Altra Industrial Motion (AIMC) 10-Q26 Oct 212021 Q3 Quarterly reportFinancial data

Company Profile

Document and Entity Information

Document and Entity Information - shares	9 Months Ended
Document and Entity Information - shares	Sep. 30, 2021	Oct. 25, 2021
Cover [Abstract]
Entity Registrant Name	ALTRA INDUSTRIAL MOTION CORP.
Entity Central Index Key	0001374535
Trading Symbol	AIMC
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Document Type	10-Q
Document Period End Date	Sep. 30, 2021
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	Q3
Amendment Flag	false
Entity Current Reporting Status	Yes
Entity Shell Company	false
Entity File Number	001-33209
Entity Tax Identification Number	61-1478870
Entity Address, Address Line One	300 Granite Street
Entity Address, Address Line Two	Suite 201
Entity Address, City or Town	Braintree
Entity Address, State or Province	MA
Entity Address, Postal Zip Code	02184
City Area Code	781
Local Phone Number	917-0600
Entity Common Stock, Shares Outstanding (in shares)		64,919,625
Entity Interactive Data Current	Yes
Entity Incorporation, State or Country Code	DE
Security Exchange Name	NASDAQ
Document Quarterly Report	true
Document Transition Report	false
Title of 12(b) Security	Common Stock, $0.001 par value

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets - USD ($) $ in Millions	Sep. 30, 2021	Dec. 31, 2020
Current assets:
Cash and cash equivalents	$ 256.8	$ 254.4
Trade receivables, less allowance for credit losses of $4.2 and $4.9 million at September 30, 2021 and December 31, 2020, respectively	251.7	240.8
Inventories	257	210.4
Income tax receivable	21.7	6.9
Prepaid expenses and other current assets	34.8	35.7
Total current assets	822	748.2
Property, plant and equipment, net	324.8	344.2
Goodwill, net	1,574.4	1,596
Intangible assets, net	1,389	1,459.6
Deferred income taxes	2.4	4.9
Other non-current assets	12.6	14.2
Operating lease right of use assets	36	41
Total assets	4,161.2	4,208.1
Current liabilities:
Accounts payable	177.4	163.6
Accrued payroll	78.8	76.2
Accruals and other current liabilities	84.9	73
Income tax payable	6.4	17.9
Current portion of long-term debt	16.8	16.6
Operating lease liabilities	12.7	13.3
Total current liabilities	377	360.6
Long-term debt, net of current portion	1,289.7	1,408.1
Deferred income taxes	354.1	359.6
Pension liabilities	32.6	35.4
Long-term taxes payable	2.7	3.6
Other long-term liabilities	11.6	14.3
Operating lease liabilities, net of current portion	25.1	29.8
Stockholders’ equity:
Common stock ($0.001 par value per share, 120,000,000 shares authorized, 64,915,615 and 64,676,567 shares issued and outstanding at September 30, 2021 and December 31, 2020, respectively)	0.1	0.1
Additional paid-in capital	1,713.7	1,706
Retained earnings	370.5	269.5
Accumulated other comprehensive income/(loss)	(15.9)	21.1
Total stockholders’ equity	2,068.4	1,996.7
Total liabilities and stockholders’ equity	$ 4,161.2	$ 4,208.1

Condensed Consolidated Balanc_2

Condensed Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Millions	Sep. 30, 2021	Dec. 31, 2020
Statement Of Financial Position [Abstract]
Allowance for credit losses	$ 4.3	$ 4.9
Common stock, par value (in USD per share)	$ 0.001	$ 0.001
Common stock, shares authorized (in shares)	120,000,000	120,000,000
Common stock, shares issued (in shares)	64,915,615	64,676,567
Common stock, shares outstanding (in shares)	64,915,615	64,676,567

Condensed Consolidated Statemen

Condensed Consolidated Statements of Operations - USD ($) shares in Millions, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Income Statement [Abstract]
Net sales	$ 469.3	$ 437.8	$ 1,430	$ 1,272.8
Cost of sales	299.4	273.7	912.5	812.3
Gross profit	169.9	164.1	517.5	460.5
Operating expenses:
Selling, general and administrative expenses	91.9	82.5	275.2	245.4
Impairment of goodwill and intangible asset				147.5
Research and development expenses	15.5	13.8	47.5	42.6
Restructuring costs	0.7	2.4	2.4	5.5
Total operating expenses	108.1	98.7	325.1	441
Income/(loss) from operations	61.8	65.4	192.4	19.5
Other non-operating income and expense:
Interest expense, net	16.1	18	49.5	54.2
Other non-operating expense/(income), net	0.1	(0.3)	(3.1)	0.8
Total other non-operating (income) expense, net	16.2	17.7	46.4	55
Income/(loss) before income taxes	45.6	47.7	146	(35.5)
Provision for income taxes	10.2	9.4	30.6	21.2
Net income/(loss)	$ 35.4	$ 38.3	$ 115.4	$ (56.7)
Weighted average shares, basic	64.9	64.6	64.8	64.6
Weighted average shares, diluted	65.5	64.9	65.4	64.6
Net income/(loss) per share:
Basic	$ 0.55	$ 0.59	$ 1.78	$ (0.88)
Diluted	0.54	0.59	1.76	(0.88)
Cash dividend declared per share	$ 0.08	$ 0.04	$ 0.22	$ 0.25

Condensed Consolidated Statem_2

Condensed Consolidated Statements of Comprehensive Income (Loss) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Statement Of Income And Comprehensive Income [Abstract]
Net income/(loss)	$ 35.4	$ 38.3	$ 115.4	$ (56.7)
Other Comprehensive income:
Change in fair value of interest rate swap, net of tax				(11.9)
Reclassification of interest rate swap, net of tax	2.2	2.6	6.9	4.3
Pension liability adjustment, net of tax	0.4	0.2	1.6	0.1
Amortization of actuarial gain (losses), net of tax	0.1		0.2
Change in fair value of net investment hedge, net of tax				31.3
Foreign currency translation adjustment	(22.3)	47.6	(45.7)	16.4
Total other comprehensive income/(loss):	(19.6)	50.4	(37)	40.2
Comprehensive income/(loss)	$ 15.8	$ 88.7	$ 78.4	$ (16.5)

Condensed Consolidated Statem_3

Condensed Consolidated Statements of Cash Flows - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020
Cash flows from operating activities
Net Income/(loss)	$ 115.4	$ (56.7)
Adjustments to reconcile net income/(loss) to net operating cash flows:
Depreciation	39.4	44.2
Amortization of intangible assets	52.9	52.3
Amortization of deferred financing costs	3.5	3.4
Gain on foreign currency, net	0	(1.2)
Accretion of debt discount	0.4	0.4
Non-cash amortization of interest rate swap expense	9	5.6
Impairment of goodwill and intangible asset		147.5
Payment for interest rate swap settlement		(34.7)
Gain on disposal and other	(0.6)
Stock-based compensation	11	10.3
Changes in assets and liabilities:
Trade receivables, net	(14.2)	7.9
Inventories	(50.2)	4.3
Accounts payable and accrued liabilities	32.7	(2.7)
Other current assets and liabilities	(26.2)	(23.2)
Other operating assets and liabilities	(3)	4.4
Net cash provided by operating activities	170.1	161.8
Cash flows from investing activities
Purchase of property, plant and equipment	(25.6)	(24.3)
Proceeds from sale of building	2.2
A&S acquisition purchase price adjustment		(1.9)
Proceeds from cross-currency interest rate swap settlement		56.2
Net cash (used in) provided by investing activities	(23.4)	30
Cash flows from financing activities
Borrowing under Revolving Credit Facility		100
Payments on Revolving Credit Facility		(100)
Payments on Term Loan Facility	(120)	(90)
Dividend payments	(13.1)	(24.9)
Net payments on financing leases, mortgages, and other obligations	(2.5)	(0.3)
Net proceeds/(payments) from China debt	2.1	(1.1)
Proceeds from issuance of common stock upon exercise of options	2.2
Shares surrendered for tax withholding	(5.5)	(3.9)
Net cash used in financing activities	(136.8)	(120.2)
Effect of exchange rate changes on cash and cash equivalents	(7.5)	(0.2)
Net change in cash and cash equivalents	2.4	71.4
Cash and cash equivalents at beginning of period	254.4	167.3
Cash and cash equivalents at end of period	256.8	238.7
Cash paid during the period for:
Interest paid on borrowings	30.8	38.8
Income taxes paid	$ 59.4	$ 43.5

Condensed Consolidated Statem_4

Condensed Consolidated Statements of Stockholders' Equity - USD ($) $ in Millions	Total	Common Stock [Member]	Additional Paid in Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income (Loss) [Member]
Beginning balance at Dec. 31, 2019	$ 1,922.3	$ 0.1	$ 1,696.7	$ 315.4	$ (89.9)
Beginning balance (in shares) at Dec. 31, 2019		64,200,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation and vesting of restricted stock, net of withholdings	6.4		6.4
Stock-based compensation and vesting of restricted stock, net of withholdings (in shares)		500,000
Net income/(loss)	(56.7)			(56.7)
Dividends declared	(16.4)			(16.4)
Total comprehensive income (loss), net of tax	40.2				40.2
Ending balance at Sep. 30, 2020	1,895.8	$ 0.1	1,703.1	242.3	(49.7)
Ending balance (in shares) at Sep. 30, 2020		64,700,000
Beginning balance at Jun. 30, 2020	1,808.5	$ 0.1	1,701.8	206.7	(100.1)
Beginning balance (in shares) at Jun. 30, 2020		64,600,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation and vesting of restricted stock, net of withholdings	1.3		1.3
Stock-based compensation and vesting of restricted stock, net of withholdings (in shares)		100,000
Net income/(loss)	38.3			38.3
Dividends declared	(2.7)			(2.7)
Total comprehensive income (loss), net of tax	50.4				50.4
Ending balance at Sep. 30, 2020	1,895.8	$ 0.1	1,703.1	242.3	(49.7)
Ending balance (in shares) at Sep. 30, 2020		64,700,000
Beginning balance at Dec. 31, 2020	1,996.7	$ 0.1	1,706	269.5	21.1
Beginning balance (in shares) at Dec. 31, 2020		64,700,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation and vesting of restricted stock, net of withholdings	5.5		5.5
Stock-based compensation and vesting of restricted stock, net of withholdings (in shares)		100,000
Issuance of common stock upon exercise of options	$ 2.2		2.2
Issuance of common stock upon exercise of options (in shares)	72,200	100,000
Net income/(loss)	$ 115.4			115.4
Dividends declared	(14.4)			(14.4)
Total comprehensive income (loss), net of tax	(37)				(37)
Ending balance at Sep. 30, 2021	2,068.4	$ 0.1	1,713.7	370.5	(15.9)
Ending balance (in shares) at Sep. 30, 2021		64,900,000
Beginning balance at Jun. 30, 2021	2,056.7	$ 0.1	1,712.6	340.3	3.7
Beginning balance (in shares) at Jun. 30, 2021		64,900,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation and vesting of restricted stock, net of withholdings	1.1		1.1
Net income/(loss)	35.4			35.4
Dividends declared	(5.2)			(5.2)
Total comprehensive income (loss), net of tax	(19.6)				(19.6)
Ending balance at Sep. 30, 2021	$ 2,068.4	$ 0.1	$ 1,713.7	$ 370.5	$ (15.9)
Ending balance (in shares) at Sep. 30, 2021		64,900,000

Condensed Consolidated Statem_5

Condensed Consolidated Statements of Stockholders' Equity (Parenthetical) - $ / shares	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Cash dividend declared	$ 0.08	$ 0.04	$ 0.22	$ 0.25
Retained Earnings [Member]
Cash dividend declared	$ 0.08	$ 0.04	$ 0.22	$ 0.25

Organization and Nature of Oper

Organization and Nature of Operations	9 Months Ended
Organization and Nature of Operations	Sep. 30, 2021
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Organization and Nature of Operations	1. Organization and Nature of Operations Headquartered in Braintree, Massachusetts, Altra Industrial Motion Corp. (the “Company,” “Altra,” “we,” or “our”) is a leading global designer, producer and marketer of a wide range of electro-mechanical power transmission and motion control products. The Company brings together strong brands with production facilities in sixteen countries. Altra’s leading brands include Ameridrives Couplings, Bauer Gear Motor, Bibby Turboflex, Boston Gear, Delroyd Worm Gear, Formsprag Clutch, Guardian Couplings, Huco, Industrial Clutch, Inertia Dynamics, Jacobs Vehicle Systems, Kilian Manufacturing, Kollmorgen, Lamiflex Couplings, Marland Clutch, Matrix, Nuttall Gear, Portescap, Stieber Clutch, Stromag, Svendborg Brakes, TB Wood’s, Thomson, Twiflex, Warner Electric, Warner Linear, and Wichita Clutch.

Basis of Presentation

Basis of Presentation	9 Months Ended
Basis of Presentation	Sep. 30, 2021
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Basis of Presentation	2. Basis of Presentation The Company’s unaudited condensed consolidated financial statements have been prepared in accordance with the instructions to Form 10-Q and do not include all of the information and note disclosures required by generally accepted accounting principles in the United States, or GAAP. These statements should be read in conjunction with the financial statements and notes thereto included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2020 , filed with the U.S. Securities and Exchange Commission (the “SEC”) on February 26, 2021. In the opinion of management, the accompanying unaudited condensed consolidated financial statements include all adjustments, consisting of normal recurring adjustments, necessary to present fairly the Company’s financial position and cash flows for the interim periods presented. The results are not necessarily indicative of future results. The Company considers events or transactions that occur after the balance sheet date but before the financial statements are issued to provide additional evidence relative to certain estimates or to identify matters that require additional disclosure.

Recent Accounting Standards

Recent Accounting Standards	9 Months Ended
Recent Accounting Standards	Sep. 30, 2021
Accounting Changes And Error Corrections [Abstract]
Recent Accounting Standards	3. Recent Accounting Standards Recent Accounting Pronouncements In March 2020, the FASB issued ASU No. 2020-04, Reference Rate Reform (Topic 848): Facilitation of the Effects of Reference Rate Reform on Financial Reporting (“ASU 2020-04”). This ASU provides relief from certain accounting consequences that could result from the global markets’ anticipated transition away from the use of the London Interbank Offered Rate (“LIBOR”) and other interbank offered rates to alternative reference rates. The relief provided by this ASU is elective and applies to all entities, subject to meeting certain criteria, that have contracts, hedging relationships, and other transactions that reference LIBOR or another reference rate expected to be discontinued because of reference rate reform. The optional amendments are effective as of March 12, 2020 through December 31, 2022. The Company is currently evaluating the effect of the adoption of this standard on the Company.

Revenue Recognition

Revenue Recognition	9 Months Ended
Revenue Recognition	Sep. 30, 2021
Revenue From Contract With Customer [Abstract]
Revenue Recognition	4. Revenue Recognition We sell our products through three primary commercial channels: original equipment manufacturers (OEMs), industrial distributors and direct to end users. Each of our segments sells similar products, which are balanced across end-user industries including, without limitation, energy, food processing, general industrial, material handling, mining, transportation, industrial automation, robotics, medical devices, and turf & garden. As the Company’s standard payment terms are less than one year, the Company has elected the practical expedient under Accounting Standards Codification (“ASC”) 606-10-32-18 to not assess whether a contract has a significant financing component. Revenue is recognized when control of the product is transferred to the customer (i.e., when the Company’s performance obligation is satisfied), which typically occurs at shipment from the Company’s manufacturing site or delivery to the customer’s named location. In determining whether control has transferred, the Company considers if there is a present right to payment and legal title, along with risks and rewards of ownership having transferred to the customer. In certain circumstances, the Company manufactures customized product without alternative use for its customers, which would generally result in the transfer of control over time. The Company has evaluated the amount of revenue subject to recognition over time and concluded that it is immaterial. The following table disaggregates our revenue for each reportable segment. The Company believes that disaggregating revenue into these categories achieves the disclosure objective to depict how the nature, amount, timing, and uncertainty of revenue and cash flows are affected by economic factors. Quarter Ended Year to Date Ended September 30, 2021 September 30, 2020 September 30, 2021 September 30, 2020 Power Transmission Technologies $ 232.5 $ 197.7 $ 691.1 $ 610.7 Automation & Specialty 237.8 240.8 741.9 665.2 Inter-segment eliminations ( 1.0 ) ( 0.7 ) ( 3.0 ) ( 3.1 ) Total net sales $ 469.3 $ 437.8 $ 1,430.0 $ 1,272.8 Net sales by geographic region based on point of shipment origin are as follows: Quarter Ended Year to Date Ended September 30, 2021 September 30, 2020 September 30, 2021 September 30, 2020 North America (primarily U.S.) $ 256.1 $ 230.2 $ 758.6 $ 681.3 Europe excluding Germany 83.9 68.8 259.1 214.9 Germany 50.0 44.1 151.5 140.7 China 48.8 56.5 176.9 150.1 Asia and other excluding China 30.5 38.2 83.9 85.8 Total net sales $ 469.3 $ 437.8 $ 1,430.0 $ 1,272.8 The payment terms and conditions in our customer contracts vary. In some cases, customers will partially prepay for their goods; in other cases, after appropriate credit evaluations, payment will be due in arrears. In addition, there are constraints that cause variability in the ultimate consideration to be recognized. These constraints typically include early payment discounts, volume rebates, rights of return, surcharges, and other customer considerations. Payments received from customers are recorded as accounts receivable when an unconditional right to the consideration exists. A contract asset is recognized when the Company satisfies a performance obligation by transferring a promised good to the customer before consideration is due. A contract liability is recognized when consideration is received from a customer prior to the Company satisfying the related performance obligation. Contract assets and contract liabilities are recognized in other current assets and other current liabilities, respectively, in the Company’s consolidated balance sheets. The Company had inconsequential contract assets for the year to date periods ended September 30, 2021 and September 30, 2020 , respectively. The opening and closing balances of the Company’s current contract liabilities as of the year to date periods ended September 30, 2021 and September 30, 2020 are as follows: Year to Date Ended September 30, 2021 September 30, 2020 Beginning balance $ 10.3 $ 8.4 Closing balance 14.3 11.2 Increase $ 4.0 $ 2.8 In the nine-month period ended September 30, 2021, substantially all outstanding revenue has been recognized related to contract liabilities outstanding at January 1, 2021 .

Fair Value of Financial Instrum

Fair Value of Financial Instruments	9 Months Ended
Fair Value of Financial Instruments	Sep. 30, 2021
Fair Value Disclosures [Abstract]
Fair Value of Financial Instruments	5. Fair Value of Financial Instruments Fair value is determined based upon the exit price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants, as determined by either the principal market or the most advantageous market. Inputs used in the valuation techniques to derive fair values are classified based on a three-level hierarchy, as follows:  Level 1- Quoted prices in active markets for identical assets or liabilities.  Level 2- Observable inputs other than Level 1 prices such as quoted prices for similar assets or liabilities; quoted prices in markets with insufficient volume or infrequent transactions (less active markets); or model-derived.  Level 3- Unobservable inputs to the valuation methodology that are significant to the measurement of fair value of assets or liabilities. The Company considers all highly liquid investments purchased with a remaining maturity of three months or less to be cash equivalents and are classified as Level 1. The carrying values of financial instruments, including cash equivalents, are carried at cost, which approximates fair value, and are classified as Level 1. Debt under the Altra Credit Agreement (as defined herein) is classified as Level 2 and is comprised of the Altra Term Loan Facility and the Altra Revolving Credit Facility (both as defined herein). The carrying amount of the Altra Term Loan Facility was $ 910.0 million and the estimated fair value of the Altra Term Loan Facility was $ 904.3 million at September 30, 2021 . There is currently no debt under the Altra Revolving Credit Facility. The carrying amount of the Notes (as defined herein) was $ 400 million and the estimated fair value of the Notes was $ 431.5 million at September 30, 2021. The Notes are classified as Level 2. The Company determines the fair value of financial instruments using quoted market prices whenever available and classified these investments as Level 1. When quoted market prices are not available for various types of financial instruments (such as derivative instruments), the Company uses standard models with market-based inputs, which take into account the present value of estimated future cash flows and the ability of the Company or the financial counterparty to perform. These investments are classified as Level 2. For cross-currency interest rate swaps and interest rate swaps, the significant inputs to these models are interest rate curves for discounting future cash flows and are adjusted for credit risk. See additional discussion of the Company’s use of financial instruments including cross-currency swaps and interest rate swaps included in Note 15. In December 2020, the Company invested $ 5.0 million for a minority equity interest in a privately held manufacturing software company, MTEK Industry AB (“MTEK”), over which the Company does not exert significant influence. The equity investment does not have a readily determinable fair value and does not qualify for the practical expedient to estimate fair value using the net asset value per share. Therefore, in accordance with ASU 2016-01, the Company elected to measure the investment at its cost less impairment, if any, adjusted for observable price changes in orderly transactions for identical or a similar investment of the same issuer. This investment is considered a Level 3 asset based on the lack of observable inputs and is classified within other non-current assets in the consolidated balance sheets. The Company will monitor its equity investment in MTEK for indicators of impairments or upward adjustments on an ongoing basis. If the Company determines that such an indicator is present, an adjustment will be recorded, which will be measured as the difference between the carrying value and estimated fair value. As of September 30, 2021 , there were no indicators that support an adjustment to MTEK’s carrying value.

Changes in Accumulated Other Co

Changes in Accumulated Other Comprehensive Income/(Loss) by Component	9 Months Ended
	Sep. 30, 2021
Equity [Abstract]
Changes in Accumulated Other Comprehensive Income/(Loss) by Component	6. Changes in Accumulated Other Comprehensive Income/(Loss) by Component The following is a reconciliation of changes in accumulated other comprehensive income/(loss) by component for the periods presented: Gains and Defined Cumulative Total Accumulated Other Comprehensive Income (Loss) by Component, June 30, 2021 $ ( 16.8 ) $ ( 2.4 ) $ 22.9 $ 3.7 Reclassification of interest rate swap to income, net of tax 2.2 — — 2.2 Pension adjustments, net of tax — 0.4 — 0.4 Amortization of actuarial gain (losses), net of tax — 0.1 — 0.1 Foreign currency translation adjustments, net of tax — — ( 22.3 ) ( 22.3 ) Net current-period Other Comprehensive Income (Loss) 2.2 0.5 ( 22.3 ) ( 19.6 ) Accumulated Other Comprehensive Income (Loss) by Component, September 30, 2021 $ ( 14.6 ) $ ( 1.9 ) $ 0.6 $ ( 15.9 ) Gains and Defined Cumulative Total Accumulated Other Comprehensive Income (Loss) by Component, January 1, 2021 $ ( 21.5 ) $ ( 3.7 ) $ 46.3 $ 21.1 Reclassification of interest rate swap to income, net of tax 6.9 — — 6.9 Pension adjustments, net of tax — 1.6 — 1.6 Amortization of actuarial gain (losses), net of tax — 0.2 — 0.2 Foreign currency translation adjustments, net of tax — — ( 45.7 ) ( 45.7 ) Net current-period Other Comprehensive Income (Loss) 6.9 1.8 ( 45.7 ) ( 37.0 ) Accumulated Other Comprehensive Income (Loss) by Component, September 30, 2021 $ ( 14.6 ) $ ( 1.9 ) $ 0.6 $ ( 15.9 ) Gains and Defined Cumulative Total Accumulated Other Comprehensive Loss by Component, June 30, 2020 $ ( 26.7 ) $ ( 1.6 ) $ ( 71.8 ) $ ( 100.1 ) Reclassification of interest rate swap to income, net of tax 2.6 — — 2.6 Pension adjustments, net of tax — 0.2 — 0.2 Foreign currency translation adjustments, net of tax — — 47.6 47.6 Net current-period Other Comprehensive Income (Loss) 2.6 0.2 47.6 50.4 Accumulated Other Comprehensive Loss by Component, September 30, 2020 $ ( 24.1 ) $ ( 1.4 ) $ ( 24.2 ) $ ( 49.7 ) Gains and Defined Cumulative Total Accumulated Other Comprehensive (Loss) by Component, January 1, 2020 $ ( 16.5 ) $ ( 1.5 ) $ ( 71.9 ) $ ( 89.9 ) Change in fair value of interest rate swap, net of tax ( 11.9 ) — — ( 11.9 ) Reclassification of interest rate swap to income, net of tax 4.3 — — 4.3 Pension adjustments, net of tax — 0.1 — 0.1 Foreign currency translation adjustments, net of tax — — 16.4 16.4 Change in fair value of net investment hedge, net of tax — — 31.3 31.3 Net current-period Other Comprehensive Income (Loss) ( 7.6 ) 0.1 47.7 40.2 Accumulated Other Comprehensive Loss by Component, September 30, 2020 $ ( 24.1 ) $ ( 1.4 ) $ ( 24.2 ) $ ( 49.7 ) Management identified a misstatement related to the classification of foreign currency translation adjustments associated with the net investment hedge for the year to date period ended September 30, 2020 . As a result, the Company reclassified $ 31.3 million from Change in fair value of interest rate swap, net of tax in Gains and (losses) on cash flow hedges to Change in fair value of net investment hedge, net of tax in Cumulative foreign currency translation adjustment to reflect the correct presentation in the table above. This adjustment had no effect on the Company’s previously reported consolidated financial statements as of and for the year to date period ended September 30, 2020 . Additionally, certain amounts related to the derivative financial instruments were reclassified in the Consolidated Statements of Comprehensive Income to conform with this presentation.

Net Income per Share

Net Income per Share	9 Months Ended
Net Income per Share	Sep. 30, 2021
Earnings Per Share [Abstract]
Net Income per Share	7. Net Income per Share Basic earnings per share is based on the weighted average number of shares of common stock outstanding, and diluted earnings per share is based on the weighted average number of shares of common stock outstanding and all potentially dilutive common stock equivalents outstanding. Common stock equivalents are included in the per share calculations when the effect of their inclusion is dilutive. The following is a reconciliation of basic to diluted net income per share: Quarter Ended Year to Date Ended September 30, 2021 September 30, 2020 September 30, 2021 September 30, 2020 Net income/(loss) $ 35.4 $ 38.3 $ 115.4 $ ( 56.7 ) Shares used in net income per common share - basic 64.9 64.6 64.8 64.6 Effect of dilutive shares 0.6 0.3 0.6 — Shares used in net income per common share - diluted 65.5 64.9 65.4 64.6 Shares excluded as their inclusion would be anti-dilutive — — — 0.1 Earnings/(Loss) per share: Basic net income $ 0.55 $ 0.59 $ 1.78 $ ( 0.88 ) Diluted net income $ 0.54 $ 0.59 $ 1.76 $ ( 0.88 )

Inventories

Inventories	9 Months Ended
Inventories	Sep. 30, 2021
Inventory Disclosure [Abstract]
Inventories	8. Inventories Inventories at September 30, 2021 and December 31, 2020 consisted of the following: September 30, 2021 December 31, 2020 Raw materials $ 128.6 $ 95.2 Work in process 25.7 22.1 Finished goods 102.7 93.1 $ 257.0 $ 210.4

Goodwill and Intangible Assets

Goodwill and Intangible Assets	9 Months Ended
Goodwill and Intangible Assets	Sep. 30, 2021
Goodwill And Intangible Assets Disclosure [Abstract]
Goodwill and Intangible Assets	9. Goodwill and Intangible Assets The Company conducts an annual impairment review of goodwill and indefinite-lived intangible assets in the fourth quarter of each year, unless events occur which trigger the need for an interim impairment review. There were no triggering events for the year to date period ended September 30, 2021. The 2020 annual goodwill impairment review indicated that the Thomson reporting unit’s fair value exceeded its carrying value by less than 10 %. All other reporting units had fair values that exceeded their carrying value by 10 % or more. Changes in goodwill from January 1, 2021 through September 30, 2021 were as follows: Power Automation Total Goodwill $ 452.4 $ 1,314.5 $ 1,766.9 Accumulated impairment loss ( 31.8 ) ( 139.1 ) ( 170.9 ) Balance January 1, 2021 $ 420.6 $ 1,175.4 $ 1,596.0 Impact of changes in foreign currency ( 7.1 ) ( 14.5 ) ( 21.6 ) Net goodwill balance September 30, 2021 $ 413.5 $ 1,160.9 $ 1,574.4 Other intangible assets as of September 30, 2021 and December 31, 2020 consisted of the following: September 30, 2021 December 31, 2020 Cost Accumulated Net Cost Accumulated Net Other intangible assets Intangible assets not subject to amortization: Tradenames and trademarks $ 255.0 $ — $ 255.0 $ 259.7 $ — $ 259.7 Intangible assets subject to amortization: In-process research and development 16.0 — 16.0 16.0 — 16.0 Customer relationships 1,202.6 228.2 974.4 1,220.2 195.0 1,025.2 Product technology and patents 211.4 67.8 143.6 211.2 52.5 158.7 Total intangible assets $ 1,685.0 $ 296.0 $ 1,389.0 $ 1,707.1 $ 247.5 $ 1,459.6 The Company recorded $ 17.6 million and $ 17.5 million of amortization expense in the quarters ended September 30, 2021 and 2020, respectively; and, recorded $ 52.9 million and $ 52.3 million of amortization expense in the year to date periods ended September 30, 2021 and 2020, respectively. The estimated amortization expense for intangible assets is approximately $ 17.7 million for the remainder of 2021 , $ 71.4 million in 2022, $ 71.1 million in 2023, $ 70.8 million in 2024, $ 70.5 million in 2025 and $ 832.5 million thereafter.

Warranty Costs

Warranty Costs	9 Months Ended
Warranty Costs	Sep. 30, 2021
Guarantees [Abstract]
Warranty Costs	10. Warranty Costs The contractual warranty period of the Company's products generally ranges from three months to two years with certain warranties extending for longer periods. Estimated expenses related to product warranties are accrued at the time products are sold to customers and are recorded in accruals and other current liabilities on the unaudited condensed consolidated balance sheets. Estimates are established using historical information as to the nature, frequency and average costs of warranty claims. Changes in the carrying amount of accrued product warranty costs for the year to date periods ended September 30, 2021 and 2020 are as follows: September 30, 2021 September 30, 2020 Balance at beginning of period $ 9.6 $ 10.0 Accrued current period warranty expense 2.7 2.7 Payments and adjustments ( 2.0 ) ( 2.9 ) Balance at end of period $ 10.3 $ 9.8

Debt

Debt	9 Months Ended
Debt	Sep. 30, 2021
Debt Disclosure [Abstract]
Debt	11. Debt Outstanding debt obligations at September 30, 2021 and December 31, 2020 were as follows: September 30, 2021 December 31, 2020 Debt: Term loan $ 910.0 $ 1,030.0 Notes 400.0 400.0 Mortgages and other 11.8 12.9 Finance leases 0.2 0.3 Total gross debt 1,322.0 1,443.2 Less: debt discount and deferred financing ( 15.5 ) ( 18.5 ) Total debt, net of debt discount and 1,306.5 1,424.7 Less: current portion of long-term debt ( 16.8 ) ( 16.6 ) Total long-term debt $ 1,289.7 $ 1,408.1 2018 Credit Agreement and Notes On October 1, 2018 (the “A&S Closing Date”), upon the closing of the combination (the “Fortive Transaction”) of Altra with four operating companies from Fortive Corporation’s (“Fortive”) Automation & Specialty platform (the “A&S Business”), the Company assumed $ 400 million aggregate principal amount of 6.125 % senior notes due 2026 (the “Notes”). The Notes will mature on October 1, 2026 . Interest on the Notes accrues from October 1, 2018, and the first interest payment date on the Notes was on April 1, 2019 . The Notes may be redeemed at the option of the issuer on or after October 1, 2023 . The Notes are guaranteed on a senior unsecured basis by the Company and certain of its domestic subsidiaries. On the A&S Closing Date, the Company entered into a new Credit Agreement (the “Altra Credit Agreement”). The Altra Credit Agreement provides for a seven-year senior secured term loan in an aggregate principal amount of $ 1,340.0 million (the “Altra Term Loan Facility”) and a five-year senior secured revolving credit facility in an aggregate committed principal amount of $ 300.0 million (the “Altra Revolving Credit Facility” and together with the Altra Term Loan Facility, the “Altra Credit Facilities”). The proceeds of the Altra Term Loan Facility were used to (i) consummate Fortive’s transfer of certain non-U.S assets, liabilities and entities constituting a portion of the A&S Business to certain subsidiaries of Altra, and the Altra subsidiaries’ assumption of substantially all of the liabilities associated with the transferred assets (the “Direct Sales”), (ii) repay in full and extinguish all outstanding indebtedness for borrowed money under the Company’s previous credit agreement (as defined herein) and (iii) pay certain fees, costs, and expenses in connection with the consummation of the Fortive Transaction. The proceeds of the Altra Revolving Credit Facility will be used for working capital and general corporate purposes. The Altra Credit Facilities are guaranteed on a senior secured basis by the Company and certain of its domestic subsidiaries, subject to certain customary exceptions. Borrowings under the Altra Term Loan Facility will bear interest at a per annum rate equal to a “Eurocurrency Rate” plus 2.00 %, in the case of Eurocurrency Rate borrowings, or equal to a “Base Rate” plus 1.00 %, in the case of Base Rate borrowings. Borrowings under the Altra Revolving Credit Facility will initially bear interest at a per annum rate equal to a Eurocurrency Rate plus 2.00 %, in the case of Eurocurrency Rate borrowings, or equal to a Base Rate plus 1.00 %, in the case of Base Rate borrowings , and thereafter will bear interest at a per annum rate equal to a Eurocurrency Rate or Base Rate, as applicable, plus an interest rate spread determined by reference to a pricing grid based on the Company’s senior secured net leverage ratio. In addition, the Company will be required to pay fees that will fluctuate between 0.250 % per annum to 0.375 % per annum on the unused amount of the Altra Revolving Credit Facility, based upon the Company’s senior secured net leverage ratio . The interest rate on the Altra Term Loan Facility was 2.084 % at September 30, 2021. The Altra Credit Agreement contains usual and customary representations and warranties, and usual and customary affirmative and negative covenants, including limitations on liens, investments, restricted payments, additional indebtedness and asset sales and mergers. In addition, the Altra Credit Agreement requires that Altra maintain a specified maximum senior secured leverage ratio and a specified minimum interest coverage ratio. The obligations of the borrowers of the Altra Credit Facilities under the Altra Credit Agreement may be accelerated upon customary events of default, including non-payment of principal, interest, fees and other amounts, inaccuracy of representation and warranties, violation of covenants, cross default and cross acceleration, voluntary and involuntary bankruptcy or insolvency proceedings, inability to pay debts as they become due, material judgments, ERISA events, actual or asserted invalidity of security documents or guarantees and change in control. The Company incurred $ 29.9 million in issuance costs, which are amortized over the term of the debt as an adjustment to the effective interest rate on the outstanding borrowings. The Company provided notice to the administrative agent of the Altra Credit Agreement on March 9, 2020 and March 16, 2020 to draw down $ 50 million and $ 50 million, respectively, under the Altra Revolving Credit Facility. At that time, the Company had increased its borrowings under the Altra Revolving Credit Facility as a precautionary action in order to increase its cash position and enhance its financial flexibility during this period of uncertainty in the global markets resulting from COVID-19. On April 14, 2020, the Company provided notice to the administrative agent of the Altra Credit Agreement to repay $ 50 million outstanding under the Altra Revolving Credit Facility. On April 27, 2020 and May 27, 2020, the Company provided notice to the administrative agent to repay $ 15 million and $ 35 million, respectively, which were outstanding under the Altra Revolving Credit Facility. As of the period ended September 30, 2021, all outstanding borrowings under the Altra Revolving Credit Facility have been repaid. As of September 30, 2021, the Company had $ 910.0 million outstanding on the Altra Credit Agreement. As of September 30, 2021 and December 31, 2020, the Company had $ 4.8 million and $ 4.5 million in letters of credit outstanding, respectively. The Company had $ 295.2 million available to borrow under the Altra Credit Facilities at September 30, 2021. Mortgages and Other Agreements The Company’s subsidiaries in Europe have entered into certain long-term fixed rate term loans that are generally secured by local property, plant and equipment. The debt has interest rates that range from 1.0 % to 2.5 %, with various quarterly and monthly installments through 2028. Financing Leases The Company leases certain equipment under finance lease arrangements, whose obligations are included in both short-term and long-term debt. Finance lease obligations amounted to approximately $ 0.2 million and $ 0.3 million at September 30, 2021 and December 31, 2020 , respectively. Finance lease right of use assets are included in property, plant and equipment with the related amortization recorded as depreciation expense. Finance lease liabilities are included in current and non-current other liabilities on the Company’s consolidated balance sheets.

Stockholders' Equity

Stockholders' Equity	9 Months Ended
Stockholders' Equity	Sep. 30, 2021
Stockholders Equity Note [Abstract]
Stockholders' Equity	12. Stockholders’ Equity Common Stock Effective October 1, 2018, the Company amended its Articles of Incorporation to increase the number of authorized shares of Altra common stock from 90.0 million shares to 120.0 million shares. As of September 30, 2021 and December 31, 2020, there were 64,915,615 and 64,676,567 shares of common stock issued and outstanding, respectively. Preferred Stock On December 20, 2006, the Company amended and restated its certificate of incorporation authorizing 10.0 million shares of undesignated Preferred Stock (“Preferred Stock”). The Preferred Stock may be issued from time to time in one or more classes or series, the shares of each class or series to have such designations and powers, preferences, rights, qualifications, limitations and restrictions as determined by the Company’s Board of Directors. There was no Preferred Stock issued or outstanding at September 30, 2021 or December 31, 2020. Restricted Common Stock The 2014 Omnibus Incentive Plan (the “2014 Plan”) was approved by the Company’s stockholders at the Company’s 2014 Annual Meeting of Stockholders. The 2014 Plan provides for various forms of stock-based compensation to our directors, executive personnel and other key employees and consultants. Under the 2014 Plan, the remaining total number of shares of common stock available for delivery pursuant to the grant of awards was 4.1 million as of September 30, 2021. The restricted stock and restricted stock units issued pursuant to the 2014 Plan generally vest ratably over a period ranging from immediately to five years from the date of grant, provided, that the vesting of the restricted stock or restricted stock units may accelerate upon the occurrence of certain events. Common stock awarded under the 2014 Plan is generally subject to restrictions on transfer, repurchase rights, and other limitations and rights as set forth in the applicable award agreements. The 2014 Plan permits the Company to grant, among other things, restricted stock, restricted stock units, stock options and performance share awards to key employees. Certain awards include vesting based upon achievement of specified performance criteria. Compensation expense recorded (in selling, general and administrative expense) during the quarters ended September 30, 2021 and 2020 was $ 3.5 million and $ 3.2 million, respectively. Compensation expense recorded (in selling, general and administrative expense) during the year to date period ended September 30, 2021 and 2020 was $ 11.0 million and $ 10.3 million, respectively. The Company recognizes stock-based compensation expense on a straight-line basis for the shares vesting ratably under the plan and uses the graded-vesting method of recognizing stock-based compensation expense for the performance share awards based on the probability of the specific performance metrics being achieved over the requisite service period. Total remaining unrecognized compensation cost is approximately $ 23.5 million as of September 30, 2021 , and will be recognized over a weighted average remaining period of three years . Stock Options The following table summarizes the stock option activity under the Company’s plan for the year to date period ended September 30, 2021: Weighted Options Weighted- Aggregate Outstanding at January 1, 2021 460.7 $ 32.48 Granted 124.7 59.40 Exercised ( 72.2 ) 30.72 Canceled/Forfeited ( 13.2 ) 39.43 Outstanding at September 30, 2021 8.3 500.0 $ 39.26 $ 9.0 Exercisable at September 30, 2021 8.0 231.3 $ 35.83 $ 4.9 Unvested and expected to vest at September 30, 2021 8.4 249.4 $ 41.99 $ 3.9 Cash proceeds from the exercise of stock options for the year to date period ended September 30, 2021 was $ 2.2 million. Restricted Stock Units The following table summarizes the Restricted Stock Unit activity under the Company’s plan for the year to date period ended September 30, 2021: Shares Weighted- Aggregate Unvested at January 1, 2021 515.8 $ 35.11 Granted 152.3 59.64 Vested ( 221.3 ) 38.40 Canceled/Forfeited ( 24.4 ) 40.22 Unvested at September 30, 2021 422.4 $ 41.96 $ 23.9 Performance Share Awards The following table summarizes the Performance Share Award activity under the Company’s plan for the year to date period ended September 30, 2021: Shares Weighted- Aggregate Unvested at January 1, 2021 268.0 $ 34.38 Granted 63.3 64.43 Vested ( 28.3 ) 45.80 Canceled/Forfeited ( 8.0 ) 39.71 Unvested at September 30, 2021 295.0 $ 39.50 $ 16.7 See Note 12, Stockholders’ Equity, to the audited consolidated financial statements of the Company's Annual Report on Form 10-K for the year ended December 31, 2020 for further information regarding stock-based compensation.

Restructuring Costs

Restructuring Costs	9 Months Ended
Restructuring Costs	Sep. 30, 2021
Restructuring And Related Activities [Abstract]
Restructuring Costs	13. Restructuring Costs From time to time, the Company has initiated various restructuring programs and incurred severance and other restructuring costs. During 2017, the Company commenced a restructuring plan (“2017 Altra Plan”) as a result of the Company’s acquisition of Stromag and to rationalize its global renewable energy business. The actions taken pursuant to the 2017 Altra Plan included reducing headcount, facility consolidations and the elimination of certain costs. The Company did not incur any costs as a result of the 2017 Altra Plan during the quarter and year to date periods ended September 30, 2021. The Company does not expect to incur any additional material costs as a result of the 2017 Altra Plan. During 2019, the Company commenced a restructuring plan (“2019 Altra Plan”) to drive efficiencies, reduce the number of facilities and optimize its operating margin. The Company expects to incur an additional $ 1 - $ 2 million in restructuring expenses under the 2019 Altra Plan over the next two years , primarily related to headcount reductions and plant consolidations. The expenses for the quarter and year to date periods ended September 30, 2021 were $ 0.7 million and $ 2.4 million, respectively, and were comprised mainly of severance costs. The following is a reconciliation of the accrued restructuring costs between January 1, 2021 and September 30, 2021: 2017 Altra 2019 Altra Total All Balance at January 1, 2021 $ 0.5 $ 1.8 $ 2.3 Restructuring expense incurred — 0.9 0.9 Cash payments ( 0.1 ) ( 1.4 ) ( 1.5 ) Balance at March 31, 2021 0.4 1.3 1.7 Restructuring expense incurred — 0.8 0.8 Cash payments ( 0.1 ) ( 1.3 ) ( 1.4 ) Balance at June 30, 2021 0.3 0.8 1.1 Restructuring expense incurred — 0.7 0.7 Cash payments ( 0.1 ) ( 1.1 ) ( 1.2 ) Balance at September 30, 2021 $ 0.2 $ 0.4 $ 0.6 The following is a reconciliation of the accrued restructuring costs between January 1, 2020 and September 30, 2020: 2017 Altra 2019 Altra Total All Balance at January 1, 2020 $ 1.5 $ 2.6 $ 4.1 Restructuring expense incurred 0.2 1.4 1.6 Cash payments ( 0.4 ) ( 1.4 ) ( 1.8 ) Balance at March 31, 2020 1.3 2.6 3.9 Restructuring expense incurred 0.3 1.2 1.5 Cash payments ( 0.6 ) ( 1.1 ) ( 1.7 ) Balance at June 30, 2020 1.0 2.7 3.7 Restructuring expense incurred — 2.4 2.4 Cash payments ( 0.2 ) ( 2.9 ) ( 3.1 ) Balance at September 30, 2020 $ 0.8 $ 2.2 $ 3.0 The following is a reconciliation of restructuring expense by segment for the quarter ended September 30, 2021: 2017 Altra 2019 Altra Total All Power Transmission Technologies $ — $ 0.4 $ 0.4 Automation & Specialty — 0.3 0.3 Total restructuring expense $ — $ 0.7 $ 0.7 The following is a reconciliation of restructuring expense by segment for the quarter ended September 30, 2020: 2017 Altra 2019 Altra Total All Power Transmission Technologies $ — $ 2.0 $ 2.0 Automation & Specialty — 0.4 0.4 Total restructuring expense $ — $ 2.4 $ 2.4 The following is a reconciliation of restructuring expense by segment for the year to date period ended September 30, 2021 2017 Altra 2019 Altra Total All Power Transmission Technologies $ — $ 1.4 $ 1.4 Automation & Specialty — 1.0 1.0 Total restructuring expense $ — $ 2.4 $ 2.4 The following is a reconciliation of restructuring expense by segment for the year to date period ended September 30, 2020: 2017 Altra 2019 Altra Total All Power Transmission Technologies $ 0.5 $ 2.6 $ 3.1 Automation & Specialty — 2.4 2.4 Total restructuring expense $ 0.5 $ 5.0 $ 5.5 The total accrued restructuring reserve as of September 30, 2021, and as of September 30, 2020 relate primarily to severance and consolidation costs under the 2017 Altra Plan and the 2019 Altra Plan and are recorded in accruals and other current liabilities on the accompanying unaudited condensed consolidated balance sheet.

Segments, Concentrations and Ge

Segments, Concentrations and Geographic Information	9 Months Ended
Segments, Concentrations and Geographic Information	Sep. 30, 2021
Segment Reporting [Abstract]
Segments, Concentrations and Geographic Information	14. Segments, Concentrations and Geographic Information Segments The internal reporting structure used by our Chief Operating Decision Maker (“CODM”) to assess performance and allocate resources determines the basis for our reportable operating segments. Our CODM is our Chief Executive Officer, and he evaluates operations and allocates resources based on a measure of income from operations. Our operations are organized in two reporting segments that are aligned with key product types and end markets served, Power Transmission Technologies (“PTT”) and Automation & Specialty (“A&S”):  Power Transmission Technologies - PTT. This segment includes the following key product offerings: o Couplings, Clutches & Brakes. Couplings are the interface between two shafts, which enable power to be transmitted from one shaft to the other. Clutches in this segment are devices that use mechanical, hydraulic, pneumatic, or friction type connections to facilitate engaging or disengaging two rotating members. Brakes are combinations of interacting parts that work to slow or stop machinery. Products in this segment are generally used in heavy industrial applications and energy markets. o Electromagnetic Clutches & Brakes. Products in this segment include brakes and clutches that are used to electronically slow, stop, engage or disengage equipment utilizing electromagnetic friction type connections. Products in this segment are used in industrial and commercial markets including agricultural machinery, material handling, motion control, and turf & garden. o Gearing. Gears are utilized to reduce the speed and increase the torque of an electric motor or engine to the level required to drive a particular piece of equipment. Gears produced by the Company are primarily utilized in industrial applications.  Automation & Specialty – A&S. This segment includes the following key brands: o Kollmorgen: Provides rotary precision motion solutions, including servo motors, stepper motors, high performance electronic drives and motion controllers and related software, and precision linear actuators. These products are used in advanced material handling, aerospace and defense, factory automation, medical, packaging, printing, semiconductor, robotic and other applications. o Portescap: Provides high-efficiency miniature motors and motion control products, including brush and brushless DC motors, can stack motors and disc magnet motors. These products are used in medical, industrial power tool and general industrial equipment applications. o Thomson: Provides systems that enable and support the transition of rotary motion to linear motion. Products include linear bearings, guides, glides, lead and ball screws, industrial linear actuators, clutch brakes, precision gears, resolvers and inductors. These products are used in factory automation, medical, mobile off-highway, material handling, food processing and other niche applications. o Jacobs Vehicle Systems (JVS): Provides renowned “Jake Brake” diesel engine braking systems and valve actuation mechanisms for the commercial vehicle market, including compression release, bleeder and exhaust brakes. These products are primarily used in heavy duty Class 8 truck applications. Segment financial information and a reconciliation of segment results to unaudited condensed consolidated results are as follows: Quarter Ended Year to Date Ended September 30, 2021 September 30, 2020 September 30, 2021 September 30, 2020 Net Sales: Power Transmission Technologies $ 232.5 $ 197.7 $ 691.1 $ 610.7 Automation & Specialty 237.8 240.8 741.9 665.2 Inter-segment eliminations ( 1.0 ) ( 0.7 ) ( 3.0 ) ( 3.1 ) Net sales $ 469.3 $ 437.8 $ 1,430.0 $ 1,272.8 Income/(loss) from operations: Segment earnings: Power Transmission Technologies $ 36.5 $ 23.5 $ 97.9 $ 73.0 Automation & Specialty 30.6 44.6 109.4 ( 48.0 ) Corporate expenses (1) ( 4.6 ) ( 0.3 ) ( 12.5 ) — Restructuring costs ( 0.7 ) ( 2.4 ) ( 2.4 ) ( 5.5 ) Income/(loss) from operations $ 61.8 $ 65.4 $ 192.4 $ 19.5 Other non-operating expense: Net interest expense 16.1 18.0 49.5 54.2 Other non-operating (income)/expense, net 0.1 ( 0.3 ) ( 3.1 ) 0.8 Total non-operating expense $ 16.2 $ 17.7 $ 46.4 $ 55.0 Income/(loss) before income taxes 45.6 47.7 146.0 ( 35.5 ) Provision for income taxes 10.2 9.4 30.6 21.2 Net income/(loss) $ 35.4 $ 38.3 $ 115.4 $ ( 56.7 ) (1) Certain expenses are maintained at the corporate level and are not allocated to the segments. These include various administrative expenses related to the Company’s corporate headquarters, certain U.S. healthcare costs and credits, depreciation on capitalized software costs, non-capitalizable software implementation costs and acquisition related expenses. Selected information by segment (continued): Quarter Ended Year to Date Ended September 30, 2021 September 30, 2020 September 30, 2021 September 30, 2020 Depreciation and amortization: Power Transmission Technologies $ 7.8 $ 8.2 $ 23.8 $ 24.6 Automation & Specialty 22.2 23.3 66.5 69.4 Corporate 0.6 0.9 2.0 2.5 Total depreciation and amortization $ 30.6 $ 32.4 $ 92.3 $ 96.5 September 30, 2021 September 30, 2020 Total assets: Power Transmission Technologies $ 1,064.3 $ 1,054.2 Automation & Specialty 2,962.8 2,956.0 Corporate (2) 134.1 135.7 Total assets $ 4,161.2 $ 4,145.9 (2) Corporate assets are primarily cash and cash equivalents, tax related asset accounts, certain capitalized software costs, and property, plant and equipment. Net sales to third parties by geographic region are as follows: Net Sales Quarter Ended Year to Date Ended September 30, 2021 September 30, 2020 September 30, 2021 September 30, 2020 North America (primarily U.S.) $ 256.1 $ 230.2 $ 758.6 $ 681.3 Europe excluding Germany 83.9 68.8 259.1 214.9 Germany 50.0 44.1 151.5 140.7 China 48.8 56.5 176.9 150.1 Asia and other excluding China 30.5 38.2 83.9 85.8 Total $ 469.3 $ 437.8 $ 1,430.0 $ 1,272.8 Net sales to third parties are attributed to the geographic regions based on the country in which the shipment originates. Amounts attributed to the geographic regions for property, plant and equipment are based on the location of the entity, which holds such assets.

Derivative Financial Instrument

Derivative Financial Instruments	9 Months Ended
Derivative Financial Instruments	Sep. 30, 2021
Derivative Instruments And Hedging Activities Disclosure [Abstract]
Derivative Financial Instruments	15. Derivative Financial Instruments The Company may manage changes in market conditions related to interest on debt obligations and foreign currency exposures by entering into derivative instruments, including interest rate and foreign currency swap agreements. All derivative instruments are recognized as either assets or liabilities on the balance sheet at fair value at the end of each period. The Company determines the fair value of financial instruments using quoted market prices whenever available. When quoted market prices are not available for various types of financial instruments (such as forwards, options and swaps), the Company uses standard models with market-based inputs, which take into account the present value of estimated future cash flows and the ability of Altra or the financial counterparty to perform. For cross-currency interest rate swaps, the significant inputs are interest rate curves for discounting future cash flows, and exchange rate curves of the foreign currency for translating future cash flows. For interest rate swaps, the significant inputs to these models are interest rate curves for discounting future cash flows that are adjusted for credit risk. Both cross-currency interest rate swaps and interest rate swaps are Level 2 investments. Refer to Note 5 for a description of the fair value levels. For designated hedging relationships, the Company formally documents the hedging relationship consistent with the requirements of ASC 815, Derivatives. Cross-Currency Interest Rate Swaps In December 2018, the Company entered into cross-currency swap agreements to hedge its net investment in Euro-denominated assets against future volatility in the exchange rate between the U.S. dollar and the Euro. By doing so, the Company synthetically converted a portion of its U.S. dollar-based long-term debt into Euro-denominated long-term debt. At inception, the cross-currency swaps were designated as net investment hedges. For net investment hedges, changes in the fair value of the effective portion of the derivatives’ gains or losses are reported as foreign currency translation gains or losses in accumulated other comprehensive income (loss) (“AOCIL”). The gains or losses on derivative instruments reported in AOCIL are reclassified to earnings in the period in which earnings are affected by the underlying item, such as a disposal or substantial liquidations of the entities being hedged. During the first quarter of 2020, the Company terminated the cross-currency interest rate swaps. The Company received the cash value of the cross-currency interest rate swaps of approximately $ 56.2 million upon termination. In addition, the Company paid the interest owed and received the interest due, resulting in the recognition of approximately $ 3.3 million in net interest income, and paid termination fees of approximately $ 0.9 million. At September 30, 2021 , the Company had a gain in AOCIL of approximately $ 44.8 million, net of $ 11.4 million of tax. That balance will remain in AOCIL until the period in which earnings are affected by the underlying item, such as a disposal or substantial liquidations of the entities being hedged. Interest Rate Swaps In January 2017, the Company entered into an interest rate swap agreement to fix the variable interest rate payable on a portion of its outstanding borrowings. This interest rate swap matured on January 31, 2020 . Additionally, in December 2018, the Company entered into an interest rate swap agreement designed to manage the cash flow risk caused by interest rate changes on the forecasted interest payments expected to occur related to a portion of its outstanding borrowings under the Altra Credit Agreement. The interest rate swap agreement was designed to manage exposure to interest rates on the Company’s variable rate indebtedness and was recognized on the balance sheet at fair value. The Company designated this interest rate swap agreement as a cash flow hedge and changes in the fair value of the swap were recognized in other comprehensive income until the hedged items were recognized in earnings. During 2020, the Company terminated the interest rate swap agreement. The Company paid the cash value of the interest rate swaps of approximately $ 34.7 million upon termination. In addition, the Company paid the interest owed and received the interest due, resulting in the recognition of approximately $ 0.1 million in net interest expense, and paid termination fees of approximately $ 0.1 million. At September 30, 2021 , the Company had a loss in AOCIL of approximately $ 13.5 million, net of $ 3.2 million of tax benefit. The loss on the interest rate swap reported in AOCIL will be reclassified to earnings in future periods when the hedged transaction affects earnings or if it is determined that it is probable that the hedged transaction will not occur. The Company reclassified $ 2.2 million, net of $ 0.7 million tax benefit, and $ 6.9 million, net of $ 2.1 million tax benefit, of non-cash interest expense from AOCIL to earnings for the quarter and year to date periods ended September 30, 2021 , respectively. The Company reclassified $ 3.4 million and $ 8.2 million from AOCIL to earnings for the quarter and year to date periods ended September 30, 2020 , respectively. Approximately $ 2.6 million, net of $ 0.8 million tax benefit, and $ 4.3 million, net of $ 1.3 million tax benefit, for the quarter and year to date periods ended September 30, 2020, respectively, represents non-cash interest expense. The following table summarizes the balance of the Company's derivative instruments designated as cash flow hedges (in millions): September 30, 2021 December 31, 2020 Cash flow hedge: Amount of Loss in AOCIL Interest rate swap agreement $ ( 16.7 ) $ ( 25.7 )

Commitments and Contingencies

Commitments and Contingencies	9 Months Ended
Commitments and Contingencies	Sep. 30, 2021
Commitments And Contingencies Disclosure [Abstract]
Commitments and Contingencies	16. Commitments and Contingencies General Litigation The Company is involved in various pending legal proceedings arising out of the ordinary course of business. These proceedings primarily involve commercial claims, product liability claims, personal injury claims, and workers’ compensation claims. With respect to these proceedings, management believes that the Company will prevail, has adequate insurance coverage or has established appropriate reserves to cover potential liabilities. Any costs that management estimates may be paid related to these proceedings or claims are accrued when the liability is considered probable and the amount can be reasonably estimated. There can be no assurance, however, as to the ultimate outcome of any of these matters, and if all or substantially all of these legal proceedings were to be determined adversely to the Company, there could be a material adverse effect on the results of operations, cash flows, or financial condition of the Company. We have established loss provisions for matters in which losses are probable and can be reasonably estimated. For matters where a reserve has not been established and for which we believe a loss is reasonably possible, as well as for matters where a reserve has been recorded but for which an exposure to loss in excess of the amount accrued is reasonably possible, we believe that such losses, individually and in the aggregate, will not have a material effect on our unaudited condensed consolidated financial statements. Our estimates regarding potential losses and materiality are based on our judgment and assessment of the claims utilizing currently available information. Although we will continue to reassess our reserves and estimates based on future developments, our objective assessment of the legal merits of such claims may not always be predictive of the outcome and actual results may vary from our current estimates. We will continue to consider the applicable guidance in ASC 450-20, based on the facts known at the time of our future filings, as it relates to legal contingencies, and will adjust our disclosures as may be required under the guidance. There were no material amounts accrued in the accompanying unaudited condensed consolidated balance sheets for potential litigation as of September 30, 2021 or December 31, 2020. The Company also risks exposure to product liability claims in connection with products it has sold and those sold by businesses that the Company acquired. Although in some cases third parties have retained responsibility for product liability claims relating to products manufactured or sold prior to the acquisition of the relevant business and in other cases the persons from whom the Company has acquired a business may be required to indemnify the Company for certain product liability claims subject to certain caps or limitations on indemnification, the Company cannot assure that those third parties will in fact satisfy their obligations with respect to liabilities retained by them or their indemnification obligations. If those third parties become unable to or otherwise do not comply with their respective obligations including indemnity obligations, or if certain product liability claims for which the Company is obligated were not retained by third parties or are not subject to these indemnities, the Company could become subject to significant liabilities or other adverse consequences. Moreover, even in cases where third parties retain responsibility for product liability claims or are required to indemnify the Company, significant claims arising from products that have been acquired could have a material adverse effect on the Company’s ability to realize the benefits from an acquisition, could result in the reduction of the value of goodwill that the Company recorded in connection with an acquisition, or could otherwise have a material adverse effect on the Company’s business, financial condition, or operations. Environmental There is contamination at some of the Company’s current facilities, primarily related to historical operations at those sites, for which the Company could be liable for the investigation and remediation under certain environmental laws. The potential for contamination also exists at other of the Company’s current or former sites, based on historical uses of those sites. The Company currently is not undertaking any material remediation or investigations and the costs or liability in connection with potential contamination conditions at these facilities cannot be predicted at this time because the potential existence of contamination has not been investigated or not enough is known about the environmental conditions or likely remedial requirements. Currently, other parties with contractual liability are addressing or have plans or obligations to address those contamination conditions that may pose a material risk to human health, safety or the environment. In addition, while the Company attempts to evaluate the risk of liability associated with these facilities at the time the Company acquired them, there may be environmental conditions currently unknown to the Company relating to prior, existing or future sites or operations or those of predecessor companies whose liabilities the Company may have assumed or acquired which could have a material adverse effect on the Company’s business. The Company is being indemnified, or expects to be indemnified, by third parties subject to certain caps or limitations on the indemnification, for certain environmental costs and liabilities associated with certain owned or operated sites. Accordingly, based on the indemnification and the experience with similar sites of the environmental consultants who the Company has hired, the Company does not expect such costs and liabilities to have a material adverse effect on its business, operations or earnings. The Company cannot assure you, however, that those third parties will in fact satisfy their indemnification obligations. If those third parties become unable to, or otherwise do not, comply with their respective indemnity obligations, or if certain contamination or other liability for which the Company is obligated is not subject to these indemnities, the Company could become subject to significant liabilities. From time to time, the Company is notified that it is a potentially responsible party and may have liability in connection with off-site disposal facilities. To date, the Company has generally resolved matters involving off-site disposal facilities for a nominal sum but there can be no assurance that the Company will be able to resolve pending or future matters in a similar fashion.

Subsequent Events

Subsequent Events	9 Months Ended
Subsequent Events	Sep. 30, 2021
Subsequent Events [Abstract]
Subsequent Events	17. Subsequent Events On October 20, 2021 , the Company declared a dividend of $ 0.08 per share for the quarter ended December 31, 2021, payable on January 4, 2022 to stockholders of record as of December 17, 2021 .

Basis of Presentation (Policies

Basis of Presentation (Policies)	9 Months Ended
Basis of Presentation (Policies)	Sep. 30, 2021
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Basis of Presentation	Basis of Presentation The Company’s unaudited condensed consolidated financial statements have been prepared in accordance with the instructions to Form 10-Q and do not include all of the information and note disclosures required by generally accepted accounting principles in the United States, or GAAP. These statements should be read in conjunction with the financial statements and notes thereto included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2020 , filed with the U.S. Securities and Exchange Commission (the “SEC”) on February 26, 2021. In the opinion of management, the accompanying unaudited condensed consolidated financial statements include all adjustments, consisting of normal recurring adjustments, necessary to present fairly the Company’s financial position and cash flows for the interim periods presented. The results are not necessarily indicative of future results. The Company considers events or transactions that occur after the balance sheet date but before the financial statements are issued to provide additional evidence relative to certain estimates or to identify matters that require additional disclosure.
Recent Accounting Pronouncements	Recent Accounting Pronouncements In March 2020, the FASB issued ASU No. 2020-04, Reference Rate Reform (Topic 848): Facilitation of the Effects of Reference Rate Reform on Financial Reporting (“ASU 2020-04”). This ASU provides relief from certain accounting consequences that could result from the global markets’ anticipated transition away from the use of the London Interbank Offered Rate (“LIBOR”) and other interbank offered rates to alternative reference rates. The relief provided by this ASU is elective and applies to all entities, subject to meeting certain criteria, that have contracts, hedging relationships, and other transactions that reference LIBOR or another reference rate expected to be discontinued because of reference rate reform. The optional amendments are effective as of March 12, 2020 through December 31, 2022. The Company is currently evaluating the effect of the adoption of this standard on the Company.
Fair Value of Financial Instruments	Fair value is determined based upon the exit price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants, as determined by either the principal market or the most advantageous market. Inputs used in the valuation techniques to derive fair values are classified based on a three-level hierarchy, as follows:  Level 1- Quoted prices in active markets for identical assets or liabilities.  Level 2- Observable inputs other than Level 1 prices such as quoted prices for similar assets or liabilities; quoted prices in markets with insufficient volume or infrequent transactions (less active markets); or model-derived.  Level 3- Unobservable inputs to the valuation methodology that are significant to the measurement of fair value of assets or liabilities. The Company considers all highly liquid investments purchased with a remaining maturity of three months or less to be cash equivalents and are classified as Level 1. The carrying values of financial instruments, including cash equivalents, are carried at cost, which approximates fair value, and are classified as Level 1. Debt under the Altra Credit Agreement (as defined herein) is classified as Level 2 and is comprised of the Altra Term Loan Facility and the Altra Revolving Credit Facility (both as defined herein). The carrying amount of the Altra Term Loan Facility was $ 910.0 million and the estimated fair value of the Altra Term Loan Facility was $ 904.3 million at September 30, 2021 . There is currently no debt under the Altra Revolving Credit Facility. The carrying amount of the Notes (as defined herein) was $ 400 million and the estimated fair value of the Notes was $ 431.5 million at September 30, 2021. The Notes are classified as Level 2. The Company determines the fair value of financial instruments using quoted market prices whenever available and classified these investments as Level 1. When quoted market prices are not available for various types of financial instruments (such as derivative instruments), the Company uses standard models with market-based inputs, which take into account the present value of estimated future cash flows and the ability of the Company or the financial counterparty to perform. These investments are classified as Level 2. For cross-currency interest rate swaps and interest rate swaps, the significant inputs to these models are interest rate curves for discounting future cash flows and are adjusted for credit risk. See additional discussion of the Company’s use of financial instruments including cross-currency swaps and interest rate swaps included in Note 15. In December 2020, the Company invested $ 5.0 million for a minority equity interest in a privately held manufacturing software company, MTEK Industry AB (“MTEK”), over which the Company does not exert significant influence. The equity investment does not have a readily determinable fair value and does not qualify for the practical expedient to estimate fair value using the net asset value per share. Therefore, in accordance with ASU 2016-01, the Company elected to measure the investment at its cost less impairment, if any, adjusted for observable price changes in orderly transactions for identical or a similar investment of the same issuer. This investment is considered a Level 3 asset based on the lack of observable inputs and is classified within other non-current assets in the consolidated balance sheets. The Company will monitor its equity investment in MTEK for indicators of impairments or upward adjustments on an ongoing basis. If the Company determines that such an indicator is present, an adjustment will be recorded, which will be measured as the difference between the carrying value and estimated fair value. As of September 30, 2021 , there were no indicators that support an adjustment to MTEK’s carrying value.
Net Income Per Share	Basic earnings per share is based on the weighted average number of shares of common stock outstanding, and diluted earnings per share is based on the weighted average number of shares of common stock outstanding and all potentially dilutive common stock equivalents outstanding. Common stock equivalents are included in the per share calculations when the effect of their inclusion is dilutive. The following is a reconciliation of basic to diluted net income per share: Quarter Ended Year to Date Ended September 30, 2021 September 30, 2020 September 30, 2021 September 30, 2020 Net income/(loss) $ 35.4 $ 38.3 $ 115.4 $ ( 56.7 ) Shares used in net income per common share - basic 64.9 64.6 64.8 64.6 Effect of dilutive shares 0.6 0.3 0.6 — Shares used in net income per common share - diluted 65.5 64.9 65.4 64.6 Shares excluded as their inclusion would be anti-dilutive — — — 0.1 Earnings/(Loss) per share: Basic net income $ 0.55 $ 0.59 $ 1.78 $ ( 0.88 ) Diluted net income $ 0.54 $ 0.59 $ 1.76 $ ( 0.88 )
Warranty Costs	Warranty Costs The contractual warranty period of the Company's products generally ranges from three months to two years with certain warranties extending for longer periods. Estimated expenses related to product warranties are accrued at the time products are sold to customers and are recorded in accruals and other current liabilities on the unaudited condensed consolidated balance sheets. Estimates are established using historical information as to the nature, frequency and average costs of warranty claims.

Revenue Recognition (Tables)

Revenue Recognition (Tables)	9 Months Ended
Revenue Recognition (Tables)	Sep. 30, 2021
Revenue From Contract With Customer [Abstract]
Disaggregates Revenue for Each Reportable Segment and Geographic Region	The following table disaggregates our revenue for each reportable segment. The Company believes that disaggregating revenue into these categories achieves the disclosure objective to depict how the nature, amount, timing, and uncertainty of revenue and cash flows are affected by economic factors. Quarter Ended Year to Date Ended September 30, 2021 September 30, 2020 September 30, 2021 September 30, 2020 Power Transmission Technologies $ 232.5 $ 197.7 $ 691.1 $ 610.7 Automation & Specialty 237.8 240.8 741.9 665.2 Inter-segment eliminations ( 1.0 ) ( 0.7 ) ( 3.0 ) ( 3.1 ) Total net sales $ 469.3 $ 437.8 $ 1,430.0 $ 1,272.8 Net sales by geographic region based on point of shipment origin are as follows: Quarter Ended Year to Date Ended September 30, 2021 September 30, 2020 September 30, 2021 September 30, 2020 North America (primarily U.S.) $ 256.1 $ 230.2 $ 758.6 $ 681.3 Europe excluding Germany 83.9 68.8 259.1 214.9 Germany 50.0 44.1 151.5 140.7 China 48.8 56.5 176.9 150.1 Asia and other excluding China 30.5 38.2 83.9 85.8 Total net sales $ 469.3 $ 437.8 $ 1,430.0 $ 1,272.8
Summary of Opening and Closing Balances of Current Contract Liability	The opening and closing balances of the Company’s current contract liabilities as of the year to date periods ended September 30, 2021 and September 30, 2020 are as follows: Year to Date Ended September 30, 2021 September 30, 2020 Beginning balance $ 10.3 $ 8.4 Closing balance 14.3 11.2 Increase $ 4.0 $ 2.8

Changes in Accumulated Other _2

Changes in Accumulated Other Comprehensive Income/(Loss) by Component (Tables)	9 Months Ended
	Sep. 30, 2021
Equity [Abstract]
Reconciliation of Changes in Accumulated Other Comprehensive Income/(Loss) by Component	The following is a reconciliation of changes in accumulated other comprehensive income/(loss) by component for the periods presented: Gains and Defined Cumulative Total Accumulated Other Comprehensive Income (Loss) by Component, June 30, 2021 $ ( 16.8 ) $ ( 2.4 ) $ 22.9 $ 3.7 Reclassification of interest rate swap to income, net of tax 2.2 — — 2.2 Pension adjustments, net of tax — 0.4 — 0.4 Amortization of actuarial gain (losses), net of tax — 0.1 — 0.1 Foreign currency translation adjustments, net of tax — — ( 22.3 ) ( 22.3 ) Net current-period Other Comprehensive Income (Loss) 2.2 0.5 ( 22.3 ) ( 19.6 ) Accumulated Other Comprehensive Income (Loss) by Component, September 30, 2021 $ ( 14.6 ) $ ( 1.9 ) $ 0.6 $ ( 15.9 ) Gains and Defined Cumulative Total Accumulated Other Comprehensive Income (Loss) by Component, January 1, 2021 $ ( 21.5 ) $ ( 3.7 ) $ 46.3 $ 21.1 Reclassification of interest rate swap to income, net of tax 6.9 — — 6.9 Pension adjustments, net of tax — 1.6 — 1.6 Amortization of actuarial gain (losses), net of tax — 0.2 — 0.2 Foreign currency translation adjustments, net of tax — — ( 45.7 ) ( 45.7 ) Net current-period Other Comprehensive Income (Loss) 6.9 1.8 ( 45.7 ) ( 37.0 ) Accumulated Other Comprehensive Income (Loss) by Component, September 30, 2021 $ ( 14.6 ) $ ( 1.9 ) $ 0.6 $ ( 15.9 ) Gains and Defined Cumulative Total Accumulated Other Comprehensive Loss by Component, June 30, 2020 $ ( 26.7 ) $ ( 1.6 ) $ ( 71.8 ) $ ( 100.1 ) Reclassification of interest rate swap to income, net of tax 2.6 — — 2.6 Pension adjustments, net of tax — 0.2 — 0.2 Foreign currency translation adjustments, net of tax — — 47.6 47.6 Net current-period Other Comprehensive Income (Loss) 2.6 0.2 47.6 50.4 Accumulated Other Comprehensive Loss by Component, September 30, 2020 $ ( 24.1 ) $ ( 1.4 ) $ ( 24.2 ) $ ( 49.7 ) Gains and Defined Cumulative Total Accumulated Other Comprehensive (Loss) by Component, January 1, 2020 $ ( 16.5 ) $ ( 1.5 ) $ ( 71.9 ) $ ( 89.9 ) Change in fair value of interest rate swap, net of tax ( 11.9 ) — — ( 11.9 ) Reclassification of interest rate swap to income, net of tax 4.3 — — 4.3 Pension adjustments, net of tax — 0.1 — 0.1 Foreign currency translation adjustments, net of tax — — 16.4 16.4 Change in fair value of net investment hedge, net of tax — — 31.3 31.3 Net current-period Other Comprehensive Income (Loss) ( 7.6 ) 0.1 47.7 40.2 Accumulated Other Comprehensive Loss by Component, September 30, 2020 $ ( 24.1 ) $ ( 1.4 ) $ ( 24.2 ) $ ( 49.7 )

Net Income per Share (Tables)

Net Income per Share (Tables)	9 Months Ended
Net Income per Share (Tables)	Sep. 30, 2021
Earnings Per Share [Abstract]
Reconciliation of Basic to Diluted Net Income per Share	The following is a reconciliation of basic to diluted net income per share: Quarter Ended Year to Date Ended September 30, 2021 September 30, 2020 September 30, 2021 September 30, 2020 Net income/(loss) $ 35.4 $ 38.3 $ 115.4 $ ( 56.7 ) Shares used in net income per common share - basic 64.9 64.6 64.8 64.6 Effect of dilutive shares 0.6 0.3 0.6 — Shares used in net income per common share - diluted 65.5 64.9 65.4 64.6 Shares excluded as their inclusion would be anti-dilutive — — — 0.1 Earnings/(Loss) per share: Basic net income $ 0.55 $ 0.59 $ 1.78 $ ( 0.88 ) Diluted net income $ 0.54 $ 0.59 $ 1.76 $ ( 0.88 )

Inventories (Tables)

Inventories (Tables)	9 Months Ended
Inventories (Tables)	Sep. 30, 2021
Inventory Disclosure [Abstract]
Summary of Inventories	Inventories at September 30, 2021 and December 31, 2020 consisted of the following: September 30, 2021 December 31, 2020 Raw materials $ 128.6 $ 95.2 Work in process 25.7 22.1 Finished goods 102.7 93.1 $ 257.0 $ 210.4

Goodwill and Intangible Assets

Goodwill and Intangible Assets (Tables)	9 Months Ended
Goodwill and Intangible Assets (Tables)	Sep. 30, 2021
Goodwill And Intangible Assets Disclosure [Abstract]
Changes in Goodwill	Changes in goodwill from January 1, 2021 through September 30, 2021 were as follows: Power Automation Total Goodwill $ 452.4 $ 1,314.5 $ 1,766.9 Accumulated impairment loss ( 31.8 ) ( 139.1 ) ( 170.9 ) Balance January 1, 2021 $ 420.6 $ 1,175.4 $ 1,596.0 Impact of changes in foreign currency ( 7.1 ) ( 14.5 ) ( 21.6 ) Net goodwill balance September 30, 2021 $ 413.5 $ 1,160.9 $ 1,574.4
Other Intangible Assets	Other intangible assets as of September 30, 2021 and December 31, 2020 consisted of the following: September 30, 2021 December 31, 2020 Cost Accumulated Net Cost Accumulated Net Other intangible assets Intangible assets not subject to amortization: Tradenames and trademarks $ 255.0 $ — $ 255.0 $ 259.7 $ — $ 259.7 Intangible assets subject to amortization: In-process research and development 16.0 — 16.0 16.0 — 16.0 Customer relationships 1,202.6 228.2 974.4 1,220.2 195.0 1,025.2 Product technology and patents 211.4 67.8 143.6 211.2 52.5 158.7 Total intangible assets $ 1,685.0 $ 296.0 $ 1,389.0 $ 1,707.1 $ 247.5 $ 1,459.6

Warranty Costs (Tables)

Warranty Costs (Tables)	9 Months Ended
Warranty Costs (Tables)	Sep. 30, 2021
Guarantees [Abstract]
Changes in Carrying Amount of Accrued Product Warranty Costs	Changes in the carrying amount of accrued product warranty costs for the year to date periods ended September 30, 2021 and 2020 are as follows: September 30, 2021 September 30, 2020 Balance at beginning of period $ 9.6 $ 10.0 Accrued current period warranty expense 2.7 2.7 Payments and adjustments ( 2.0 ) ( 2.9 ) Balance at end of period $ 10.3 $ 9.8

Debt (Tables)

Debt (Tables)	9 Months Ended
Debt (Tables)	Sep. 30, 2021
Debt Disclosure [Abstract]
Outstanding Debt Obligations	Outstanding debt obligations at September 30, 2021 and December 31, 2020 were as follows: September 30, 2021 December 31, 2020 Debt: Term loan $ 910.0 $ 1,030.0 Notes 400.0 400.0 Mortgages and other 11.8 12.9 Finance leases 0.2 0.3 Total gross debt 1,322.0 1,443.2 Less: debt discount and deferred financing ( 15.5 ) ( 18.5 ) Total debt, net of debt discount and 1,306.5 1,424.7 Less: current portion of long-term debt ( 16.8 ) ( 16.6 ) Total long-term debt $ 1,289.7 $ 1,408.1

Stockholders' Equity (Tables)

Stockholders' Equity (Tables)	9 Months Ended
Stockholders' Equity (Tables)	Sep. 30, 2021
Stockholders Equity Note [Abstract]
Summary of Stock Option Activity	The following table summarizes the stock option activity under the Company’s plan for the year to date period ended September 30, 2021: Weighted Options Weighted- Aggregate Outstanding at January 1, 2021 460.7 $ 32.48 Granted 124.7 59.40 Exercised ( 72.2 ) 30.72 Canceled/Forfeited ( 13.2 ) 39.43 Outstanding at September 30, 2021 8.3 500.0 $ 39.26 $ 9.0 Exercisable at September 30, 2021 8.0 231.3 $ 35.83 $ 4.9 Unvested and expected to vest at September 30, 2021 8.4 249.4 $ 41.99 $ 3.9
Summary of Restricted Stock Unit Activity	The following table summarizes the Restricted Stock Unit activity under the Company’s plan for the year to date period ended September 30, 2021: Shares Weighted- Aggregate Unvested at January 1, 2021 515.8 $ 35.11 Granted 152.3 59.64 Vested ( 221.3 ) 38.40 Canceled/Forfeited ( 24.4 ) 40.22 Unvested at September 30, 2021 422.4 $ 41.96 $ 23.9
Summary of Performance Share Awards Activity	The following table summarizes the Performance Share Award activity under the Company’s plan for the year to date period ended September 30, 2021: Shares Weighted- Aggregate Unvested at January 1, 2021 268.0 $ 34.38 Granted 63.3 64.43 Vested ( 28.3 ) 45.80 Canceled/Forfeited ( 8.0 ) 39.71 Unvested at September 30, 2021 295.0 $ 39.50 $ 16.7

Restructuring Costs (Tables)

Restructuring Costs (Tables)	9 Months Ended
Restructuring Costs (Tables)	Sep. 30, 2021
Restructuring And Related Activities [Abstract]
Reconciliation of Accrued Restructuring Costs	The following is a reconciliation of the accrued restructuring costs between January 1, 2021 and September 30, 2021: 2017 Altra 2019 Altra Total All Balance at January 1, 2021 $ 0.5 $ 1.8 $ 2.3 Restructuring expense incurred — 0.9 0.9 Cash payments ( 0.1 ) ( 1.4 ) ( 1.5 ) Balance at March 31, 2021 0.4 1.3 1.7 Restructuring expense incurred — 0.8 0.8 Cash payments ( 0.1 ) ( 1.3 ) ( 1.4 ) Balance at June 30, 2021 0.3 0.8 1.1 Restructuring expense incurred — 0.7 0.7 Cash payments ( 0.1 ) ( 1.1 ) ( 1.2 ) Balance at September 30, 2021 $ 0.2 $ 0.4 $ 0.6 The following is a reconciliation of the accrued restructuring costs between January 1, 2020 and September 30, 2020: 2017 Altra 2019 Altra Total All Balance at January 1, 2020 $ 1.5 $ 2.6 $ 4.1 Restructuring expense incurred 0.2 1.4 1.6 Cash payments ( 0.4 ) ( 1.4 ) ( 1.8 ) Balance at March 31, 2020 1.3 2.6 3.9 Restructuring expense incurred 0.3 1.2 1.5 Cash payments ( 0.6 ) ( 1.1 ) ( 1.7 ) Balance at June 30, 2020 1.0 2.7 3.7 Restructuring expense incurred — 2.4 2.4 Cash payments ( 0.2 ) ( 2.9 ) ( 3.1 ) Balance at September 30, 2020 $ 0.8 $ 2.2 $ 3.0
Reconciliation of Restructuring Expense by Segment	The following is a reconciliation of restructuring expense by segment for the quarter ended September 30, 2021: 2017 Altra 2019 Altra Total All Power Transmission Technologies $ — $ 0.4 $ 0.4 Automation & Specialty — 0.3 0.3 Total restructuring expense $ — $ 0.7 $ 0.7 The following is a reconciliation of restructuring expense by segment for the quarter ended September 30, 2020: 2017 Altra 2019 Altra Total All Power Transmission Technologies $ — $ 2.0 $ 2.0 Automation & Specialty — 0.4 0.4 Total restructuring expense $ — $ 2.4 $ 2.4 The following is a reconciliation of restructuring expense by segment for the year to date period ended September 30, 2021 2017 Altra 2019 Altra Total All Power Transmission Technologies $ — $ 1.4 $ 1.4 Automation & Specialty — 1.0 1.0 Total restructuring expense $ — $ 2.4 $ 2.4 The following is a reconciliation of restructuring expense by segment for the year to date period ended September 30, 2020: 2017 Altra 2019 Altra Total All Power Transmission Technologies $ 0.5 $ 2.6 $ 3.1 Automation & Specialty — 2.4 2.4 Total restructuring expense $ 0.5 $ 5.0 $ 5.5

Segments, Concentrations and _2

Segments, Concentrations and Geographic Information (Tables)	9 Months Ended
	Sep. 30, 2021
Segment Reporting [Abstract]
Segment Financial Information and Reconciliation of Segments Revenue to Unaudited Condensed Consolidated Revenue	Segment financial information and a reconciliation of segment results to unaudited condensed consolidated results are as follows: Quarter Ended Year to Date Ended September 30, 2021 September 30, 2020 September 30, 2021 September 30, 2020 Net Sales: Power Transmission Technologies $ 232.5 $ 197.7 $ 691.1 $ 610.7 Automation & Specialty 237.8 240.8 741.9 665.2 Inter-segment eliminations ( 1.0 ) ( 0.7 ) ( 3.0 ) ( 3.1 ) Net sales $ 469.3 $ 437.8 $ 1,430.0 $ 1,272.8 Income/(loss) from operations: Segment earnings: Power Transmission Technologies $ 36.5 $ 23.5 $ 97.9 $ 73.0 Automation & Specialty 30.6 44.6 109.4 ( 48.0 ) Corporate expenses (1) ( 4.6 ) ( 0.3 ) ( 12.5 ) — Restructuring costs ( 0.7 ) ( 2.4 ) ( 2.4 ) ( 5.5 ) Income/(loss) from operations $ 61.8 $ 65.4 $ 192.4 $ 19.5 Other non-operating expense: Net interest expense 16.1 18.0 49.5 54.2 Other non-operating (income)/expense, net 0.1 ( 0.3 ) ( 3.1 ) 0.8 Total non-operating expense $ 16.2 $ 17.7 $ 46.4 $ 55.0 Income/(loss) before income taxes 45.6 47.7 146.0 ( 35.5 ) Provision for income taxes 10.2 9.4 30.6 21.2 Net income/(loss) $ 35.4 $ 38.3 $ 115.4 $ ( 56.7 ) (1) Certain expenses are maintained at the corporate level and are not allocated to the segments. These include various administrative expenses related to the Company’s corporate headquarters, certain U.S. healthcare costs and credits, depreciation on capitalized software costs, non-capitalizable software implementation costs and acquisition related expenses.
Reconciliation of Segment Assets to Consolidated Assets	Selected information by segment (continued): Quarter Ended Year to Date Ended September 30, 2021 September 30, 2020 September 30, 2021 September 30, 2020 Depreciation and amortization: Power Transmission Technologies $ 7.8 $ 8.2 $ 23.8 $ 24.6 Automation & Specialty 22.2 23.3 66.5 69.4 Corporate 0.6 0.9 2.0 2.5 Total depreciation and amortization $ 30.6 $ 32.4 $ 92.3 $ 96.5 September 30, 2021 September 30, 2020 Total assets: Power Transmission Technologies $ 1,064.3 $ 1,054.2 Automation & Specialty 2,962.8 2,956.0 Corporate (2) 134.1 135.7 Total assets $ 4,161.2 $ 4,145.9 (2) Corporate assets are primarily cash and cash equivalents, tax related asset accounts, certain capitalized software costs, and property, plant and equipment.
Net Sales to Third Parties by Geographic Region	Net sales to third parties by geographic region are as follows: Net Sales Quarter Ended Year to Date Ended September 30, 2021 September 30, 2020 September 30, 2021 September 30, 2020 North America (primarily U.S.) $ 256.1 $ 230.2 $ 758.6 $ 681.3 Europe excluding Germany 83.9 68.8 259.1 214.9 Germany 50.0 44.1 151.5 140.7 China 48.8 56.5 176.9 150.1 Asia and other excluding China 30.5 38.2 83.9 85.8 Total $ 469.3 $ 437.8 $ 1,430.0 $ 1,272.8

Derivative Financial Instrume_2

Derivative Financial Instruments (Tables)	9 Months Ended
Derivative Financial Instruments (Tables)	Sep. 30, 2021
Derivative Instruments And Hedging Activities Disclosure [Abstract]
Summary of Balance of Company's Derivative Instruments Designated as Cash Flow Hedge	The following table summarizes the balance of the Company's derivative instruments designated as cash flow hedges (in millions): September 30, 2021 December 31, 2020 Cash flow hedge: Amount of Loss in AOCIL Interest rate swap agreement $ ( 16.7 ) $ ( 25.7 )

Organization and Nature of Op_2

Organization and Nature of Operations - Additional Information (Detail)	9 Months Ended
	Sep. 30, 2021Country
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Number of countries in which the company has production facilities	16

Revenue Recognition - Additiona

Revenue Recognition - Additional Information (Detail)	9 Months Ended
Revenue Recognition - Additional Information (Detail)	Sep. 30, 2021Channel
Revenue From Contract With Customer [Abstract]
Number of distribution channels	3

Revenue Recognition - Disaggreg

Revenue Recognition - Disaggregates Revenue for Each Reportable Segment and Geographic Region (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Disaggregation Of Revenue [Line Items]
Net sales	$ 469.3	$ 437.8	$ 1,430	$ 1,272.8
North America (primarily U.S.) [Member]
Disaggregation Of Revenue [Line Items]
Net sales	256.1	230.2	758.6	681.3
Europe Excluding Germany [Member]
Disaggregation Of Revenue [Line Items]
Net sales	83.9	68.8	259.1	214.9
Germany [Member]
Disaggregation Of Revenue [Line Items]
Net sales	50	44.1	151.5	140.7
China [Member]
Disaggregation Of Revenue [Line Items]
Net sales	48.8	56.5	176.9	150.1
Asia and Other Excluding China [Member]
Disaggregation Of Revenue [Line Items]
Net sales	30.5	38.2	83.9	85.8
Operating Segments [Member] \| Power Transmission Technologies [Member]
Disaggregation Of Revenue [Line Items]
Net sales	232.5	197.7	691.1	610.7
Operating Segments [Member] \| Automation & Specialty [Member]
Disaggregation Of Revenue [Line Items]
Net sales	237.8	240.8	741.9	665.2
Intersegment Eliminations [Member]
Disaggregation Of Revenue [Line Items]
Net sales	$ (1)	$ (0.7)	$ (3)	$ (3.1)

Revenue Recognition - Summary o

Revenue Recognition - Summary of Opening and Closing Balances of Current Contract Liability (Detail) - ASU 2014-09 [Member] - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020
Disaggregation Of Revenue [Line Items]
Beginning balance	$ 10.3	$ 8.4
Closing balance	14.3	11.2
Increase	$ 4	$ 2.8

Fair Value of Financial Instr_2

Fair Value of Financial Instruments - Additional Information (Detail) - USD ($)	9 Months Ended
	Sep. 30, 2021	Dec. 31, 2020
MTEK [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Minority equity interest in a privately held manufacturing software company	$ 5,000,000
Notes [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Debt	400,000,000	$ 400,000,000
Estimated fair value	431,500,000
Altra Credit Agreement [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Debt	910,000,000	$ 1,030,000,000
Outstanding debt under credit facility	910,000,000
Altra Credit Agreement [Member] \| Altra Term Loan Facility [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Debt	910,000,000
Estimated fair value	904,300,000
Altra Credit Agreement [Member] \| Revolving Credit Facility [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Outstanding debt under credit facility	$ 0

Changes in Accumulated Other _3

Changes in Accumulated Other Comprehensive Income/(Loss) by Component - Reconciliation of Changes in Accumulated Other Comprehensive Income/(Loss) by Component (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Accumulated Other Comprehensive Income (Loss) by Component			$ 21.1
Beginning balance	$ 2,056.7	$ 1,808.5	1,996.7	$ 1,922.3	$ 1,922.3
Change in fair value of interest rate swap, net of tax				(11.9)
Reclassification of interest rate swap, net of tax	2.2	2.6	6.9	4.3
Pension liability adjustment, net of tax	0.4	0.2	1.6	0.1
Amortization of actuarial gain (losses), net of tax	0.1		0.2
Foreign currency translation adjustment	(22.3)	47.6	(45.7)	16.4
Change in fair value of net investment hedge, net of tax				31.3
Net current-period Other Comprehensive Income (Loss)	(19.6)	50.4	(37)	40.2
Accumulated Other Comprehensive Income (Loss) by Component	(15.9)		(15.9)		21.1
Ending balance	2,068.4	1,895.8	2,068.4	1,895.8	1,996.7
Gains and Losses on Cash Flow Hedges [Member]
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Accumulated Other Comprehensive Income (Loss) by Component	(16.8)	(26.7)	(21.5)	(16.5)	(16.5)
Change in fair value of interest rate swap, net of tax				(11.9)
Reclassification of interest rate swap, net of tax	2.2	2.6	6.9	4.3
Net current-period Other Comprehensive Income (Loss)	2.2	2.6	6.9	(7.6)
Accumulated Other Comprehensive Income (Loss) by Component	(14.6)	(24.1)	(14.6)	(24.1)	(21.5)
Defined Benefit Pension Plans [Member]
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Accumulated Other Comprehensive Income (Loss) by Component	(2.4)	(1.6)	(3.7)	(1.5)	(1.5)
Pension liability adjustment, net of tax	0.4	0.2	1.6	0.1
Amortization of actuarial gain (losses), net of tax	0.1		0.2
Net current-period Other Comprehensive Income (Loss)	0.5	0.2	1.8	0.1
Accumulated Other Comprehensive Income (Loss) by Component	(1.9)	(1.4)	(1.9)	(1.4)	(3.7)
Cumulative Foreign Currency Translation Adjustment [Member]
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Accumulated Other Comprehensive Income (Loss) by Component	22.9	(71.8)	46.3	(71.9)	(71.9)
Foreign currency translation adjustment	(22.3)	47.6	(45.7)	16.4
Change in fair value of net investment hedge, net of tax				31.3
Net current-period Other Comprehensive Income (Loss)	(22.3)	47.6	(45.7)	47.7
Accumulated Other Comprehensive Income (Loss) by Component	0.6	(24.2)	0.6	(24.2)	46.3
Accumulated Other Comprehensive Income (Loss) [Member]
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	3.7	(100.1)	21.1	(89.9)	(89.9)
Ending balance	$ (15.9)	$ (49.7)	$ (15.9)	$ (49.7)	$ 21.1

Changes in Accumulated Other _4

Changes in Accumulated Other Comprehensive Income/(Loss) by Component - Additional Information (Detail) $ in Millions	9 Months Ended
	Sep. 30, 2020USD ($)
Equity [Abstract]
Change in fair value of net investment hedge	$ 31.3

Net Income per Share - Reconcil

Net Income per Share - Reconciliation of Basic to Diluted Net Income per Share (Detail) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Earnings Per Share [Abstract]
Net income/(loss)	$ 35.4	$ 38.3	$ 115.4	$ (56.7)
Shares used in net income per common share - basic	64.9	64.6	64.8	64.6
Effect of dilutive shares	0.6	0.3	0.6
Shares used in net income per common share - diluted	65.5	64.9	65.4	64.6
Shares excluded as their inclusion would be anti-dilutive				0.1
Earnings/(Loss) per share:
Basic net income	$ 0.55	$ 0.59	$ 1.78	$ (0.88)
Diluted net income	$ 0.54	$ 0.59	$ 1.76	$ (0.88)

Inventories - Summary of Invent

Inventories - Summary of Inventories (Detail) - USD ($) $ in Millions	Sep. 30, 2021	Dec. 31, 2020
Inventory Disclosure [Abstract]
Raw materials	$ 128.6	$ 95.2
Work in process	25.7	22.1
Finished goods	102.7	93.1
Inventories, net	$ 257	$ 210.4

Goodwill and Intangible Asset_2

Goodwill and Intangible Assets - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Goodwill And Intangible Assets [Line Items]
Amortization expense	$ 17.6	$ 17.5	$ 52.9	$ 52.3
Estimated amortization expense, remainder of 2021	17.7		17.7
Estimated amortization expense, year 2022	71.4		71.4
Estimated amortization expense, year 2023	71.1		71.1
Estimated amortization expense, year 2024	70.8		70.8
Estimated amortization expense, year 2025	70.5		70.5
Estimated amortization expense, thereafter	$ 832.5		$ 832.5
Thomson Reporting Unit [Member]
Goodwill And Intangible Assets [Line Items]
Reporting unit, percentage of fair value in excess of carrying amount	10.00%		10.00%
All Other Reporting Units [Member]
Goodwill And Intangible Assets [Line Items]
Reporting unit, percentage of fair value in excess of carrying amount	10.00%		10.00%

Goodwill and Intangible Asset_3

Goodwill and Intangible Assets - Changes in Goodwill (Detail) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2021	Dec. 31, 2020
Goodwill [Roll Forward]
Goodwill		$ 1,766.9
Accumulated impairment loss		(170.9)
Goodwill, Beginning balance	$ 1,596
Impact of changes in foreign currency	(21.6)
Net goodwill, ending balance	1,574.4
Power Transmission Technologies [Member]
Goodwill [Roll Forward]
Goodwill		452.4
Accumulated impairment loss		(31.8)
Goodwill, Beginning balance	420.6
Impact of changes in foreign currency	(7.1)
Net goodwill, ending balance	413.5
Automation & Specialty [Member]
Goodwill [Roll Forward]
Goodwill		1,314.5
Accumulated impairment loss		$ (139.1)
Goodwill, Beginning balance	1,175.4
Impact of changes in foreign currency	(14.5)
Net goodwill, ending balance	$ 1,160.9

Goodwill and Intangible Asset_4

Goodwill and Intangible Assets - Other Intangible Assets (Detail) - USD ($) $ in Millions	Sep. 30, 2021	Dec. 31, 2020
Schedule Of Finite And Indefinite Lived Intangible Assets [Line Items]
Total intangible assets, cost	$ 1,685	$ 1,707.1
Total intangible assets, accumulated amortization	296	247.5
Total intangible assets, net	1,389	1,459.6
In-process Research and Development [Member]
Schedule Of Finite And Indefinite Lived Intangible Assets [Line Items]
Intangible assets subject to amortization, cost	16	16
Intangible assets subject to amortization, net	16	16
Customer Relationships [Member]
Schedule Of Finite And Indefinite Lived Intangible Assets [Line Items]
Intangible assets subject to amortization, cost	1,202.6	1,220.2
Total intangible assets, accumulated amortization	228.2	195
Intangible assets subject to amortization, net	974.4	1,025.2
Product Technology and Patents [Member]
Schedule Of Finite And Indefinite Lived Intangible Assets [Line Items]
Intangible assets subject to amortization, cost	211.4	211.2
Total intangible assets, accumulated amortization	67.8	52.5
Intangible assets subject to amortization, net	143.6	158.7
Tradenames and Trademarks [Member]
Schedule Of Finite And Indefinite Lived Intangible Assets [Line Items]
Intangible assets not subject to amortization, cost	$ 255	$ 259.7

Warranty Costs - Additional Inf

Warranty Costs - Additional Information (Detail)	9 Months Ended
Warranty Costs - Additional Information (Detail)	Sep. 30, 2021
Minimum [Member]
Guarantor Obligations [Line Items]
Product warranty period	3 months
Maximum [Member]
Guarantor Obligations [Line Items]
Product warranty period	2 years

Warranty Costs - Changes in Car

Warranty Costs - Changes in Carrying Amount of Accrued Product Warranty Costs (Detail) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020
Movement in Liabilities for Guarantees on Long-Duration Contracts, Guaranteed Benefit Liability, Gross [Roll Forward]
Balance at beginning of period	$ 9.6	$ 10
Accrued current period warranty expense	2.7	2.7
Payments and adjustments	(2)	(2.9)
Balance at end of period	$ 10.3	$ 9.8

Debt - Outstanding Debt Obligat

Debt - Outstanding Debt Obligations (Detail) - USD ($) $ in Millions	Sep. 30, 2021	Dec. 31, 2020
Debt Instrument [Line Items]
Finance leases	$ 0.2	$ 0.3
Total gross debt	1,322	1,443.2
Less: debt discount and deferred financing costs	(15.5)	(18.5)
Total debt, net of debt discount and deferred financing costs	1,306.5	1,424.7
Less: current portion of long-term debt	(16.8)	(16.6)
Total long-term debt	1,289.7	1,408.1
Term Loan [Member]
Debt Instrument [Line Items]
Debt	910	1,030
Notes [Member]
Debt Instrument [Line Items]
Debt	400	400
Mortgages and Other [Member]
Debt Instrument [Line Items]
Debt	$ 11.8	$ 12.9

Debt - Additional Information (

Debt - Additional Information (Detail)	Oct. 01, 2018USD ($)Company	Sep. 30, 2021USD ($)	Sep. 30, 2020USD ($)	Dec. 31, 2020USD ($)	May 27, 2020USD ($)	Apr. 27, 2020USD ($)	Apr. 14, 2020USD ($)	Mar. 16, 2020USD ($)	Mar. 09, 2020USD ($)
Debt Instrument [Line Items]
Amortization of deferred financing costs		$ 3,500,000	$ 3,400,000
Finance lease obligations		$ 200,000		$ 300,000
Mortgages and Other Agreements [Member]
Debt Instrument [Line Items]
Description about maturity date of debt instrument		The debt has interest rates that range from 1.0% to 2.5%, with various quarterly and monthly installments through 2028.
Minimum [Member] \| Mortgages and Other Agreements [Member]
Debt Instrument [Line Items]
Debt instrument, interest rate percentage		1.00%
Maximum [Member] \| Mortgages and Other Agreements [Member]
Debt Instrument [Line Items]
Debt instrument, interest rate percentage		2.50%
Altra Credit Agreement [Member]
Debt Instrument [Line Items]
Amortization of deferred financing costs		$ 29,900,000
Notice provided to administrate agent of credit facility to draw amount								$ 50,000,000	$ 50,000,000
Notice provided to administrate agent of credit facility to repay outstanding amount					$ 35,000,000	$ 15,000,000	$ 50,000,000
Outstanding debt		910,000,000
Letters of credit outstanding		$ 4,800,000		$ 4,500,000
Altra Credit Agreement [Member] \| Altra Term Loan Facility [Member]
Debt Instrument [Line Items]
Debt instrument, term	7 years
Maximum amount available	$ 1,340,000,000
Debt instrument, description of variable rate basis		Borrowings under the Altra Term Loan Facility will bear interest at a per annum rate equal to a “Eurocurrency Rate” plus 2.00%, in the case of Eurocurrency Rate borrowings, or equal to a “Base Rate” plus 1.00%, in the case of Base Rate borrowings.
Credit facility, commitment fee description		the Company will be required to pay fees that will fluctuate between 0.250% per annum to 0.375% per annum on the unused amount of the Altra Revolving Credit Facility, based upon the Company’s senior secured net leverage ratio
Line of credit facility, interest rate during period		2.084%
Altra Credit Agreement [Member] \| Altra Term Loan Facility [Member] \| Eurocurrency Rate [Member]
Debt Instrument [Line Items]
Applicable margins for loans	2.00%
Altra Credit Agreement [Member] \| Altra Term Loan Facility [Member] \| Base Rate [Member]
Debt Instrument [Line Items]
Applicable margins for loans	1.00%
Altra Credit Agreement [Member] \| Altra Term Loan Facility [Member] \| Minimum [Member]
Debt Instrument [Line Items]
Credit facility, unused capacity, commitment fee percentage	0.25%
Altra Credit Agreement [Member] \| Altra Term Loan Facility [Member] \| Maximum [Member]
Debt Instrument [Line Items]
Credit facility, unused capacity, commitment fee percentage	0.375%
Altra Credit Agreement [Member] \| Altra Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Debt instrument, term	5 years
Maximum amount available	$ 300,000,000
Debt instrument, description of variable rate basis		Borrowings under the Altra Revolving Credit Facility will initially bear interest at a per annum rate equal to a Eurocurrency Rate plus 2.00%, in the case of Eurocurrency Rate borrowings, or equal to a Base Rate plus 1.00%, in the case of Base Rate borrowings
Amount available under credit facility		$ 295,200,000
Altra Credit Agreement [Member] \| Altra Revolving Credit Facility [Member] \| Eurocurrency Rate [Member]
Debt Instrument [Line Items]
Applicable margins for loans	2.00%
Altra Credit Agreement [Member] \| Altra Revolving Credit Facility [Member] \| Base Rate [Member]
Debt Instrument [Line Items]
Applicable margins for loans	1.00%
A&S Business [Member]
Debt Instrument [Line Items]
Business combination, number of operating companies in transaction \| Company	4
A&S Business [Member] \| 6.125% Senior Notes Due 2026 [Member] \| Newco [Member]
Debt Instrument [Line Items]
Debt instrument, aggregate principal amount	$ 400,000,000
Debt instrument, interest rate percentage	6.125%
Debt instrument, maturity date	Oct. 1, 2026
Debt instrument, interest payment terms		Interest on the Notes accrues from October 1, 2018, and the first interest payment date on the Notes was on April 1, 2019. The Notes may be redeemed at the option of the issuer on or after October 1, 2023.
Debt instrument, first interest payment date	Apr. 1, 2019
Debt instrument, redemption, description		The Notes may be redeemed at the option of the issuer on or after October 1, 2023
Debt instrument, redemption period, start date	Oct. 1, 2023

Stockholders' Equity - Addition

Stockholders' Equity - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020	Oct. 01, 2018	Sep. 30, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock, shares authorized (in shares)	120,000,000		120,000,000		120,000,000	120,000,000	90,000,000
Common stock, shares issued (in shares)	64,915,615		64,915,615		64,676,567
Common stock, shares outstanding (in shares)	64,915,615		64,915,615		64,676,567
Preferred Stock, shares authorized (in shares)	10,000,000		10,000,000
Preferred Stock, shares issued (in shares)	0		0		0
Preferred Stock, shares outstanding (in shares)	0		0		0
Compensation expense	$ 3.5	$ 3.2	$ 11	$ 10.3
Remaining compensation cost yet to be recognized	$ 23.5		$ 23.5
Remaining compensation cost yet to be recognized , period			3 years
Cash proceeds from exercise of stock options			$ 2.2
2014 Plan [Member] \| Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares of common stock available for delivery pursuant to the grant of awards (in shares)	4,100,000		4,100,000
2014 Plan [Member] \| Restricted Shares and Restricted Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted shares for vesting period			5 years

Stockholders' Equity - Summary

Stockholders' Equity - Summary of Stock Option Activity (Detail) $ / shares in Units, $ in Millions	9 Months Ended
	Sep. 30, 2021USD ($)$ / sharesshares
Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract]
Weighted Average Remaining Contractual Life (in Years)	8 years 3 months 18 days
Weighted Average Remaining Contractual Life (in Years), options exercisable at September 30, 2021	8 years
Weighted Average Remaining Contractual Life (in Years), options unvested and expected to vest at September 30, 2021	8 years 4 months 24 days
Aggregate Intrinsic Value, options outstanding \| $	$ 9
Aggregate Intrinsic Value, options exercisable at September 30, 2021 \| $	4.9
Aggregate Intrinsic Value, options unvested and expected to vest at September 30, 2021 \| $	$ 3.9
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Options outstanding, beginning balance \| shares	460,700
Options granted \| shares	124,700
Options exercised \| shares	(72,200)
Options canceled/forfeited \| shares	(13,200)
Options outstanding, ending balance \| shares	500,000
Options exercisable at September 30, 2021 \| shares	231,300
Options unvested and expected to vest at September 30, 2021 \| shares	249,400
Weighted-average grant date fair value
Weighted-average grant date fair value, options beginning balance \| $ / shares	$ 32.48
Weighted-average grant date fair value, options granted \| $ / shares	59.40
Weighted-average grant date fair value, options exercised \| $ / shares	30.72
Weighted-average grant date fair value, options canceled/forfeited \| $ / shares	39.43
Weighted-average grant date fair value, options ending balance \| $ / shares	39.26
Weighted-average grant date fair value, options exercisable at September 30, 2021 \| $ / shares	35.83
Weighted-average grant date fair value, options unvested and expected to vest at September 30, 2021 \| $ / shares	$ 41.99

Stockholders' Equity - Summar_2

Stockholders' Equity - Summary of Restricted Stock Unit Activity (Detail) - Restricted Stock Units (RSUs) [Member] $ / shares in Units, $ in Millions	9 Months Ended
	Sep. 30, 2021USD ($)$ / sharesshares
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Shares unvested, beginning balance \| shares	515,800
Shares granted \| shares	152,300
Shares vested \| shares	(221,300)
Shares canceled/forfeited \| shares	(24,400)
Shares unvested, ending balance \| shares	422,400
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]
Weighted-average grant date fair value, beginning balance \| $ / shares	$ 35.11
Weighted-average grant date fair value, shares granted \| $ / shares	59.64
Weighted-average grant date fair value, shares vested \| $ / shares	38.40
Weighted-average grant date fair value, shares canceled/forfeited \| $ / shares	40.22
Weighted-average grant date fair value, ending balance \| $ / shares	$ 41.96
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Aggregate Intrinsic Value [Abstract]
Aggregate Intrinsic Value at September 30, 2021 \| $	$ 23.9

Stockholders' Equity - Summar_3

Stockholders' Equity - Summary of Performance Share Awards Activity (Detail) - Performance Share Awards $ / shares in Units, $ in Millions	9 Months Ended
	Sep. 30, 2021USD ($)$ / sharesshares
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Shares unvested, beginning balance \| shares	268,000
Shares granted \| shares	63,300
Shares vested \| shares	(28,300)
Shares canceled/forfeited \| shares	(8,000)
Shares unvested, ending balance \| shares	295,000
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]
Weighted-average grant date fair value, beginning balance \| $ / shares	$ 34.38
Weighted-average grant date fair value, shares granted \| $ / shares	64.43
Weighted-average grant date fair value, shares vested \| $ / shares	45.80
Weighted-average grant date fair value, shares canceled/forfeited \| $ / shares	39.71
Weighted-average grant date fair value, ending balance \| $ / shares	$ 39.50
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Intrinsic Value, Amount Per Share [Abstract]
Aggregate Intrinsic Value at September 30, 2021 \| $	$ 16.7

Restructuring Costs - Additiona

Restructuring Costs - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended						9 Months Ended
	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Sep. 30, 2021	Sep. 30, 2020
Restructuring Cost And Reserve [Line Items]
Restructuring costs	$ 0.7	$ 0.8	$ 0.9	$ 2.4	$ 1.5	$ 1.6	$ 2.4	$ 5.5
2019 Altra Plan [Member]
Restructuring Cost And Reserve [Line Items]
Expected period to incur restructuring expense							2 years
Restructuring costs	0.7	$ 0.8	$ 0.9	$ 2.4	$ 1.2	$ 1.4	$ 2.4	$ 5
2019 Altra Plan [Member] \| Severance [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring costs	0.7						2.4
2019 Altra Plan [Member] \| Minimum [Member]
Restructuring Cost And Reserve [Line Items]
Expected additional restructuring cost remaining	1						1
2019 Altra Plan [Member] \| Maximum [Member]
Restructuring Cost And Reserve [Line Items]
Expected additional restructuring cost remaining	$ 2						$ 2

Restructuring Costs - Reconcili

Restructuring Costs - Reconciliation of Accrued Restructuring Costs (Detail) - USD ($) $ in Millions	3 Months Ended						9 Months Ended
	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Sep. 30, 2021	Sep. 30, 2020
Restructuring Reserve [Roll Forward]
Beginning Balance	$ 1.1	$ 1.7	$ 2.3	$ 3.7	$ 3.9	$ 4.1	$ 2.3	$ 4.1
Restructuring expense incurred	0.7	0.8	0.9	2.4	1.5	1.6	2.4	5.5
Cash payments	(1.2)	(1.4)	(1.5)	(3.1)	(1.7)	(1.8)
Ending Balance	0.6	1.1	1.7	3	3.7	3.9	0.6	3
2017 Altra Plan [Member]
Restructuring Reserve [Roll Forward]
Beginning Balance	0.3	0.4	0.5	1	1.3	1.5	0.5	1.5
Restructuring expense incurred					0.3	0.2		0.5
Cash payments	(0.1)	(0.1)	(0.1)	(0.2)	(0.6)	(0.4)
Ending Balance	0.2	0.3	0.4	0.8	1	1.3	0.2	0.8
2019 Altra Plan [Member]
Restructuring Reserve [Roll Forward]
Beginning Balance	0.8	1.3	1.8	2.7	2.6	2.6	1.8	2.6
Restructuring expense incurred	0.7	0.8	0.9	2.4	1.2	1.4	2.4	5
Cash payments	(1.1)	(1.3)	(1.4)	(2.9)	(1.1)	(1.4)
Ending Balance	$ 0.4	$ 0.8	$ 1.3	$ 2.2	$ 2.7	$ 2.6	$ 0.4	$ 2.2

Restructuring Costs - Summary o

Restructuring Costs - Summary of Reconciliation of Restructuring Expense by Segment (Detail) - USD ($) $ in Millions	3 Months Ended						9 Months Ended
	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Sep. 30, 2021	Sep. 30, 2020
Restructuring Cost And Reserve [Line Items]
Restructuring expense	$ 0.7	$ 0.8	$ 0.9	$ 2.4	$ 1.5	$ 1.6	$ 2.4	$ 5.5
2017 Altra Plan [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring expense					0.3	0.2		0.5
2019 Altra Plan [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring expense	0.7	$ 0.8	$ 0.9	2.4	$ 1.2	$ 1.4	2.4	5
Operating Segments [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring expense	0.7			2.4			2.4	5.5
Operating Segments [Member] \| Power Transmission Technologies [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring expense	0.4			2			1.4	3.1
Operating Segments [Member] \| Automation & Specialty [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring expense	0.3			0.4			1	2.4
Operating Segments [Member] \| 2017 Altra Plan [Member] \| Power Transmission Technologies [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring expense								0.5
Operating Segments [Member] \| 2019 Altra Plan [Member] \| Power Transmission Technologies [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring expense	0.4			2			1.4	2.6
Operating Segments [Member] \| 2019 Altra Plan [Member] \| Automation & Specialty [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring expense	$ 0.3			$ 0.4			$ 1	$ 2.4

Segments, Concentrations and _3

Segments, Concentrations and Geographic Information - Additional Information (Detail)	9 Months Ended
	Sep. 30, 2021Segment
Segment Reporting [Abstract]
Number of reporting segments	2

Segments, Concentrations and _4

Segments, Concentrations and Geographic Information - Segment Financial Information and Reconciliation of Segments Revenue to Unaudited Condensed Consolidated Revenue (Detail) - USD ($) $ in Millions	3 Months Ended						9 Months Ended
	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Sep. 30, 2021	Sep. 30, 2020
Revenues from External Customers and Long-Lived Assets [Line Items]
Net sales	$ 469.3			$ 437.8			$ 1,430	$ 1,272.8
Income/(loss) from operations	61.8			65.4			192.4	19.5
Restructuring costs	(0.7)	$ (0.8)	$ (0.9)	(2.4)	$ (1.5)	$ (1.6)	(2.4)	(5.5)
Net interest expense	16.1			18			49.5	54.2
Other non-operating (income)/expense, net	0.1			(0.3)			(3.1)	0.8
Total other non-operating (income) expense, net	16.2			17.7			46.4	55
Income/(loss) before income taxes	45.6			47.7			146	(35.5)
Provision for income taxes	10.2			9.4			30.6	21.2
Net income/(loss)	35.4			38.3			115.4	(56.7)
Operating Segments [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Restructuring costs	(0.7)			(2.4)			(2.4)	(5.5)
Operating Segments [Member] \| Power Transmission Technologies [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Net sales	232.5			197.7			691.1	610.7
Income/(loss) from operations	36.5			23.5			97.9	73
Restructuring costs	(0.4)			(2)			(1.4)	(3.1)
Operating Segments [Member] \| Automation & Specialty [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Net sales	237.8			240.8			741.9	665.2
Income/(loss) from operations	30.6			44.6			109.4	(48)
Restructuring costs	(0.3)			(0.4)			(1)	(2.4)
Intersegment Eliminations [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Net sales	(1)			(0.7)			(3)	$ (3.1)
Corporate [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Income/(loss) from operations	$ (4.6)			$ (0.3)			$ (12.5)

Segments, Concentrations and _5

Segments, Concentrations and Geographic Information - Reconciliation of Segment Assets to Consolidated Assets (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Revenues from External Customers and Long-Lived Assets [Line Items]
Total depreciation and amortization	$ 30.6	$ 32.4	$ 92.3	$ 96.5
Total assets	4,161.2	4,145.9	4,161.2	4,145.9	$ 4,208.1
Corporate [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Total depreciation and amortization	0.6	0.9	2	2.5
Total assets	134.1	135.7	134.1	135.7
Power Transmission Technologies [Member] \| Operating Segments [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Total depreciation and amortization	7.8	8.2	23.8	24.6
Total assets	1,064.3	1,054.2	1,064.3	1,054.2
Automation & Specialty [Member] \| Operating Segments [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Total depreciation and amortization	22.2	23.3	66.5	69.4
Total assets	$ 2,962.8	$ 2,956	$ 2,962.8	$ 2,956

Segments, Concentrations and _6

Segments, Concentrations and Geographic Information - Net Sales to Third Parties by Geographic Region (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Revenues from External Customers and Long-Lived Assets [Line Items]
Net sales	$ 469.3	$ 437.8	$ 1,430	$ 1,272.8
North America (primarily U.S.) [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Net sales	256.1	230.2	758.6	681.3
Europe Excluding Germany [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Net sales	83.9	68.8	259.1	214.9
Germany [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Net sales	50	44.1	151.5	140.7
China [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Net sales	48.8	56.5	176.9	150.1
Asia and Other Excluding China [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Net sales	$ 30.5	$ 38.2	$ 83.9	$ 85.8

Derivative Financial Instrume_3

Derivative Financial Instruments - Additional Information (Detail) - USD ($) $ in Millions	1 Months Ended	3 Months Ended			9 Months Ended		12 Months Ended
	Jan. 31, 2017	Sep. 30, 2021	Sep. 30, 2020	Mar. 31, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Derivative [Line Items]
Gain (loss) in AOCIL						$ (31.3)
Cross Currency Interest Rate Swap [Member]
Derivative [Line Items]
Proceeds from cross-currency interest rate swaps upon termination				$ 56.2
Paid termination fees				0.9
Gain (loss) in AOCIL					$ 44.8
AOCIL tax expense (benefit)					11.4
Cross Currency Interest Rate Swap [Member] \| Interest Income [Member]
Derivative [Line Items]
Cumulative translation adjustment recognized net interest income (expense), net amount				$ 3.3
Interest Rate Swap [Member]
Derivative [Line Items]
Paid termination fees							$ 0.1
Gain (loss) in AOCIL					(13.5)
AOCIL tax expense (benefit)					3.2
Maturity date of interest rate swap	Jan. 31, 2020
Fair value of swap							34.7
Net interest expense							$ 0.1
Non-cash interest expense from AOCIL to earnings		$ 2.2	$ 2.6		6.9	4.3
Non-cash interest expense, tax benefit from AOCIL to earnings		$ 0.7	0.8		$ 2.1	1.3
Reclassification from AOCIL to earnings			$ 3.4			$ 8.2

Derivative Financial Instrume_4

Derivative Financial Instruments - Summary of Balance of Company's Derivative Instruments Designated as Cash Flow Hedge (Detail) - USD ($) $ in Millions	9 Months Ended		12 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Derivative [Line Items]
Amount of Loss in AOCIL		$ (31.3)
Interest Rate Swap Agreement [Member]
Derivative [Line Items]
Amount of Loss in AOCIL	$ (13.5)
Designated as Hedging Instrument [Member] \| Cash Flow Hedging [Member] \| Interest Rate Swap Agreement [Member]
Derivative [Line Items]
Amount of Loss in AOCIL	$ (16.7)		$ (25.7)

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Detail) - USD ($) $ in Millions	Sep. 30, 2021	Dec. 31, 2020
Commitments And Contingencies Disclosure [Abstract]
Loss contingency accrual	$ 0	$ 0

Subsequent Events - Additional

Subsequent Events - Additional Information (Detail) - $ / shares	Oct. 20, 2021	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Subsequent Event [Line Items]
Cash dividends declared (in USD per share)		$ 0.08	$ 0.04	$ 0.22	$ 0.25
Subsequent Event [Member]
Subsequent Event [Line Items]
Cash dividends declared (in USD per share)	$ 0.08
Dividend declaration date	Oct. 20, 2021
Dividend payable date	Jan. 4, 2022
Dividend record date	Dec. 17, 2021