and Stockholders' Equity	6,175,683	3,204,812
Guarantor Subsidiaries [Member]
Current assets:
Cash and cash equivalents	136,499	149,799
Accounts receivable, net	1,051,410	663,034
Inventories, net	907,605	527,226
Prepaid expenses and other current assets	214,011	198,817
Total current assets	2,309,525	1,538,876
Intercompany receivable, net	1,361,615	655,372
Investments in consolidated subsidiaries	0	0
Deferred income taxes, net	0	0
Property and equipment, net	250,517	138,955
Goodwill	2,461,725	1,220,812
Intangibles, net	1,332,104	426,187
Other assets, net	0	5,622
Total Assets	7,715,486	3,985,824
Current liabilities:
Accounts payable	843,907	468,891
Accrued expenses	564,331	204,173
Current portions of long-term debt	9,961	9,641
Total current liabilities	1,418,199	682,705
Intercompany payable, net	0	0
Borrowings under revolving lines of credit, net	89,352	0
Long-term debt, net	0	0
Deferred income taxes, net	128,846	168,209
Long-term obligations under equipment financing and other, net	13,639	23,147
Other long-term liabilities	5,207	2,547
Total liabilities	1,655,243	876,608
Convertible preferred stock	0
Total stockholders' equity	6,060,243	3,109,216
Total Liabilities and Stockholders' Equity	7,715,486	3,985,824
Non-Guarantor Subsidiaries [Member]
Current assets:
Cash and cash equivalents	1,959	1,582
Accounts receivable, net	40,262	42,633
Inventories, net	28,442	24,698
Prepaid expenses and other current assets	6,638	6,126
Total current assets	77,301	75,039
Intercompany receivable, net	0	0
Investments in consolidated subsidiaries	0	0
Deferred income taxes, net	0	0
Property and equipment, net	10,961	10,564
Goodwill	30,054	31,174
Intangibles, net	2,262	2,882
Other assets, net	0	0
Total Assets	120,578	119,659
Current liabilities:
Accounts payable	22,482	21,903
Accrued expenses	5,760	5,941
Current portions of long-term debt	0	0
Total current liabilities	28,242	27,844
Intercompany payable, net	39,459	36,491
Borrowings under revolving lines of credit, net	3,090	3,205
Long-term debt, net	0	0
Deferred income taxes, net	622	996
Long-term obligations under equipment financing and other, net	0	66
Other long-term liabilities	83	0
Total liabilities	71,496	68,602
Convertible preferred stock	0
Total stockholders' equity	49,082	51,057
Total Liabilities and Stockholders' Equity	120,578	119,659
Eliminations and Other [Member]
Current assets:
Cash and cash equivalents	(8,531)	(13,131)
Accounts receivable, net	(1,139)	(1,140)
Inventories, net	0	0
Prepaid expenses and other current assets	0	0
Total current assets	(9,670)	(14,271)
Intercompany receivable, net	(1,361,615)	(655,372)
Investments in consolidated subsidiaries	(6,109,325)	(3,160,273)
Deferred income taxes, net	(22,475)	(30,822)
Property and equipment, net	0	0
Goodwill	0	0
Intangibles, net	0	0
Other assets, net	0	0
Total Assets	(7,503,085)	(3,860,738)
Current liabilities:
Accounts payable	(9,671)	(14,271)
Accrued expenses	0	0
Current portions of long-term debt	0	0
Total current liabilities	(9,671)	(14,271)
Intercompany payable, net	(1,361,615)	(655,372)
Borrowings under revolving lines of credit, net	0	0
Long-term debt, net	0	0
Deferred income taxes, net	(22,474)	(30,822)
Long-term obligations under equipment financing and other, net	0	0
Other long-term liabilities	0	0
Total liabilities	(1,393,760)	(700,465)
Convertible preferred stock	0
Total stockholders' equity	(6,109,325)	(3,160,273)
Total Liabilities and Stockholders' Equity	$ (7,503,085)	$ (3,860,738)

Supplemental Guarantor Inform_4

Supplemental Guarantor Information - Condensed Consolidating Statements of Operations (Detail) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016
Net sales	$ 6,418,311	$ 4,376,670	$ 4,127,109
Cost of products sold	4,824,990	3,300,731	3,114,040
Gross profit	1,593,321	1,075,939	1,013,069
Operating expense
Selling, general and administrative	1,187,192	743,376	707,893
Depreciation	60,318	34,002	31,876
Amortization	141,185	82,465	68,316
Total operating expense	1,388,695	859,843	808,085
Intercompany charges (income)	0	0	0
Income (loss) from operations	204,626	216,096	204,984
Interest expense, financing costs, and other	136,544	52,751	58,452
Intercompany interest expense (income)	0	0	0
Income (loss) before provision for income taxes	68,082	163,345	146,532
Provision for (benefit from) income taxes	(30,544)	62,481	56,615
Income (loss) before equity in net income of subsidiaries	98,626	100,864	89,917
Equity in net income of subsidiaries	0	0	0
Net income (loss)	98,626	100,864	89,917
Parent Company [Member]
Net sales	0	0	0
Cost of products sold	0	0	0
Gross profit	0	0	0
Operating expense
Selling, general and administrative	5,909	26,962	58,592
Depreciation	1,989	1,534	1,357
Amortization	0	0	0
Total operating expense	7,898	28,496	59,949
Intercompany charges (income)	(6,734)	(4,664)	(51,942)
Income (loss) from operations	(1,164)	(23,832)	(8,007)
Interest expense, financing costs, and other	124,169	38,660	42,835
Intercompany interest expense (income)	(24,270)	(24,458)	(21,536)
Income (loss) before provision for income taxes	(101,063)	(38,034)	(29,306)
Provision for (benefit from) income taxes	11,398	(3,284)	(472)
Income (loss) before equity in net income of subsidiaries	(112,461)	(34,750)	(28,834)
Equity in net income of subsidiaries	211,087	135,614	118,751
Net income (loss)	98,626	100,864	89,917
Guarantor Subsidiaries [Member]
Net sales	6,239,332	4,198,935	3,949,313
Cost of products sold	4,685,616	3,162,896	2,977,174
Gross profit	1,553,716	1,036,039	972,139
Operating expense
Selling, general and administrative	1,147,390	685,690	619,045
Depreciation	56,598	30,758	28,975
Amortization	140,664	81,880	67,649
Total operating expense	1,344,652	798,328	715,669
Intercompany charges (income)	6,565	4,342	49,285
Income (loss) from operations	202,499	233,369	207,185
Interest expense, financing costs, and other	11,648	14,033	14,965
Intercompany interest expense (income)	22,738	22,927	19,928
Income (loss) before provision for income taxes	168,113	196,409	172,292
Provision for (benefit from) income taxes	(42,261)	64,399	55,613
Income (loss) before equity in net income of subsidiaries	210,374	132,010	116,679
Equity in net income of subsidiaries	0	0	0
Net income (loss)	210,374	132,010	116,679
Non-Guarantor Subsidiaries [Member]
Net sales	178,979	177,735	178,042
Cost of products sold	139,374	137,835	137,112
Gross profit	39,605	39,900	40,930
Operating expense
Selling, general and administrative	33,893	30,724	30,256
Depreciation	1,731	1,710	1,544
Amortization	521	585	667
Total operating expense	36,145	33,019	32,467
Intercompany charges (income)	169	322	2,657
Income (loss) from operations	3,291	6,559	5,806
Interest expense, financing costs, and other	727	58	652
Intercompany interest expense (income)	1,532	1,531	1,608
Income (loss) before provision for income taxes	1,032	4,970	3,546
Provision for (benefit from) income taxes	319	1,366	1,474
Income (loss) before equity in net income of subsidiaries	713	3,604	2,072
Equity in net income of subsidiaries	0	0	0
Net income (loss)	713	3,604	2,072
Eliminations and Other [Member]
Net sales	0	0	(246)
Cost of products sold	0	0	(246)
Gross profit	0	0	0
Operating expense
Selling, general and administrative	0	0	0
Depreciation	0	0	0
Amortization	0	0	0
Total operating expense	0	0	0
Intercompany charges (income)	0	0	0
Income (loss) from operations	0	0	0
Interest expense, financing costs, and other	0	0	0
Intercompany interest expense (income)	0	0	0
Income (loss) before provision for income taxes	0	0	0
Provision for (benefit from) income taxes	0	0	0
Income (loss) before equity in net income of subsidiaries	0	0	0
Equity in net income of subsidiaries	(211,087)	(135,614)	(118,751)
Net income (loss)	$ (211,087)	$ (135,614)	$ (118,751)

Supplemental Guarantor Inform_5

Supplemental Guarantor Information - Condensed Consolidating Statements of Comprehensive Income (Detail) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016
Net income (loss)	$ 98,626	$ 100,864	$ 89,917
Other comprehensive income (loss):
Foreign currency translation adjustment	(2,687)	3,706	1,024
Total other comprehensive income (loss)	(2,687)	3,706	1,024
Comprehensive income (loss)	95,939	104,570	90,941
Parent Company [Member]
Net income (loss)	98,626	100,864	89,917
Other comprehensive income (loss):
Foreign currency translation adjustment	(2,687)	3,706	1,024
Total other comprehensive income (loss)	(2,687)	3,706	1,024
Comprehensive income (loss)	95,939	104,570	90,941
Guarantor Subsidiaries [Member]
Net income (loss)	210,374	132,010	116,679
Other comprehensive income (loss):
Foreign currency translation adjustment	0	0	0
Total other comprehensive income (loss)	0	0	0
Comprehensive income (loss)	210,374	132,010	116,679
Non-Guarantor Subsidiaries [Member]
Net income (loss)	713	3,604	2,072
Other comprehensive income (loss):
Foreign currency translation adjustment	(2,687)	3,706	1,024
Total other comprehensive income (loss)	(2,687)	3,706	1,024
Comprehensive income (loss)	(1,974)	7,310	3,096
Eliminations and Other [Member]
Net income (loss)	(211,087)	(135,614)	(118,751)
Other comprehensive income (loss):
Foreign currency translation adjustment	2,687	(3,706)	(1,024)
Total other comprehensive income (loss)	2,687	(3,706)	(1,024)
Comprehensive income (loss)	$ (208,400)	$ (139,320)	$ (119,775)

Supplemental Guarantor Inform_6

Supplemental Guarantor Information - Condensed Consolidating Statements of Cash Flows (Detail) - USD ($) $ in Thousands	Jan. 02, 2018	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016
Net cash provided by (used in) operating activities		$ 539,381	$ 315,200	$ 120,648
Investing Activities
Purchases of property and equipment		(46,010)	(39,828)	(26,315)
Acquisition of businesses		(2,740,480)	(129,390)	(1,018,188)
Proceeds from the sale of assets		2,149	2,233	1,882
Intercompany activity		0	0	0
Net cash provided by (used in) investing activities		(2,784,341)	(166,985)	(1,042,621)
Financing Activities
Borrowings under revolving lines of credit		2,807,741	2,464,128	1,892,459
Repayments under revolving lines of credit		(2,707,741)	(2,833,230)	(1,541,532)
Borrowings under term loan		970,000	0	490,793
Repayments under term loan		(445,850)	(4,500)	(230,918)
Repayments under equipment financing facilities and other		(11,593)	(10,034)	(4,724)
Borrowings under senior notes		1,300,000	0	300,000
Payment of debt issuance costs	$ (65,800)	(65,788)	(1,669)	(28,325)
Proceeds from secondary offering of common stock		0	345,503	0
Payment of issuance costs from secondary offering of common stock			(14,684)
Proceeds from issuance of convertible preferred stock		400,000	0	0
Payment of stock issuance costs		(1,279)	(14,684)	0
Payment of dividends on preferred stock		(12,978)	0	0
Proceeds from issuance of common stock related to equity awards		7,514	11,341	24,160
Taxes paid related to net share settlement of equity awards		(3,975)	(392)	(2)
Excess tax benefit from stock-based compensation		0	2,937	4,956
Intercompany activity		0	0	0
Net cash provided by (used in) financing activities		2,236,051	(40,600)	906,867
Effect of exchange rate changes on cash and cash equivalents		586	(751)	831
Net increase (decrease) in cash and cash equivalents		(8,323)	106,864	(14,275)
Cash and cash equivalents, beginning of period		138,250	31,386	45,661
Cash and cash equivalents, end of period		129,927	138,250	31,386
Revolving Lines of Credit [Member]
Financing Activities
Borrowings under revolving lines of credit		2,807,741	2,464,128	1,892,459
Repayments under revolving lines of credit		(2,707,741)	(2,833,230)	(1,541,532)
Parent Company [Member]
Net cash provided by (used in) operating activities		(100,302)	(2,466)	(22,799)
Investing Activities
Purchases of property and equipment		(14,354)	(3,517)	(3,654)
Acquisition of businesses		(2,740,480)	(129,390)	(1,018,188)
Proceeds from the sale of assets		0	0	0
Intercompany activity		699,970	(203,163)	475,099
Net cash provided by (used in) investing activities		(2,054,864)	(336,070)	(546,743)
Financing Activities
Borrowings under term loan		970,000		490,793
Repayments under term loan		(445,850)	(4,500)	(230,918)
Repayments under equipment financing facilities and other		0	0	(45)
Borrowings under senior notes		1,300,000		300,000
Payment of debt issuance costs		(58,266)	(1,669)	(19,402)
Proceeds from secondary offering of common stock			345,503
Payment of issuance costs from secondary offering of common stock			(14,684)
Proceeds from issuance of convertible preferred stock		400,000
Payment of stock issuance costs		(1,279)
Payment of dividends on preferred stock		(12,978)
Proceeds from issuance of common stock related to equity awards		7,514	11,341	24,160
Taxes paid related to net share settlement of equity awards		(3,975)	(392)	(2)
Excess tax benefit from stock-based compensation			2,937	4,956
Intercompany activity		0	0	0
Net cash provided by (used in) financing activities		2,155,166	338,536	569,542
Effect of exchange rate changes on cash and cash equivalents		0	0	0
Net increase (decrease) in cash and cash equivalents		0	0	0
Cash and cash equivalents, beginning of period		0	0	0
Cash and cash equivalents, end of period		0	0	0
Parent Company [Member] | Revolving Lines of Credit [Member]
Financing Activities
Borrowings under revolving lines of credit		0	0	0
Repayments under revolving lines of credit		0	0	0
Guarantor Subsidiaries [Member]
Net cash provided by (used in) operating activities		638,451	313,396	143,427
Investing Activities
Purchases of property and equipment		(29,132)	(34,584)	(20,008)
Acquisition of businesses		0	0	0
Proceeds from the sale of assets		2,121	2,150	1,882
Intercompany activity		0	0	0
Net cash provided by (used in) investing activities		(27,011)	(32,434)	(18,126)
Financing Activities
Borrowings under term loan		0		0
Repayments under term loan		0	0	0
Repayments under equipment financing facilities and other		(11,593)	(10,049)	(4,659)
Borrowings under senior notes		0		0
Payment of debt issuance costs		(7,522)	0	(8,923)
Proceeds from secondary offering of common stock			0
Payment of issuance costs from secondary offering of common stock			0
Proceeds from issuance of convertible preferred stock		0
Payment of stock issuance costs		0
Payment of dividends on preferred stock		0
Proceeds from issuance of common stock related to equity awards		0	0	0
Taxes paid related to net share settlement of equity awards		0	0	0
Excess tax benefit from stock-based compensation			0	0
Intercompany activity		(705,625)	209,018	(474,814)
Net cash provided by (used in) financing activities		(624,740)	(168,610)	(130,670)
Effect of exchange rate changes on cash and cash equivalents		0	0	0
Net increase (decrease) in cash and cash equivalents		(13,300)	112,352	(5,369)
Cash and cash equivalents, beginning of period		149,799	37,447	42,816
Cash and cash equivalents, end of period		136,499	149,799	37,447
Guarantor Subsidiaries [Member] | Revolving Lines of Credit [Member]
Financing Activities
Borrowings under revolving lines of credit		2,766,447	2,445,084	1,877,729
Repayments under revolving lines of credit		(2,666,447)	(2,812,663)	(1,520,003)
Non-Guarantor Subsidiaries [Member]
Net cash provided by (used in) operating activities		(680)	4,888	4,751
Investing Activities
Purchases of property and equipment		(2,524)	(1,727)	(2,653)
Acquisition of businesses		0	0	0
Proceeds from the sale of assets		28	83	0
Intercompany activity		0	0	0
Net cash provided by (used in) investing activities		(2,496)	(1,644)	(2,653)
Financing Activities
Borrowings under term loan		0		0
Repayments under term loan		0	0	0
Repayments under equipment financing facilities and other		0	15	(20)
Borrowings under senior notes		0		0
Payment of debt issuance costs		0	0	0
Proceeds from secondary offering of common stock			0
Payment of issuance costs from secondary offering of common stock			0
Proceeds from issuance of convertible preferred stock		0
Payment of stock issuance costs		0
Payment of dividends on preferred stock		0
Proceeds from issuance of common stock related to equity awards		0	0	0
Taxes paid related to net share settlement of equity awards		0	0	0
Excess tax benefit from stock-based compensation			0	0
Intercompany activity		2,967	(2,279)	(285)
Net cash provided by (used in) financing activities		2,967	(3,787)	(7,104)
Effect of exchange rate changes on cash and cash equivalents		586	(751)	831
Net increase (decrease) in cash and cash equivalents		377	(1,294)	(4,175)
Cash and cash equivalents, beginning of period		1,582	2,876	7,051
Cash and cash equivalents, end of period		1,959	1,582	2,876
Non-Guarantor Subsidiaries [Member] | Revolving Lines of Credit [Member]
Financing Activities
Borrowings under revolving lines of credit		41,294	19,044	14,730
Repayments under revolving lines of credit		(41,294)	(20,567)	(21,529)
Eliminations and Other [Member]
Net cash provided by (used in) operating activities		1,912	(618)	(4,731)
Investing Activities
Purchases of property and equipment		0	0	0
Acquisition of businesses		0	0	0
Proceeds from the sale of assets		0	0	0
Intercompany activity		(699,970)	203,163	(475,099)
Net cash provided by (used in) investing activities		(699,970)	203,163	(475,099)
Financing Activities
Borrowings under term loan		0		0
Repayments under term loan		0	0	0
Repayments under equipment financing facilities and other		0	0	0
Borrowings under senior notes		0		0
Payment of debt issuance costs		0	0	0
Proceeds from secondary offering of common stock			0
Payment of issuance costs from secondary offering of common stock			0
Proceeds from issuance of convertible preferred stock		0
Payment of stock issuance costs		0
Payment of dividends on preferred stock		0
Proceeds from issuance of common stock related to equity awards		0	0	0
Taxes paid related to net share settlement of equity awards		0	0	0
Excess tax benefit from stock-based compensation			0	0
Intercompany activity		702,658	(206,739)	475,099
Net cash provided by (used in) financing activities		702,658	(206,739)	475,099
Effect of exchange rate changes on cash and cash equivalents		0	0	0
Net increase (decrease) in cash and cash equivalents		4,600	(4,194)	(4,731)
Cash and cash equivalents, beginning of period		(13,131)	(8,937)	(4,206)
Cash and cash equivalents, end of period		(8,531)	(13,131)	(8,937)
Eliminations and Other [Member] | Revolving Lines of Credit [Member]
Financing Activities
Borrowings under revolving lines of credit		0	0	0
Repayments under revolving lines of credit		$ 0	$ 0	$ 0

Allowance for Doubtful Accoun_3

Allowance for Doubtful Accounts (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016
Allowance For Doubtful Accounts [Abstract]
Balance at beginning of Year	$ 11,829	$ 14,812	$ 6,298
Charged to Operations	10,948	2,914	13,681
Write-offs	(5,193)	(5,897)	(5,167)
Balance at end of year	$ 17,584	$ 11,829	$ 14,812

Fair Value Measurement - Additi

Fair Value Measurement - Additional Information (Detail) - Fair Value, Inputs, Level 2 [Member] $ in Millions	12 Months Ended
	Sep. 30, 2018USD ($)
Senior Notes Due in 2023 [Member]
Fair Value, Concentration of Risk, Financial Statement Captions [Line Items]
Debt instrument maturity year	2,023
Senior Notes Due in 2025 [Member]
Fair Value, Concentration of Risk, Financial Statement Captions [Line Items]
Debt instrument maturity year	2,025
Carrying Value [Member] | Senior Notes Due in 2023 [Member]
Fair Value, Concentration of Risk, Financial Statement Captions [Line Items]
Senior notes	$ 300
Carrying Value [Member] | Senior Notes Due in 2025 [Member]
Fair Value, Concentration of Risk, Financial Statement Captions [Line Items]
Senior notes	1,300
Fair Value [Member] | Senior Notes Due in 2023 [Member]
Fair Value, Concentration of Risk, Financial Statement Captions [Line Items]
Senior notes	311
Fair Value [Member] | Senior Notes Due in 2025 [Member]
Fair Value, Concentration of Risk, Financial Statement Captions [Line Items]
Senior notes	$ 1,200

Employee Benefit Plans - Additi

Employee Benefit Plans - Additional Information (Details) $ in Millions	12 Months Ended
	Sep. 30, 2018USD ($)	Sep. 30, 2017USD ($)	Sep. 30, 2016USD ($)
Defined Contribution Plan Service Period	90 days
Description of Defined Contribution Pension and Other Postretirement Plans	The Company currently matches the first 50% of participant contributions limited to 6% of a participant’s gross compensation (maximum Company match is 3%).
Defined Contribution Plan, Maximum Annual Contributions Per Employee, Percent	100.00%
Defined Contribution Plan Minimum Annual Contributions Per Employee Percent	1.00%
Defined First 50% of Participant Contribution Plan	50.00%
Defined Contribution Plan, Cost Recognized	$ 11.8	$ 8.2	$ 7.3
Pension Contributions	0.2	$ 0.1	$ 0.1
Multi-employer defined benefit plans aggregated expense	$ 1.8
Minimum [Member]
Defined Contribution Plan Qualifying Age	21
Maximum [Member]
Defined Contribution Plan, Employer Matching Contribution, Percent of Employees' Gross Pay	6.00%
Defined Contribution Plan, Employer Matching Contribution, Percent of Match	3.00%

Financial Derivatives - Additio

Financial Derivatives - Additional Information (Details) - USD ($) $ in Millions	Mar. 31, 2017	Mar. 28, 2013	Sep. 30, 2018	Sep. 30, 2015
Derivative, Notional Amount		$ 213.8
Derivative Amortized Amount		$ 2.8
Derivative, Fair Value, Net				$ 2.4
Unrealized Gain (Loss) on Derivatives	$ 2.4
Interest Rate Swap Fixed Rate Of One Point Three Eight Percent [Member]
Derivative, Maturity Date			Mar. 31, 2017
Derivative, Fixed Interest Rate			1.38%
Derivative Amortization Frequency			quarter