Dorman Products (DORM) 10-Q 25 Oct 21 2021 Q3 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	9 Months Ended
	Sep. 25, 2021	Oct. 21, 2021
Cover [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Sep. 25, 2021
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	Q3
Trading Symbol	DORM
Title of 12(b) Security	Common stock, par value $0.01 per share
Security Exchange Name	NASDAQ
Entity Registrant Name	Dorman Products, Inc.
Entity Central Index Key	0000868780
Current Fiscal Year End Date	--12-25
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity File Number	0-18914
Entity Incorporation, State or Country Code	PA
Entity Tax Identification Number	23-2078856
Entity Address, Address Line One	3400 East Walnut Street
Entity Address, City or Town	Colmar
Entity Address, State or Province	PA
Entity Address, Postal Zip Code	18915
City Area Code	215
Local Phone Number	997-1800
Entity Common Stock, Shares Outstanding		31,623,755
Document Quarterly Report	true
Document Transition Report	false

Condensed Consolidated Statemen

Condensed Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 25, 2021	Sep. 26, 2020	Sep. 25, 2021	Sep. 26, 2020
Income Statement [Abstract]
Net sales	$ 348,426	$ 300,620	$ 947,073	$ 791,532
Cost of goods sold	231,572	192,819	615,574	519,786
Gross profit	116,854	107,801	331,499	271,746
Selling, general and administrative expenses	72,663	63,028	205,049	184,288
Income from operations	44,191	44,773	126,450	87,458
Interest expense, net	733	63	918	545
Other income, net	(95)	(46)	(334)	(2,862)
Income before income taxes	43,553	44,756	125,866	89,775
Provision for income taxes	10,449	10,497	28,414	18,856
Net income	$ 33,104	$ 34,259	$ 97,452	$ 70,919
Earnings per share:
Basic	$ 1.04	$ 1.06	$ 3.06	$ 2.19
Diluted	$ 1.04	$ 1.06	$ 3.04	$ 2.19
Weighted average shares outstanding:
Basic	31,692	32,281	31,895	32,317
Diluted	31,842	32,371	32,039	32,394

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Sep. 25, 2021	Dec. 26, 2020
Current assets:
Cash and cash equivalents	$ 57,263	$ 155,576
Accounts receivable, less allowance for doubtful accounts of $1,248 and $1,260	463,113	460,878
Inventories	475,462	298,719
Prepaids and other current assets	17,297	7,758
Total current assets	1,013,135	922,931
Property, plant and equipment, net	116,309	91,009
Operating lease right-of-use assets	57,698	39,002
Goodwill	200,026	91,080
Intangible assets, net	182,827	25,207
Deferred tax asset, net		12,450
Other assets	45,853	38,982
Total assets	1,615,848	1,220,661
Current liabilities:
Accounts payable	149,925	117,878
Accrued compensation	21,081	19,711
Accrued customer rebates and returns	180,594	155,751
Revolving credit facility	249,360
Other accrued liabilities	21,800	29,305
Total current liabilities	622,760	322,645
Long-term operating lease liabilities	52,530	37,083
Other long-term liabilities	4,706	3,555
Deferred tax liabilities, net	31,328	3,819
Commitments and contingencies (Note 7)
Shareholders’ equity:
Common stock, $0.01 par value; 50,000,000 shares authorized; 31,658,703 and 32,168,740 shares issued and outstanding in 2021 and 2020, respectively	317	322
Additional paid-in capital	73,325	64,085
Retained earnings	830,882	789,152
Total shareholders’ equity	904,524	853,559
Total liabilities and shareholders' equity	$ 1,615,848	$ 1,220,661

Condensed Consolidated Balanc_2

Condensed Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Sep. 25, 2021	Dec. 26, 2020
Statement Of Financial Position [Abstract]
Allowance for doubtful accounts and customer credits	$ 1,248	$ 1,260
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	50,000,000	50,000,000
Common stock, shares issued	31,658,703	32,168,740
Common stock, shares outstanding	31,658,703	32,168,740

Condensed Consolidated Statem_2

Condensed Consolidated Statements of Shareholders' Equity - USD ($) $ in Thousands	Total	Common Stock [Member]	Additional Paid-In Capital [Member]	Retained Earnings [Member]
Beginning Balance at Dec. 28, 2019	$ 773,584	$ 326	$ 52,605	$ 720,653
Beginning Balance, Shares at Dec. 28, 2019		32,556,263
Exercise of stock options, shares		2,896
Compensation expense under Incentive Stock Plan	3,966		3,966
Purchase and cancellation of common stock	(17,313)	$ (2)	(421)	(16,890)
Purchase and cancellation of common stock, Shares		(234,116)
Cancellation of non-vested stock, net of issuances	504		504
Cancellation of non-vested stock, net of issuances, shares		(14,782)
Other stock-related activity, net of tax	(295)		239	(534)
Other stock related activity, net of tax, Shares		(5,575)
Net income	70,919			70,919
Ending Balance at Sep. 26, 2020	831,365	$ 324	56,893	774,148
Ending Balance, Shares at Sep. 26, 2020		32,304,686
Beginning Balance at Jun. 27, 2020	807,132	$ 326	55,406	751,400
Beginning Balance, Shares at Jun. 27, 2020		32,440,413
Exercise of stock options, shares		2,886
Compensation expense under Incentive Stock Plan	1,248		1,248
Purchase and cancellation of common stock	(11,448)	$ (1)	(244)	(11,203)
Purchase and cancellation of common stock, Shares		(135,787)
Cancellation of non-vested stock, net of issuances	(1)	$ (1)
Cancellation of non-vested stock, net of issuances, shares		(2,937)
Other stock-related activity, net of tax	175		483	(308)
Other stock related activity, net of tax, Shares		111
Net income	34,259			34,259
Ending Balance at Sep. 26, 2020	831,365	$ 324	56,893	774,148
Ending Balance, Shares at Sep. 26, 2020		32,304,686
Beginning Balance at Dec. 26, 2020	$ 853,559	$ 322	64,085	789,152
Beginning Balance, Shares at Dec. 26, 2020	32,168,740	32,168,740
Exercise of stock options	$ 909		909
Exercise of stock options, shares		19,606
Compensation expense under Incentive Stock Plan	6,212		6,212
Purchase and cancellation of common stock	(54,613)	$ (5)	(970)	(53,638)
Purchase and cancellation of common stock, Shares		(539,075)
Issuance of non-vested stock, net of cancellations	2,493		2,493
Issuance of non-vested stock, net of cancellations, Shares		19,984
Other stock-related activity, net of tax	(1,488)		596	(2,084)
Other stock related activity, net of tax, Shares		(10,552)
Net income	97,452			97,452
Ending Balance at Sep. 25, 2021	$ 904,524	$ 317	73,325	830,882
Ending Balance, Shares at Sep. 25, 2021	31,658,703	31,658,703
Beginning Balance at Jun. 26, 2021	$ 892,985	$ 319	71,947	820,719
Beginning Balance, Shares at Jun. 26, 2021		31,891,890
Exercise of stock options	173		173
Exercise of stock options, shares		2,260
Compensation expense under Incentive Stock Plan	1,721		1,721
Purchase and cancellation of common stock	(23,364)	$ (2)	(421)	(22,941)
Purchase and cancellation of common stock, Shares		(234,044)
Cancellation of non-vested stock, net of issuances, shares		(537)
Other stock-related activity, net of tax	(95)		(95)
Other stock related activity, net of tax, Shares		(866)
Net income	33,104			33,104
Ending Balance at Sep. 25, 2021	$ 904,524	$ 317	$ 73,325	$ 830,882
Ending Balance, Shares at Sep. 25, 2021	31,658,703	31,658,703

Condensed Consolidated Statem_3

Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	9 Months Ended
	Sep. 25, 2021	Sep. 26, 2020
Cash Flows from Operating Activities:
Net income	$ 97,452	$ 70,919
Adjustments to reconcile net income to cash provided by operating activities:
Depreciation, amortization and accretion	24,931	22,544
Gain on equity method investment		(2,498)
Provision for doubtful accounts	61	197
Benefit for deferred income taxes	(414)	(1,154)
Provision for stock-based compensation	6,212	4,069
Payment of contingent consideration	(2,418)
Changes in assets and liabilities:
Accounts receivable	20,746	(11,685)
Inventories	(97,156)	3,093
Prepaids and other current assets	(7,216)	1,360
Other assets	(3,639)	(1,923)
Accounts payable	20,456	20,334
Accrued customer rebates and returns	23,786	24,690
Accrued compensation and other liabilities	(5,200)	15,773
Cash provided by operating activities	77,601	145,719
Cash Flows from Investing Activities:
Acquisition, net of cash acquired	(345,483)	(14,308)
Property, plant and equipment additions	(15,274)	(12,061)
Cash used in investing activities	(360,757)	(26,369)
Cash Flows from Financing Activities:
Proceeds of revolving credit line	252,360	99,000
Payments of revolving credit line	(3,000)	(99,000)
Payment of contingent consideration	(7,982)
Payment of debt issuance costs	(4,215)
Proceeds from exercise of stock options	909
Other stock-related activity	1,055	112
Purchase and cancellation of common stock	(54,272)	(17,313)
Cash provided by (used in) financing activities	184,855	(17,201)
Effect of exchange rate changes on Cash and Cash Equivalents	(12)
Net (Decrease) Increase in Cash and Cash Equivalents	(98,313)	102,149
Cash and Cash Equivalents, Beginning of Period	155,576	68,353
Cash and Cash Equivalents, End of Period	57,263	170,502
Supplemental Cash Flow Information
Cash paid for interest expense	567	680
Cash paid for income taxes	$ 37,500	$ 19,575

Basis of Presentation

Basis of Presentation	9 Months Ended
	Sep. 25, 2021
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Basis of Presentation	1. Basis of Presentation As used herein, unless the context requires otherwise, “Dorman,” the “Company,” “we,” “us,” or “our” refers to Dorman Products, Inc. and its subsidiaries. Our ticker symbol on the NASDAQ Global Select Market is “DORM.” The accompanying unaudited condensed consolidated financial statements have been prepared under U.S. generally accepted accounting principles (“GAAP”) for interim financial information and under the rules and regulations of the U.S. Securities and Exchange Commission. However, they do not include all the information and footnotes required by GAAP for complete financial statements. In the opinion of management, all adjustments (consisting of only normal recurring adjustments) considered necessary for a fair presentation have been included. Operating results for the three and nine months ended September 25, 2021 are not necessarily indicative of the results that may be expected for the fiscal year ending December 25, 2021 or any future period. We may experience significant fluctuations from quarter to quarter in our results of operations due to the timing of orders placed by our customers. The introduction of new products and product lines to customers may cause significant fluctuations from quarter to quarter. These financial statements should be read in conjunction with the consolidated financial statements and footnotes thereto included in our Annual Report on Form 10-K for the fiscal year ended December 26, 2020.

Business Acquisitions and Inves

Business Acquisitions and Investments	9 Months Ended
	Sep. 25, 2021
Business Combinations [Abstract]
Business Acquisitions and Investments	2. Business Acquisitions and Investments DPL Holding Corporation (“Dayton Parts”) On August 10, 2021, we acquired 100% of the equity interests of Dayton Parts, a manufacturer of chassis and other parts designed to serve the heavy-duty vehicle sector of the aftermarket for a purchase price of $345.5 million in cash (net of $8.8 million of acquired cash), subject to certain customary post-acquisition purchase price adjustments. The acquisition was funded by cash on hand as well as through the refinancing of our revolving credit facility discussed further in Note 6. The transaction was accounted for as a business combination under the acquisition method of accounting. We have preliminarily allocated the purchase price to tangible and identifiable intangible assets acquired and liabilities assumed based on their estimated fair values. We are in the process of completing the valuation of identifiable intangible assets, current and deferred taxes, fixed assets, and pre-acquisition contingencies and, therefore, the fair values set forth below are subject to adjustment upon finalizing the valuations. We expect to complete the purchase price allocation during the fourth quarter of fiscal 2021. The table below details the estimated fair values of the assets acquired and the liabilities assumed at the acquisition date: (in thousands) Accounts receivable $ 23,061 Inventories 79,625 Prepaids and other current assets 2,403 Property, plant and equipment 29,861 Goodwill 108,946 Identifiable intangible assets 160,400 Operating lease right-of-use assets 21,248 Other assets 877 Accounts payable (11,968 ) Accrued compensation (2,784 ) Other current liabilities (7,409 ) Long-term operating lease liabilities (18,444 ) Deferred tax liabilities (40,333 ) Net cash consideration $ 345,483 The estimated valuation of the intangible assets acquired, and related amortization periods are as follows: (in thousands) Fair Value Amortization Period (in years) Customer relationships $ 124,100 20 Product portfolio 25,300 20 Trade names 11,000 10 Total $ 160,400 The fair values assigned to intangible assets were estimated by discounting expected cash flows based on the relief from royalty and multiperiod excess earnings valuation methodologies. These valuation methods rely on management judgment, including expected future cash flows resulting from existing customer relationships, customer attrition rates, contributory effects of other assets utilized in the business, royalty rates and other factors. The goodwill recognized is attributable primarily to strategic and synergistic opportunities related to the Company’s and Dayton Parts’ existing automotive aftermarket businesses, the assembled workforce of Dayton Parts and other factors. The goodwill is not expected to be deductible for tax purposes. The financial results of the acquisition have been included in the unaudited condensed consolidated financial statements since the date of acquisition. The net sales and net income of Dayton Parts included in the unaudited condensed consolidated financial statements for both the three and nine months ended September 25, 2021 were $27.4 million and $0.3 million, respectively. The unaudited pro forma information for the periods set forth below gives effect to the Dayton Parts acquisition as if it had occurred as of December 29, 2019, the beginning of the earliest period presented in these financial statements. The pro forma information is presented for informational purposes only and is not necessarily indicative of the results of operations that would have been achieved had the acquisition been consummated as of that time. Three Months Ended Nine Months Ended (in thousands) September 25, 2021 September 26, 2020 September 25, 2021 September 26, 2020 Net sales $ 371,408 $ 345,525 $ 1,070,238 $ 918,874 Net income $ 37,089 $ 36,085 $ 108,016 $ 62,832 Diluted earnings per share $ 1.16 $ 1.11 $ 3.37 $ 1.94 Power Train Industries, Inc. (“PTI”) On January 2, 2020, we acquired the remaining outstanding stock of PTI not already owned by the Company. The total purchase price for PTI was approximately $30.7 million, which included $18.4 million paid for the remaining 60% of the outstanding stock, subject to customary purchase price adjustments, and $12.3 million which represents the fair value of the previously held 40% equity interest in PTI that was acquired by the Company in 2016. As a result of the acquisition, we recorded a gain of $2.5 million in other (expense) income, net during the quarter ended March 28, 2020 from the increase in fair value of our original 40% interest in PTI. We previously accounted for our 40% interest as an equity-method investment.

Sales of Accounts Receivable

Sales of Accounts Receivable	9 Months Ended
	Sep. 25, 2021
Receivables [Abstract]
Sales of Accounts Receivable	3. Sales of Accounts Receivable We have entered several customer-sponsored programs administered by unrelated financial institutions that permit us to sell certain accounts receivable at discounted rates to the financial institutions. Transactions under these agreements were accounted for as sales of accounts receivable and the related accounts receivable were removed from our Condensed Consolidated Balance Sheet at the times of the sales transactions. Under these agreements, we sold $690.0

Inventories

Inventories	9 Months Ended
	Sep. 25, 2021
Inventory Disclosure [Abstract]
Inventories	4. Inventories Inventories include the cost of material, freight, direct labor and overhead utilized in the processing of our products and are stated at the lower of cost or net realizable value. Inventories were as follows: (in thousands) September 25, 2021 December 26, 2020 Raw materials $ 10,467 $ — Bulk product 198,205 136,726 Finished product 257,141 157,484 Packaging materials 9,649 4,509 Total $ 475,462 $ 298,719

Goodwill and Intangible Assets

Goodwill and Intangible Assets	9 Months Ended
	Sep. 25, 2021
Goodwill And Intangible Assets Disclosure [Abstract]
Goodwill and Intangible Assets	5. Goodwill and Intangible Assets Goodwill Goodwill included the following: (in thousands) September 25, 2021 December 26, 2020 Balance at beginning of period $ 91,080 $ 74,458 Goodwill acquired 108,946 16,622 Balance at end of period $ 200,026 $ 91,080 Intangible Assets Intangible assets included the following: September 25, 2021 December 26, 2020 Intangible assets subject to amortization Gross Carrying Value Accumulated Amortization Net Carrying Value Gross Carrying Value Accumulated Amortization Net Carrying Value (in thousands) Customer relationships $ 149,150 $ 9,140 $ 140,010 $ 25,050 $ 7,141 $ 17,909 Trade names 17,760 2,075 15,685 6,760 1,585 5,175 Product Portfolio 25,300 42 25,258 — — — Technology 2,167 508 1,659 2,167 323 1,844 Other 430 215 215 430 151 279 Total $ 194,807 $ 11,980 $ 182,827 $ 34,407 $ 9,200 $ 25,207 Amortization expense was $1.2 million and $0.8 million during the three months ended September 25, 2021 and September 26, 2020, respectively, and $2.9 million and $2.5 million during the nine months ended September 25, 2021 and September 26, 2020, respectively.

Debt

Debt	9 Months Ended
	Sep. 25, 2021
Debt Disclosure [Abstract]
Debt	6. Debt On August 10, 2021, in connection with the acquisition of Dayton Parts, we entered into a new credit agreement that provides for a $600 million revolving credit facility, including a letter of credit sub-facility of up to $60 million (the “New Facility”). The New Facility replaced our previous $100 million revolving credit facility. The New Facility matures on August 10, 2026 and is guaranteed by the Company’s material domestic subsidiaries (together with the Company, the “Credit Parties”) and is supported by a security interest in substantially all of the Credit Parties’ personal property and assets, subject to certain exceptions. Borrowings under the New Facility bear interest at a rate per annum equal to, at the Company’s option, either a LIBOR rate (subject to a 0.00% floor) or a base rate, in each case plus an applicable margin of, initially (i) in the case of LIBOR rate, 1.250% or (ii) in the case of base rate loans, 0.250%. The applicable margin for (i) base rate loans ranges from 0.000% to 1.000% per annum and (ii) for LIBOR loans ranges from 1.000% to 2.000% per annum, in each case, based on the Total Net Leverage Ratio (as defined in the New Facility). The commitment fee is initially equal to 0.150% and thereafter ranges from 0.125% to 0.250% based on the Total Net Leverage Ratio. As of September 25, 2021, the interest rate on the outstanding borrowings under the New Facility was 1.33% and the commitment fee was 0.15%. The New Facility contains affirmative and negative covenants, including, but not limited to, covenants regarding capital expenditures, share repurchases, and financial covenants related to the ratio of consolidated interest expense to consolidated EBITDA and the ratio of total net indebtedness to consolidated EBITDA, each as defined by the New Facility. As of September 25, 2021, we were not in default with respect to the New Facility .

Commitments and Contingencies

Commitments and Contingencies	9 Months Ended
	Sep. 25, 2021
Commitments And Contingencies Disclosure [Abstract]
Commitments and Contingencies	7. Commitments and Contingencies Acquisitions We have contingent consideration related to certain of our prior acquisitions due to the uncertainty of the ultimate amount of payment which will become due as earnout payments if performance targets are achieved. During the nine months ended September 25, 2021, we paid $10.4 million in contingent consideration in connection with prior acquisitions based upon performance targets. If the performance targets associated with prior acquisitions are fully achieved, the maximum additional contingent payments to be made under the related acquisition agreements would be $3.6 million. Other Contingencies We are a party to or otherwise involved in legal proceedings that arise in the ordinary course of business, such as various claims and legal actions involving contracts, employment claims, competitive practices, intellectual property infringement, product liability claims and other matters arising out of the conduct of our business. In the opinion of management, none of the actions, individually or in the aggregate, taking into account relevant insurance coverage, would likely have a material financial impact on the Company, and we believe the range of reasonably possible losses from current matters, taking into account relevant insurance coverage, is immaterial. However, legal matters are subject to inherent uncertainties, and the possibility exists that the ultimate resolution of any of these matters could have a material adverse impact on the Company’s cash flows, financial position and results of operations in the period in which any such effects are recorded.

Revenue Recognition

Revenue Recognition	9 Months Ended
	Sep. 25, 2021
Revenue From Contract With Customer [Abstract]
Revenue Recognition	8 . Revenue Recognition Our primary source of revenue is from contracts with and purchase orders from customers. In many instances, our contract with a customer is the customer’s purchase order. Upon acceptance of the purchase order, a contract exists with a customer as it indicates approval and We record estimates for cash discounts, defective and slow-moving product returns, promotional rebates, core return deposits and other discounts in the period the related product revenue is recognized (“Customer Credits”). The provision for Customer Credits is recorded as a reduction from gross sales, and reserves for Customer Credits are shown as an increase of accrued customer rebates and returns. Customer Credits are estimated based on contractual provisions, historical experience, and our assessment of current market conditions. Actual Customer Credits have not differed materially from estimated amounts for each period presented. Amounts billed to customers for shipping and handling are included in net sales. Costs associated with shipping and handling are included in cost of goods sold. We have concluded that our estimates of variable consideration are not constrained. All our revenue was recognized under the point of time approach during the nine months ended September 25, 2021 and September 26, 2020. We do not have significant financing arrangements with our customers, as our credit terms are all 365 days or less. Also, we do not receive noncash consideration (such as materials or equipment) from our customers to facilitate the fulfillment of our contracts. Disaggregated Revenue The following tables present our disaggregated net sales by type of major good / product line, and geography. Three Months Ended Nine Months Ended (in thousands) September 25, 2021 September 26, 2020 September 25, 2021 September 26, 2020 Powertrain $ 136,770 $ 120,565 $ 386,732 $ 323,396 Chassis 118,273 87,977 302,219 227,273 Automotive body 78,477 74,445 214,180 197,624 Hardware 14,906 17,633 43,942 43,239 Net sales $ 348,426 $ 300,620 $ 947,073 $ 791,532 Three Months Ended Nine Months Ended (in thousands) September 25, 2021 September 26, 2020 September 25, 2021 September 26, 2020 Net sales to U.S. customers $ 328,315 $ 280,330 $ 896,545 $ 744,285 Net sales to non-U.S. customers 20,111 20,290 50,528 47,247 Net sales $ 348,426 $ 300,620 $ 947,073 $ 791,532

Stock-Based Compensation

Stock-Based Compensation	9 Months Ended
	Sep. 25, 2021
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Stock-Based Compensation	9 . Stock-Based Compensation Restricted Stock Awards (“RSAs”) and Restricted Stock Units (“RSUs”) Vesting of RSA and RSU grants is conditional based on continued employment or service for a specified period and, in certain circumstances, the attainment of performance goals. We retain the shares underlying the grant, and any dividends paid thereon, until the vesting conditions have been met. For time-based RSA and RSU grants, compensation cost related to the stock is recognized on a straight-line basis over the vesting period and is calculated using the closing price per share of our common stock on the grant date. For performance-based RSA grants tied to growth in adjusted pre-tax income, compensation cost related to the award is recognized over the performance period and is calculated using the closing price per share of our common stock on the grant date and an estimate of the probable outcome of the performance conditions at each reporting date. Since March 2020, we have made performance-based RSU grants that vest based on our total shareholder return ranking relative to the total shareholder return of the companies comprising the S&P Mid-Cap 400 Growth Index over a three-year performance period. For these awards, compensation cost related to the award is recognized on a straight-line basis over the performance period and is calculated using the simulated fair value per share of our common stock based on the application of a Monte Carlo simulation model. For the nine months ended September 25, 2021, we granted 17,714 performance-based RSUs with a grant date fair value of $131.02 per share. Compensation cost related to RSA and RSU grants was $1.4 million and $1.0 million for the three months ended September 25, 2021 and September 26, 2020, respectively, and $4.5 million and $3.0 million for the nine months ended September 25, 2021 and September 26, 2020, respectively, and were included in selling, general and administrative expense in the Condensed Consolidated Statements of Operations. The following table summarizes our RSA and RSU activity for the nine months ended September 25, 2021: Shares Weighted Average Fair Value Balance at December 26, 2020 217,735 $ 72.77 Granted 76,984 $ 106.23 Vested (36,042 ) $ 67.05 Canceled (45,451 ) $ 74.61 Balance at September 25, 2021 213,226 $ 85.42 As of September 25, 2021, there was Stock Options We expense the grant-date fair value of stock options as compensation cost on a straight-line basis over the vesting period for which related services are performed. The compensation cost charged against income was $0.3 million for each of the three months ended September 25, 2021 and September 26, 2020, and $0.9 million and $0.8 million for the nine months ended September 25, 2021 and September 26, 2020, respectively. These costs are included as selling, general and administrative expense in the Condensed Consolidated Statements of Operations. We use the Black-Scholes option valuation model to estimate the fair value of stock options granted. Expected volatility and expected dividend yield are based on the actual historical experience of our common stock. The expected life represents the period that options granted are expected to be outstanding and was calculated using historical option exercise data. The risk-free rate was based on a U.S. Treasury security with terms equal to the expected time of exercise as of the grant date. The following table summarizes our stock option activity for the nine months ended September 25, 2021 : Shares Weighted Average Exercise Price Weighted Average Remaining Term (In years) Aggregate Intrinsic Value Balance at December 26, 2020 250,779 $ 70.21 Granted 58,393 $ 101.47 Forfeited (9,457 ) $ 79.02 Exercised (39,794 ) $ 66.11 Balance at September 25, 2021 259,921 $ 77.54 5.3 $ 5,228,021 Options exercisable at September 25, 2021 94,762 $ 73.84 3.6 $ 2,159,758 As of September 25, 2021, there was $3.0 million of unrecognized compensation cost related to unvested stock options that is expected to be recognized over a weighted average period of 2.8 years. Employee Stock Purchase Plan There were 31,462 shares and 10,735 shares purchased during the nine months ended September 25, 2021 and September 26, 2020, respectively. During the nine months ended

Earnings Per Share

Earnings Per Share	9 Months Ended
	Sep. 25, 2021
Earnings Per Share [Abstract]
Earnings Per Share	10 . Earnings Per Share Basic earnings per share is calculated by dividing our net income by the weighted average number of common shares outstanding during the period, excluding unvested RSAs and RSUs that are considered to be contingently issuable. To calculate diluted earnings per share, common share equivalents are added to the weighted average number of common shares outstanding. Common share equivalents are calculated using the treasury stock method and are computed based on outstanding stock-based awards. Stock-based awards that were excluded from the calculation of diluted earnings per share as their effect would have been anti-dilutive were 19,000 shares and 34,000 shares for the three months ended September 25, 2021 and September 26, 2020, respectively, and 16,000 shares and 141,000 shares for the nine months ended September 25, 2021 and September 26, 2020, respectively. The following table sets forth the computation of basic and diluted earnings per share: Three Months Ended Nine Months Ended (in thousands, except per share data) September 25, 2021 September 26, 2020 September 25, 2021 September 26, 2020 Numerator Net income $ 33,104 $ 34,259 $ 97,452 $ 70,919 Denominator: Weighted average basic shares outstanding 31,692 32,281 31,895 32,317 Effect of stock-based compensation awards 150 90 144 77 Weighted average diluted shares outstanding 31,842 32,371 32,039 32,394 Earnings Per Share: Basic $ 1.04 $ 1.06 $ 3.06 $ 2.19 Diluted $ 1.04 $ 1.06 $ 3.04 $ 2.19

Common Stock Repurchases

Common Stock Repurchases	9 Months Ended
	Sep. 25, 2021
Common Stock Repurchases [Abstract]
Common Stock Repurchases	11 . Common Stock Repurchases We periodically repurchase, at the then-current market price, and cancel common stock issued to the Dorman Products, Inc. 401(k) Retirement Plan and Trust (the “401(k) Plan”). Under the 401(k) Plan, participants can no longer purchase shares of Dorman common stock as an investment option. Shares are generally purchased from the 401(k) Plan when participants sell units as permitted by the 401(k) Plan or elect to leave the 401(k) Plan upon retirement, termination or other reasons. The following table summarizes the repurchase and cancellation of common stock in the 401(k) Plan: Three Months Ended Nine Months Ended September 25, 2021 September 26, 2020 September 25, 2021 September 26, 2020 Shares repurchased and canceled 1,426 8,930 4,568 15,280 Total cost of shares repurchased and canceled (in thousands) $ 146 $ 723 $ 462 $ 1,123 Average price per share $ 102.62 $ 80.95 $ 101.16 $ 73.49 Our Board of Directors has authorized the repurchase of up to $500 million of our common stock through December 31, 2022 under a previously announced share repurchase program. Under this program, share repurchases may be made from time to time depending on market conditions, share price, share availability and other factors at our discretion. The share repurchase program does not obligate us to acquire any specific number of shares. At September 25, 2021, $153.0 million was available for repurchase under this share repurchase program. The following table summarizes the repurchase and cancellation of common stock under the share repurchase program: Three Months Ended Nine Months Ended September 25, 2021 September 26, 2020 September 25, 2021 September 26, 2020 Shares repurchased and canceled 232,618 126,857 534,507 218,836 Total cost of shares repurchased and canceled (in thousands) $ 23,218 $ 10,726 $ 54,152 $ 16,191 Average price per share $ 99.81 $ 84.55 $ 101.31 $ 73.99

Income Taxes

Income Taxes	9 Months Ended
	Sep. 25, 2021
Income Tax Disclosure [Abstract]
Income Taxes	1 2 . Income Taxes At September 25, 2021, we had $1.2 million of net unrecognized tax benefits, all of which would lower our effective tax rate if recognized. We recognize interest and penalties related to uncertain tax positions in income tax expense. As of September 25, 2021, accrued interest and penalties related to uncertain tax positions were not material. We file income tax returns in the United States, Canada, China, India, and Mexico. All years before 2017 are closed for U.S. federal tax purposes. Tax years before 2016 are closed for the states in which we file. Tax years before 2018 are closed for tax purposes in Canada. Tax years before 2018 are closed for tax purposes in China. Tax years before 2016 are closed for tax purposes in Mexico. All tax years remain open for India.

Related-Party Transactions

Related-Party Transactions	9 Months Ended
	Sep. 25, 2021
Related Party Transactions [Abstract]
Related-Party Transactions	13 . Related-Party Transactions We lease our Colmar, PA facility and a portion of our Lewisberry, PA facility from entities in which Steven L. Berman, our Executive Chairman, and certain of his family members are owners. Each lease is a non-cancelable operating lease. Total rental payments to those entities under these lease arrangements will be $2.3 million in fiscal 2021 and were $1.8 million in fiscal 2020. The lease for our corporate headquarters in Colmar, PA was renewed during November 2016, effective as of January 1, 2018, and will expire on December 31, 2022. The lease for our Lewisberry, PA operating facility was signed in September 2020 and will expire on December 31, 2027. In the opinion of our Audit Committee, the terms and rates of these leases were no less favorable than those which could have been obtained from an unaffiliated party when the lease for our corporate headquarters in Colmar, PA was renewed during November 2016 and when the lease for our Lewisberry, PA operating facility was signed in September 2020. We are a partner in a joint venture with one of our suppliers and own minority interests in two other suppliers. Each of these investments is accounted for under the equity method.

Fair Value Disclosures

Fair Value Disclosures	9 Months Ended
	Sep. 25, 2021
Fair Value Disclosures [Abstract]
Fair Value Disclosures	1 4 . Fair Value Disclosures The carrying value of financial instruments such as cash, accounts receivable, accounts payable, debt under our revolving credit facility, and other current assets and liabilities approximate their fair value based on the short-term nature of these instruments.

Business Acquisitions and Inv_2

Business Acquisitions and Investments (Tables) - Dayton Parts [Member]	9 Months Ended
	Sep. 25, 2021
Schedule of Estimated Fair Values of Assets Acquired and Liabilities Assumed	The table below details the estimated fair values of the assets acquired and the liabilities assumed at the acquisition date: (in thousands) Accounts receivable $ 23,061 Inventories 79,625 Prepaids and other current assets 2,403 Property, plant and equipment 29,861 Goodwill 108,946 Identifiable intangible assets 160,400 Operating lease right-of-use assets 21,248 Other assets 877 Accounts payable (11,968 ) Accrued compensation (2,784 ) Other current liabilities (7,409 ) Long-term operating lease liabilities (18,444 ) Deferred tax liabilities (40,333 ) Net cash consideration $ 345,483
Schedule of Valuation of Intangible Assets Acquired and Related Amortization Periods	The estimated valuation of the intangible assets acquired, and related amortization periods are as follows: (in thousands) Fair Value Amortization Period (in years) Customer relationships $ 124,100 20 Product portfolio 25,300 20 Trade names 11,000 10 Total $ 160,400
Summary of Unaudited Proforma Information	The pro forma information is presented for informational purposes only and is not necessarily indicative of the results of operations that would have been achieved had the acquisition been consummated as of that time. Three Months Ended Nine Months Ended (in thousands) September 25, 2021 September 26, 2020 September 25, 2021 September 26, 2020 Net sales $ 371,408 $ 345,525 $ 1,070,238 $ 918,874 Net income $ 37,089 $ 36,085 $ 108,016 $ 62,832 Diluted earnings per share $ 1.16 $ 1.11 $ 3.37 $ 1.94

Inventories (Tables)

Inventories (Tables)	9 Months Ended
	Sep. 25, 2021
Inventory Disclosure [Abstract]
Inventories	Inventories include the cost of material, freight, direct labor and overhead utilized in the processing of our products and are stated at the lower of cost or net realizable value. Inventories were as follows: (in thousands) September 25, 2021 December 26, 2020 Raw materials $ 10,467 $ — Bulk product 198,205 136,726 Finished product 257,141 157,484 Packaging materials 9,649 4,509 Total $ 475,462 $ 298,719

Goodwill and Intangible Assets

Goodwill and Intangible Assets (Tables)	9 Months Ended
	Sep. 25, 2021
Goodwill And Intangible Assets Disclosure [Abstract]
Schedule of Goodwill	Goodwill Goodwill included the following: (in thousands) September 25, 2021 December 26, 2020 Balance at beginning of period $ 91,080 $ 74,458 Goodwill acquired 108,946 16,622 Balance at end of period $ 200,026 $ 91,080
Schedule of Intangible Assets	Intangible Assets Intangible assets included the following: September 25, 2021 December 26, 2020 Intangible assets subject to amortization Gross Carrying Value Accumulated Amortization Net Carrying Value Gross Carrying Value Accumulated Amortization Net Carrying Value (in thousands) Customer relationships $ 149,150 $ 9,140 $ 140,010 $ 25,050 $ 7,141 $ 17,909 Trade names 17,760 2,075 15,685 6,760 1,585 5,175 Product Portfolio 25,300 42 25,258 — — — Technology 2,167 508 1,659 2,167 323 1,844 Other 430 215 215 430 151 279 Total $ 194,807 $ 11,980 $ 182,827 $ 34,407 $ 9,200 $ 25,207

Revenue Recognition (Tables)

Revenue Recognition (Tables)	9 Months Ended
	Sep. 25, 2021
Revenue From Contract With Customer [Abstract]
Summary of Disaggregated Net Sales	The following tables present our disaggregated net sales by type of major good / product line, and geography. Three Months Ended Nine Months Ended (in thousands) September 25, 2021 September 26, 2020 September 25, 2021 September 26, 2020 Powertrain $ 136,770 $ 120,565 $ 386,732 $ 323,396 Chassis 118,273 87,977 302,219 227,273 Automotive body 78,477 74,445 214,180 197,624 Hardware 14,906 17,633 43,942 43,239 Net sales $ 348,426 $ 300,620 $ 947,073 $ 791,532 Three Months Ended Nine Months Ended (in thousands) September 25, 2021 September 26, 2020 September 25, 2021 September 26, 2020 Net sales to U.S. customers $ 328,315 $ 280,330 $ 896,545 $ 744,285 Net sales to non-U.S. customers 20,111 20,290 50,528 47,247 Net sales $ 348,426 $ 300,620 $ 947,073 $ 791,532

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	9 Months Ended
	Sep. 25, 2021
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Summary of Restricted Stock and RSU Award Activity	The following table summarizes our RSA and RSU activity for the nine months ended September 25, 2021: Shares Weighted Average Fair Value Balance at December 26, 2020 217,735 $ 72.77 Granted 76,984 $ 106.23 Vested (36,042 ) $ 67.05 Canceled (45,451 ) $ 74.61 Balance at September 25, 2021 213,226 $ 85.42
Summary of Stock Option Activity	The following table summarizes our stock option activity for the nine months ended September 25, 2021 : Shares Weighted Average Exercise Price Weighted Average Remaining Term (In years) Aggregate Intrinsic Value Balance at December 26, 2020 250,779 $ 70.21 Granted 58,393 $ 101.47 Forfeited (9,457 ) $ 79.02 Exercised (39,794 ) $ 66.11 Balance at September 25, 2021 259,921 $ 77.54 5.3 $ 5,228,021 Options exercisable at September 25, 2021 94,762 $ 73.84 3.6 $ 2,159,758

Earnings Per Share (Tables)

Earnings Per Share (Tables)	9 Months Ended
	Sep. 25, 2021
Earnings Per Share [Abstract]
Schedule of Computation of Basic and Diluted Earnings per Share	The following table sets forth the computation of basic and diluted earnings per share: Three Months Ended Nine Months Ended (in thousands, except per share data) September 25, 2021 September 26, 2020 September 25, 2021 September 26, 2020 Numerator Net income $ 33,104 $ 34,259 $ 97,452 $ 70,919 Denominator: Weighted average basic shares outstanding 31,692 32,281 31,895 32,317 Effect of stock-based compensation awards 150 90 144 77 Weighted average diluted shares outstanding 31,842 32,371 32,039 32,394 Earnings Per Share: Basic $ 1.04 $ 1.06 $ 3.06 $ 2.19 Diluted $ 1.04 $ 1.06 $ 3.04 $ 2.19

Common Stock Repurchases (Table

Common Stock Repurchases (Tables)	9 Months Ended
	Sep. 25, 2021
Common Stock Repurchases [Abstract]
Summary of Shares Repurchase and Cancellation	The following table summarizes the repurchase and cancellation of common stock in the 401(k) Plan: Three Months Ended Nine Months Ended September 25, 2021 September 26, 2020 September 25, 2021 September 26, 2020 Shares repurchased and canceled 1,426 8,930 4,568 15,280 Total cost of shares repurchased and canceled (in thousands) $ 146 $ 723 $ 462 $ 1,123 Average price per share $ 102.62 $ 80.95 $ 101.16 $ 73.49 Three Months Ended Nine Months Ended September 25, 2021 September 26, 2020 September 25, 2021 September 26, 2020 Shares repurchased and canceled 232,618 126,857 534,507 218,836 Total cost of shares repurchased and canceled (in thousands) $ 23,218 $ 10,726 $ 54,152 $ 16,191 Average price per share $ 99.81 $ 84.55 $ 101.31 $ 73.99

Business Acquisitions and Inv_3

Business Acquisitions and Investments - Additional Information (Detail) - USD ($) $ in Thousands	Aug. 10, 2021	Jan. 02, 2020	Sep. 25, 2021	Sep. 26, 2020	Mar. 28, 2020	Sep. 25, 2021	Sep. 26, 2020
Business Acquisition [Line Items]
Business acquisition, purchase price						$ 345,483	$ 14,308
Net sales			$ 348,426	$ 300,620		947,073	791,532
Net income			33,104	$ 34,259		97,452	$ 70,919
Power Train Industries, Inc. [Member]
Business Acquisition [Line Items]
Equity method investment, ownership percentage		40.00%
Dayton Parts [Member]
Business Acquisition [Line Items]
Business acquisition, percentage of outstanding stock acquired	100.00%
Business acquisition, purchase price	$ 345,500
Business acquisition, net of acquired cash	$ 8,800
Net sales			27,400			27,400
Net income			$ 300			$ 300
Power Train Industries, Inc. [Member]
Business Acquisition [Line Items]
Business acquisition, percentage of outstanding stock acquired		60.00%
Total purchase price		$ 30,700
Business acquisition, value of outstanding stock acquired		18,400
Business combination, separately recognized transactions, net gains and losses					$ 2,500
Fair value of previously held equity interest		$ 12,300

Business Acquisitions and Inv_4

Business Acquisitions and Investments - Schedule of Estimated Fair Values of Assets Acquired and Liabilities Assumed (Detail) - USD ($) $ in Thousands	Sep. 25, 2021	Aug. 10, 2021	Dec. 26, 2020	Dec. 28, 2019
Business Acquisition [Line Items]
Goodwill	$ 200,026		$ 91,080	$ 74,458
Dayton Parts [Member]
Business Acquisition [Line Items]
Accounts receivable		$ 23,061
Inventories		79,625
Prepaids and other current assets		2,403
Property, plant and equipment		29,861
Goodwill		108,946
Identifiable intangible assets		160,400
Operating lease right-of-use assets		21,248
Other assets		877
Accounts payable		(11,968)
Accrued compensation		(2,784)
Other current liabilities		(7,409)
Long-term operating lease liabilities		(18,444)
Deferred tax liabilities		(40,333)
Net cash consideration		$ 345,483

Business Acquisitions and Inv_5

Business Acquisitions and Investments - Schedule of Estimated Valuation of Intangible Assets Acquired and Related Amortization Periods (Detail) - Dayton Parts [Member] $ in Thousands	Aug. 10, 2021USD ($)
Business Acquisition [Line Items]
Valuation,Intangible assets	$ 160,400
Customer Relationships [Member]
Business Acquisition [Line Items]
Valuation,Intangible assets	$ 124,100
Amortization Period (in years)	20 years
Product Portfolio [Member]
Business Acquisition [Line Items]
Valuation,Intangible assets	$ 25,300
Amortization Period (in years)	20 years
Trade Names [Member]
Business Acquisition [Line Items]
Valuation,Intangible assets	$ 11,000
Amortization Period (in years)	10 years

Business Acquisitions and Inv_6

Business Acquisitions and Investments - Summary of Unaudited Proforma Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 25, 2021	Sep. 26, 2020	Sep. 25, 2021	Sep. 26, 2020
Business Combination [Abstract]
Net sales	$ 371,408	$ 345,525	$ 1,070,238	$ 918,874
Net income	$ 37,089	$ 36,085	$ 108,016	$ 62,832
Diluted earnings per share	$ 1.16	$ 1.11	$ 3.37	$ 1.94

Sales of Accounts Receivable -

Sales of Accounts Receivable - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 25, 2021	Sep. 26, 2020	Sep. 25, 2021	Sep. 26, 2020
Sale Of Accounts Receivable [Line Items]
Sale of accounts receivable			$ 690,000	$ 568,300
Selling, general and administrative expenses	$ 72,663	$ 63,028	$ 205,049	184,288
Maximum credit terms allow to customers			365 days
Accounts Receivable Sales Programs [Member]
Sale Of Accounts Receivable [Line Items]
Selling, general and administrative expenses	$ 3,100	$ 1,300	$ 8,600	$ 10,900

Inventories - Inventories (Deta

Inventories - Inventories (Detail) - USD ($) $ in Thousands	Sep. 25, 2021	Dec. 26, 2020
Inventory Disclosure [Abstract]
Raw materials	$ 10,467
Bulk product	198,205	$ 136,726
Finished product	257,141	157,484
Packaging materials	9,649	4,509
Total	$ 475,462	$ 298,719

Goodwill and Intangible Asset_2

Goodwill and Intangible Assets - Schedule of Goodwill (Detail) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 25, 2021	Dec. 26, 2020
Goodwill And Intangible Assets Disclosure [Abstract]
Balance at beginning of period	$ 91,080	$ 74,458
Goodwill acquired	108,946	16,622
Balance at end of period	$ 200,026	$ 91,080

Goodwill and Intangible Asset_3

Goodwill and Intangible Assets - Schedule of Intangible Assets (Detail) - USD ($) $ in Thousands	Sep. 25, 2021	Dec. 26, 2020
Finite Lived Intangible Assets [Line Items]
Gross Carrying Value	$ 194,807	$ 34,407
Accumulated Amortization	11,980	9,200
Net Carrying Value	182,827	25,207
Customer Relationships [Member]
Finite Lived Intangible Assets [Line Items]
Gross Carrying Value	149,150	25,050
Accumulated Amortization	9,140	7,141
Net Carrying Value	140,010	17,909
Trade Names [Member]
Finite Lived Intangible Assets [Line Items]
Gross Carrying Value	17,760	6,760
Accumulated Amortization	2,075	1,585
Net Carrying Value	15,685	5,175
Product Portfolio [Member]
Finite Lived Intangible Assets [Line Items]
Gross Carrying Value	25,300
Accumulated Amortization	42
Net Carrying Value	25,258
Technology [Member]
Finite Lived Intangible Assets [Line Items]
Gross Carrying Value	2,167	2,167
Accumulated Amortization	508	323
Net Carrying Value	1,659	1,844
Other [Member]
Finite Lived Intangible Assets [Line Items]
Gross Carrying Value	430	430
Accumulated Amortization	215	151
Net Carrying Value	$ 215	$ 279

Goodwill and Intangible Asset_4

Goodwill and Intangible Assets - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 25, 2021	Sep. 26, 2020	Sep. 25, 2021	Sep. 26, 2020
Goodwill And Intangible Assets Disclosure [Abstract]
Amortization expense	$ 1.2	$ 0.8	$ 2.9	$ 2.5

Debt - Additional Information (

Debt - Additional Information (Detail) - USD ($)	Aug. 10, 2021	Sep. 25, 2021
Previous Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Credit facility maximum borrowing capacity	$ 100,000,000
Revolving Credit Facility [Member] | Initial [Member]
Debt Instrument [Line Items]
Credit facility, commitment fee percentage	0.15%
Credit facility, interest rate description		Borrowings under the New Facility bear interest at a rate per annum equal to, at the Company’s option, either a LIBOR rate (subject to a 0.00% floor) or a base rate, in each case plus an applicable margin of, initially (i) in the case of LIBOR rate, 1.250% or (ii) in the case of base rate loans, 0.250%. The applicable margin for (i) base rate loans ranges from 0.000% to 1.000% per annum and (ii) for LIBOR loans ranges from 1.000% to 2.000% per annum, in each case, based on the Total Net Leverage Ratio (as defined in the New Facility). The commitment fee is initially equal to 0.150% and thereafter ranges from 0.125% to 0.250% based on the Total Net Leverage Ratio.
Revolving Credit Facility [Member] | Maximum [Member]
Debt Instrument [Line Items]
Credit facility, commitment fee percentage	0.25%
Revolving Credit Facility [Member] | Minimum [Member]
Debt Instrument [Line Items]
Credit facility, commitment fee percentage	0.125%
Revolving Credit Facility [Member] | LIBOR Rate [Member] | Initial [Member]
Debt Instrument [Line Items]
Credit facility, interest rate	1.25%
Revolving Credit Facility [Member] | LIBOR Rate [Member] | Maximum [Member]
Debt Instrument [Line Items]
Credit facility, interest rate	2.00%
Revolving Credit Facility [Member] | LIBOR Rate [Member] | Minimum [Member]
Debt Instrument [Line Items]
Credit facility, interest rate	1.00%
Revolving Credit Facility [Member] | Floor Rate [Member]
Debt Instrument [Line Items]
Credit facility, interest rate	0.00%
Revolving Credit Facility [Member] | Base Rate [Member] | Initial [Member]
Debt Instrument [Line Items]
Credit facility, interest rate	0.25%
Revolving Credit Facility [Member] | Base Rate [Member] | Maximum [Member]
Debt Instrument [Line Items]
Credit facility, interest rate	1.00%
Revolving Credit Facility [Member] | Base Rate [Member] | Minimum [Member]
Debt Instrument [Line Items]
Credit facility, interest rate	0.00%
Dayton Parts [Member] | New Facility [Member]
Debt Instrument [Line Items]
Credit facility maximum borrowing capacity	$ 600,000,000
Credit facility, expiration date	Aug. 10, 2026
Credit facility, commitment fee percentage		0.15%
Credit facility, outstanding borrowing interest rate		1.33%
Dayton Parts [Member] | Letter of Credit [Member] | Maximum [Member]
Debt Instrument [Line Items]
Credit facility maximum borrowing capacity	$ 60,000,000

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Detail) $ in Millions	9 Months Ended
	Sep. 25, 2021USD ($)
Commitments And Contingencies Disclosure [Abstract]
Contingent consideration paid	$ 10.4
Maximum additional contingent payments upon full achievement of targets	$ 3.6

Revenue Recognition - Additiona

Revenue Recognition - Additional Information (Detail)	9 Months Ended
	Sep. 25, 2021
Revenue From Contract With Customer [Abstract]
Maximum credit terms allow to customers	365 days

Revenue Recognition - Summary o

Revenue Recognition - Summary of Disaggregated Net Sales (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 25, 2021	Sep. 26, 2020	Sep. 25, 2021	Sep. 26, 2020
Disaggregation Of Revenue [Line Items]
Net sales	$ 348,426	$ 300,620	$ 947,073	$ 791,532
U.S. Customers [Member]
Disaggregation Of Revenue [Line Items]
Net sales	328,315	280,330	896,545	744,285
Non-U.S. Customers [Member]
Disaggregation Of Revenue [Line Items]
Net sales	20,111	20,290	50,528	47,247
Powertrain [Member]
Disaggregation Of Revenue [Line Items]
Net sales	136,770	120,565	386,732	323,396
Chassis [Member]
Disaggregation Of Revenue [Line Items]
Net sales	118,273	87,977	302,219	227,273
Automotive Body [Member]
Disaggregation Of Revenue [Line Items]
Net sales	78,477	74,445	214,180	197,624
Hardware [Member]
Disaggregation Of Revenue [Line Items]
Net sales	$ 14,906	$ 17,633	$ 43,942	$ 43,239

Stock-Based Compensation - Addi

Stock-Based Compensation - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 25, 2021	Sep. 26, 2020	Sep. 25, 2021	Sep. 26, 2020
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Granted, Shares			76,984
Weighted-average grant-date fair value			$ 106.23
Compensation cost related to stock options	$ 0.3	$ 0.3	$ 0.9	$ 0.8
Employee Stock Purchase Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of common stock shares purchased			31,462	10,735
Compensation cost			$ 0.7	$ 0.3
Performance-Based Restricted Stock Units [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Granted, Shares			17,714
Weighted-average grant-date fair value			$ 131.02
RSA and RSU [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Compensation cost related to restricted stock	1.4	$ 1	$ 4.5	$ 3
Restricted Stock and Restricted Stock Units Award [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Unrecognized compensation cost related to non-vested stock options	10.9		$ 10.9
Unrecognized compensation cost related to nonvested stock options, weighted-average period			2 years 3 months 18 days
Stock Options [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Unrecognized compensation cost related to non-vested stock options	$ 3		$ 3
Unrecognized compensation cost related to nonvested stock options, weighted-average period			2 years 9 months 18 days

Stock-Based Compensation - Summ

Stock-Based Compensation - Summary of RSA and RSU Award Activity (Detail)	9 Months Ended
	Sep. 25, 2021$ / sharesshares
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Beginning Balance, Shares | shares	217,735
Granted, Shares | shares	76,984
Vested, Shares | shares	(36,042)
Canceled, Shares | shares	(45,451)
Ending Balance, Shares | shares	213,226
Beginning Balance, Weighted Average Fair Value | $ / shares	$ 72.77
Granted, Weighted Average Fair Value | $ / shares	106.23
Vested, Weighted Average Fair Value | $ / shares	67.05
Canceled, Weighted Average Fair Value | $ / shares	74.61
Ending Balance, Weighted Average Fair Value | $ / shares	$ 85.42

Stock-Based Compensation - Su_2

Stock-Based Compensation - Summary of Stock Option Activity (Detail) $ / shares in Units, $ in Thousands	9 Months Ended
	Sep. 25, 2021USD ($)$ / sharesshares
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Beginning Balance, Shares | shares	250,779
Granted, Shares | shares	58,393
Forfeited, Shares | shares	(9,457)
Exercised, Shares | shares	(39,794)
Ending Balance, Shares | shares	259,921
Options Exercisable, Shares | shares	94,762
Beginning Balance, Weighted Average Exercise Price | $ / shares	$ 70.21
Granted, Weighted Average Exercise Price | $ / shares	101.47
Forfeited, Weighted Average Exercise Price | $ / shares	79.02
Exercised, Weighted Average Exercise Price | $ / shares	66.11
Ending Balance, Weighted Average Exercise Price | $ / shares	77.54
Options Exercisable, Weighted Average Exercise Price | $ / shares	$ 73.84
Ending Balance, Weighted Average Remaining Terms (years)	5 years 3 months 18 days
Options Exercisable, Weighted Average Remaining Terms (years)	3 years 7 months 6 days
Ending Balance, Aggregate Intrinsic Value | $	$ 5,228,021
Options Exercisable, Aggregate Intrinsic Value | $	$ 2,159,758

Earnings Per Share - Additional

Earnings Per Share - Additional Information (Detail) - shares	3 Months Ended		9 Months Ended
	Sep. 25, 2021	Sep. 26, 2020	Sep. 25, 2021	Sep. 26, 2020
Earnings Per Share [Abstract]
Stock-based awards considered as anti-dilutive	19,000	34,000	16,000	141,000

Earnings Per Share - Schedule o

Earnings Per Share - Schedule of Computation of Basic and Diluted Earnings per Share (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 25, 2021	Sep. 26, 2020	Sep. 25, 2021	Sep. 26, 2020
Numerator
Net income	$ 33,104	$ 34,259	$ 97,452	$ 70,919
Denominator:
Weighted average basic shares outstanding	31,692	32,281	31,895	32,317
Effect of stock-based compensation awards	150	90	144	77
Weighted average diluted shares outstanding	31,842	32,371	32,039	32,394
Earnings Per Share:
Basic	$ 1.04	$ 1.06	$ 3.06	$ 2.19
Diluted	$ 1.04	$ 1.06	$ 3.04	$ 2.19

Common Stock Repurchases - Summ

Common Stock Repurchases - Summary of Shares Repurchase and Cancellation (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 25, 2021	Sep. 26, 2020	Sep. 25, 2021	Sep. 26, 2020
Common Stock Repurchases [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares repurchased and canceled	1,426	8,930	4,568	15,280
Total cost of shares repurchased and canceled (in thousands)	$ 146	$ 723	$ 462	$ 1,123
Average price per share	$ 102.62	$ 80.95	$ 101.16	$ 73.49
Share Repurchase Program [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares repurchased and canceled	232,618	126,857	534,507	218,836
Total cost of shares repurchased and canceled (in thousands)	$ 23,218	$ 10,726	$ 54,152	$ 16,191
Average price per share	$ 99.81	$ 84.55	$ 101.31	$ 73.99

Common Stock Repurchases - Addi

Common Stock Repurchases - Additional Information (Detail) - Share Repurchase Program [Member]	9 Months Ended
	Sep. 25, 2021USD ($)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share repurchase program shares authorized to be repurchased	$ 500,000,000
Share repurchase program shares authorized to be repurchased expiration date	Dec. 31, 2022
Shares available for repurchase under share repurchase program amount	$ 153,000,000

Income Taxes - Additional Infor

Income Taxes - Additional Information (Detail) $ in Millions	Sep. 25, 2021USD ($)
Income Tax Disclosure [Abstract]
Net unrecognized tax benefits	$ 1.2

Related Party Transactions - Ad

Related Party Transactions - Additional Information (Detail) $ in Millions	9 Months Ended	12 Months Ended
	Sep. 25, 2021Supplier	Dec. 25, 2021USD ($)	Dec. 26, 2020USD ($)
Related Party Transaction [Line Items]
Rental payments based upon the terms of the lease | $			$ 1.8
Lease effective date	Jan. 1, 2018
Joint Venture [Member]
Related Party Transaction [Line Items]
Number of suppliers with company partners Joint Venture | Supplier	1
Minority interests in number of suppliers | Supplier	2
Scenario, Forecast [Member]
Related Party Transaction [Line Items]
Rental payments based upon the terms of the lease | $		$ 2.3
Colmar, PA [Member]
Related Party Transaction [Line Items]
Lease expiration date	Dec. 31, 2022
Lewisberry, PA [Member]
Related Party Transaction [Line Items]
Lease expiration date	Dec. 31, 2027