ON Semiconductor (ON) 10-K 16 Feb 21 2020 FY Annual report Financial data

Cover Page

Cover Page - USD ($)	12 Months Ended
	Dec. 31, 2020	Feb. 10, 2021	Jul. 03, 2020
Document Information [Line Items]
Document Type	10-K
Document Annual Report	true
Document Period End Date	Dec. 31, 2020
Current Fiscal Year End Date	--12-31
Document Transition Report	false
Entity File Number	001-39317
Entity Registrant Name	ON SEMICONDUCTOR CORP
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	36-3840979
Entity Address, Address Line One	5005 E. McDowell Road
Entity Address, City or Town	Phoenix
Entity Address, State or Province	AZ
Entity Address, Postal Zip Code	85008
City Area Code	602
Local Phone Number	244-6600
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
ICFR Auditor Attestation Flag	true
Entity Shell Company	false
Entity Public Float			$ 7,783,044,394
Entity Common Stock, Shares Outstanding		411,881,071
Documents Incorporated by Reference	Documents Incorporated by Reference Portions of the registrant's Definitive Proxy Statement relating to its 2021 Annual Meeting of Stockholders, which is expected to be filed pursuant to Regulation 14A within 120 days after the registrant's fiscal year ended December 31, 2020, are incorporated by reference into Part III of this Form 10-K.
Entity Central Index Key	0001097864
Document Fiscal Period Focus	FY
Document Fiscal Year Focus	2020
Amendment Flag	false
Common Stock
Document Information [Line Items]
Title of 12(b) Security	Common Stock, par value $0.01 per share
Trading Symbol	ON
Security Exchange Name	NASDAQ
Series B Preferred Stock
Document Information [Line Items]
Title of 12(b) Security	Preferred Stock, Series B Junior Participating, Purchase Rights
Security Exchange Name	NASDAQ

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Assets
Cash and cash equivalents	$ 1,080.7	$ 894.2
Receivables, net	676	705
Inventories	1,251.4	1,232.4
Other current assets	176	188.4
Total current assets	3,184.1	3,020
Property, plant and equipment, net	2,512.3	2,591.6
Goodwill	1,663.4	1,659.2
Intangible assets, net	469	590.5
Deferred tax assets	429	307.8
Other assets	410.2	256.4
Total assets	8,668	8,425.5
Liabilities, Non-Controlling Interest and Stockholders’ Equity
Accounts payable	572.9	543.6
Accrued expenses and other current liabilities	570	538.8
Current portion of long-term debt	531.6	736
Total current liabilities	1,674.5	1,818.4
Long-term debt	2,959.7	2,876.5
Deferred tax liabilities	57.3	60.2
Other long-term liabilities	418.4	346.3
Total liabilities	5,109.9	5,101.4
Commitments and contingencies (Note 13)
ON Semiconductor Corporation stockholders’ equity:
Common stock ($0.01 par value, 1,250,000,000 shares authorized, 570,766,439 and 565,562,607 shares issued, 411,842,629 and 411,312,664 shares outstanding, respectively)	5.7	5.7
Additional paid-in capital	4,133.1	3,809.5
Accumulated other comprehensive loss	(57.6)	(54.3)
Accumulated earnings	1,425.5	1,191.3
Less: Treasury stock, at cost; 158,923,810 and 154,249,943 shares, respectively	(1,968.2)	(1,650.5)
Total ON Semiconductor Corporation stockholders’ equity	3,538.5	3,301.7
Non-controlling interest	19.6	22.4
Total stockholders' equity	3,558.1	3,324.1
Total liabilities and stockholders' equity	$ 8,668	$ 8,425.5

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2020	Dec. 31, 2019
Stockholders' Equity:
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized (in shares)	1,250,000,000	1,250,000,000
Common stock, shares issued (in shares)	570,766,439	565,562,607
Common stock, shares outstanding (in shares)	411,842,629	411,312,664
Treasury stock, shares (in shares)	158,923,810	154,249,943

Consolidated Statements of Oper

Consolidated Statements of Operations and Comprehensive Income - USD ($) shares in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Income Statement [Abstract]
Revenue	$ 5,255,000,000	$ 5,517,900,000	$ 5,878,300,000
Cost of revenue (exclusive of amortization shown below)	3,539,200,000	3,544,300,000	3,639,600,000
Gross profit	1,715,800,000	1,973,600,000	2,238,700,000
Operating expenses:
Research and development	642,900,000	640,900,000	650,700,000
Selling and marketing	278,700,000	301,000,000	324,700,000
General and administrative	258,700,000	284,000,000	293,300,000
Litigation settlement	0	169,500,000	0
Amortization of acquisition-related intangible assets	120,300,000	115,200,000	111,700,000
Restructuring, asset impairments and other charges, net	65,200,000	28,700,000	4,300,000
Goodwill and intangible asset impairment	1,300,000	1,600,000	6,800,000
Total operating expenses	1,367,100,000	1,540,900,000	1,391,500,000
Operating income	348,700,000	432,700,000	847,200,000
Other income (expense), net:
Interest expense	(168,400,000)	(148,300,000)	(128,200,000)
Interest income	4,900,000	10,200,000	6,100,000
Loss on debt refinancing and prepayment	0	(6,200,000)	(4,600,000)
Gain on divestiture of business	0	0	5,000,000
Licensing income	0	0	36,600,000
Other expense	(8,600,000)	(11,800,000)	(7,100,000)
Other income (expense), net	(172,100,000)	(156,100,000)	(92,200,000)
Income before income taxes	176,600,000	276,600,000	755,000,000
Income tax (provision) benefit	59,800,000	(62,700,000)	(125,100,000)
Net income	236,400,000	213,900,000	629,900,000
Less: Net income attributable to non-controlling interest	(2,200,000)	(2,200,000)	(2,500,000)
Net income attributable to ON Semiconductor Corporation	234,200,000	211,700,000	627,400,000
Comprehensive income (loss), net of tax:
Net income	236,400,000	213,900,000	629,900,000
Foreign currency translation adjustments	1,800,000	100,000	700,000
Effects of cash flow hedges	(5,100,000)	(16,500,000)	2,000,000
Other comprehensive income (loss), net of tax	(3,300,000)	(16,400,000)	2,700,000
Comprehensive income	233,100,000	197,500,000	632,600,000
Comprehensive income attributable to non-controlling interest	(2,200,000)	(2,200,000)	(2,500,000)
Comprehensive income attributable to ON Semiconductor Corporation	$ 230,900,000	$ 195,300,000	$ 630,100,000
Net income per share of common stock attributable to ON Semiconductor Corporation:
Basic (in dollars per share)	$ 0.57	$ 0.52	$ 1.48
Diluted (in dollars per share)	$ 0.56	$ 0.51	$ 1.44
Weighted-average shares of common stock outstanding:
Basic (in shares)	410.7	410.9	423.8
Diluted (in shares)	418.8	416	435.9

Consolidated Statements of Stoc

Consolidated Statements of Stockholders' Equity - USD ($) $ in Millions	Total	1.00% NotesConvertible Debt	Cumulative Effect, Period of Adoption, Adjustment	Common Stock	Additional Paid-in Capital	Additional Paid-in Capital1.00% NotesConvertible Debt	Additional Paid-in CapitalCumulative Effect, Period of Adoption, Adjustment	Accumulated Other Comprehensive Loss	Accumulated (Deficit) Earnings	Accumulated (Deficit) EarningsCumulative Effect, Period of Adoption, Adjustment	Treasury Stock	Treasury Stock1.00% NotesConvertible Debt	Non-Controlling Interest
Balance, beginning (in shares) at Dec. 31, 2017				551,873,115							126,754,921
Balance, beginning at Dec. 31, 2017	$ 2,801			$ 5.5	$ 3,593.5			$ (40.6)	$ 351.5		$ (1,131.1)		$ 22.2
Balance, beginning (Accounting Standards Update 2016-16) at Dec. 31, 2017			$ (1.4)							$ (1.4)
Balance, beginning (Accounting Standards Update 2014-09) at Dec. 31, 2017			$ 2.1				$ 0			$ 2.1
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock option exercises (in shares)				794,165
Stock option exercises	5.7			$ 0	5.7
Shares issued pursuant to the employee stock purchase plan (in shares)				1,516,012
Shares issued pursuant to the ESPP	24.9				24.9
RSUs and stock grant awards issued (in shares)				4,518,328
RSUs and stock grant awards issued	0			$ 0.1	(0.1)
Shares withheld for employee taxes on RSUs (in shares)											(1,343,961)
Payment of tax withholding for RSUs	(31.6)										$ (31.6)
Share-based compensation	$ 78.3				78.3
Repurchase of common stock (in shares)	(16,800,000)										(16,768,511)
Repurchase of common stock and repurchases of shares under bond hedges	$ (315.3)										$ (315.3)
Dividend to non-controlling shareholder	(2.2)												(2.2)
Comprehensive income	632.6							2.7	627.4				2.5
Balance, ending (in shares) at Dec. 31, 2018				558,701,620							144,867,393
Balance, ending at Dec. 31, 2018	3,194.1			$ 5.6	3,702.3			(37.9)	979.6		$ (1,478)		22.5
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock option exercises (in shares)				266,363
Stock option exercises	1.7			$ 0	1.7
Shares issued pursuant to the employee stock purchase plan (in shares)				1,666,559
Shares issued pursuant to the ESPP	26.2				26.2
RSUs and stock grant awards issued (in shares)				4,928,065
RSUs and stock grant awards issued	0			$ 0.1	(0.1)
Shares withheld for employee taxes on RSUs (in shares)											(1,620,543)
Payment of tax withholding for RSUs	(33.5)										$ (33.5)
Share-based compensation	$ 79.4				79.4
Repurchase of common stock (in shares)	(7,800,000)										(7,762,007)
Repurchase of common stock and repurchases of shares under bond hedges	$ (139)										$ (139)
Dividend to non-controlling shareholder	(2.3)												(2.3)
Comprehensive income	197.5							(16.4)	211.7				2.2
Balance, ending (in shares) at Dec. 31, 2019				565,562,607							154,249,943
Balance, ending at Dec. 31, 2019	3,324.1			$ 5.7	3,809.5			(54.3)	1,191.3		$ (1,650.5)		22.4
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock option exercises (in shares)				5,625
Stock option exercises	0				0
Shares issued pursuant to the employee stock purchase plan (in shares)				1,838,256
Shares issued pursuant to the ESPP	23.6				23.6
RSUs and stock grant awards issued (in shares)				3,359,951
RSUs and stock grant awards issued	0			$ 0	0
Shares withheld for employee taxes on RSUs (in shares)											(1,062,377)
Payment of tax withholding for RSUs	(20)										$ (20)
Share-based compensation	$ 67.7				67.7
Repurchase of common stock (in shares)	(3,600,000)										(3,611,413)	(11,823,348)
Repurchase of common stock and repurchases of shares under bond hedges	$ (65.4)	$ 0				$ 321					$ (65.4)	$ (321)
Dividend to non-controlling shareholder	(5)												(5)
Shares issued to settle excess over principal for 1.00% Notes	0				(88.7)						$ 88.7
Shares issued to settle excess over principal for 1.00% Notes (in shares)											11,823,271
Comprehensive income	233.1							(3.3)	234.2				2.2
Balance, ending (in shares) at Dec. 31, 2020				570,766,439							158,923,810
Balance, ending at Dec. 31, 2020	$ 3,558.1			$ 5.7	$ 4,133.1			$ (57.6)	$ 1,425.5		$ (1,968.2)		$ 19.6

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Cash flows from operating activities:
Net income	$ 236,400,000	$ 213,900,000	$ 629,900,000
Adjustments to reconcile net income to net cash provided by operating activities and other adjustments:
Depreciation and amortization	625,100,000	593,100,000	508,700,000
(Gain) loss on sale or disposal of fixed assets	(3,200,000)	1,900,000	2,400,000
Gain on divestiture of business	0	0	(5,000,000)
Loss on debt refinancing and prepayment	0	6,200,000	4,600,000
Amortization of debt discount and issuance costs	12,100,000	13,000,000	13,200,000
Payments for term debt modification	0	0	(1,100,000)
Share-based compensation	67,700,000	79,400,000	78,300,000
Non-cash interest on convertible notes	38,200,000	37,800,000	36,100,000
Non-cash asset impairment charges	17,500,000	3,400,000	2,400,000
Goodwill and intangible asset impairment charges	1,300,000	1,600,000	6,800,000
Change in deferred tax balances	(122,600,000)	11,200,000	69,200,000
Other	10,500,000	(100,000)	(1,600,000)
Changes in assets and liabilities (exclusive of the impact of acquisitions and divestitures):
Receivables	31,400,000	4,700,000	(2,700,000)
Inventories	(26,300,000)	34,600,000	(129,500,000)
Other assets	(60,000,000)	(34,600,000)	(37,400,000)
Accounts payable	34,200,000	(79,900,000)	44,800,000
Accrued expenses and other current liabilities	(18,500,000)	(201,700,000)	56,500,000
Other long-term liabilities	40,500,000	10,200,000	(1,400,000)
Net cash provided by operating activities	884,300,000	694,700,000	1,274,200,000
Cash flows from investing activities:
Purchase of property, plant and equipment	(383,600,000)	(534,600,000)	(514,800,000)
Proceeds from sale of property, plant and equipment	6,300,000	1,900,000	36,500,000
Deposits utilized for purchases of property, plant and equipment	2,200,000	4,600,000	4,100,000
Purchase of business, net of cash acquired	(4,500,000)	(888,000,000)	(70,900,000)
Settlement of purchase price and purchase of equity interest and assets, net of cash acquired	26,000,000	0	(24,600,000)
Purchase of license and deposit made for manufacturing facility	(100,000,000)	(100,000,000)	0
Proceeds from divestiture of business and release of escrow	0	5,200,000	8,400,000
Proceeds from repayment of note receivable	0	0	10,200,000
Other	0	0	2,200,000
Net cash used in investing activities	(453,600,000)	(1,510,900,000)	(548,900,000)
Cash flows from financing activities:
Proceeds for the issuance of common stock under the ESPP	23,600,000	26,200,000	25,000,000
Proceeds from exercise of stock options	0	1,700,000	5,700,000
Payments of tax withholding for RSUs	(20,000,000)	(33,500,000)	(31,600,000)
Repurchase of common stock	(65,400,000)	(139,000,000)	(315,300,000)
Issuance and borrowings under debt agreements	1,858,000,000	1,404,800,000	15,300,000
Payment of debt issuance and other financing costs	(2,400,000)	(24,000,000)	0
Repayment of borrowings under debt agreements	(2,023,900,000)	(594,400,000)	(298,400,000)
Release of escrow related to prior acquisition	0	(10,400,000)	0
Payment of finance lease obligations	0	(800,000)	(3,600,000)
Payments related to prior acquisition	(8,900,000)	(5,200,000)	0
Dividend to non-controlling shareholder	(5,000,000)	(2,300,000)	(2,200,000)
Net cash provided by (used in) financing activities	(244,000,000)	623,100,000	(605,100,000)
Effect of exchange rate changes on cash, cash equivalents and restricted cash	600,000	200,000	300,000
Net increase (decrease) in cash, cash equivalents and restricted cash	187,300,000	(192,900,000)	120,500,000
Cash, cash equivalents and restricted cash, beginning of period (Note 18)	894,200,000	1,087,100,000	966,600,000
Cash, cash equivalents and restricted cash, end of period (Note 18)	$ 1,081,500,000	$ 894,200,000	$ 1,087,100,000

Background and Basis of Present

Background and Basis of Presentation	12 Months Ended
	Dec. 31, 2020
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Background and Basis of Presentation	Note 1: Background and Basis of Presentation ON Semiconductor Corporation, together with its wholly and majority-owned subsidiaries (the "Company"), prepares its consolidated financial statements in accordance with GAAP. As of December 31, 2020, the Company was organized into three operating segments, which also represent its three reportable segments: PSG, ASG and ISG. Additional information about the Company's operating and reportable segments is included in Note 3: ''Revenue and Segment Information''. The Company assessed certain accounting matters that generally require consideration of forecasted financial information in the context of the information reasonably available as of December 31, 2020, and through the filing date of this Form 10-K. The accounting matters assessed included, but were not limited to, the allowance for doubtful accounts, share-based compensation, inventory valuation, carrying value of indefinite-lived intangible assets, other long-lived assets and goodwill, valuation allowance for tax assets, contingencies and revenue recognition. Future assessment of the current expectations, including of the magnitude and duration of the COVID-19 pandemic, as well as other factors, could result in a material adverse impact to the consolidated financial statements in future reporting periods. Unless otherwise noted, all dollar amounts are in millions, except per share amounts.

Significant Accounting Policies

Significant Accounting Policies	12 Months Ended
	Dec. 31, 2020
Accounting Policies [Abstract]
Significant Accounting Policies	Note 2: Significant Accounting Policies Principles of Consolidation The accompanying consolidated financial statements include the assets, liabilities, revenue and expenses of all wholly-owned and majority-owned subsidiaries over which the Company exercises control and, when applicable, entities in which the Company has a controlling financial interest or is the primary beneficiary. Investments in affiliates where the Company does not exert a controlling financial interest are not consolidated. All intercompany balances and transactions have been eliminated. Use of Estimates The preparation of financial statements in accordance with GAAP requires management to make estimates and assumptions that affect the reported amount of assets and liabilities at the date of the financial statements and the reported amount of revenue and expenses during the reporting period. Management evaluates these estimates and judgments on an ongoing basis and bases its estimates on experience, current and expected future conditions, third-party evaluations and various other assumptions that management believes are reasonable under the circumstances. Significant estimates have been used by management in conjunction with the following: (i) future payouts for customer incentives and amounts subject to allowances and returns; (ii) valuation and obsolescence relating to inventories; (iii) variable and share-based compensation; and (iv) measurement of valuation allowances against deferred tax assets, and evaluations of uncertain tax positions. Additionally, during periods where it becomes applicable, significant estimates will be used by management in determining the future cash flows used to assess and test for impairment of indefinite-lived intangible assets, long-lived assets and goodwill and in assumptions used in connection with business combinations. Actual results may differ from the estimates and assumptions used in the consolidated financial statements. Cash and Cash Equivalents Cash and cash equivalents include cash on hand, demand deposits and highly liquid investments with original maturities at the time of purchase of three months or less. The Company maintains amounts on deposit at various financial institutions, which may at times exceed federally insured limits. However, management periodically evaluates the credit-worthiness of those institutions and has not experienced any losses on such deposits. Inventories Inventories are stated at the lower of standard cost (which approximates actual cost on a first-in, first-out basis) or net realizable value. General market conditions, as well as the Company's design activities, can cause certain of its products to become obsolete. The Company writes down excess and obsolete inventories based upon a regular analysis of inventory on hand compared to historical and projected end-user demand. The determination of projected end-user demand requires the use of estimates and assumptions related to projected unit sales for each product. These write downs can influence results from operations. For example, when demand for a given part falls, all or a portion of the related inventory that is considered to be in excess of anticipated demand is written down, impacting cost of revenue and gross profit. However, the majority of product inventory that has been previously written down is ultimately discarded. Although the Company does sell some products that have previously been written down, such sales have historically been consistently insignificant and the related impact on the Company's gross profit has also been insignificant. Property, Plant and Equipment Property, plant and equipment are recorded at cost and are depreciated over estimated useful lives of 30-50 years for buildings and 3-10 years for computers, machinery and equipment using straight-line methods. Expenditures for maintenance and repairs are charged to operations in the period in which the expense is incurred. When assets are retired or otherwise disposed of, the related costs and accumulated depreciation are removed from the balance sheet and any resulting gain or loss is reflected in operations in the period realized. The Company evaluates the recoverability of the carrying amount of its property, plant and equipment whenever events or changes in circumstances indicate that the carrying value of an asset group may not be fully recoverable. A potential impairment charge is evaluated when the undiscounted expected cash flows derived from an asset group are less than its carrying amount. Impairment losses, if applicable, are measured as the amount by which the carrying value of an asset group exceeds its fair value and are recognized in operating results. Judgment is used when applying these impairment rules to determine the timing of the impairment test, the undiscounted cash flows used to assess impairments and the fair value of the asset group. Business Combination Purchase Price Allocation The allocation of the purchase price of business combinations is based on management estimates and assumptions, which utilize established valuation techniques appropriate for the technology industry. These techniques include the income approach, cost approach or market approach, depending upon which approach is the most appropriate based on the nature and reliability of available data. Management records the acquired assets and liabilities at fair value. If the income approach is used, the fair value determination is predicated upon the value of the future cash flows that an asset is expected to generate over its economic life. The cost approach takes into account the cost to replace (or reproduce) the asset and the effects on the asset's value of physical, functional and/or economic obsolescence that has occurred with respect to the asset. The market approach is used to estimate value from an analysis of actual market transactions or offerings for economically comparable assets available as of the valuation date. Determining the fair value of acquired technology assets is judgmental in nature and requires the use of significant estimates and assumptions, including the discount rate, revenue growth rates, projected gross margins, and estimated research and development and other operating expenses. Goodwill Goodwill represents the excess of the purchase price over the estimated fair value of the net assets acquired in a business combination. The Company evaluates its goodwill for impairment annually during the fourth quarter and whenever events or changes in circumstances indicate the carrying value of a reporting unit may not be recoverable. The Company’s divisions are one level below the operating segments, constituting individual businesses, at which level the Company’s segment management conducts regular reviews of the operating results. The Company's divisions, either individually or in a combination, constitute reporting units for purposes of allocating and testing goodwill. The Company's impairment evaluation consists of a qualitative assessment. If this assessment indicates that it is more likely than not the estimated fair value of a reporting unit exceeds its carrying value, goodwill is not considered impaired. Otherwise, the Company performs a quantitative impairment test by comparing the fair value of a reporting unit with its carrying value, including goodwill. If the carrying value of the net assets associated with the reporting unit exceeds the fair value of the reporting unit, goodwill is considered impaired and will be determined as the amount by which the reporting unit's carrying value exceeds its fair value, not to exceed the carrying amount of goodwill. The Company can bypass the qualitative assessment for any period and proceed directly to the quantitative impairment test. Determining the fair value of the Company's reporting units is subjective in nature and involves the use of significant estimates and assumptions, including projected net cash flows, discount rates and long-term growth rates. The Company determines the fair value of its reporting units based on an income approach derived from the present value of estimated future cash flows. The assumptions about estimated cash flows include factors such as future revenue, gross profit, operating expenses and industry trends. The Company considers historical rates and current market conditions when determining the discount and long-term growth rates to use in its analysis. The Company considers other valuation methods, such as the cost approach or market approach, if it is determined that these methods provide a more representative approximation of fair value. Intangible Assets The Company's acquisitions have resulted in intangible assets consisting of values assigned to customer relationships, patents, developed technology, licenses, IPRD and trademarks. IPRD is considered an indefinite-lived intangible asset until the abandonment or completion of the associated research and development efforts. If abandoned, the assets would be impaired. If the activities are completed, a determination is made regarding the useful lives of such assets and methods of amortization. The Company is required to test its IPRD assets for impairment annually using the guidance for indefinite-lived intangible assets. The Company calculates the fair value of the IPRD asset and records an impairment charge if the carrying amount exceeds fair value. The Company determines the fair value based on an income approach, which is calculated as the present value of the estimated future cash flows of the IPRD asset. The assumptions about estimated cash flows include factors such as future revenue, gross profit, operating expenses and industry trends. The Company can bypass the qualitative assessment for any asset in any period and proceed directly to the quantitative impairment test. The remaining intangible assets are considered long-lived assets and are stated at cost less accumulated amortization. These intangible assets are amortized over their estimated useful lives and are reviewed for impairment when events or changes in circumstances indicate that the carrying amount of an asset group containing these assets may not be recoverable. Leases The Company determines if an arrangement is a lease at its inception. Operating lease arrangements are comprised primarily of real estate and equipment agreements for which the right-of-use ("ROU") assets are included in other assets and the corresponding lease liabilities, depending on their maturity, are included in accrued expenses and other current liabilities or other long-term liabilities in the Consolidated Balance Sheet. ROU assets represent the right to use an underlying asset for the lease term and lease liabilities represent the obligation to make lease payments arising from the lease. ROU assets and lease liabilities are recognized at the lease commencement date based on the estimated present value of lease payments over the lease term. The lease term includes options to extend the lease when it is reasonably certain that the option will be exercised. Leases with a term of 12 months or less are not recorded on the Consolidated Balance Sheet. The Company uses its estimated incremental borrowing rate in determining the present value of lease payments considering the term of the lease, which is derived from information available at the lease commencement date, giving consideration to publicly available data for instruments with similar characteristics. The Company accounts for the lease and non-lease components as a single lease component. Debt Issuance Costs Debt issuance costs for line-of-credit agreements, including the Company's Revolving Credit Facility, are capitalized and amortized over the term of the underlying agreements on a straight-line basis. Amortization of these debt issuance costs is included in interest expense while the unamortized balance is included in other assets. Debt issuance costs for the Company's convertible notes and term debt are recorded as a direct deduction from the carrying amounts of the such debt, consistent with debt discounts, and are amortized over their term using the effective interest method. Amortization of these debt issuance costs is included in interest expense. Contingencies The Company is involved in a variety of legal matters, IP matters, environmental, financing and indemnification contingencies that arise in the ordinary course of business. Based on the information available, management evaluates the relevant range and likelihood of potential outcomes and records the appropriate liability when the amount is deemed probable and reasonably estimable. Treasury Stock Treasury stock is recorded at cost, inclusive of fees, commissions and other expenses, when outstanding common shares are repurchased by the Company, including when outstanding shares are withheld to satisfy tax withholding obligations in connection with certain shares pursuant to RSUs under the Company's share-based compensation plans. Reissuance of shares held in treasury stock is accounted for on a first-in, first-out basis. Revenue Recognition The Company generates revenue from sales of its semiconductor products to OEMs, electronic manufacturing service providers and distributors. The Company also generates revenue, to a much lesser extent, from product development agreements and manufacturing services provided to customers. The Company recognizes revenue when it satisfies a performance obligation in an amount reflecting the consideration to which it expects to be entitled. For sales agreements, the Company has identified the promise to transfer products, each of which is distinct, as the performance obligation. For product development agreements, the Company has identified the completion of a service defined in the agreement as the performance obligation. The Company applies a five-step approach in determining the amount and timing of revenue to be recognized: (1) identifying the contract with a customer; (2) identifying the performance obligations in the contract; (3) determining the transaction price; (4) allocating the transaction price to the performance obligations in the contract; and (5) recognizing revenue when the performance obligation is satisfied. Sales agreements with customers are renewable periodically and contain terms and conditions with respect to payment, delivery, warranty and supply, but typically do not require minimum purchase commitments. In the absence of a sales agreement, the Company’s standard terms and conditions apply. The Company considers the customer purchase orders, governed by sales agreements or the Company’s standard terms and conditions, to be the contract with the customer. The Company evaluates certain factors including the customer’s ability to pay (or credit risk). Most of the Company’s OEM customers negotiate pricing terms on an annual basis, distributors generally negotiate pricing terms on a quarterly basis, while the pricing terms for electronic manufacturing service providers are negotiated periodically during the year. Pricing terms on product development agreements are negotiated at the beginning of a project. The Company allocates the transaction price to each distinct product based on its relative stand-alone selling price. In determining the transaction price, the Company evaluates whether the price is subject to refund or adjustment to determine the net consideration to which the Company expects to be entitled. The Company’s OEM customers do not have the right to return products, other than pursuant to the provisions of the Company’s standard warranty. Sales to distributors, however, are typically made pursuant to agreements that provide return rights and stock rotation provisions permitting limited levels of product returns. Sales to certain distributors, primarily those with ship and credit rights, can also be subject to price adjustment on certain products. Although payment terms vary, most distributor agreements require payment within 30 days. In addition, the Company offers cash discounts to certain customers for payments received within an agreed upon time, generally ten days after shipment. The Company recognizes revenue when it satisfies a performance obligation. The Company recognizes revenue from sales agreements upon transferring control of a product to the customer. This typically occurs when products are shipped or delivered, depending on the delivery terms, or when products that are consigned at customer locations are consumed. The Company recognizes revenue from product development agreements over time based on the cost-to-cost method. Sales returns and allowances, which include ship and credit reserves for distributors, are estimated based on historical claims data and expected future claims. Provisions for discounts and rebates to customers, estimated returns and allowances, ship and credit claims and other adjustments are provided for in the same period the related revenue are recognized, and are netted against revenue. For non-quality related returns, the Company recognizes a related asset for the right to recover returned products with a corresponding reduction to cost of goods sold. The Company records a reserve for cash discounts as a reduction to accounts receivable and a reduction to revenue, based on the experience with each customer. Frequently, the Company receives orders with multiple delivery dates that may extend across reporting periods. Each delivery constitutes an individual performance obligation, which consists of transferring control of the products to the customers based on their stand-alone selling price. The Company invoices the customer for each delivery upon shipment and recognizes revenue in accordance with delivery terms. As scheduled delivery dates are within one year, revenue allocated to future shipments of partially completed contracts are not disclosed. The Company records freight and handling costs associated with outbound freight after control over a product has transferred to a customer as a fulfillment cost and includes it in cost of revenue. Taxes assessed by government authorities on revenue-producing transactions, including value-added and excise taxes, are presented on a net basis (excluded from revenue). The Company generally warrants that products sold to its customers will, at the time of shipment, be free from defects in workmanship and materials and conform to specifications. The Company’s standard warranty extends for a period of two years from the date of delivery, except in the case of image sensor products, which are warrantied for one year from the date of delivery. At the time revenue is recognized, the Company establishes an accrual for estimated warranty expenses associated with its sales and records them as a component of the cost of revenue. Research and Development Costs Research and development costs are expensed as incurred. Income Taxes Income taxes are accounted for using the asset and liability method. Under this method, deferred income tax assets and liabilities are recognized for the future tax consequences attributable to temporary differences between the financial statement carrying amounts of existing assets and liabilities and their respective tax bases. Deferred income tax assets and liabilities are measured using enacted tax rates expected to apply to taxable income in the years in which these temporary differences are expected to be recovered or settled. The effect on deferred tax assets and liabilities of a change in tax rates is recognized in income in the period that includes the enactment date. A valuation allowance is provided for those deferred tax assets for which management cannot conclude that it is more likely than not that such deferred tax assets will be realized. In determining the amount of the valuation allowance, estimated future taxable income, feasible tax planning strategies, future reversals of existing temporary differences and taxable income in prior carryback years, if a carryback is permitted, are considered. If the Company determines it is more likely than not that all or a portion of the remaining deferred tax assets will not be realized, the valuation allowance will be increased with a charge to income tax expense. Conversely, if the Company determines it is more likely than not to be able to utilize all or a portion of the deferred tax assets for which a valuation allowance has been provided, the related portion of the valuation allowance will be recorded as a reduction to income tax expense. The Company recognizes and measures benefits for uncertain tax positions using a two-step approach. The first step is to evaluate the tax position taken or expected to be taken in a tax return by determining if the weight of available evidence indicates that is it more likely than not that the tax positions will be sustained upon audit, including resolution of any related appeals or litigation processes. For tax positions that are more likely than not to be sustained upon audit, the second step is to measure the tax benefit as the largest amount that is more than 50% likely to be realized upon settlement. No tax benefit is recognized for tax positions that are not more likely than not to be sustained. The Company's practice is to recognize interest and/or penalties related to income tax matters in income tax expense. Significant judgment is required to evaluate uncertain tax positions. Evaluations are based upon a number of factors, including changes in facts or circumstances, changes in tax law, correspondence with tax authorities during the course of tax audits and effective settlement of audit issues. Changes in the recognition or measurement of uncertain tax positions could result in significant increases or decreases in income tax expense in the period in which the change is made, which could have a significant impact to the Company's effective tax rate. Foreign Currencies Most of the Company's foreign subsidiaries conduct business primarily in U.S. dollars and, as a result, utilize the U.S. dollar as their functional currency. For the remeasurement of financial statements of these subsidiaries, assets and liabilities in foreign currencies that are receivable or payable in cash are remeasured at current exchange rates, while inventories and other non-monetary assets in foreign currencies are remeasured at historical rates. Gains and losses resulting from the remeasurement of such financial statements are included in the operating results, as are gains and losses incurred on foreign currency transactions. Some of the Company's Japanese subsidiaries utilize Japanese Yen as their functional currency. The assets and liabilities of these subsidiaries are translated at current exchange rates, while revenue and expenses are translated at the average rates in effect for the period. The related translation gains and losses are included in other comprehensive income or loss within the Consolidated Statements of Operations and Comprehensive Income. Share-Based Compensation Share-based compensation is measured at the grant date, based on the estimated fair value of the award, and is recognized as expense over the employee's requisite service period and for awards with performance conditions, over the performance measurement period. The Company has outstanding awards that vest based on service, performance and market conditions. Defined Benefit Pension Plans The Company maintains defined benefit pension plans covering certain of its foreign employees. Net periodic pension costs and pension obligations are determined based on actuarial assumptions, including discount rates for plan obligations, assumed rates of return on pension plan assets and assumed rates of compensation increases for employees participating in plans. These assumptions are based upon management's judgment and consultation with actuaries, considering all known trends and uncertainties. The service cost component of the net periodic pension cost is allocated between the cost of revenue, research and development, selling and marketing and general and administrative line items, while the other components are included in other expense in the Consolidated Statements of Operations and Comprehensive Income. Fair Value Measurement The Company measures certain of its financial and non-financial assets at fair value by using the fair value hierarchy that prioritizes certain inputs into individual fair value measurement approaches. Fair value is the exchange price that would be received for an asset or paid to transfer a liability in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants on the measurement date. Valuation techniques used to measure fair value must maximize the use of observable inputs and minimize the use of unobservable inputs. The fair value hierarchy is based on three levels of inputs, of which the first two are considered observable and the last unobservable, that may be used to measure fair value, as follows: • Level 1 - Quoted prices in active markets for identical assets or liabilities; • Level 2 - Inputs other than Level 1 that are observable, either directly or indirectly, such as quoted prices for similar assets or liabilities; quoted prices in markets that are not active; or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the assets or liabilities; and • Level 3 - Unobservable inputs that are supported by little or no market activity and that are significant to the fair value of the assets or liabilities. Companies may choose to measure certain financial instruments and certain other items at fair value. Unrealized gains and losses on items for which the fair value option has been elected must be reported in earnings. The Company has elected not to carry any of its debt instruments at fair value.

Revenue and Segment Information

Revenue and Segment Information	12 Months Ended
	Dec. 31, 2020
Segment Reporting, Measurement Disclosures [Abstract]
Revenue and Segment Information	Note 3: Revenue and Segment Information Revenue recognized for product sales amounted to $5,227.8 million, $5,492.0 million and $5,849.0 million for the years ended December 31, 2020, 2019 and 2018, respectively. Revenue recognized for product development agreements amounted to $27.2 million, $25.9 million and $29.3 million for the years ended December 31, 2020, 2019 and 2018, respectively. The Company is organized into three operating and reportable segments consisting of PSG, ASG and ISG. The Company's wafer manufacturing facilities fabricate ICs for all business units, as necessary, and their operating costs are reflected in the segments' cost of revenue on the basis of product costs. Because operating segments are generally defined by the products they design and sell, they do not make sales to each other. The Company does not allocate income taxes or interest expense to its operating segments as the operating segments are principally evaluated on gross profit. Additionally, restructuring, asset impairments and other charges, net and certain other manufacturing and operating expenses, which include corporate research and development costs, unallocated inventory reserves and miscellaneous nonrecurring expenses, are not allocated to any segment. In addition to the operating and reportable segments, the Company also operates global operations, sales and marketing, information systems and finance and administration groups. A portion of the expenses for each of these groups are allocated to the segments based on specific and general criteria and are included in the segment results. Revenue and gross profit for the Company’s operating and reportable segments are as follows (in millions): PSG ASG ISG Total For year ended December 31, 2020: Revenue from external customers $ 2,606.1 $ 1,910.4 $ 738.5 $ 5,255.0 Segment gross profit 801.7 730.5 237.7 1,769.9 For year ended December 31, 2019: Revenue from external customers $ 2,788.3 $ 1,972.3 $ 757.3 $ 5,517.9 Segment gross profit 976.0 794.8 275.4 2,046.2 For year ended December 31, 2018: Revenue from external customers $ 3,038.2 $ 2,071.2 $ 768.9 $ 5,878.3 Segment gross profit 1,110.1 878.3 317.1 2,305.5 The Company had one customer, a distributor, whose revenue accounted for approximately 11% of the total revenue for the year ended December 31, 2020. There were no customers whose revenue exceeded 10% or more of total revenue for the years ended December 31, 2019 or 2018. Gross profit is exclusive of the amortization of acquisition-related intangible assets. Depreciation expense is included in segment gross profit. Reconciliations of segment gross profit to consolidated gross profit are as follows (in millions): Year Ended December 31, 2020 2019 2018 Gross profit for reportable segments $ 1,769.9 $ 2,046.2 $ 2,305.5 Less: unallocated manufacturing costs (54.1) (72.6) (66.8) Consolidated gross profit $ 1,715.8 $ 1,973.6 $ 2,238.7 Revenue for the Company's operating and reportable segments disaggregated into geographic locations based on sales billed from the respective country and sales channels are as follows (in millions): Year Ended December 31, 2020 PSG ASG ISG Total Geographic Location Singapore $ 978.0 $ 695.0 $ 126.5 $ 1,799.5 Hong Kong 723.2 410.6 177.8 1,311.6 United Kingdom 395.7 264.5 145.7 805.9 United States 282.8 282.0 163.8 728.6 Other 226.4 258.3 124.7 609.4 Total $ 2,606.1 $ 1,910.4 $ 738.5 $ 5,255.0 Sales Channel Distributors $ 1,776.4 $ 986.4 $ 406.8 $ 3,169.6 OEM 673.6 794.6 297.5 1,765.7 Electronic Manufacturing Service Providers 156.1 129.4 34.2 319.7 Total $ 2,606.1 $ 1,910.4 $ 738.5 $ 5,255.0 Year Ended December 31, 2019 PSG ASG ISG Total Geographic Location Singapore $ 864.7 $ 679.7 $ 168.7 $ 1,713.1 Hong Kong 843.5 436.8 137.0 1,417.3 United Kingdom 467.1 303.5 151.0 921.6 United States 356.3 332.6 121.4 810.3 Other 256.7 219.7 179.2 655.6 Total $ 2,788.3 $ 1,972.3 $ 757.3 $ 5,517.9 Sales Channel Distributors $ 1,740.6 $ 971.5 $ 461.0 $ 3,173.1 OEM 857.5 860.3 258.8 1,976.6 Electronic Manufacturing Service Providers 190.2 140.5 37.5 368.2 Total $ 2,788.3 $ 1,972.3 $ 757.3 $ 5,517.9 Year Ended December 31, 2018 PSG ASG ISG Total Geographic Location Singapore $ 1,086.6 $ 704.2 $ 164.2 $ 1,955.0 Hong Kong 847.9 496.5 144.7 1,489.1 United Kingdom 488.5 319.8 138.2 946.5 United States 398.5 339.2 125.0 862.7 Other 216.7 211.5 196.8 625.0 Total $ 3,038.2 $ 2,071.2 $ 768.9 $ 5,878.3 Sales Channel Distributors $ 2,011.1 $ 1,066.4 $ 464.2 $ 3,541.7 OEM 846.8 860.7 263.4 1,970.9 Electronic Manufacturing Service Providers 180.3 144.1 41.3 365.7 Total $ 3,038.2 $ 2,071.2 $ 768.9 $ 5,878.3 The Company operates in various geographic locations. Sales to unaffiliated customers have little correlation with the location of manufacturers. It is, therefore, not meaningful to present operating profit by geographical location. The Company does not discretely allocate assets to its operating segments, nor does management evaluate operating segments using discrete asset information. The Company’s consolidated assets are not specifically ascribed to its individual reportable segments. Rather, assets used in operations are generally shared across the Company’s operating and reportable segments. Property, plant and equipment, net by geographic location, are summarized as follows (in millions): As of December 31, 2020 2019 United States $ 686.6 $ 616.7 South Korea 455.5 485.4 Philippines 386.6 433.5 China 229.6 243.6 Japan 209.3 218.1 Czech Republic 216.1 213.4 Malaysia 190.2 204.4 Other 138.4 176.5 $ 2,512.3 $ 2,591.6 The following table illustrates the product technologies under each of the Company's reportable segments based on the Company's operating strategy. Because many products are sold into different end-markets, the total revenue reported for a segment is not indicative of actual sales in the end-market associated with that segment, but rather is the sum of the revenue from the product lines assigned to that segment. These segments represent the Company's view of the business and as such are used to evaluate progress of major initiatives and allocation of resources. PSG ASG ISG Analog products Analog products LSI products Discrete products ASIC products Sensors MOSFET products Connectivity products Power Module products ECL products Isolation products Foundry products / services Memory products Gate Driver products Gate Driver products LSI products Standard Logic products Standard Logic products WBG products

Recent Accounting Pronouncement

Recent Accounting Pronouncements	12 Months Ended
	Dec. 31, 2020
Accounting Standards Update and Change in Accounting Principle [Abstract]
Recent Accounting Pronouncements	Note 4: Recent Accounting Pronouncements Adopted: ASU 2020-04 – Facilitation of the Effects of Reference Rate Reform on Financial Reporting ("ASU 2020-04") In March 2020, the FASB issued ASU 2020-04 to address constituents’ concerns about certain accounting consequences that could result from the global markets’ anticipated transition away from the use of the LIBO Rate and other interbank offered rates to alternative reference rates. ASU 2020-04 includes optional expedients and the relief provided is elective and applies to all entities, subject to meeting certain criteria, that have contracts, hedging relationships, and other transactions that reference LIBO Rate or another reference rate expected to be discontinued because of reference rate reform. These amendments are effective for entities as of March 12, 2020 through December 31, 2022. The Company elected to apply the provisions of ASU 2020-04 for its contracts and hedging relationships as of March 12, 2020. The adoption of ASU 2020-04 did not have a material impact on the Company's consolidated financial statements. ASU 2019-12 – Income taxes (Topic 740): Simplifying the accounting for income taxes ("ASU 2019-12") In December 2019, the FASB issued ASU 2019-12, which simplifies the accounting for income taxes by removing certain exceptions to the general principles in Income taxes (Topic 740). The amendments also improve consistent application of and simplify GAAP for other areas of Topic 740 by clarifying and amending existing guidance. This guidance is effective for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2020, with early adoption permitted. The Company early adopted ASU 2019-12 during the quarter ended April 3, 2020. The adoption of ASU 2019-12 did not have a material impact on the Company's consolidated financial statements. ASU 2018-14 – Defined Benefit Plans – General (Topic 715-20): Disclosure Framework – Changes to the Disclosure Requirements of Defined Benefit Plans ("ASU 2018-14") During 2018, the FASB issued ASU 2018-14, which amended ASC 715: Compensation - Retirement Benefits, to add, remove, and clarify disclosure requirements related to defined benefit pension and other postretirement plans. ASU 2018-14 added requirements to disclose, among others, a narrative description of the reasons for significant gains and losses affecting the benefit obligation for the period, and also removed certain other disclosure requirements. For public business entities, the provisions of ASU 2018-14 is effective for fiscal years ending after December 15, 2020. The adoption of ASU 2018-14 did not have a material impact on the Company’s consolidated financial statements. ASU No. 2016-02 - Leases (Topic 842) ("ASU 2016-02"), ASU No. 2018-10 - Codification improvements to Topic 842, Leases ("ASU 2018-10"), ASU No. 2018-11 - Leases (Topic 842) ("ASU 2018-11") (collectively, the "New Leasing Standard") The New Leasing Standard became effective for public business entities for fiscal years beginning after December 15, 2018, including interim periods within those fiscal years. The Company adopted the New Leasing Standard as of January 1, 2019 using the effective date method by recording right-of-use assets of $112.3 million, net of deferred rent liabilities of $5.1 million that were reclassified to right-of-use assets, and lease liabilities of $117.4 million. Under this method, periods prior to 2019 remain unchanged. The Company applied the practical expedients relating to the leases that commenced before January 1, 2019 whereby the Company elected to not reassess the following: (i) whether any expired or existing contracts contain leases; (ii) the lease classification for any expired or existing leases; and (iii) initial direct costs for any existing leases. Pending Adoption: ASU 2020-06 - Accounting for Convertible Instruments and Contracts in an Entity’s Own Equity ("ASU 2020-06") In August 2020, the FASB issued ASU 2020-06, which simplifies the guidance on the issuer’s accounting for convertible debt instruments by removing the separation models for (1) convertible debt with a cash conversion feature and (2) convertible instruments with a beneficial conversion feature. As a result, entities will not separately present in equity an embedded conversion feature in such debt and will account for a convertible debt instrument wholly as debt, unless certain other conditions are met. The elimination of these models will reduce reported interest expense and increase reported net income for entities that have issued a convertible instrument that is within the scope of ASU 2020-06. Also, ASU 2020-06 requires the application of the if-converted method for calculating diluted earnings per share and the treasury stock method will be no longer available. ASU 2020-06 is applicable for fiscal years beginning after December 15, 2021, with early adoption permitted no earlier than fiscal years beginning after December 15, 2020. The Company does not intend to early adopt ASU 2020-06; however, based on the application of the new standard on the 1.625% Notes, there would be a decrease in interest expense and an increase in the dilutive effect of convertible notes included in diluted weighted average shares of common stock outstanding for calculating earnings per share.

Acquisitions, Divestitures and

Acquisitions, Divestitures and Licensing Transactions	12 Months Ended
	Dec. 31, 2020
Business Combinations [Abstract]
Acquisitions, Divestitures and Licensing Transactions	Note 5: Acquisitions, Divestiture and Licensing Transactions The Company pursues strategic acquisitions and divestitures from time to time to leverage its existing capabilities and further build its business. Acquisition costs are not included as components of consideration transferred and instead are accounted for as expenses in the period in which the costs are incurred. During the years ended December 31, 2020 and 2019, the Company incurred acquisition and divestiture related costs of approximately $1.0 million and $11.3 million, respectively, which are included in operating expenses in the Company's Consolidated Statements of Operations and Comprehensive Income. The decrease in 2020 was due to the lack of any significant acquisition-related activities. Pending Acquisition of Manufacturing Facility and Related Assets On April 22, 2019, the Company entered into the Asset Purchase Agreement with GFUS and GLOBALFOUNDRIES Inc. pursuant to which the Company will acquire GFUS’s East Fishkill, New York site and fabrication facilities and certain other assets and liabilities on or around the Closing Date, subject to certain conditions, for the Total Consideration of $400.0 million. On April 22, 2019, the Company paid GFUS $70.0 million of the Total Consideration in cash as a non-refundable deposit, which will be applied toward and reduce the Total Consideration. Also on April 22, 2019, the parties entered into certain ancillary agreements pursuant to which, the Company will be provided with technology transfer and development services as well as foundry services prior to the Closing Date, and GFUS will be provided foundry services for a limited period of time following the Closing Date, and the Company paid GFUS a license fee of $30.0 million in cash for certain technology. This amount has been recorded as an intangible asset in the Consolidated Balance Sheets. On October 1, 2020, the Company entered into an amendment to the APA Amendment pursuant to which the Company paid GFUS a non-refundable deposit in the amount of $100.0 million in cash on October 5, 2020 (the "Additional Deposit"). The Additional Deposit will be applied toward and reduce the Total Consideration, and the remaining $230.0 million of the Total Consideration will be paid on or around the Closing Date. Other terms and conditions of the Asset Purchase Agreement remain unchanged. In connection with the APA Amendment, the Company also entered into an amendment to an ancillary agreement relating to the provision of foundry services entered into in connection with the execution of the Asset Purchase Agreement, which provides the Company certain additional tools and flexibility in its capital expenditures and manufacturing plans for 2021. 2019 Acquisition On June 19, 2019, the Company acquired 100% of the outstanding shares of Quantenna, a global leader and innovator of high performance Wi-Fi solutions, whereby Quantenna became a wholly-owned subsidiary of the Company. The acquisition of Quantenna created a strong platform for addressing connectivity solutions for industrial IoT by combining the Company's expertise in power management and Bluetooth technologies with Quantenna's Wi-Fi technologies and software capabilities. Following the acquisition, Quantenna changed its name to ON Semiconductor Connectivity Solutions, Inc. The purchase price consideration for the acquisition totaled $1,039.3 million, and was funded by a combination of a draw of $900.0 million against the Revolving Credit Facility and cash on hand. From the closing date of the Quantenna acquisition through December 31, 2019, the Company recognized approximately $84.8 million in revenue and $39.3 million in net loss relating to Quantenna, which included the amortization of fair market value step-up of inventory and intangible assets and restructuring charges. The operations of Quantenna have since been integrated with that of the Company. The following table presents the allocation of the purchase price of Quantenna for the assets acquired and liabilities assumed based on their relative fair values, which was finalized during the year ended December 31, 2019 (in millions): Purchase Price Allocation Cash and cash equivalents $ 133.4 Receivables 22.2 Inventories 41.8 Other current assets 4.3 Property, plant and equipment 16.9 Goodwill 726.7 Intangible assets (excluding IPRD) 87.1 IPRD 23.8 Deferred tax assets 29.2 Other non-current assets 12.7 Total assets acquired 1,098.1 Accounts payable 22.6 Other current liabilities 17.5 Deferred tax liabilities 3.3 Other non-current liabilities 15.4 Total liabilities assumed 58.8 Net assets acquired/purchase price $ 1,039.3 Acquired intangible assets of $110.9 million include developed technology of $58.3 million (which are estimated to have a useful life of eight years). The value assigned to developed technology was determined using the income approach. The total weighted average amortization period for the acquired intangibles is eight years. IPRD assets are amortized over the estimated useful life of the assets upon successful completion of the related projects. The value assigned to IPRD was determined by estimating the net cash flows from the projects when completed and discounting the net cash flows to their present value using a discount rate of approximately 12.0%. The cash flows from IPRD’s significant products commenced from 2020 onwards. The acquisition produced $726.7 million of goodwill, which has been assigned to a reporting unit within ASG. The goodwill is attributable to a combination of Quantenna's assembled workforce, expectations regarding a more meaningful engagement by the customers due to the scale of the combined company and other product and operating synergies. Goodwill arising from the Quantenna acquisition is not deductible for tax purposes. Pro-Forma Results of Operations Unaudited pro-forma consolidated results of operations for the year ended December 31, 2020 is not required because the results of the acquired business are included in the Consolidated Statements of Operations and Comprehensive Income for this period. The following unaudited pro-forma consolidated results of operations for the years ended December 31, 2019 and December 31, 2018 have been prepared as if the acquisition of Quantenna had occurred on January 1, 2018 and includes adjustments for amortization of intangibles, interest expense from financing, restructuring, and the effect of purchase accounting adjustments including the step-up of inventory (in millions, except per share data): Year Ended December 31, 2019 December 31, 2018 Revenue $ 5,613.2 $ 6,098.8 Net income 218.2 567.2 Net income attributable to ON Semiconductor Corporation 216.0 564.7 Net income per common share attributable to ON Semiconductor Corporation: Basic 0.53 1.33 Diluted 0.52 1.30 2018 Acquisition On May 8, 2018, the Company acquired 100% of the outstanding shares of SensL, a company specializing in SiPM, single photon avalanche diode and LiDAR sensing products for the automotive, medical, industrial and consumer markets, for $71.6 million, funded with cash on hand. This acquisition positioned the Company to extend its products in automotive sensing applications for ADAS and autonomous driving by adding LiDAR capabilities to the Company’s existing capabilities in imaging and radar. The following table presents the allocation of the purchase price of SensL for the assets acquired and liabilities assumed based on their fair values (in millions): Purchase Price Allocation Current assets (including cash and cash equivalents of $0.7) $ 4.2 Property, plant and equipment and other non-current assets 1.8 Goodwill 18.9 Intangible assets (excluding IPRD) 31.4 IPRD 20.0 Total assets acquired 76.3 Current liabilities 0.7 Other non-current liabilities 4.0 Total liabilities assumed 4.7 Net assets acquired/purchase price $ 71.6 Acquired intangible assets of $31.4 million include developed technology of $30.0 million (which are estimated to have a weighted-average useful life of seven years). The total weighted average amortization period for the acquired intangibles is seven years. IPRD assets are amortized over the estimated useful life of the assets upon successful completion of the related projects. The value assigned to IPRD was determined by estimating the net cash flows from the projects when completed and discounting the net cash flows to their present value using a discount rate of 30.0%. The cash flows from IPRD’s significant products commenced in 2019. The acquisition produced $18.9 million of goodwill, which was allocated to ISG. Goodwill is attributable to a combination of SensL’s assembled workforce, expectations regarding a more meaningful engagement by the customers due to the scale of the combined company and other product and operating synergies. Goodwill arising from the SensL acquisition is not deductible for tax purposes. Unaudited pro-forma consolidated results of operations for the year ended December 31, 2018 is not included considering the significance of the acquisition to the results of the Company. 2018 Divestiture On June 25, 2018, the Company divested the transient voltage suppressing diodes business it acquired from Fairchild to TSC America, Inc. for $5.6 million in cash and recorded a gain of $4.6 million after writing off the carrying values of the assets and liabilities disposed. There were certain other insignificant transactions resulting in a total gain of $5.0 million during the year ended December 31, 2018. Licensing Transactions During 2016 and 2017, the Company entered into an asset purchase agreement with Huaian Imaging Device Manufacturer Corporation ("HIDM") pursuant to which the Company provided perpetual, non-exclusive licenses relating to certain technologies to HIDM and recognized $10.0 million of licensing income during the year ended December 31, 2018. On November 29, 2017, the Company and QST Co. Ltd ("QST") entered into an IP license and technology transfer agreement ("IP Agreement") to grant QST patent licenses and IP rights to certain of the Company’s technologies. Pursuant to the IP Agreement, QST receives perpetual, worldwide, nonexclusive and nontransferable patents licenses and IP rights upon the payment of license fees of which the Company recognized licensing income of $22.7 million during the year ended December 31, 2018. The Company also recognized certain insignificant amounts of licensing income relating to other transactions during the year ended December 31, 2018.

Goodwill and Intangible Assets

Goodwill and Intangible Assets	12 Months Ended
	Dec. 31, 2020
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill and Intangible Assets	Note 6: Goodwill and Intangible Assets Goodwill Goodwill is tested for impairment at the reporting unit level, which is one level below the Company's operating segments. The Company performed qualitative assessments for the annual impairment analysis during the fourth quarters of 2020 and 2019 and concluded that it is more likely than not that the fair value of its reporting units exceed their carrying amounts and a quantitative impairment test was not required. The following table summarizes goodwill by operating and reportable segments (in millions): As of December 31, 2020 As of December 31, 2019 As of December 31, 2018 Goodwill Accumulated Impairment Losses Carrying Value Goodwill Accumulated Impairment Losses Carrying Value Goodwill Accumulated Impairment Losses Carrying Value Operating and Reportable Segments: ASG $ 1,566.3 $ (418.9) $ 1,147.4 $ 1,563.4 $ (418.9) $ 1,144.5 $ 836.7 $ (418.9) $ 417.8 ISG 114.7 — 114.7 114.4 — 114.4 114.4 — 114.4 PSG 433.2 (31.9) 401.3 432.2 (31.9) 400.3 432.2 (31.9) 400.3 Total $ 2,114.2 $ (450.8) $ 1,663.4 $ 2,110.0 $ (450.8) $ 1,659.2 $ 1,383.3 $ (450.8) $ 932.5 The Company recorded a goodwill impairment charge of $3.3 million in 2018 as a result of the licensing transaction with QST, which represented the entire goodwill assigned to a reporting unit within PSG. The following table summarizes the change in goodwill (in millions): Net balance as of December 31, 2018 $ 932.5 Addition due to business combination 726.7 Net balance as of December 31, 2019 1,659.2 Addition due to business combination 4.2 Net balance as of December 31, 2020 $ 1,663.4 Intangible Assets Intangible assets, net, were as follows (in millions): As of December 31, 2020 Original Accumulated Accumulated Impairment Losses Carrying Customer relationships $ 581.5 $ (411.7) $ (17.6) $ 152.2 Developed technology 794.7 (532.9) (2.6) 259.2 IPRD 49.5 — (25.4) 24.1 Licenses 30.0 — — 30.0 Other intangibles 79.3 (60.6) (15.2) 3.5 Total intangible assets $ 1,535.0 $ (1,005.2) $ (60.8) $ 469.0 As of December 31, 2019 Original Accumulated Accumulated Impairment Losses Carrying Customer relationships $ 585.2 $ (386.8) $ (20.1) $ 178.3 Developed technology 779.5 (440.3) (2.6) 336.6 IPRD 64.7 — (24.1) 40.6 Licenses 30.0 — — 30.0 Other intangibles 79.3 (59.1) (15.2) 5.0 Total intangible assets $ 1,538.7 $ (886.2) $ (62.0) $ 590.5 During the years ended December 31, 2020 and December 31, 2019, the Company completed certain of its IPRD projects resulting in the reclassification of $15.2 million and $23.2 million, respectively, from IPRD to developed technology. During the year ended December 31, 2018, the Company determined that the value of one of its IPRD projects under ISG was impaired and recorded a charge of $3.5 million. Amortization expense for intangible assets for the years ended December 31, 2020, 2019 and 2018 amounted to $120.3 million, $115.2 million and $111.7 million, respectively. Amortization expense for intangible assets, with the exception of the $24.1 million of IPRD assets that will be amortized once the corresponding projects have been completed, is expected to be as follows over the next five years, and thereafter (in millions): Total 2021 $ 99.2 2022 83.8 2023 65.9 2024 54.1 2025 41.1 Thereafter 100.8 Total estimated amortization expense $ 444.9

Restructuring, Asset Impairment

Restructuring, Asset Impairments and Other Charges, net	12 Months Ended
	Dec. 31, 2020
Restructuring Charges [Abstract]
Restructuring, Asset Impairments and Other, net	Note 7: Restructuring, Asset Impairments and Other Charges, net Details of restructuring, asset impairments and other charges, net are as follows (in millions): Restructuring Asset Impairments (1) Other Total Year Ended December 31, 2020 Voluntary separation program $ 27.5 $ — $ — $ 27.5 2020 Involuntary separation program 11.8 — — 11.8 General workforce reduction 12.3 — — 12.3 Other — 17.5 (3.9) 13.6 Total $ 51.6 $ 17.5 $ (3.9) $ 65.2 Year Ended December 31, 2019 General workforce reduction $ 8.4 $ — $ — $ 8.4 Post-Quantenna acquisition restructuring 15.7 — — 15.7 Other 0.8 3.4 0.4 4.6 Total $ 24.9 $ 3.4 $ 0.4 $ 28.7 Year Ended December 31, 2018 Other $ 3.9 $ 4.6 $ (4.2) $ 4.3 Total $ 3.9 $ 4.6 $ (4.2) $ 4.3 _______________________ (1) The asset impairment charges recorded during the year ended December 31, 2020 related to a) property, plant and equipment amounting to $9.1 million b) investments in certain entities where the Company does not exert a significant influence amounting to $7.0 million and c) lease right-of-use assets of $1.4 million. Summary of changes in accrued restructuring charges as follows (in millions): Estimated employee separation charges Estimated costs to exit Total Balance as of December 31, 2018 $ 0.3 $ 0.2 $ 0.5 Charges 24.9 — 24.9 Usage (25.1) (0.1) (25.2) Balance as of December 31, 2019 $ 0.1 $ 0.1 $ 0.2 Charges 51.6 — 51.6 Usage (45.5) (0.1) (45.6) Balance as of December 31, 2020 $ 6.2 $ — $ 6.2 Year ended December 31, 2020: Voluntary Separation Program During the first quarter of 2020, the Company offered the VSP to employees that met certain criteria. Participation was subject to management review and approval. The purpose of the VSP was to allow employees to voluntarily separate employment during a specific time and with enhanced separation compensation and benefits, thereby enabling the Company to optimize its cost structure and progress towards its target financial model. Management approved 243 employees for participation in the VSP during the first quarter, after which the VSP was terminated. The aggregate expense for the VSP amounted to $27.5 million for the 243 employees, all of whom had exited by the end of the second quarter of 2020. All amounts under the VSP have been paid during 2020, and there are no payments remaining as of December 31, 2020. 2020 Involuntary Separation Program During the second quarter of 2020, the Company implemented the ISP restructuring program. Under the ISP, the Company notified approximately 191 employees of their employment termination with aggregate severance costs and other benefits amounting to $11.8 million. All notified employees have exited during 2020 and an insignificant amount remained accrued as of December 31, 2020. The Company currently does not anticipate additional employee terminations under this program. General workforce reduction In addition to the VSP and the ISP, the Company undertook certain general workforce reduction measures during 2020. During the first three quarters of 2020, the Company notified approximately 153 employees of their employment termination with aggregate severance costs and other benefits amounting $6.2 million. All notified employees have exited during 2020 and an insignificant amount remained accrued as of December 31, 2020. During the fourth quarter of 2020, the Company notified approximately 106 employees of their employment termination with aggregate severance costs and other benefits amounting to approximately $6.1 million, of which 67 employees have exited as of the end of the year. As of December 31, 2020, $5.3 million remained accrued and is expected to be paid during the first quarter of 2021. Year ended December 31, 2019: General workforce reductions and post-Quantenna acquisition restructuring During the first quarter of 2019, the Company approved and began to implement certain restructuring actions aimed at cost savings, primarily through workforce reductions. As of December 31, 2019, the Company had notified approximately 143 employees of their employment termination, all of whom had exited by December 31, 2019. For the year ended December 31, 2020, the expense for this program amounted to $8.4 million, all of which was paid as of December 31, 2019. Following the acquisition of Quantenna and during the quarter ended June 28, 2019, the Company implemented a cost-reduction plan resulting in the elimination of approximately eight executive positions from Quantenna’s workforce, primarily as a result of redundancies. During the year ended December 31, 2019, the Company terminated an additional ten employees. The total restructuring expense of $15.7 million was attributable to the accelerated vesting of stock awards previously issued by Quantenna, executive retention and other severance benefits. All severance benefits for this program were paid as of December 31, 2019. Year ended December 31, 2018: The Company did not have any significant restructuring activities during the year ended December 31, 2018.

Balance Sheet Information

Balance Sheet Information	12 Months Ended
	Dec. 31, 2020
Balance Sheet Related Disclosures [Abstract]
Balance Sheet Information	Note 8: Balance Sheet Information Certain significant amounts included in the Company's Consolidated Balance Sheets consist of the following (in millions): As of December 31, 2020 December 31, 2019 Inventories: Raw materials $ 135.7 $ 138.4 Work in process 829.7 772.9 Finished goods 286.0 321.1 $ 1,251.4 $ 1,232.4 Property, plant and equipment, net: Land $ 119.7 $ 125.2 Buildings 850.0 860.6 Machinery and equipment 4,538.0 4,275.2 Property, plant and equipment, gross 5,507.7 5,261.0 Less: Accumulated depreciation (2,995.4) (2,669.4) $ 2,512.3 $ 2,591.6 Accrued expenses: Accrued payroll and related benefits $ 166.8 $ 153.4 Sales related reserves 233.3 247.3 Income taxes payable 25.5 22.5 Other 144.4 115.6 $ 570.0 $ 538.8 Assets classified as held-for-sale, consisting primarily of land and buildings, are required to be recorded at the lower of carrying value or fair value less any costs to sell. The carrying value of these assets as of December 31, 2020 was $7.4 million, and is reported as other current assets on the Company’s Consolidated Balance Sheet. Depreciation expense for property, plant and equipment, including amortization of finance leases, totaled $444.1 million, $409.7 million and $359.3 million for 2020, 2019 and 2018, respectively. Included within sales related reserves are ship and credit reserves for distributors amounting to $180.2 million and $178.7 million as of December 31, 2020 and 2019, respectively. Leases Operating lease arrangements are comprised primarily of real estate and equipment agreements. The Company's existing leases do not contain significant restrictive provisions or residual value guarantees; however, certain leases contain renewal options and provisions for payment of real estate taxes, insurance and maintenance costs by the Company. The components of lease expense are as follows (in millions): Year Ended December 31, 2020 December 31, 2019 Operating lease $ 38.2 35.0 Variable lease 4.2 4.0 Short-term lease 4.1 2.6 Total lease expense $ 46.5 41.6 The lease liabilities included in the following captions in the Consolidated Balance Sheet are as follows (in millions): As of December 31, 2020 December 31, 2019 Accrued expenses and other current liabilities $ 32.2 26.1 Other long-term liabilities 115.7 87.9 Total lease liabilities $ 147.9 114.0 Operating lease assets of $136.3 million and $110.2 million are included in other assets in the Consolidated Balance Sheet as of December 31, 2020 and December 31, 2019, respectively. As of December 31, 2020, the weighted-average remaining lease-term was 6.9 years and the weighted-average discount rate was 4.9%. As of December 31, 2020, there was an insignificant amount of commitments for operating leases that have not yet commenced. The reconciliation of the maturities of the operating leases to the lease liabilities recorded in the Consolidated Balance Sheet as of December 31, 2020 is as follows (in millions): 2021 $ 36.5 2022 30.1 2023 23.1 2024 20.8 2025 14.2 Thereafter 49.9 Total lease payments $ 174.6 Less: Interest (26.7) Total lease liabilities $ 147.9 Total rent expense associated with operating leases for 2018 was $43.6 million.

Long-Term Debt

Long-Term Debt	12 Months Ended
	Dec. 31, 2020
Debt Disclosure [Abstract]
Long-Term Debt	Note 9: Long-Term Debt The Company's long-term debt consists of the following (annualized interest rates, dollars in millions): As of December 31, 2020 December 31, 2019 Amended Credit Agreement: Revolving Credit Facility due 2024, interest payable monthly at 1.90% and 3.30%, respectively $ 700.0 $ 800.0 Term Loan "B" Facility due 2026, interest payable monthly at 2.15% and 3.80%, respectively 1,614.5 1,630.9 3.875% Notes due 2028 (1) 700.0 — 1.00% Notes due 2020 (2) — 690.0 1.625% Notes due 2023 (3) 575.0 575.0 Other long-term debt (4) — 53.3 Gross long-term debt, including current maturities 3,589.5 3,749.2 Less: Debt discount (5) (69.7) (102.7) Less: Debt issuance costs (6) (28.5) (34.0) Net long-term debt, including current maturities 3,491.3 3,612.5 Less: Current maturities (531.6) (736.0) Net long-term debt $ 2,959.7 $ 2,876.5 _______________________ (1) Interest is payable on March 1 and September 1 of each year at 3.875% annually. (2) Interest was payable on June 1 and December 1 of each year at 1.00% annually. Balance was fully repaid during 2020. (3) Interest is payable on April 15 and October 15 of each year at 1.625% annually. (4) Consisted of a term loan, finance lease and other facility at certain international locations where interest is payable monthly or quarterly, with interest rates ranging between 1.00% and 1.48% and maturity dates in 2020. (5) Debt discount of $6.5 million and zero for the 3.875% Notes, zero and $20.4 million for the 1.00% Notes, $54.2 million and $71.8 million for the 1.625% Notes and $9.0 million and $10.5 million for the Term Loan "B" Facility, in each case as of December 31, 2020 and December 31, 2019, respectively. (6) Debt issuance costs of $2.3 million and zero for the 3.875% Notes, zero and $2.8 million for the 1.00% Notes, $5.2 million and $6.9 million for the 1.625% Notes and $21.0 million and $24.3 million for the Term Loan "B" Facility, in each case as of December 31, 2020 and December 31, 2019, respectively. Maturities Expected maturities relating to the Company’s gross long-term debt (including current maturities) as of December 31, 2020 are as follows (in millions): Annual 2021 $ 591.4 2022 16.3 2023 16.3 2024 716.4 2025 16.3 Thereafter 2,232.8 Total $ 3,589.5 Amended Credit Agreement The Company obtained capital for the acquisition of Fairchild and other general corporate purposes under a Credit Agreement dated as of April 15, 2016, by and among the Company, as borrower, the several lenders party thereto, Deutsche Bank AG, New York Branch, as administrative agent and collateral agent, and certain other parties (as subsequently amended, the "Amended Credit Agreement"). The Amended Credit Agreement provides for a $1.97 billion revolving credit facility (the "Revolving Credit Facility") and a $2.4 billion term loan "B" facility (the “Term Loan "B" Facility”). Amendments to the Amended Credit Agreement Between 2016 and 2019, the Company, the Guarantors (as defined in the Amended Credit Agreement), the several lenders party thereto and the Agent (as defined in the Amended Credit Agreement) entered into seven amendments to the Amended Credit Agreement. These amendments, among others, reduced the interest rates payable under the Term Loan "B" Facility and the Revolving Credit Facility, increased the amounts that may be borrowed under the Term Loan "B" Facility and the Revolving Credit Facility and also amended certain financial covenants. As part of the seventh amendment to the Amended Credit Agreement executed during 2019, the Company drew an additional $500.0 million under Term Loan "B" Facility and utilized the additional borrowings to repay $500.0 million of the outstanding balance under the Revolving Credit Facility. The maturity date of borrowings under the Revolving Credit Facility and Term Loan "B" Facility currently is June 12, 2024 and September 19, 2026, respectively. On June 23, 2020, the Company entered into the Eighth Amendment ("Eighth Amendment") to the Amended Credit Agreement to change certain defined terms and to modify certain terms and conditions of the Amended Credit Agreement to align with the domestication of certain foreign subsidiaries. There was no impact to the consolidated financial statements due to the Eighth Amendment. See Note 16: ''Income Taxes'' for additional information on the domestication. The obligations under the Amended Credit Agreement are guaranteed by the Guarantors and collateralized by a pledge of substantially all of the assets of the Company and the Guarantors, including a pledge of the equity interests in certain of the Company’s domestic and first tier foreign subsidiaries, subject to customary exceptions. The obligations under the Amended Credit Agreement are also collateralized by mortgage on certain real property assets of the Company and its domestic subsidiaries. The Amended Credit Agreement includes a maximum total net leverage ratio as a financial maintenance covenant, which the Company was in compliance as of December 31, 2020. It also contains other customary affirmative and negative covenants and events of default. Loss on debt refinancing and prepayment In connection with an amendment during 2019, the Company incurred fees to lenders, third parties, legal and other costs amounting to $17.5 million, of which a significant portion was capitalized. Management recorded a loss on debt refinancing amounting to $5.8 million, which included a proportionate write-off of the unamortized debt discount and issuance costs and the third party fees incurred for the transaction. In connection with another amendment during 2019, the Company incurred third party, legal and other fees of $6.6 million and recorded $0.4 million as loss on extinguishment of debt, while capitalizing the remaining cost incurred. The loss on debt refinancing and prepayment amounted to $6.2 million for the year ended December 31, 2019. No such losses were recorded during the year ended December 31, 2020. Borrowing and repayments under the Revolving Credit Facility On March 24, 2020, the Company borrowed $1,165.0 million under the Revolving Credit Facility as a precautionary measure in order to increase the Company’s cash position and provide financial flexibility in light of the uncertainty resulting from the impact of the COVID-19 pandemic. Due to better macroeconomic and business conditions, on August 21, 2020, the Company used the net proceeds from the issuance of the 3.875% Notes along with cash on hand to repay $1,200 million of such outstanding borrowings. Additionally, on December 31, 2020, the Company repaid $65.0 million of outstanding borrowings under the Revolving Credit Facility. As of December 31, 2020, approximately $1,269.0 million was available for future borrowings under the Revolving Credit Facility. Issuance of 3.875% Notes On August 21, 2020, the Company completed its private offering of $700.0 million aggregate principal amount of the 3.875% Notes. The 3.875% Notes were offered in the United States to qualified institutional buyers pursuant to Rule 144A under the Securities Act and outside the United States pursuant to Regulation S under the Securities Act. The 3.875% Notes are fully and unconditionally guaranteed, on a joint and several basis, by each of the Company’s subsidiaries that is a borrower or Guarantor under the Amended Credit Agreement and will also be fully and unconditionally guaranteed by any of the Company’s subsidiaries that becomes a borrower or guarantees any indebtedness under the Amended Credit Agreement in the future. The 3.875% Notes and the guarantees thereof are the Company’s and the Guarantors’ general unsecured obligations, respectively, and (i) rank equally in right of payment with all of the Company’s and the Guarantors’ existing and future senior indebtedness (including the 1.625% Notes); (ii) rank senior to any subordinated indebtedness that the Company or the Guarantors may incur; (iii) are effectively subordinated to all of the Company’s or the Guarantors’ existing and future secured indebtedness (including indebtedness under the Amended Credit Agreement), in each case, to the extent of the value of the assets securing such indebtedness; and (iv) are structurally subordinated in right of payment to all existing and future obligations of the Company’s subsidiaries that are not Guarantors of the 3.875% Notes. The 3.875% Notes bear interest at a rate of 3.875% per year, payable semi-annually on March 1 and September 1 of each year, beginning on March 1, 2021, and will mature on September 1, 2028, unless earlier redeemed or repurchased by the Company. The original issue discount and debt issuance costs incurred by the Company in connection with the offering of the 3.875% Notes amounted to $9.4 million, which has been capitalized and will be amortized to interest expense through the maturity date of September 1, 2028. The net proceeds from the issuance of the 3.875% Notes were used entirely to repay borrowings under the Revolving Credit Facility. Maturity and Settlement of 1.00% Notes due 2020 The 1.00% Notes matured on December 1, 2020. The maturity of the notes resulted in the Company paying $690.0 million in cash to holders of the 1.00% Notes, representing the principal portion of the 1.00% Notes, using the available cash and cash equivalents. The excess over the principal amount was settled on December 1, 2020 by issuing shares of the Company's common stock held in treasury. The transaction resulted in a net impact of $88.7 million to additional paid-in capital and treasury stock, measured based on the acquisition cost of the reissued shares with no overall impact to equity. At the time of issuance of the 1.00% Notes, the Company concurrently entered into hedge transactions with certain of the initial purchasers of the 1.00% Notes. According to the terms of these hedge contracts, on December 1, 2020, the Company repurchased an equivalent amount of shares of its common stock at the prevailing fair market value, to effectively offset the issuance of shares, which resulted in an impact of $321.0 million to additional paid-in capital and treasury stock, with no overall impact to equity. Also at the time of issuance of the 1.00% Notes, the Company sold warrants to certain bank counterparties whereby the holders of the warrants have the option to purchase the equivalent number of shares of the Company’s common stock at a price of $25.96 per share from the Company. These warrants can be exercised by the holders beginning in March and expire no later than April 2021. The Company currently anticipates the holders to exercise the warrants to purchase up to 37.3 million shares of common stock from the Company, which will be settled on a net-share basis depending on the average stock price on the day of exercise. 1.625% Notes due 2023 On March 31, 2017, the Company completed a private placement of $575.0 million of its 1.625% Notes to qualified institutional buyers pursuant to Rule 144A under the Securities Act. The 1.625% Notes are governed by an indenture between the Company, as the issuer, the guarantors named therein and Wells Fargo Bank, National Association, as trustee (the "1.625% Indenture"). The 1.625% Notes are convertible by holders into cash and shares of the Company’s common stock at a conversion rate of 48.2567 shares of common stock per $1,000 principal amount of notes (subject to adjustment in certain events), which is equivalent to an initial conversion price of $20.72 per share of common stock. The Company will settle conversion of all 1.625% Notes validly tendered for conversion in cash, shares of the Company’s common stock or a combination of cash and shares to be determined by the Company. Holders may convert their 1.625% only under the following circumstances: (i) during any calendar quarter commencing after the calendar quarter ending on June 30, 2017 (and only during such calendar quarter), if the last reported sale price of the Company’s common stock for at least 20 trading days (whether or not consecutive) during the period of 30 consecutive trading days ending on the last trading day of the immediately preceding calendar quarter is greater than or equal to 130% of the conversion price on each applicable trading day; (ii) during the five The last reported sale price of the Company’s common stock for at least 20 trading days during the period of 30 consecutive trading days ending on December 31, 2020 was greater than or equal to $26.94 (130% of the conversion price) on each applicable trading day. As a result, the Company recorded the outstanding balance of the 1.625% Notes amounting to $515.6 million, net of unamortized discount and issuance costs, as a current portion of long-term debt as of December 31, 2020, and as required by the 1.625% Indenture, gave notice to the trustee, the conversion agent and each holder on December 31, 2020 that each holder has the right to surrender any portion of its 1.625% Notes (in minimum denominations of $1,000 in principal amount or an integral multiple thereof) for conversion during the calendar quarter ending March 31, 2021 (and only during such calendar quarter unless the trigger remains) pursuant to the terms of the 1.625% Indenture. Other Long-term Debt Note Payable to Fujitsu On October 1, 2018, the Company assumed a yen-denominated non-collateralized loan obligation amounting to $50.6 million as a result of the Company acquiring a majority ownership in OSA. Amortization and maturity of the loan was at the request of the lender, FSL. Upon acquiring 100% ownership in OSA, the Company repaid the balance in full during the year ended December 31, 2020.

Earnings Per Share and Equity

Earnings Per Share and Equity	12 Months Ended
	Dec. 31, 2020
Equity [Abstract]
Earnings Per Share and Equity	Note 10: Earnings Per Share and Equity Earnings Per Share Net income per share of common stock attributable to ON Semiconductor Corporation is shown below (in millions, except per share data): Year ended December 31, 2020 2019 2018 Net income attributable to ON Semiconductor Corporation $ 234.2 $ 211.7 $ 627.4 Basic weighted-average shares of common stock outstanding 410.7 410.9 423.8 Add: Incremental shares for: Dilutive effect of share-based awards 1.9 1.9 4.3 Dilutive effect of convertible notes and warrants 6.2 3.2 7.8 Diluted weighted average shares of common stock outstanding 418.8 416.0 435.9 Net income per share of common stock attributable to ON Semiconductor Corporation: Basic $ 0.57 $ 0.52 $ 1.48 Diluted $ 0.56 $ 0.51 $ 1.44 Basic income per share of common stock is computed by dividing net income attributable to the Company by the weighted average number of shares of common stock outstanding during the period. To calculate the diluted weighted-average shares of common stock outstanding, treasury stock method has been applied to calculate the number of incremental shares from the assumed issuance of shares relating to RSUs. Share-based awards of approximately 0.8 million, 0.8 million and 0.6 million for the years ended December 31, 2020, 2019 and 2018, respectively, were excluded as the impact was considered to be anti-dilutive. The dilutive impact related to the Company’s 1.00% Notes and 1.625% Notes, for the period such notes were outstanding, has been determined in accordance with the net share settlement requirements, under which the Company’s convertible notes are assumed to be convertible into cash up to the par value, with the excess of par value being convertible into common stock. The 1.00% Notes matured and were repaid and settled on December 1, 2020. While the dilutive impact of the warrants that were issued concurrently with the issuance of the 1.00% Notes which have an exercise price of $25.96 have been included in the calculation of diluted weighted-average common shares outstanding, the warrants issued concurrently with the issuance of the 1.625% Notes which have an exercise price of $30.70 were still anti-dilutive and excluded. Prior to conversion, the convertible note hedges are not considered for purposes of the earnings per share calculations, as their effect would be anti-dilutive. Upon conversion, the convertible note hedges are expected to offset the dilutive effect of the 1.625% Notes when the stock price is above $20.72 per share. Equity Share Repurchase Programs On December 1, 2014, the Company announced the "Capital Allocation Policy" under which the Company intends to return to stockholders approximately 80 percent of free cash flow, less repayments of long-term debt, subject to a variety of factors, including the strategic plans, market and economic conditions and the discretion of the Board of Directors. For the purposes of the Capital Allocation Policy, the Company defines "free cash flow" as net cash provided by operating activities less purchases of property, plant and equipment. On December 1, 2014, the Company announced the 2014 Share Repurchase Program pursuant to the Capital Allocation Policy. Under the Company’s 2014 Share Repurchase Program, the Company had the ability to repurchase up to $1.0 billion (exclusive of fees, commissions and other expenses) of the Company’s common stock over a period of four years from December 1, 2014, subject to certain contingencies. The 2014 Share Repurchase Program, which did not require the Company to purchase any particular amount of common stock and was subject to the discretion of the Board of Directors, expired on November 30, 2018 with approximately $288.2 million remaining unutilized. The Company repurchased common stock for an aggregate purchase price of approximately $315.0 million under the 2014 Share Repurchase Program during the year ended December 31, 2018. On November 15, 2018, the Company announced the 2018 Share Repurchase Program pursuant to the Capital Allocation Policy. Under the 2018 Share Repurchase Program, the Company is authorized to repurchase up to $1.5 billion of its common shares from December 1, 2018 through December 31, 2022, exclusive of any fees, commissions or other expenses. The Company may repurchase its common stock from time to time in privately negotiated transactions or open market transactions, including pursuant to a trading plan in accordance with Rule 10b5-1 and Rule 10b-18 of the Exchange Act, or by any combination of such methods or other methods. The timing of any repurchases and the actual number of shares repurchased will depend on a variety of factors, including the Company’s stock price, corporate and regulatory requirements, restrictions under the Company’s debt obligations and other market and economic conditions. There were $65.3 million and $138.9 million in repurchases of the Company's common stock under the 2018 Share Repurchase Program during the years ended December 31, 2020 and December 31, 2019, respectively. As of December 31, 2020, the remaining authorized amount under the 2018 Share Repurchase Program was $1,295.8 million. Information relating to the Company's 2018 and 2014 Share Repurchase Programs is as follows (in millions, except per share data): Year ended December 31, 2020 2019 2018 Number of repurchased shares (1) 3.6 7.8 16.8 Aggregate purchase price $ 65.3 $ 138.9 $ 315.0 Fees, commissions and other expenses 0.1 0.1 0.3 Total cash used for share repurchases $ 65.4 $ 139.0 $ 315.3 Weighted-average purchase price per share (2) $ 18.08 $ 17.89 $ 18.78 Available under the 2018 Share Repurchase Program $ 1,295.8 $ 1,361.1 $ 1,500.0 _______________________ (1) None of these shares had been reissued or retired as of December 31, 2020, but may be reissued or retired later. (2) Exclusive of fees, commission or other expenses Reissuance of shares held in treasury stock In connection with the maturity of the 1.00% Notes, the Company reissued shares of common stock held in treasury to settle the excess over the principal amount. This was the first time the Company reissued shares held in treasury stock and accounted for such reissuance on a first-in, first-out basis. Pursuant to the hedge transactions entered concurrently with the issuance of the 1.00% Notes, the Company repurchased an equivalent number of shares of its common stock at the prevailing fair market value, to effectively offset the reissuance from treasury stock. This repurchase did not reduce the authorized amount remaining under the 2018 Share Repurchase Program. Shares for Restricted Stock Units Tax Withholding Treasury stock is recorded at cost and is presented as a reduction of stockholders’ equity in the accompanying consolidated financial statements. Shares with a fair market value equal to the applicable amount of the employee withholding taxes due are withheld upon the vesting of RSUs to pay the applicable amount of employee withholding taxes and are considered common stock repurchases. The Company then pays the applicable amount of withholding taxes in cash. The amounts remitted during the years ended December 31, 2020, 2019 and 2018 were $20.0 million, $33.5 million and $31.6 million, respectively, for which the Company withheld approximately 1.1 million, 1.6 million and 1.3 million shares of common stock, respectively, that were underlying the RSUs that vested. None of these shares had been reissued or retired as of December 31, 2020, but may be reissued or retired later. These deemed repurchases in connection with tax withholding upon vesting were not made under the 2018 Share Repurchase Program or 2014 Share Repurchase Program, and the amounts spent in connection with such deemed repurchases did not reduce the authorized amount remaining under the 2018 Share Repurchase Program. Non-Controlling Interest Leshan operates assembly and test operations in Leshan, China. The Company owns 80% of the outstanding equity interests in Leshan, and the results of Leshan have been consolidated in the Company's financial statements. At December 31, 2020, the Leshan non-controlling interest balance was $19.6 million. This balance included the Leshan non-controlling interest's $2.2 million share of the earnings for the year ended December 31, 2020 offset by $5.0 million of dividends paid to the non-controlling shareholder. At December 31, 2019, the Leshan non-controlling interest balance was $22.4 million. This balance included the Leshan non-controlling interest's $2.2 million share of the earnings for the year ended December 31, 2019 offset by $2.3 million of dividends paid to the non-controlling shareholder. OSA operates a front-end wafer fabrication facility in Aizuwakamatsu, Japan. During 2018, the Company acquired an incremental 50% equity interest in OSA for approximately $24.6 million, net of cash acquired, to increase its ownership to 60% of the outstanding equity interest. During 2020, the Company acquired the remaining 40% of the equity interest in OSA from FSL, whereby OSA became a wholly-owned subsidiary of the Company. The purchase price payable to FSL for the remaining 40% equity, offset by the purchase price adjustment, resulted in the Company receiving $26.0 million in settlement of the purchase price from FSL during the year ended December 31, 2020. The results of OSA have been consolidated in the Company’s financial statements since 2018 when the Company became the majority owner. Stockholders' Rights Plan On June 7, 2020, the Board of Directors authorized and declared a dividend of one preferred share purchase right (a "Right") to be issued as of 5:00 p.m. New York City time on June 18, 2020 for each outstanding share of common stock to the stockholders of record on that date. In connection with the Rights, the Company and Computershare Trust Company, N.A., as rights agent, entered into a Rights Agreement, dated as of June 8, 2020 (the "Rights Agreement"). Each Right entitles the registered holder of common stock to purchase from the Company one one-hundred-thousandth of a share (a "Unit") of Series B Junior Participating Preferred Stock, par value $0.01 per share, at a purchase price of $100.80 per Unit (the "Purchase Price"), subject to adjustment as provided in the Rights Agreement. Subject to certain exceptions, if a person or group becomes the beneficial owner of more than 15% of the Company’s outstanding shares of common stock, the Rights will become exercisable for that number of shares of Common Stock having a market value of two times the Purchase Price. The Rights, which have a de minimis value as of December 31, 2020, expire on the earlier of (i) the close of business on June 7, 2021, (ii) the time at which the Rights are redeemed pursuant to the Rights Agreement, (iii) the closing of any merger or other acquisition transaction involving the Company that has been approved by the Board of Directors, at which time the Rights are terminated, and (iv) the time at which the Rights are exchanged pursuant to the Rights Agreement. The Rights are in all respects subject to and governed by the provisions of the Rights Agreement.

Share-Based Compensation

Share-Based Compensation	12 Months Ended
	Dec. 31, 2020
Share-based Payment Arrangement [Abstract]
Share-Based Compensation	Note 11: Share-Based Compensation Total share-based compensation expense related to the Company's RSUs, stock grant awards and ESPP were recorded within the Consolidated Statements of Operations and Comprehensive Income as follows (in millions): Year Ended December 31, 2020 2019 2018 Cost of revenue $ 11.5 $ 10.6 $ 7.0 Research and development 18.2 17.0 14.3 Selling and marketing 12.9 14.8 14.1 General and administrative 25.1 37.0 42.9 Share-based compensation expense 67.7 79.4 78.3 Income tax benefit (14.2) (16.7) (16.4) Share-based compensation expense, net of taxes $ 53.5 $ 62.7 $ 61.9 At December 31, 2020, total unrecognized share-based compensation expense, net of estimated forfeitures, related to non-vested RSUs with service, performance and market conditions was $74.5 million, which is expected to be recognized over a weighted-average period of 1.6 years. There was an insignificant amount of stock options exercised during the year ended December 31, 2020. Upon option exercise, vesting of RSUs, stock grant awards or completion of a purchase under the ESPP, the Company issues new shares of common stock. Share-Based Compensation Information The fair value per unit of RSU and stock grant award is determined on the grant date. There were no employee stock options granted during the years ended December 31, 2020, 2019 and 2018. Share-based compensation expense is based on awards ultimately expected to vest. Forfeitures are estimated at the time of grant and revised, if necessary, in subsequent periods if actual forfeitures differ from those estimates. The annualized pre-vesting forfeitures for RSUs were estimated to be approximately 5% for the years ended December 31, 2020, 2019 and 2018. Plan Descriptions On March 23, 2010, the Company adopted the Amended and Restated SIP, which was subsequently approved by the Company's stockholders at the annual stockholder meeting on May 18, 2010 and reapproved by the Company’s stockholders at the annual stockholder meeting on May 20, 2015. The Amended and Restated SIP provides key employees, directors and consultants with various equity-based incentives as described in the plan document. The Amended and Restated SIP is administered by the Board of Directors or a committee thereof, which is authorized to determine, among other things, the key employees, directors or consultants who will receive awards under the plan, the amount and type of award, exercise prices or performance criteria, if applicable, and vesting schedules. On May 15, 2012, stockholders approved certain amendments to the Amended and Restated SIP to increase the number of shares of common stock subject to all awards under the Amended and Restated SIP by 33.0 million. On May 17, 2017, stockholders approved certain amendments to the Amended and Restated SIP to increase the number of shares of common stock subject to all awards under the Amended and Restated SIP by 27.9 million to 87.0 million, exclusive of shares of common stock subject to awards that were previously granted pursuant to the 2000 SIP that have or will become available for grant pursuant to the Amended and Restated SIP. Generally, RSUs granted under the Amended and Restated SIP vest ratably over three years for awards with service conditions and over two years for awards with performance or market conditions, or a combination thereof, and are settled in shares of the Company's common stock upon vesting. Generally, upon the termination of an RSU holder's employment, all unvested RSUs will immediately cancel, except under circumstances where the service condition has been fulfilled. As of December 31, 2020, there was an aggregate of 16.5 million shares of common stock available for grant under the Amended and Restated SIP. Restricted Stock Units A roll forward of the beginning to ending balance of RSUs outstanding as of December 31, 2020 is as follows (number of shares in millions): Number of Shares Weighted-Average Grant Date Fair Value Nonvested shares of RSUs at December 31, 2019 8.9 $ 20.84 Granted 6.5 19.50 Released (3.3) 18.57 Canceled (0.8) 20.86 Nonvested shares of RSUs at December 31, 2020 11.3 20.73 During 2020, the Company awarded 2.7 million RSUs to certain officers and employees of the Company that vest upon the achievement of certain performance criteria and market conditions. The number of units expected to vest is evaluated each reporting period and compensation expense is recognized for those units for which achievement of the performance criteria is considered probable. Compensation expense for RSUs with market conditions are recognized based on the grant date fair value irrespective of the achievement of the condition. As of December 31, 2020, unrecognized compensation expense, net of estimated forfeitures related to non-vested RSUs granted under the Amended and Restated SIP with service, performance and market conditions, was $69.7 million, $0.8 million and $4.0 million, respectively. For RSUs with time-based service conditions, expense is being recognized over the vesting period; for RSUs with performance criteria, expense is recognized over the period when the performance criteria is expected to be achieved; for RSUs with market conditions, expense is recognized over the period in which the condition is assessed irrespective of whether it would be achieved or not. Unrecognized compensation cost for awards with certain performance criteria that are not expected to be achieved is not included here. Total compensation expense related to performance-based, service-based, and market-based RSUs was $58.1 million for the year ended December 31, 2020, which included $52.5 million for RSUs with time-based service conditions that were granted in 2020 and prior that are expected to vest. Stock Grant Awards During the year ended December 31, 2020, the Company granted 0.1 million shares of stock under stock grant awards to certain directors of the Company with immediate vesting at a weighted-average grant date fair value of $18.19 per share. Total compensation expense related to stock grant awards for the year ended December 31, 2020 was $1.5 million. Employee Stock Purchase Plan On February 17, 2000, the Company adopted the ESPP. Subject to local legal requirements, each of the Company's eligible employees may elect to contribute up to 10% of eligible payroll applied towards the purchase of shares of the Company's common stock at a price equal to 85% of the fair market value of such shares as determined under the plan. Employees are limited to annual purchases of $25,000 under this plan. In addition, during each quarterly offering period, employees may not purchase stock exceeding the lesser of: (i) 500 shares; or (ii) the number of shares equal to $6,250 divided by the fair market value of the stock on the first day of the offering period. During the years ended December 31, 2020, 2019 and 2018 employees purchased approximately 1.8 million, 1.7 million and 1.5 million shares, respectively, under the ESPP. On May 17, 2017, stockholders approved an amendment to the Company’s ESPP, which increased the number of shares reserved and available to be issued pursuant to the ESPP to a total of 28.5 million. As of December 31, 2020, there were approximately 3.0 million shares available for issuance under the ESPP. Total compensation expense related to the ESPP for the year ended December 31, 2020 was $8.1 million.

Employee Benefit Plans

Employee Benefit Plans	12 Months Ended
	Dec. 31, 2020
Defined Benefit Plans and Other Postretirement Benefit Plans Disclosures [Abstract]
Employee Benefit Plans	Note 12: Employee Benefit Plans Defined Benefit Pension Plans The Company maintains defined benefit pension plans for employees of certain of its foreign subsidiaries. Such plans conform to local practice in terms of providing minimum benefits mandated by law, collective agreements or customary practice. The Company recognizes the aggregate amount of all overfunded plans as assets and the aggregate amount of all underfunded plans as liabilities in its Consolidated Balance Sheets. The Company's expected long-term rate of return on plan assets is updated at least annually, taking into consideration its asset allocation, historical returns on similar types of assets and the current economic environment. For estimation purposes, the Company assumes its long-term asset mix will generally be consistent with the current mix. The Company determines its discount rates using highly rated corporate bond yields and government bond yields. Benefits under all of the plans are valued utilizing the projected unit credit cost method. The Company's policy is to fund its defined benefit plans in accordance with local requirements and regulations. The funding is primarily driven by the current assessment of the economic environment and projected benefit payments of foreign subsidiaries. The measurement date for determining the defined benefit obligations for all plans is December 31 of each year. The Company recognizes actuarial gains and losses during the period the Company's annual pension plan actuarial valuations are prepared, which generally occurs during the fourth calendar quarter of each year, or during any interim period where a revaluation is deemed necessary. For the years ended December 31, 2020, 2019 and 2018, the Company recognized actuarial losses amounting to $4.0 million, $15.6 million and $6.1 million, respectively. For 2020, the net actuarial loss of $8.1 million which was primarily due to a decrease in the discount rates and other insignificant changes in actuarial assumptions, was partially offset by better than expected return on plan assets amounting to $4.1 million. Following is a summary of the status of the Company's foreign defined benefit pension plans and the net periodic pension cost (amounts in millions): Year Ended December 31, 2020 2019 2018 Service cost $ 10.9 $ 9.4 $ 9.6 Interest cost 4.7 5.0 4.7 Expected return on plan assets (6.3) (6.0) (6.1) Curtailment gain (1.6) — (0.3) Actuarial losses 4.0 15.6 6.1 Total net periodic pension cost $ 11.7 $ 24.0 $ 14.0 Weighted average assumptions Discount rate used for net periodic pension costs 1.43 % 1.74 % 1.66 % Discount rate used for pension benefit obligations 1.31 % 1.43 % 1.74 % Expected return on plan assets 3.06 % 3.23 % 3.18 % Rate of compensation increase 3.26 % 3.07 % 3.22 % The long-term rate of return on plan assets was determined using the weighted-average method, which incorporates factors that include the historical inflation rates, interest rate yield curve and current market conditions. 2020 2019 Change in projected benefit obligation (PBO) Projected benefit obligation at the beginning of the year $ 322.9 $ 290.8 Service cost 10.9 9.4 Interest cost 4.7 5.0 Net actuarial loss 8.1 25.8 Benefits paid by plan assets (8.9) (5.7) Benefits paid by the Company (7.4) (3.8) Curtailments and settlements (1.6) (0.2) Translation and other loss 22.5 1.6 Projected benefit obligation at the end of the year $ 351.2 $ 322.9 Accumulated benefit obligation at the end of the year $ 288.3 $ 258.8 Change in plan assets Fair value of plan assets at the beginning of the year $ 190.2 $ 174.9 Actual return on plan assets 10.4 16.2 Benefits paid from plan assets (8.9) (5.7) Employer contributions 4.3 4.6 Settlements — (0.2) Translation and other gain 13.3 0.4 Fair value of plan assets at the end of the year $ 209.3 $ 190.2 As of December 31, 2020 2019 Plans with underfunded or non-funded projected benefit obligation (1) Projected benefit obligation $ 248.7 $ 314.7 Fair value of plan assets 97.7 180.5 Plans with underfunded or non-funded accumulated benefit obligation Accumulated benefit obligation $ 189.4 $ 193.6 Fair value of plan assets 97.7 115.2 Amounts recognized in the balance sheet consist of Non-current assets $ 9.0 $ — Current liabilities (0.3) (0.3) Non-current liabilities (150.6) (132.4) Funded status $ (141.9) $ (132.7) (1) Certain pension plans that were in an underfunded status as of December 31, 2019 changed to an overfunded status as of December 31, 2020. Plan Assets The Company's overall investment strategy is to focus on stable and low credit risk investments aimed at providing a positive rate of return to the plan assets. The Company has an investment mix with a wide diversification of asset types and fund strategies that are aligned with each region and foreign location's economy and market conditions. Investments in government securities are generally guaranteed by the respective government offering the securities. Investments in corporate bonds, equity securities, and foreign mutual funds are made with the expectation that these investments will give an adequate rate of long-term returns despite periods of high volatility. Other types of investments include investments in cash deposits, money market funds and insurance contracts. Asset allocations are based on the anticipated required funding amounts, timing of benefit payments, historical returns on similar assets and the influence of the current economic environment. The following table sets forth, by level within the fair value hierarchy, a summary of investments measured at fair value and the asset allocations of the plan assets in the Company's foreign pension plans (in millions): As of December, 31, 2020 Allocation Total Level 1 Level 2 Level 3 Asset Category Cash/Money Markets 2 % $ 4.1 $ 4.1 $ — $ — Foreign Government/Treasury Securities (1) 10 % 21.4 21.4 — — Corporate Bonds, Debentures (2) 18 % 36.9 — 36.9 — Equity Securities (3) 23 % 48.5 — 48.5 — Mutual Funds 5 % 9.5 — 9.5 — Investment and Insurance Contracts (4) 42 % 88.9 — 31.4 57.5 100 % $ 209.3 $ 25.5 $ 126.3 $ 57.5 As of December, 31, 2019 Allocation Total Level 1 Level 2 Level 3 Asset Category Cash/Money Markets 3 % $ 4.5 $ 4.5 $ — $ — Foreign Government/Treasury Securities (1) 10 % 19.4 19.4 — — Corporate Bonds, Debentures (2) 19 % 35.3 — 35.3 — Equity Securities (3) 21 % 40.4 — 40.4 — Mutual Funds 4 % 8.0 — 8.0 — Investment and Insurance Contracts (4) 43 % 82.6 — 30.6 52.0 100 % $ 190.2 $ 23.9 $ 114.3 $ 52.0 _______________________ (1) Includes investments primarily in guaranteed return securities. (2) Includes investments in government bonds and corporate bonds of developed countries, emerging market government bonds, emerging market corporate bonds and convertible bonds. (3) Includes investments in equity securities of developed countries and emerging markets. (4) Includes certain investments with insurance companies that guarantee a minimum rate of return on the investment. When available, the Company uses observable market data, including pricing on recently closed market transactions and quoted prices, which are included in Level 2. When data is unobservable, valuation methodologies using comparable market data are utilized and included in Level 3. Activity during the years ended December 31, 2020 and 2019, respectively, for plan assets with fair value measurement using significant unobservable inputs (Level 3) were as follows (in millions): Investment and Insurance Contracts Balance at December 31, 2018 $ 50.6 Actual return on plan assets 3.3 Purchase, sales and settlements. net (0.9) Foreign currency impact (1.0) Balance at December 31, 2019 $ 52.0 Actual return on plan assets 0.8 Purchase, sales and settlements, net (0.3) Foreign currency impact 5.0 Balance at December 31, 2020 $ 57.5 The expected benefit payments from the Company's defined benefit plans from 2021 through 2025 and the five years thereafter are as follows (in millions): 2021 $ 7.0 2022 10.6 2023 14.0 2024 15.8 2025 17.9 Five years thereafter 114.3 Total $ 179.6 The total underfunded status was $141.9 million at December 31, 2020. The Company expects to contribute $22.1 million during 2021 to its foreign defined benefit plans. Defined Contribution Plans The Company has a deferred compensation savings plan for all eligible U.S. employees established under the provisions of Section 401(k) of the Internal Revenue Code (the "Code"). Eligible employees may contribute a percentage of their salary subject to certain limitations. The Company has elected to match 100% of employee contributions between 0% and 4% of their salary, with an annual limit of $11,400. The Company recognized $19.4 million, $18.1 million and $19.2 million of expense relating to matching contributions in 2020, 2019 and 2018, respectively. Certain foreign subsidiaries have defined contribution plans in which eligible employees participate. The Company recognized compensation expense of $21.8 million, $20.6 million and $20.5 million relating to these plans for the years ended 2020, 2019 and 2018, respectively.

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2020
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Note 13: Commitments and Contingencies Purchase Obligations The Company has agreements with suppliers, external manufacturers and other vendors for capital expenditures, inventory purchases, manufacturing services, information technology and other goods and services. The following is a schedule by year of future minimum purchase obligations under non-cancelable arrangements entered into during the ordinary course of business as of December 31, 2020 (in millions): Year Ending December 31, 2021 $ 524.9 2022 (1) 598.9 2023 259.5 2024 248.0 2025 3.5 Thereafter 3.5 Total $ 1,638.3 (1) During 2019, the Company incurred additional commitments related to the pending acquisition of a manufacturing facility, of which $70.0 million and $100.0 million were deposited with the seller during the years ended December 31, 2019 and 2020, respectively. The remaining commitment of $230.0 million will be owed on or around December 31, 2022. Environmental Contingencies The Company’s headquarters in Phoenix, Arizona are located on property that is a "Superfund" site, which is a property listed on the National Priorities List and subject to clean-up activities under the Comprehensive Environmental Response, Compensation, and Liability Act ("CERCLA"). Motorola and Freescale (acquired by NXP Semiconductors N.V.) have been involved in the clean-up activities of on-site solvent contaminated soil and groundwater and off-site contaminated groundwater pursuant to consent decrees with the State of Arizona. As part of the Company’s separation from Motorola in 1999, Motorola retained responsibility for this contamination, and Motorola and Freescale have agreed to indemnify the Company with respect to remediation costs and other costs or liabilities related to this matter. Any costs to the Company in connection with this matter have not been, and, based on the information available, are not expected to be, material. The Company’s former front-end manufacturing location in Aizu, Japan is located on property where soil and ground water contamination was detected. The Company believes that the contamination originally occurred during a time when the facility was operated by a prior owner. The Company worked with local authorities to implement a remediation plan and has completed remaining remediation. The majority of the cost of remediation was covered by insurance. During 2018, semi-annual groundwater monitoring indicated that the treatment was effective, and accordingly, we ceased such monitoring and have determined that this remediation project is complete. Any costs to the Company in connection with this matter have not been, and, based on the information available, are not expected to be material. The Company’s manufacturing facility in the Czech Republic has undergone remediation to respond to releases of hazardous substances that occurred during the years that this facility was operated by government-owned entities. The remediation projects consisted primarily of monitoring groundwater wells located on-site and off-site with additional action plans developed to respond in the event certain contamination levels are exceeded. The government of the Czech Republic has agreed to indemnify the Company and its respective subsidiaries, subject to specified limitations, for remediation costs associated with this historical contamination. The Company has completed remediation on this project, and accordingly, has ceased all related monitoring efforts. Any costs to the Company in connection with this matter have not been, and, based on the information available, are not expected to be material. The Company’s design center in East Greenwich, Rhode Island is located on property that has localized soil contamination. In connection with the purchase of the facility, the Company entered into a Settlement Agreement and Covenant Not to Sue with the State of Rhode Island. This agreement requires that remedial actions be undertaken and a quarterly groundwater monitoring program be initiated by the former owners of the property. Any costs to the Company in connection with this matter have not been, and, based on the information available, are not expected to be material. As a result of the acquisition of AMIS in 2008, the Company is a "primary responsible party" to an environmental remediation and clean-up plan at AMIS’s former corporate headquarters in Santa Clara, California. Costs incurred by AMIS include implementation of the clean-up plan, operations and maintenance of remediation systems, and other project management costs. However, AMIS’s former parent company, a subsidiary of Nippon Mining, contractually agreed to indemnify AMIS and the Company for any obligations relating to environmental remediation and clean-up activities at this location. Any costs to the Company in connection with this matter have not been, and, based on the information available, are not expected to be material. Through its acquisition of Fairchild, the Company acquired a facility in South Portland, Maine. This facility has ongoing environmental remediation projects to respond to certain releases of hazardous substances that occurred prior to the leveraged recapitalization of Fairchild from its former parent company, National Semiconductor Corporation, which is now owned by Texas Instruments Incorporated. Although the Company may incur certain liabilities with respect to these remediation projects, pursuant to a 1997 asset purchase agreement entered into in connection with the Fairchild recapitalization, National Semiconductor Corporation agreed to indemnify Fairchild, without limitation and for an indefinite period of time, for all future costs related to these projects. Any costs to the Company in connection with this matter have not been, and, based on the information available, are not expected to be material. Under a 1999 asset purchase agreement pursuant to which Fairchild purchased the power device business of Samsung, Samsung agreed to indemnify Fairchild in an amount up to $150.0 million for remediation costs and other liabilities related to historical contamination at Samsung’s Bucheon, South Korea operations. Any costs to the Company in connection with this matter have not been, and, based on the information available, are not expected to be material. Under a 2001 asset purchase agreement pursuant to which Fairchild purchased a manufacturing facility in Mountain Top, Pennsylvania, Intersil Corp. (subsequently acquired by Renesas Electronics Corporation) agreed to indemnify Fairchild for remediation costs and other liabilities related to historical contamination at the facility. Any costs to the Company incurred to respond to the above conditions and projects have not been, and are not expected to be material, and any future payments the Company makes in connection with such liabilities are not expected to be material. The Company was notified by the EPA that it has been identified as a PRP under CERCLA in the Chemetco Superfund matter. Chemetco, a defunct reclamation services supplier that operated in Hartford, Illinois at what is now a Superfund site, has performed reclamation services for the Company in the past. The EPA is pursuing Chemetco customers for contribution to the site clean-up activities. The Company has joined a PRP group, which is cooperating with the EPA in the evaluation and funding of the clean-up activities. Any costs to the Company in connection with this matter have not been, and, based on the information available, are not expected to be material. Financing Contingencies In the ordinary course of business, the Company provides standby letters of credit or other guarantee instruments to certain parties initiated by either the Company or its subsidiaries, as required for transactions, including, but not limited to, material purchase commitments, agreements to mitigate collection risk, leases, utilities or customs guarantees. As of December 31, 2020, the Company's Revolving Credit Facility included $15.0 million available for the issuance of letters of credit. There were $0.9 million letters of credit outstanding under the Revolving Credit Facility as of December 31, 2020, which reduced the Company's borrowing capacity. The Company also had outstanding guarantees and letters of credit outside of its Revolving Credit Facility totaling $9.7 million as of December 31, 2020. As part of obtaining financing in the ordinary course of business, the Company issued guarantees related to certain of its subsidiaries, which totaled $0.9 million as of December 31, 2020. Based on historical experience and information currently available, the Company believes that it will not be required to make payments under the standby letters of credit or guarantee arrangements for the foreseeable future. Indemnification Contingencies The Company is a party to a variety of agreements entered into in the ordinary course of business pursuant to which it may be obligated to indemnify the other parties for certain liabilities that arise out of or relate to the subject matter of the agreements. Some of the agreements entered into by the Company require it to indemnify the other party against losses due to IP infringement, property damage (including environmental contamination), personal injury, failure to comply with applicable laws, the Company’s negligence or willful misconduct or breach of representations and warranties and covenants related to such matters as title to sold assets. The Company faces risk of exposure to warranty and product liability claims in the event that its products fail to perform as expected or such failure of its products results, or is alleged to result, in economic damage, bodily injury or property damage. In addition, if any of the Company’s designed products are alleged to be defective, the Company may be required to participate in their recall. Depending on the significance of any particular customer and other relevant factors, the Company may agree to provide more favorable rights to such customer for valid defective product claims. The Company and its subsidiaries provide for indemnification of directors, officers and other persons in accordance with limited liability company operating agreements, certificates of incorporation, by-laws, articles of association or similar organizational documents, as the case may be. Section 145 of the Delaware General Corporation Law ("DGCL") authorizes a court to award, or a corporation’s board of directors to grant, indemnity to directors and officers under certain circumstances and subject to certain limitations. The terms of Section 145 of the DGCL are sufficiently broad to permit indemnification under certain circumstances for liabilities, including reimbursement of expenses incurred, arising under the Exchange Act. As permitted by the DGCL, the Company’s Amended and Restated Certificate of Incorporation (as amended, the "Certificate of Incorporation"), contains provisions relating to the limitation of liability and indemnification of directors and officers. The Certificate of Incorporation eliminates the personal liability of each of the Company’s directors to the fullest extent permitted by Section 102(b)(7) of the DGCL, as it may be amended or supplemented, and provides that the Company will indemnify its directors and officers to the fullest extent permitted by Section 145 of the DGCL, as amended from time to time. The Company has entered into indemnification agreements with each of its directors and executive officers. The form of agreement (the "Indemnification Agreement") provides, subject to certain exceptions and conditions specified in the Indemnification Agreement, that the Company will indemnify each indemnitee to the fullest extent permitted by Delaware law against all expenses, judgments, fines and amounts paid in settlement actually and reasonably incurred by such person in connection with a proceeding or claim in which such person is involved because of his or her status as one of the Company’s directors or executive officers. In addition, the Indemnification Agreement provides that the Company will, to the extent not prohibited by law and subject to certain exceptions and repayment conditions, advance specified indemnifiable expenses incurred by the indemnitee in connection with such proceeding or claim. The Company also maintains directors’ and officers’ insurance policies that indemnify its directors and officers against various liabilities, including certain liabilities under the Exchange Act, which might be incurred by any director or officer in his or her capacity as such. The agreement and plan of merger relating to the acquisition of Fairchild (the "Fairchild Agreement") provides for indemnification and insurance rights in favor of Fairchild’s then current and former directors, officers and employees. Specifically, the Company has agreed that, for no fewer than six years following the Fairchild acquisition, the Company will: (a) indemnify and hold harmless each such indemnitee against losses and expenses (including advancement of attorneys’ fees and expenses) in connection with any proceeding asserted against the indemnified party in connection with such person’s servings as a director, officer, employee or other fiduciary of Fairchild or its subsidiaries prior to the effective time of the acquisition; (b) maintain in effect all provisions of the certificate of incorporation or bylaws of Fairchild or any of its subsidiaries or any other agreements of Fairchild or any of its subsidiaries with any indemnified party regarding elimination of liability, indemnification of officers, directors and employees and advancement of expenses in existence on the date of the Fairchild Agreement for acts or omissions occurring prior to the effective time of the acquisition; and (c) subject to certain qualifications, provide to Fairchild’s then current directors and officers an insurance and indemnification policy that provides coverage for events occurring prior to the effective time of the acquisition that is no less favorable than Fairchild’s then-existing policy, or, if insurance coverage that is no less favorable is unavailable, the best available coverage. Similarly, the agreement and plan of merger relating to the acquisition of Quantenna (the "Quantenna Agreement") provides for indemnification and insurance rights in favor of Quantenna’s then current and former directors, officers, employees and agents. Specifically, the Company has agreed that, for no fewer than six years following the Quantenna acquisition, the Company will: (a) indemnify and hold harmless each such indemnified party to the fullest extent permitted by Delaware law in the event of any threatened or actual claim suit, action, proceeding or investigation against the indemnified party based in whole or in part on, or pertaining to, such person’s serving as a director, officer, employee or agent of Quantenna or its subsidiaries or predecessors prior to the effective time of the acquisition or in connection with the Quantenna Agreement; (b) maintain in effect provisions of the certificate of incorporation and bylaws of Quantenna and each of its subsidiaries regarding the elimination of liability of directors and indemnification of officers, directors and employees that are no less advantageous to the intended beneficiaries than the corresponding provisions in the certificate of incorporation and bylaws of Quantenna and each of its subsidiaries in existence on the date of the Quantenna Agreement; and (c) obtain and fully pay the premium for a non-cancelable extension of directors’ and officers’ liability coverage of Quantenna’s directors’ and officers’ policies and Quantenna’s fiduciary liability insurance policies in effect as of the date of the Quantenna Agreement. While the Company’s future obligations under certain agreements may contain limitations on liability for indemnification, other agreements do not contain such limitations and under such agreements it is not possible to predict the maximum potential amount of future payments due to the conditional nature of the Company’s obligations and the unique facts and circumstances involved in each particular agreement. Historically, payments made by the Company under any of these indemnities have not had a material effect on the Company’s business, financial condition, results of operations or cash flows. Additionally, the Company does not believe that any amounts that it may be required to pay under these indemnities in the future will be material to the Company’s business, financial position, results of operations, or cash flows. Legal Matters From time to time, the Company is party to various legal proceedings arising in the ordinary course of business, including indemnification claims, claims of alleged infringement of patents, trademarks, copyrights and other IP rights, claims of alleged non-compliance with contract provisions and claims related to alleged violations of laws and regulations. The Company regularly evaluates the status of the legal proceedings in which it is involved to assess whether a loss is probable or there is a reasonable possibility that a loss, or an additional loss, may have been incurred and determines if accruals are appropriate. If accruals are not appropriate, the Company further evaluates each legal proceeding to assess whether an estimate of possible loss or range of possible loss can be made for disclosure. Although litigation is inherently unpredictable, the Company believes that it has adequate provisions for any probable and estimable losses. Nevertheless, it is possible that the Company’s consolidated financial position, results of operations or liquidity could be materially and adversely affected in any particular period by the resolution of a legal proceeding. The Company’s estimates do not represent its maximum exposure. Legal expenses related to defense, negotiations, settlements, rulings and advice of outside legal counsel are expensed as incurred. The Company is currently involved in a variety of legal matters that arise in the ordinary course of business. Based on information currently available, except as disclosed below, the Company is not involved in any pending or threatened legal proceedings that it believes could reasonably be expected to have a material adverse effect on its financial condition, results of operations or liquidity. The litigation process is inherently uncertain, and the Company cannot guarantee that the outcome of any litigation matter will be favorable to the Company. Patent Litigation with PI On October 19, 2019, the Company and PI entered into a Settlement Agreement (the "Settlement Agreement") pursuant to which the parties agreed to withdraw all outstanding legal and administrative disputes on the terms set forth in a binding term sheet previously entered into by and among the Company and PI on October 4, 2019. Pursuant to the Settlement Agreement, the Company paid PI $175.0 million in cash on October 22, 2019, and the parties have dismissed all previously pending litigation and administrative proceedings. In addition, each party agreed to release the other party from any claims to damages or monetary relief for alleged acts of patent infringement across the various patent infringement litigations and not to file any additional action for legal or equitable relief until June 30, 2023. Neither party granted any licenses to the other. Litigation with AcBel Polytech, Inc. On November 27, 2013, Fairchild and Fairchild Semiconductor Corporation were named as defendants in a complaint filed by AcBel Polytech, Inc. ("AcBel") in the U.S. District Court for the District of Massachusetts. The lawsuit alleged a number of causes of action, including breach of warranty, fraud, negligence and strict liability. In parallel to the litigation with AcBel, Fairchild filed an arbitration against its distributor, Synnex Technology International Corp ("Synnex"), in Hong Kong in response to Synnex’s failure to pass along Fairchild’s limited warranty to AcBel. On July 31, 2020, the Company entered into a settlement agreement and release in respect of the dispute with Synnex and AcBel. On August 6, 2020, the Company paid its full aggregate liability of $6.0 million in accordance with the settlement agreement and all applicable claims were released. Intellectual Property Matters The Company faces risk of exposure from claims of infringement of the IP rights of others. In the ordinary course of business, the Company receives letters asserting that the Company’s products or components breach another party’s rights. Such letters may request royalty payments from the Company, that the Company cease and desist using certain IP or other remedies.

Fair Value Measurements

Fair Value Measurements	12 Months Ended
	Dec. 31, 2020
Fair Value Disclosures [Abstract]
Fair Value Measurements	Note 14: Fair Value Measurements Fair Value of Financial Instruments The following table summarizes the Company's financial assets and liabilities, excluding pension assets, measured at fair value on a recurring basis (in millions): Fair Value Hierarchy Description As of December, 31, 2020 Level 1 Level 2 Level 3 Assets: Cash, cash equivalents: Demand and time deposits $ 8.5 $ 8.5 — — Fair Value Hierarchy Description As of December, 31, 2019 Level 1 Level 2 Level 3 Assets: Cash, cash equivalents: Demand and time deposits $ 28.2 $ 28.2 — — Other The carrying amounts of other current assets and liabilities, such as accounts receivable and accounts payable, approximate fair value based on the short-term nature of these instruments. Fair Value of Long-Term Debt, including Current Portion The carrying amounts and fair value of the Company’s long-term borrowings are as follows (in millions): As of December 31, 2020 2019 Carrying Amount Fair Value Carrying Amount Fair Value Long-term debt, including current portion (1) Convertible notes $ 515.6 $ 967.1 $ 1,163.1 $ 1,730.2 Long-term debt 2,975.7 2,966.8 2,449.3 2,427.8 _______________________ (1) Long-term debt is carried on the Consolidated Balance Sheets at historical cost net of debt discount and issuance costs. The fair value of the Company's 1.00% Notes (as of December 31, 2019), 3.875% Notes (as of December 31, 2020) and 1.625% Notes (as of December 31, 2020 and December 31, 2019) were estimated based on market prices in active markets (Level 1). The fair value of other long-term debt was estimated based on discounting the remaining principal and interest payments using current market rates for similar debt (Level 2) at December 31, 2020 and December 31, 2019. Fair Values Measured on a Non-Recurring Basis Our non-financial assets, such as property, plant and equipment, goodwill and intangible assets are recorded at fair value upon a business combination and are remeasured at fair value only if an impairment charge is recognized. The Company uses unobservable inputs to the valuation methodologies that are significant to the fair value measurements, and the valuations require management's judgment due to the absence of quoted market prices. The Company determines the fair value of its held and used assets, goodwill and intangible assets using an income, cost or market approach as determined reasonable. As of December 31, 2020 and December 31, 2019, there were no non-financial assets included in the Company's Consolidated Balance Sheet that were remeasured at fair value on a non-recurring basis. The following table shows the adjustments to fair value of certain of the Company's non-financial assets that had an impact on the Company's results of operations (in millions): Year Ended December 31, 2020 2019 2018 Nonrecurring fair value measurements Asset impairments (Level 3) $ 17.5 $ 3.4 $ 2.4 Goodwill and IPRD impairments (Level 3) 1.3 1.6 6.8 $ 18.8 $ 5.0 $ 9.2

Financial Instruments

Financial Instruments	12 Months Ended
	Dec. 31, 2020
Investments, All Other Investments [Abstract]
Financial Instruments	Note 15: Financial Instruments Foreign Currencies As a multinational business, the Company's transactions are denominated in a variety of currencies. When appropriate, the Company uses forward foreign currency contracts to reduce its overall exposure to the effects of currency fluctuations on its results of operations and cash flows. The Company's policy prohibits trading in currencies for which there are no underlying exposures and entering into trades for any currency to intentionally increase the underlying exposure. The Company primarily hedges existing assets and liabilities associated with transactions currently on its balance sheet, which are undesignated hedges for accounting purposes. As of December 31, 2020 and 2019, the Company had outstanding foreign exchange contracts with notional amounts of $263.4 million and $183.3 million, respectively. Such contracts were obtained through financial institutions and were scheduled to mature within one to three months from the time of purchase. Management believes that these financial instruments should not subject the Company to increased risks from foreign exchange movements because gains and losses on these contracts should offset losses and gains on the underlying assets, liabilities and transactions to which they are related. The following schedule summarizes the Company's net foreign exchange positions in U.S. dollars (in millions): As of December 31, 2020 2019 Buy (Sell) Notional Amount Buy (Sell) Notional Amount Japanese Yen $ 71.2 $ 71.2 $ 49.8 $ 49.8 Philippine Peso 57.2 57.2 36.4 36.4 Euro 47.7 47.7 — — Korean Won 34.4 34.4 18.1 18.1 Chinese Yuan 17.7 17.7 20.2 20.2 Malaysian Ringgit 11.7 11.7 20.4 20.4 Czech Koruna — — 11.9 11.9 Other currencies - Buy 12.4 12.4 21.9 21.9 Other currencies - Sell (11.1) 11.1 (4.6) 4.6 $ 241.2 263.4 $ 174.1 $ 183.3 Amounts receivable or payable under the contracts are included in other current assets or accrued expenses and other current liabilities in the accompanying Consolidated Balance Sheets. For the years ended December 31, 2020, 2019 and 2018, realized and unrealized foreign currency transactions totaled a loss of $6.2 million, $5.0 million and $8.0 million, respectively. The realized and unrealized foreign currency transactions are included in other income (expense) in the Company's Consolidated Statements of Operations and Comprehensive Income. Cash Flow Hedges All derivatives are recognized on the balance sheet at their fair value and classified based on each instrument’s maturity date. Foreign currency risk The purpose of the Company's foreign currency hedging activities is to protect the Company from the risk that the eventual cash flows resulting from transactions in foreign currencies will be adversely affected by changes in exchange rates. The Company enters into forward contracts that are designated as foreign currency cash flow hedges of selected forecasted payments denominated in currencies other than U.S. dollars. The Company did not have outstanding derivatives for its foreign currency exposure designated as cash flow hedges as of December 31, 2020 and 2019. See Note 17: ''Changes in Accumulated Other Comprehensive Loss'' for the effective amounts related to derivative instruments designated as cash flow hedges affecting accumulated other comprehensive loss and the Consolidated Statements of Operations and Comprehensive Income for the year ended December 31, 2020. Interest rate risk The Company uses interest rate swap contracts to mitigate its exposure to interest rate fluctuations. On April 17, 2020, the Company entered into interest rate swap agreements for notional amounts totaling $1.25 billion (effective as of April 30, 2020) and $750.0 million (effective as of December 31, 2020) and $750.0 million (effective as of December 31, 2021) with maturity dates of December 31, 2020, December 31, 2021 and December 31, 2022, respectively. The Company did not identify any ineffectiveness with respect to the notional amounts of the interest rate swap contracts effective as of December 31, 2020 and December 31, 2019 amounting to $1.5 billion and $1.0 billion, respectively. Convertible Note Hedges The Company entered into convertible note hedges in connection with the issuance of the 1.625% Notes. Other

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2020
Income Tax Disclosure [Abstract]
Income Taxes	Note 16: Income Taxes The Company's geographic sources of income (loss) before income taxes and non-controlling interest are as follows (in millions): Year ended December 31, 2020 2019 2018 United States $ (181.2) $ (308.2) $ (181.8) Foreign 357.8 584.8 936.8 Income before income taxes $ 176.6 $ 276.6 $ 755.0 The Company's provision (benefit) for income taxes is as follows (in millions): Year ended December 31, 2020 2019 2018 Current: Federal $ 0.6 $ 1.2 $ (2.0) State and local 0.1 — (2.2) Foreign 54.0 48.5 55.3 54.7 49.7 51.1 Deferred: Federal (69.2) (5.0) 99.4 State and local (66.4) — — Foreign 21.1 18.0 (25.4) (114.5) 13.0 74.0 Total provision (benefit) $ (59.8) $ 62.7 $ 125.1 A reconciliation of the U.S. federal statutory income tax rate to the Company's effective income tax rate is as follows: Year ended December 31, 2020 2019 2018 U.S. federal statutory rate 21.0 % 21.0 % 21.0 % Increase (decrease) resulting from: State and local taxes, net of federal tax benefit (1.4) (2.6) (1.0) Impact of U.S. Tax Reform and related effects (1) — — 4.7 Impact of foreign operations 7.6 3.8 (1.2) Impact of U.S. tax method changes (2) — — (6.4) Impact of the Domestication (3) (35.7) — — Change in valuation allowance and related effects (4) (24.4) 1.8 0.6 Non-deductible share-based compensation costs 1.7 (0.5) (0.5) U.S. federal R&D credit (3.6) (3.7) (1.1) Nondeductible officer compensation 1.1 1.5 0.4 Other (0.1) 1.4 0.1 Total (33.8) % 22.7 % 16.6 % (1) For the year ended December 31, 2018, this primarily included expense of (i) $31.8 million, or 4.2%, related to the recognition of deferred tax liability for undistributed prior years' earnings of the foreign subsidiaries, (ii) $1.8 million, or 0.3% related to the limitation on deductibility of prior years’ executive compensation, and (iii) $1.5 million, or 0.2% related to the impact of the mandatory repatriation tax. These adjustments were made pursuant to SAB 118. (2) For the year ended December 31, 2018, this included a one-time benefit of $48.2 million, or 6.4%, related to U.S. tax method changes made during the year that impacted the Company’s GILTI inclusion. (3) On July 6, 2020, the Company completed a simplification of its corporate structure by repatriating the economic rights of its non-U.S. IP to the United States via domestication of certain foreign subsidiaries (the "Domestication"). The Domestication more closely aligns the Company's corporate structure with its operating structure in accordance with the OECD’s BEPS conclusions and changes to U.S. and European tax laws. The impact of the Domestication, which is regarded as a change in tax status, resulted in a benefit primarily from recognizing certain deferred tax assets, net of deferred tax liabilities, of $63.0 million, or 35.7%. (4) For the year ended December 31, 2020, this included a benefit of $49.4 million, or 28.0%, for the release of a partial state valuation allowance due to an increase to forecasted domestic income as a result of the Domestication of certain foreign subsidiaries and an expense of $61.8 million, or 35.0%, primarily related to the expiration of Japan net operating losses, netted with the offsetting benefit of $61.8 million, or 35.0%, primarily for the decrease in the related valuation allowance for those same Japan net operating losses. For the year ended December 31, 2019, this included an expense of $11.2 million, or 4.0%, primarily related to the write-off of Hong Kong NOL and expiration of Japan NOL, netted with the offsetting benefit of $11.2 million, or 4.0%, primarily for the decrease in related valuation allowance for those same Hong Kong and Japan NOLs. For the year ended December 31, 2018, this included an expense of $135.2 million, or 17.9%, primarily related to the expiration of Japan NOLs, netted with the offsetting benefit of $135.2 million, or 17.9%, primarily for the decrease in the related valuation allowance for those same Japan NOLs. The Company’s effective tax rate for 2020 was a benefit of (33.8)%, which differs from the U.S. federal income tax rate of 21%, primarily due to the Domestication of certain foreign subsidiaries and a partial release of state valuation allowance, partially offset by foreign taxes for which the Company will not receive a U.S. tax credit as well as period costs related to the Company's GILTI inclusion. The Company’s effective tax rate for 2019 was 22.7%, which differs from the U.S. federal income tax rate of 21%, primarily due to foreign taxes for which the Company will not receive a U.S. tax credit as well as period costs related to the Company's GILTI inclusion. The Company's effective tax rate for 2018 was 16.6%, which differs from the U.S. federal statutory income tax rate of 21% primarily due to a one-time benefit of U.S. tax method changes made during the year that impacted the Company's GILTI inclusion. The tax effects of temporary differences in the recognition of income and expense for tax and financial reporting purposes that give rise to significant portions of the net deferred tax asset (liability) are as follows (in millions): As of December 31, 2020 2019 NOL and tax credit carryforwards $ 471.6 $ 612.9 163 (j) interest expense carryforward 65.7 49.3 Lease liabilities (1) 32.5 22.1 ROU asset (1) (32.5) (22.1) Tax-deductible goodwill and amortizable intangibles (38.0) (48.6) Capitalization of research and development expenses 90.7 42.7 Reserves and accruals 68.4 27.5 Property, plant and equipment (95.8) (81.2) Inventories 84.3 22.0 Undistributed earnings of foreign subsidiaries (57.5) (63.7) Share-based compensation 7.7 10.3 Pension 21.2 26.3 Other 3.2 8.0 Deferred tax assets and liabilities before valuation allowance 621.5 605.5 Valuation allowance (249.9) (357.9) Net deferred tax asset $ 371.6 $ 247.6 (1) The deferred tax assets and liabilities disclosure as of December 31, 2019 has been adjusted to reflect the gross deferred tax right-of-use asset and related gross deferred lease liability recognized in accordance with the New Leasing Standard. As of December 31, 2020 and 2019, the Company had approximately $99.0 million and $521.9 million, respectively, of federal NOL carryforwards, before reduction for unrecognized tax benefits, which are subject to annual limitations prescribed in Section 382 of the Internal Revenue Code. The decrease is due to current year utilization. If not utilized, a portion of the NOLs will expire in varying amounts from 2028 to 2036; however, a small portion of the NOL that was generated after December 31, 2017 is carried forward indefinitely. As of December 31, 2020 and 2019, the Company had approximately $153.4 million and $134.5 million, respectively, of federal credit carryforwards, before consideration of valuation allowance or reduction for unrecognized tax benefits, which are subject to annual limitations prescribed in Section 383 of the Internal Revenue Code. If not utilized, the credits will expire in varying amounts from 2028 to 2040. As of December 31, 2020 and 2019, the Company had approximately $741.3 million and $825.8 million, respectively, of state NOL carryforwards, before consideration of valuation allowance or reduction for unrecognized tax benefits. The decrease is primarily due to current year utilization. If not utilized, a portion of the NOLs will expire in varying amounts starting in 2021. Certain states have adopted the federal rule allowing unlimited NOL carryover for NOLs generated in tax years beginning after December 31, 2017. Therefore, a portion of the state NOLs generated after 2017 carry forward indefinitely. As of December 31, 2020 and 2019, the Company had $141.1 million and $138.6 million, respectively, of state credit carryforwards before consideration of valuation allowance or reduction for unrecognized tax benefits. If not utilized, a portion of the credits will begin to expire in varying amounts starting in 2021. As of December 31, 2020 and 2019, the Company had approximately $581.6 million and $757.1 million, respectively, of foreign NOL carryforwards, before consideration of valuation allowance. The decrease is primarily due to expiration of Japan NOLs as discussed above. If not utilized, a portion of the NOLs will begin to expire in varying amounts starting in 2021. A significant portion of these NOLs will expire by 2025. As of December 31, 2020 and 2019, the Company had $69.4 million and $76.8 million, respectively, of foreign credit carryforwards before consideration of valuation allowance. If not utilized, the majority of these credits will expire by 2026. The Company continues to maintain a valuation allowance of $128.5 million on a portion of its Japan NOLs, which expire in varying amounts from 2021 to 2024. In addition to the valuation allowance on the Japan NOLs, the Company maintains a partial valuation allowance of $72.5 million on its U.S. state deferred tax assets, and a valuation allowance on foreign net operating losses and tax credits in certain other foreign jurisdictions. At December 31, 2020, 2019 and 2018, respectively, the Company was not indefinitely reinvested with respect to the earnings of its foreign subsidiaries and has therefore accrued withholding taxes that would be owed upon future distributions of such earnings. The Company maintains liabilities for unrecognized tax benefits. These liabilities involve considerable judgment and estimation and are continuously monitored by management based on the best information available, including changes in tax regulations, the outcome of relevant court cases, and other information. The Company is currently under examination by various taxing authorities. Although the outcome of any tax audit is uncertain, the Company believes that it has adequately provided in its consolidated financial statements for any additional taxes that the Company may be required to pay as a result of such examinations. If the payment ultimately proves not to be necessary, the reversal of these tax liabilities would result in tax benefits being recognized in the period the Company determines such liabilities are no longer necessary. However, if an ultimate tax assessment exceeds the Company's estimate of tax liabilities, additional tax expense will be recorded. The impact of such adjustments could have a material impact on the Company's results of operations in future periods. The activity for unrecognized gross tax benefits is as follows (in millions): 2020 2019 2018 Balance at beginning of year $ 130.0 $ 112.2 $ 114.8 Acquired balances — 15.5 — Additions for tax benefits related to the current year 11.9 9.4 7.4 Additions for tax benefits of prior years 12.3 8.0 2.8 Reductions for tax benefits of prior years (1.4) (0.2) (1.9) Lapse of statute (1.3) (8.2) (10.9) Settlements (0.5) (6.7) — Balance at end of year $ 151.0 $ 130.0 $ 112.2 Included in the December 31, 2020 balance of $151.0 million is $116.0 million related to unrecognized tax benefits that, if recognized, would affect the annual effective tax rate. Also included in the balance of unrecognized tax benefits as of December 31, 2020 is $35.0 million of benefit that, if recognized, would result in adjustments to other tax accounts, primarily deferred taxes. Although the Company cannot predict the timing of resolution with taxing authorities, if any, the Company believes it is reasonably possible that its unrecognized tax benefits will be reduced by $48.8 million in the next 12 months due to settlement with tax authorities or expiration of the applicable statute of limitations. The Company recognized approximately $0.2 million of tax expense for interest and penalties during the year ended December 31, 2020. The Company had approximately $5.3 million, $5.1 million, and $5.1 million of accrued interest and penalties at December 31, 2020, 2019, and 2018, respectively.

Changes in Accumulated Other Co

Changes in Accumulated Other Comprehensive Loss	12 Months Ended
	Dec. 31, 2020
Equity [Abstract]
Changes in Accumulated Other Comprehensive Loss	Note 17: Changes in Accumulated Other Comprehensive Loss Amounts comprising the Company's accumulated other comprehensive loss and reclassifications are as follows (in millions): Currency Translation Adjustments Effects of Cash Flow Hedges Total Balance December 31, 2018 $ (42.5) 4.6 $ (37.9) Other comprehensive income (loss) prior to reclassifications 0.1 (19.6) (19.5) Amounts reclassified from accumulated other comprehensive loss — 3.1 3.1 Net current period other comprehensive income (loss) (1) 0.1 (16.5) (16.4) Balance December 31, 2019 (42.4) (11.9) (54.3) Other comprehensive income prior to reclassifications 1.8 14.9 16.7 Amounts reclassified from accumulated other comprehensive loss — (20.0) (20.0) Net current period other comprehensive income (loss) (1) 1.8 (5.1) (3.3) Balance December 31, 2020 $ (40.6) $ (17.0) $ (57.6) _______________________ (1) Effects of cash flow hedges are net of tax benefit of $1.7 million and $4.4 million for the years ended December 31, 2020 and December 31, 2019, respectively. Amounts reclassified from accumulated other comprehensive loss to the specific caption within the Consolidated Statements of Operations and Comprehensive Income were as follows: Year Ended December 31, To caption 2020 2019 Interest rate swaps $ 20.0 $ (3.1) Interest expense Total reclassifications $ 20.0 $ (3.1)

Supplemental Disclosures

Supplemental Disclosures	12 Months Ended
	Dec. 31, 2020
Supplemental Cash Flow Elements [Abstract]
Supplemental Disclosures	Note 18: Supplemental Disclosures Supplemental Disclosure of Cash Flow Information Certain of the Company's cash and non-cash activities were as follows (in millions): Year ended December 31, 2020 2019 2018 Non-cash investing activities: Capital expenditures in accounts payable and other long-term liabilities $ 162.5 $ 155.3 $ 233.9 Sale of property in exchange of note receivable 7.2 — — Right-of-use assets obtained in exchange of lease liabilities (1) 58.2 17.5 Non-cash financing activities: Liability incurred for purchase of business $ — $ 12.7 $ — Debt assumed through purchase of equity interest and assets — — 50.6 Cash paid for: Interest expense $ 109.1 $ 97.2 $ 80.0 Income taxes 52.5 62.9 53.2 Operating lease payments in operating cash flows (1) 36.9 37.6 (1) These disclosures are not applicable for the year ended December 31, 2018 due to the method of adoption of the New Leasing Standard. See Note 9: ''Long-Term Debt'' and 10: ''Earnings Per Share and Equity'' for shares of common stock issued and repurchased in connection with the maturity and settlement of the 1.00% Notes. Following is a reconciliation of the captions in the Consolidated Balance Sheets to the Consolidated Statements of Cash Flows (in millions): As of December 31, 2020 2019 2018 Consolidated Balance Sheets: Cash and cash equivalents $ 1,080.7 $ 894.2 $ 1,069.6 Restricted cash (included in other current assets) 0.8 — 17.5 Cash, cash equivalents and restricted cash in Consolidated Statements of Cash Flows $ 1,081.5 $ 894.2 $ 1,087.1 The restricted cash balance as of December 31, 2018, which included the consideration held in escrow for the acquisition of Aptina in 2014, was settled during the year ended December 31, 2019, upon satisfaction of certain outstanding items contained in the merger agreement relating to such acquisition.

Supplementary Financial Informa

Supplementary Financial Information - Selected Quarterly Financial Data (Unaudited)	12 Months Ended
	Dec. 31, 2020
Quarterly Financial Information Disclosure [Abstract]
Supplementary Financial Information - Selected Quarterly Financial Data (Unaudited)	Note 19: Supplementary Financial Information - Selected Quarterly Financial Data (Unaudited) Consolidated unaudited quarterly financial information is as follows (in millions, except per share data): Quarters ended in 2020 April 3 July 3 October 2 December 31 Revenue $ 1,277.9 $ 1,213.5 $ 1,317.3 $ 1,446.3 Gross Profit (exclusive of the amortization of acquisition-related intangible assets) 402.7 374.3 441.2 497.6 Net income (loss) attributable to ON Semiconductor Corporation (14.0) (1.4) 160.6 89.0 Diluted net income (loss) per common share attributable to ON Semiconductor Corporation (0.03) 0.00 0.38 0.21 Quarters ended in 2019 March 29 June 28 September 27 (1) December 31 Revenue $ 1,386.6 $ 1,347.7 $ 1,381.8 $ 1,401.8 Gross Profit (exclusive of the amortization of acquisition-related intangible assets) 513.7 499.0 475.2 485.7 Net income (loss) attributable to ON Semiconductor Corporation 114.1 101.8 (60.7) 56.5 Diluted net income (loss) per common share attributable to ON Semiconductor Corporation 0.27 0.24 (0.15) 0.14 (1) The net loss for the quarter ended September 27, 2019 was primarily due to the expensing of $169.5 million relating to the settlement of litigation with PI.

Schedule II - Valuation and Qua

Schedule II - Valuation and Qualifying Accounts	12 Months Ended
	Dec. 31, 2020
SEC Schedule, 12-09, Valuation and Qualifying Accounts [Abstract]
Schedule II - Valuation and Qualifying Accounts	Description Balance at Beginning of Period Charged (Credited) to Costs and Expenses Charged to Other Accounts Deductions/Write-offs Balance at End of Period Allowance for deferred tax assets Year ended December 31, 2018 $ 462.3 $ 4.6 $ 15.8 (1) $ (135.2) (2) $ 347.5 Year ended December 31, 2019 347.5 5.0 16.6 (3) (11.2) (4) 357.9 Year ended December 31, 2020 357.9 (43.1) (5) 11.0 (1) (75.9) (2) 249.9 ______________________ (1) Primarily represents the effects of cumulative translation adjustments. (2) Primarily relates to the expiration of Japan net operating losses. See Note 16: "Income Taxes." (3) Primarily represents the effects of cumulative translation adjustments and includes $14.0 million of additional allowance for deferred tax assets arising from the Quantenna acquisition. (4) Primarily relates to the write-off of Hong Kong net operating losses upon the liquidation of Sanyo Semiconductor (H.K.) Co., Ltd. as well as the expiration of Japan net operating losses. (5) Primarily relates to the release of state valuation as a result of the Domestication of certain foreign subsidiaries. See Note 16: "Income Taxes."

Significant Accounting Polici_2

Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2020
Accounting Policies [Abstract]
Principles of Consolidation	Principles of Consolidation The accompanying consolidated financial statements include the assets, liabilities, revenue and expenses of all wholly-owned and majority-owned subsidiaries over which the Company exercises control and, when applicable, entities in which the Company has a controlling financial interest or is the primary beneficiary. Investments in affiliates where the Company does not exert a controlling financial interest are not consolidated. All intercompany balances and transactions have been eliminated.
Use of Estimates	Use of Estimates The preparation of financial statements in accordance with GAAP requires management to make estimates and assumptions that affect the reported amount of assets and liabilities at the date of the financial statements and the reported amount of revenue and expenses during the reporting period. Management evaluates these estimates and judgments on an ongoing basis and bases its estimates on experience, current and expected future conditions, third-party evaluations and various other assumptions that management believes are reasonable under the circumstances. Significant estimates have been used by management in conjunction with the following: (i) future payouts for customer incentives and amounts subject to allowances and returns; (ii) valuation and obsolescence relating to inventories; (iii) variable and share-based compensation; and (iv) measurement of valuation allowances against deferred tax assets, and evaluations of uncertain tax positions. Additionally, during periods where it becomes applicable, significant estimates will be used by management in determining the future cash flows used to assess and test for impairment of indefinite-lived intangible assets, long-lived assets and goodwill and in assumptions used in connection with business combinations. Actual results may differ from the estimates and assumptions used in the consolidated financial statements.
Cash and Cash Equivalents	Cash and Cash Equivalents Cash and cash equivalents include cash on hand, demand deposits and highly liquid investments with original maturities at the time of purchase of three months or less. The Company maintains amounts on deposit at various financial institutions, which may at times exceed federally insured limits. However, management periodically evaluates the credit-worthiness of those institutions and has not experienced any losses on such deposits.
Inventories	Inventories Inventories are stated at the lower of standard cost (which approximates actual cost on a first-in, first-out basis) or net realizable value. General market conditions, as well as the Company's design activities, can cause certain of its products to become obsolete. The Company writes down excess and obsolete inventories based upon a regular analysis of inventory on hand compared to historical and projected end-user demand. The determination of projected end-user demand requires the use of estimates and assumptions related to projected unit sales for each product. These write downs can influence results from operations. For example, when demand for a given part falls, all or a portion of the related inventory that is considered to be in
Property, Plant and Equipment	Property, Plant and Equipment Property, plant and equipment are recorded at cost and are depreciated over estimated useful lives of 30-50 years for buildings and 3-10 years for computers, machinery and equipment using straight-line methods. Expenditures for maintenance and repairs are charged to operations in the period in which the expense is incurred. When assets are retired or otherwise disposed of, the related costs and accumulated depreciation are removed from the balance sheet and any resulting gain or loss is reflected in operations in the period realized.
Business Combination Purchase Price Allocation	Business Combination Purchase Price AllocationThe allocation of the purchase price of business combinations is based on management estimates and assumptions, which utilize established valuation techniques appropriate for the technology industry. These techniques include the income approach, cost approach or market approach, depending upon which approach is the most appropriate based on the nature and reliability of available data. Management records the acquired assets and liabilities at fair value. If the income approach is used, the fair value determination is predicated upon the value of the future cash flows that an asset is expected to generate over its economic life. The cost approach takes into account the cost to replace (or reproduce) the asset and the effects on the asset's value of physical, functional and/or economic obsolescence that has occurred with respect to the asset. The market approach is used to estimate value from an analysis of actual market transactions or offerings for economically comparable assets available as of the valuation date. Determining the fair value of acquired technology assets is judgmental in nature and requires the use of significant estimates and assumptions, including the discount rate, revenue growth rates, projected gross margins, and estimated research and development and other operating expenses.
Goodwill	Goodwill Goodwill represents the excess of the purchase price over the estimated fair value of the net assets acquired in a business combination. The Company evaluates its goodwill for impairment annually during the fourth quarter and whenever events or changes in circumstances indicate the carrying value of a reporting unit may not be recoverable. The Company’s divisions are one level below the operating segments, constituting individual businesses, at which level the Company’s segment management conducts regular reviews of the operating results. The Company's divisions, either individually or in a combination, constitute reporting units for purposes of allocating and testing goodwill. The Company's impairment evaluation consists of a qualitative assessment. If this assessment indicates that it is more likely than not the estimated fair value of a reporting unit exceeds its carrying value, goodwill is not considered impaired. Otherwise, the Company performs a quantitative impairment test by comparing the fair value of a reporting unit with its carrying value, including goodwill. If the carrying value of the net assets associated with the reporting unit exceeds the fair value of the reporting unit, goodwill is considered impaired and will be determined as the amount by which the reporting unit's carrying value exceeds its fair value, not to exceed the carrying amount of goodwill. The Company can bypass the qualitative assessment for any period and proceed directly to the quantitative impairment test.
Intangible Assets	Intangible Assets The Company's acquisitions have resulted in intangible assets consisting of values assigned to customer relationships, patents, developed technology, licenses, IPRD and trademarks. IPRD is considered an indefinite-lived intangible asset until the abandonment or completion of the associated research and development efforts. If abandoned, the assets would be impaired. If the activities are completed, a determination is made regarding the useful lives of such assets and methods of amortization. The Company is required to test its IPRD assets for impairment annually using the guidance for indefinite-lived intangible assets. The Company calculates the fair value of the IPRD asset and records an impairment charge if the carrying amount exceeds fair value. The Company determines the fair value based on an income approach, which is calculated as the present value of the estimated future cash flows of the IPRD asset. The assumptions about estimated cash flows include factors such as future revenue, gross profit, operating expenses and industry trends. The Company can bypass the qualitative assessment for any asset in any period and proceed directly to the quantitative impairment test.
Leases	Leases The Company determines if an arrangement is a lease at its inception. Operating lease arrangements are comprised primarily of real estate and equipment agreements for which the right-of-use ("ROU") assets are included in other assets and the corresponding lease liabilities, depending on their maturity, are included in accrued expenses and other current liabilities or other long-term liabilities in the Consolidated Balance Sheet. ROU assets represent the right to use an underlying asset for the lease term and lease liabilities represent the obligation to make lease payments arising from the lease. ROU assets and lease liabilities are recognized at the lease commencement date based on the estimated present value of lease payments over the lease term. The lease term includes options to extend the lease when it is reasonably certain that the option will be exercised. Leases with a term of 12 months or less are not recorded on the Consolidated Balance Sheet. The Company uses its estimated incremental borrowing rate in determining the present value of lease payments considering the term of the lease, which is derived from information available at the lease commencement date, giving consideration to publicly available data for instruments with similar characteristics. The Company accounts for the lease and non-lease components as a single lease component.
Debt Issuance Costs	Debt Issuance Costs Debt issuance costs for line-of-credit agreements, including the Company's Revolving Credit Facility, are capitalized and amortized over the term of the underlying agreements on a straight-line basis. Amortization of these debt issuance costs is included in interest expense while the unamortized balance is included in other assets. Debt issuance costs for the Company's convertible notes and term debt are recorded as a direct deduction from the carrying amounts of the such debt, consistent with debt discounts, and are amortized over their term using the effective interest method. Amortization of these debt issuance costs is included in interest expense.
Contingencies	ContingenciesThe Company is involved in a variety of legal matters, IP matters, environmental, financing and indemnification contingencies that arise in the ordinary course of business. Based on the information available, management evaluates the relevant range and likelihood of potential outcomes and records the appropriate liability when the amount is deemed probable and reasonably estimable.
Treasury Stock	Treasury Stock Treasury stock is recorded at cost, inclusive of fees, commissions and other expenses, when outstanding common shares are repurchased by the Company, including when outstanding shares are withheld to satisfy tax withholding obligations in connection with certain shares pursuant to RSUs under the Company's share-based compensation plans. Reissuance of shares
Revenue Recognition	Revenue Recognition The Company generates revenue from sales of its semiconductor products to OEMs, electronic manufacturing service providers and distributors. The Company also generates revenue, to a much lesser extent, from product development agreements and manufacturing services provided to customers. The Company recognizes revenue when it satisfies a performance obligation in an amount reflecting the consideration to which it expects to be entitled. For sales agreements, the Company has identified the promise to transfer products, each of which is distinct, as the performance obligation. For product development agreements, the Company has identified the completion of a service defined in the agreement as the performance obligation. The Company applies a five-step approach in determining the amount and timing of revenue to be recognized: (1) identifying the contract with a customer; (2) identifying the performance obligations in the contract; (3) determining the transaction price; (4) allocating the transaction price to the performance obligations in the contract; and (5) recognizing revenue when the performance obligation is satisfied. Sales agreements with customers are renewable periodically and contain terms and conditions with respect to payment, delivery, warranty and supply, but typically do not require minimum purchase commitments. In the absence of a sales agreement, the Company’s standard terms and conditions apply. The Company considers the customer purchase orders, governed by sales agreements or the Company’s standard terms and conditions, to be the contract with the customer. The Company evaluates certain factors including the customer’s ability to pay (or credit risk). Most of the Company’s OEM customers negotiate pricing terms on an annual basis, distributors generally negotiate pricing terms on a quarterly basis, while the pricing terms for electronic manufacturing service providers are negotiated periodically during the year. Pricing terms on product development agreements are negotiated at the beginning of a project. The Company allocates the transaction price to each distinct product based on its relative stand-alone selling price. In determining the transaction price, the Company evaluates whether the price is subject to refund or adjustment to determine the net consideration to which the Company expects to be entitled. The Company’s OEM customers do not have the right to return products, other than pursuant to the provisions of the Company’s standard warranty. Sales to distributors, however, are typically made pursuant to agreements that provide return rights and stock rotation provisions permitting limited levels of product returns. Sales to certain distributors, primarily those with ship and credit rights, can also be subject to price adjustment on certain products. Although payment terms vary, most distributor agreements require payment within 30 days. In addition, the Company offers cash discounts to certain customers for payments received within an agreed upon time, generally ten days after shipment. The Company recognizes revenue when it satisfies a performance obligation. The Company recognizes revenue from sales agreements upon transferring control of a product to the customer. This typically occurs when products are shipped or delivered, depending on the delivery terms, or when products that are consigned at customer locations are consumed. The Company recognizes revenue from product development agreements over time based on the cost-to-cost method. Sales returns and allowances, which include ship and credit reserves for distributors, are estimated based on historical claims data and expected future claims. Provisions for discounts and rebates to customers, estimated returns and allowances, ship and credit claims and other adjustments are provided for in the same period the related revenue are recognized, and are netted against revenue. For non-quality related returns, the Company recognizes a related asset for the right to recover returned products with a corresponding reduction to cost of goods sold. The Company records a reserve for cash discounts as a reduction to accounts receivable and a reduction to revenue, based on the experience with each customer. Frequently, the Company receives orders with multiple delivery dates that may extend across reporting periods. Each delivery constitutes an individual performance obligation, which consists of transferring control of the products to the customers based on their stand-alone selling price. The Company invoices the customer for each delivery upon shipment and recognizes revenue in accordance with delivery terms. As scheduled delivery dates are within one year, revenue allocated to future shipments of partially completed contracts are not disclosed. The Company records freight and handling costs associated with outbound freight after control over a product has transferred to a customer as a fulfillment cost and includes it in cost of revenue. Taxes assessed by government authorities on revenue-producing transactions, including value-added and excise taxes, are presented on a net basis (excluded from revenue). The Company generally warrants that products sold to its customers will, at the time of shipment, be free from defects in workmanship and materials and conform to specifications. The Company’s standard warranty extends for a period of two years from the date of delivery, except in the case of image sensor products, which are warrantied for one year from the date of
Research and Development Costs	Research and Development Costs Research and development costs are expensed as incurred.
Income Taxes	Income Taxes Income taxes are accounted for using the asset and liability method. Under this method, deferred income tax assets and liabilities are recognized for the future tax consequences attributable to temporary differences between the financial statement carrying amounts of existing assets and liabilities and their respective tax bases. Deferred income tax assets and liabilities are measured using enacted tax rates expected to apply to taxable income in the years in which these temporary differences are expected to be recovered or settled. The effect on deferred tax assets and liabilities of a change in tax rates is recognized in income in the period that includes the enactment date. A valuation allowance is provided for those deferred tax assets for which management cannot conclude that it is more likely than not that such deferred tax assets will be realized. In determining the amount of the valuation allowance, estimated future taxable income, feasible tax planning strategies, future reversals of existing temporary differences and taxable income in prior carryback years, if a carryback is permitted, are considered. If the Company determines it is more likely than not that all or a portion of the remaining deferred tax assets will not be realized, the valuation allowance will be increased with a charge to income tax expense. Conversely, if the Company determines it is more likely than not to be able to utilize all or a portion of the deferred tax assets for which a valuation allowance has been provided, the related portion of the valuation allowance will be recorded as a reduction to income tax expense. The Company recognizes and measures benefits for uncertain tax positions using a two-step approach. The first step is to evaluate the tax position taken or expected to be taken in a tax return by determining if the weight of available evidence indicates that is it more likely than not that the tax positions will be sustained upon audit, including resolution of any related appeals or litigation processes. For tax positions that are more likely than not to be sustained upon audit, the second step is to measure the tax benefit as the largest amount that is more than 50% likely to be realized upon settlement. No tax benefit is recognized for tax positions that are not more likely than not to be sustained. The Company's practice is to recognize interest and/or penalties related to income tax matters in income tax expense. Significant judgment is required to evaluate uncertain tax positions. Evaluations are based upon a number of factors, including changes in facts or circumstances, changes in tax law, correspondence with tax authorities during the course of tax audits and effective settlement of audit issues. Changes in the recognition or measurement of uncertain tax positions could result in significant increases or decreases in income tax expense in the period in which the change is made, which could have a significant impact to the Company's effective tax rate.
Foreign Currencies	Foreign Currencies Most of the Company's foreign subsidiaries conduct business primarily in U.S. dollars and, as a result, utilize the U.S. dollar as their functional currency. For the remeasurement of financial statements of these subsidiaries, assets and liabilities in foreign currencies that are receivable or payable in cash are remeasured at current exchange rates, while inventories and other non-monetary assets in foreign currencies are remeasured at historical rates. Gains and losses resulting from the remeasurement of such financial statements are included in the operating results, as are gains and losses incurred on foreign currency transactions.
Share-Based Compensation	Share-Based Compensation Share-based compensation is measured at the grant date, based on the estimated fair value of the award, and is recognized as expense over the employee's requisite service period and for awards with performance conditions, over the performance measurement period. The Company has outstanding awards that vest based on service, performance and market conditions.
Defined Benefit Pension Plans	Defined Benefit Pension Plans The Company maintains defined benefit pension plans covering certain of its foreign employees. Net periodic pension costs and
Fair Value Measurement	Fair Value Measurement The Company measures certain of its financial and non-financial assets at fair value by using the fair value hierarchy that prioritizes certain inputs into individual fair value measurement approaches. Fair value is the exchange price that would be received for an asset or paid to transfer a liability in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants on the measurement date. Valuation techniques used to measure fair value must maximize the use of observable inputs and minimize the use of unobservable inputs. The fair value hierarchy is based on three levels of inputs, of which the first two are considered observable and the last unobservable, that may be used to measure fair value, as follows: • Level 1 - Quoted prices in active markets for identical assets or liabilities; • Level 2 - Inputs other than Level 1 that are observable, either directly or indirectly, such as quoted prices for similar assets or liabilities; quoted prices in markets that are not active; or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the assets or liabilities; and • Level 3 - Unobservable inputs that are supported by little or no market activity and that are significant to the fair value of the assets or liabilities. Companies may choose to measure certain financial instruments and certain other items at fair value. Unrealized gains and losses on items for which the fair value option has been elected must be reported in earnings. The Company has elected not to carry any of its debt instruments at fair value.
Recent Accounting Pronouncements	Adopted: ASU 2020-04 – Facilitation of the Effects of Reference Rate Reform on Financial Reporting ("ASU 2020-04") In March 2020, the FASB issued ASU 2020-04 to address constituents’ concerns about certain accounting consequences that could result from the global markets’ anticipated transition away from the use of the LIBO Rate and other interbank offered rates to alternative reference rates. ASU 2020-04 includes optional expedients and the relief provided is elective and applies to all entities, subject to meeting certain criteria, that have contracts, hedging relationships, and other transactions that reference LIBO Rate or another reference rate expected to be discontinued because of reference rate reform. These amendments are effective for entities as of March 12, 2020 through December 31, 2022. The Company elected to apply the provisions of ASU 2020-04 for its contracts and hedging relationships as of March 12, 2020. The adoption of ASU 2020-04 did not have a material impact on the Company's consolidated financial statements. ASU 2019-12 – Income taxes (Topic 740): Simplifying the accounting for income taxes ("ASU 2019-12") In December 2019, the FASB issued ASU 2019-12, which simplifies the accounting for income taxes by removing certain exceptions to the general principles in Income taxes (Topic 740). The amendments also improve consistent application of and simplify GAAP for other areas of Topic 740 by clarifying and amending existing guidance. This guidance is effective for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2020, with early adoption permitted. The Company early adopted ASU 2019-12 during the quarter ended April 3, 2020. The adoption of ASU 2019-12 did not have a material impact on the Company's consolidated financial statements. ASU 2018-14 – Defined Benefit Plans – General (Topic 715-20): Disclosure Framework – Changes to the Disclosure Requirements of Defined Benefit Plans ("ASU 2018-14") During 2018, the FASB issued ASU 2018-14, which amended ASC 715: Compensation - Retirement Benefits, to add, remove, and clarify disclosure requirements related to defined benefit pension and other postretirement plans. ASU 2018-14 added requirements to disclose, among others, a narrative description of the reasons for significant gains and losses affecting the benefit obligation for the period, and also removed certain other disclosure requirements. For public business entities, the provisions of ASU 2018-14 is effective for fiscal years ending after December 15, 2020. The adoption of ASU 2018-14 did not have a material impact on the Company’s consolidated financial statements. ASU No. 2016-02 - Leases (Topic 842) ("ASU 2016-02"), ASU No. 2018-10 - Codification improvements to Topic 842, Leases ("ASU 2018-10"), ASU No. 2018-11 - Leases (Topic 842) ("ASU 2018-11") (collectively, the "New Leasing Standard") The New Leasing Standard became effective for public business entities for fiscal years beginning after December 15, 2018, including interim periods within those fiscal years. The Company adopted the New Leasing Standard as of January 1, 2019 using the effective date method by recording right-of-use assets of $112.3 million, net of deferred rent liabilities of $5.1 million that were reclassified to right-of-use assets, and lease liabilities of $117.4 million. Under this method, periods prior to 2019 remain unchanged. The Company applied the practical expedients relating to the leases that commenced before January 1, 2019 whereby the Company elected to not reassess the following: (i) whether any expired or existing contracts contain leases; (ii) the lease classification for any expired or existing leases; and (iii) initial direct costs for any existing leases. Pending Adoption: ASU 2020-06 - Accounting for Convertible Instruments and Contracts in an Entity’s Own Equity ("ASU 2020-06") In August 2020, the FASB issued ASU 2020-06, which simplifies the guidance on the issuer’s accounting for convertible debt instruments by removing the separation models for (1) convertible debt with a cash conversion feature and (2) convertible instruments with a beneficial conversion feature. As a result, entities will not separately present in equity an embedded conversion feature in such debt and will account for a convertible debt instrument wholly as debt, unless certain other conditions are met. The elimination of these models will reduce reported interest expense and increase reported net income for entities that have issued a convertible instrument that is within the scope of ASU 2020-06. Also, ASU 2020-06 requires the application of the if-converted method for calculating diluted earnings per share and the treasury stock method will be no longer available. ASU 2020-06 is applicable for fiscal years beginning after December 15, 2021, with early adoption permitted no earlier than fiscal years beginning after December 15, 2020. The Company does not intend to early adopt ASU 2020-06; however, based on the application of the new standard on the 1.625% Notes, there would be a decrease in interest expense and an increase in the dilutive effect of convertible notes included in diluted weighted average shares of common stock outstanding for calculating earnings per share.

Segment Information (Tables)

Segment Information (Tables)	12 Months Ended
	Dec. 31, 2020
Segment Reporting, Measurement Disclosures [Abstract]
Revenue and Gross Profit from Reportable Segments	Revenue and gross profit for the Company’s operating and reportable segments are as follows (in millions): PSG ASG ISG Total For year ended December 31, 2020: Revenue from external customers $ 2,606.1 $ 1,910.4 $ 738.5 $ 5,255.0 Segment gross profit 801.7 730.5 237.7 1,769.9 For year ended December 31, 2019: Revenue from external customers $ 2,788.3 $ 1,972.3 $ 757.3 $ 5,517.9 Segment gross profit 976.0 794.8 275.4 2,046.2 For year ended December 31, 2018: Revenue from external customers $ 3,038.2 $ 2,071.2 $ 768.9 $ 5,878.3 Segment gross profit 1,110.1 878.3 317.1 2,305.5
Reconciliation of Operating Profit (Loss) from Segments to Consolidated	Gross profit is exclusive of the amortization of acquisition-related intangible assets. Depreciation expense is included in segment gross profit. Reconciliations of segment gross profit to consolidated gross profit are as follows (in millions): Year Ended December 31, 2020 2019 2018 Gross profit for reportable segments $ 1,769.9 $ 2,046.2 $ 2,305.5 Less: unallocated manufacturing costs (54.1) (72.6) (66.8) Consolidated gross profit $ 1,715.8 $ 1,973.6 $ 2,238.7
Disaggregation of Revenue	Revenue for the Company's operating and reportable segments disaggregated into geographic locations based on sales billed from the respective country and sales channels are as follows (in millions): Year Ended December 31, 2020 PSG ASG ISG Total Geographic Location Singapore $ 978.0 $ 695.0 $ 126.5 $ 1,799.5 Hong Kong 723.2 410.6 177.8 1,311.6 United Kingdom 395.7 264.5 145.7 805.9 United States 282.8 282.0 163.8 728.6 Other 226.4 258.3 124.7 609.4 Total $ 2,606.1 $ 1,910.4 $ 738.5 $ 5,255.0 Sales Channel Distributors $ 1,776.4 $ 986.4 $ 406.8 $ 3,169.6 OEM 673.6 794.6 297.5 1,765.7 Electronic Manufacturing Service Providers 156.1 129.4 34.2 319.7 Total $ 2,606.1 $ 1,910.4 $ 738.5 $ 5,255.0 Year Ended December 31, 2019 PSG ASG ISG Total Geographic Location Singapore $ 864.7 $ 679.7 $ 168.7 $ 1,713.1 Hong Kong 843.5 436.8 137.0 1,417.3 United Kingdom 467.1 303.5 151.0 921.6 United States 356.3 332.6 121.4 810.3 Other 256.7 219.7 179.2 655.6 Total $ 2,788.3 $ 1,972.3 $ 757.3 $ 5,517.9 Sales Channel Distributors $ 1,740.6 $ 971.5 $ 461.0 $ 3,173.1 OEM 857.5 860.3 258.8 1,976.6 Electronic Manufacturing Service Providers 190.2 140.5 37.5 368.2 Total $ 2,788.3 $ 1,972.3 $ 757.3 $ 5,517.9 Year Ended December 31, 2018 PSG ASG ISG Total Geographic Location Singapore $ 1,086.6 $ 704.2 $ 164.2 $ 1,955.0 Hong Kong 847.9 496.5 144.7 1,489.1 United Kingdom 488.5 319.8 138.2 946.5 United States 398.5 339.2 125.0 862.7 Other 216.7 211.5 196.8 625.0 Total $ 3,038.2 $ 2,071.2 $ 768.9 $ 5,878.3 Sales Channel Distributors $ 2,011.1 $ 1,066.4 $ 464.2 $ 3,541.7 OEM 846.8 860.7 263.4 1,970.9 Electronic Manufacturing Service Providers 180.3 144.1 41.3 365.7 Total $ 3,038.2 $ 2,071.2 $ 768.9 $ 5,878.3
Summary of Property, Plant and Equipment by Geographic Location	Property, plant and equipment, net by geographic location, are summarized as follows (in millions): As of December 31, 2020 2019 United States $ 686.6 $ 616.7 South Korea 455.5 485.4 Philippines 386.6 433.5 China 229.6 243.6 Japan 209.3 218.1 Czech Republic 216.1 213.4 Malaysia 190.2 204.4 Other 138.4 176.5 $ 2,512.3 $ 2,591.6
Schedule of Segments and Product Lines	These segments represent the Company's view of the business and as such are used to evaluate progress of major initiatives and allocation of resources. PSG ASG ISG Analog products Analog products LSI products Discrete products ASIC products Sensors MOSFET products Connectivity products Power Module products ECL products Isolation products Foundry products / services Memory products Gate Driver products Gate Driver products LSI products Standard Logic products Standard Logic products WBG products

Acquisitions, Divestitures an_2

Acquisitions, Divestitures and Licensing Transactions (Tables)	12 Months Ended
	Dec. 31, 2020
Business Acquisition [Line Items]
Schedule of Pro Forma Information	The following unaudited pro-forma consolidated results of operations for the years ended December 31, 2019 and December 31, 2018 have been prepared as if the acquisition of Quantenna had occurred on January 1, 2018 and includes adjustments for amortization of intangibles, interest expense from financing, restructuring, and the effect of purchase accounting adjustments including the step-up of inventory (in millions, except per share data): Year Ended December 31, 2019 December 31, 2018 Revenue $ 5,613.2 $ 6,098.8 Net income 218.2 567.2 Net income attributable to ON Semiconductor Corporation 216.0 564.7 Net income per common share attributable to ON Semiconductor Corporation: Basic 0.53 1.33 Diluted 0.52 1.30
Quantenna
Business Acquisition [Line Items]
Schedule of Purchase Price Allocation	The following table presents the allocation of the purchase price of Quantenna for the assets acquired and liabilities assumed based on their relative fair values, which was finalized during the year ended December 31, 2019 (in millions): Purchase Price Allocation Cash and cash equivalents $ 133.4 Receivables 22.2 Inventories 41.8 Other current assets 4.3 Property, plant and equipment 16.9 Goodwill 726.7 Intangible assets (excluding IPRD) 87.1 IPRD 23.8 Deferred tax assets 29.2 Other non-current assets 12.7 Total assets acquired 1,098.1 Accounts payable 22.6 Other current liabilities 17.5 Deferred tax liabilities 3.3 Other non-current liabilities 15.4 Total liabilities assumed 58.8 Net assets acquired/purchase price $ 1,039.3
SensL Technologies, Ltd.
Business Acquisition [Line Items]
Schedule of Purchase Price Allocation	The following table presents the allocation of the purchase price of SensL for the assets acquired and liabilities assumed based on their fair values (in millions): Purchase Price Allocation Current assets (including cash and cash equivalents of $0.7) $ 4.2 Property, plant and equipment and other non-current assets 1.8 Goodwill 18.9 Intangible assets (excluding IPRD) 31.4 IPRD 20.0 Total assets acquired 76.3 Current liabilities 0.7 Other non-current liabilities 4.0 Total liabilities assumed 4.7 Net assets acquired/purchase price $ 71.6

Goodwill and Intangible Assets

Goodwill and Intangible Assets (Tables)	12 Months Ended
	Dec. 31, 2020
Goodwill and Intangible Assets Disclosure [Abstract]
Summary of Goodwill by Operating Segment	The following table summarizes goodwill by operating and reportable segments (in millions): As of December 31, 2020 As of December 31, 2019 As of December 31, 2018 Goodwill Accumulated Impairment Losses Carrying Value Goodwill Accumulated Impairment Losses Carrying Value Goodwill Accumulated Impairment Losses Carrying Value Operating and Reportable Segments: ASG $ 1,566.3 $ (418.9) $ 1,147.4 $ 1,563.4 $ (418.9) $ 1,144.5 $ 836.7 $ (418.9) $ 417.8 ISG 114.7 — 114.7 114.4 — 114.4 114.4 — 114.4 PSG 433.2 (31.9) 401.3 432.2 (31.9) 400.3 432.2 (31.9) 400.3 Total $ 2,114.2 $ (450.8) $ 1,663.4 $ 2,110.0 $ (450.8) $ 1,659.2 $ 1,383.3 $ (450.8) $ 932.5
Schedule of Change in Goodwill	The following table summarizes the change in goodwill (in millions): Net balance as of December 31, 2018 $ 932.5 Addition due to business combination 726.7 Net balance as of December 31, 2019 1,659.2 Addition due to business combination 4.2 Net balance as of December 31, 2020 $ 1,663.4
Summary of Intangible Assets, Net	Intangible assets, net, were as follows (in millions): As of December 31, 2020 Original Accumulated Accumulated Impairment Losses Carrying Customer relationships $ 581.5 $ (411.7) $ (17.6) $ 152.2 Developed technology 794.7 (532.9) (2.6) 259.2 IPRD 49.5 — (25.4) 24.1 Licenses 30.0 — — 30.0 Other intangibles 79.3 (60.6) (15.2) 3.5 Total intangible assets $ 1,535.0 $ (1,005.2) $ (60.8) $ 469.0 As of December 31, 2019 Original Accumulated Accumulated Impairment Losses Carrying Customer relationships $ 585.2 $ (386.8) $ (20.1) $ 178.3 Developed technology 779.5 (440.3) (2.6) 336.6 IPRD 64.7 — (24.1) 40.6 Licenses 30.0 — — 30.0 Other intangibles 79.3 (59.1) (15.2) 5.0 Total intangible assets $ 1,538.7 $ (886.2) $ (62.0) $ 590.5
Summary of Amortization Expense	Amortization expense for intangible assets, with the exception of the $24.1 million of IPRD assets that will be amortized once the corresponding projects have been completed, is expected to be as follows over the next five years, and thereafter (in millions): Total 2021 $ 99.2 2022 83.8 2023 65.9 2024 54.1 2025 41.1 Thereafter 100.8 Total estimated amortization expense $ 444.9

Restructuring, Asset Impairme_2

Restructuring, Asset Impairments and Other Charges, net (Tables)	12 Months Ended
	Dec. 31, 2020
Restructuring Charges [Abstract]
Summary of Restructuring, Asset Impairments and Other, Net	Details of restructuring, asset impairments and other charges, net are as follows (in millions): Restructuring Asset Impairments (1) Other Total Year Ended December 31, 2020 Voluntary separation program $ 27.5 $ — $ — $ 27.5 2020 Involuntary separation program 11.8 — — 11.8 General workforce reduction 12.3 — — 12.3 Other — 17.5 (3.9) 13.6 Total $ 51.6 $ 17.5 $ (3.9) $ 65.2 Year Ended December 31, 2019 General workforce reduction $ 8.4 $ — $ — $ 8.4 Post-Quantenna acquisition restructuring 15.7 — — 15.7 Other 0.8 3.4 0.4 4.6 Total $ 24.9 $ 3.4 $ 0.4 $ 28.7 Year Ended December 31, 2018 Other $ 3.9 $ 4.6 $ (4.2) $ 4.3 Total $ 3.9 $ 4.6 $ (4.2) $ 4.3 _______________________
Rollforward of Accrued Restructuring Charges	Summary of changes in accrued restructuring charges as follows (in millions): Estimated employee separation charges Estimated costs to exit Total Balance as of December 31, 2018 $ 0.3 $ 0.2 $ 0.5 Charges 24.9 — 24.9 Usage (25.1) (0.1) (25.2) Balance as of December 31, 2019 $ 0.1 $ 0.1 $ 0.2 Charges 51.6 — 51.6 Usage (45.5) (0.1) (45.6) Balance as of December 31, 2020 $ 6.2 $ — $ 6.2

Balance Sheet Information (Tabl

Balance Sheet Information (Tables)	12 Months Ended
	Dec. 31, 2020
Balance Sheet Related Disclosures [Abstract]
Supplemental Balance Sheet Information	Certain significant amounts included in the Company's Consolidated Balance Sheets consist of the following (in millions): As of December 31, 2020 December 31, 2019 Inventories: Raw materials $ 135.7 $ 138.4 Work in process 829.7 772.9 Finished goods 286.0 321.1 $ 1,251.4 $ 1,232.4 Property, plant and equipment, net: Land $ 119.7 $ 125.2 Buildings 850.0 860.6 Machinery and equipment 4,538.0 4,275.2 Property, plant and equipment, gross 5,507.7 5,261.0 Less: Accumulated depreciation (2,995.4) (2,669.4) $ 2,512.3 $ 2,591.6 Accrued expenses: Accrued payroll and related benefits $ 166.8 $ 153.4 Sales related reserves 233.3 247.3 Income taxes payable 25.5 22.5 Other 144.4 115.6 $ 570.0 $ 538.8
Components of Lease Expense and Lease Liabilities	The components of lease expense are as follows (in millions): Year Ended December 31, 2020 December 31, 2019 Operating lease $ 38.2 35.0 Variable lease 4.2 4.0 Short-term lease 4.1 2.6 Total lease expense $ 46.5 41.6 The lease liabilities included in the following captions in the Consolidated Balance Sheet are as follows (in millions): As of December 31, 2020 December 31, 2019 Accrued expenses and other current liabilities $ 32.2 26.1 Other long-term liabilities 115.7 87.9 Total lease liabilities $ 147.9 114.0
Reconciliation of the Maturities of Operating Leases	The reconciliation of the maturities of the operating leases to the lease liabilities recorded in the Consolidated Balance Sheet as of December 31, 2020 is as follows (in millions): 2021 $ 36.5 2022 30.1 2023 23.1 2024 20.8 2025 14.2 Thereafter 49.9 Total lease payments $ 174.6 Less: Interest (26.7) Total lease liabilities $ 147.9

Long-Term Debt (Tables)

Long-Term Debt (Tables)	12 Months Ended
	Dec. 31, 2020
Debt Disclosure [Abstract]
Schedule of Long-Term Debt	The Company's long-term debt consists of the following (annualized interest rates, dollars in millions): As of December 31, 2020 December 31, 2019 Amended Credit Agreement: Revolving Credit Facility due 2024, interest payable monthly at 1.90% and 3.30%, respectively $ 700.0 $ 800.0 Term Loan "B" Facility due 2026, interest payable monthly at 2.15% and 3.80%, respectively 1,614.5 1,630.9 3.875% Notes due 2028 (1) 700.0 — 1.00% Notes due 2020 (2) — 690.0 1.625% Notes due 2023 (3) 575.0 575.0 Other long-term debt (4) — 53.3 Gross long-term debt, including current maturities 3,589.5 3,749.2 Less: Debt discount (5) (69.7) (102.7) Less: Debt issuance costs (6) (28.5) (34.0) Net long-term debt, including current maturities 3,491.3 3,612.5 Less: Current maturities (531.6) (736.0) Net long-term debt $ 2,959.7 $ 2,876.5 _______________________ (1) Interest is payable on March 1 and September 1 of each year at 3.875% annually. (2) Interest was payable on June 1 and December 1 of each year at 1.00% annually. Balance was fully repaid during 2020. (3) Interest is payable on April 15 and October 15 of each year at 1.625% annually. (4) Consisted of a term loan, finance lease and other facility at certain international locations where interest is payable monthly or quarterly, with interest rates ranging between 1.00% and 1.48% and maturity dates in 2020. (5) Debt discount of $6.5 million and zero for the 3.875% Notes, zero and $20.4 million for the 1.00% Notes, $54.2 million and $71.8 million for the 1.625% Notes and $9.0 million and $10.5 million for the Term Loan "B" Facility, in each case as of December 31, 2020 and December 31, 2019, respectively. (6) Debt issuance costs of $2.3 million and zero for the 3.875% Notes, zero and $2.8 million for the 1.00% Notes, $5.2 million and $6.9 million for the 1.625% Notes and $21.0 million and $24.3 million for the Term Loan "B" Facility, in each case as of December 31, 2020 and December 31, 2019, respectively.
Schedule of Annual Maturities Relating to Long-Term Debt	Expected maturities relating to the Company’s gross long-term debt (including current maturities) as of December 31, 2020 are as follows (in millions): Annual 2021 $ 591.4 2022 16.3 2023 16.3 2024 716.4 2025 16.3 Thereafter 2,232.8 Total $ 3,589.5

Earnings Per Share and Equity (

Earnings Per Share and Equity (Tables)	12 Months Ended
	Dec. 31, 2020
Equity [Abstract]
Schedule of Net Income Per Share	Net income per share of common stock attributable to ON Semiconductor Corporation is shown below (in millions, except per share data): Year ended December 31, 2020 2019 2018 Net income attributable to ON Semiconductor Corporation $ 234.2 $ 211.7 $ 627.4 Basic weighted-average shares of common stock outstanding 410.7 410.9 423.8 Add: Incremental shares for: Dilutive effect of share-based awards 1.9 1.9 4.3 Dilutive effect of convertible notes and warrants 6.2 3.2 7.8 Diluted weighted average shares of common stock outstanding 418.8 416.0 435.9 Net income per share of common stock attributable to ON Semiconductor Corporation: Basic $ 0.57 $ 0.52 $ 1.48 Diluted $ 0.56 $ 0.51 $ 1.44
Schedule of Share Repurchase Program	Information relating to the Company's 2018 and 2014 Share Repurchase Programs is as follows (in millions, except per share data): Year ended December 31, 2020 2019 2018 Number of repurchased shares (1) 3.6 7.8 16.8 Aggregate purchase price $ 65.3 $ 138.9 $ 315.0 Fees, commissions and other expenses 0.1 0.1 0.3 Total cash used for share repurchases $ 65.4 $ 139.0 $ 315.3 Weighted-average purchase price per share (2) $ 18.08 $ 17.89 $ 18.78 Available under the 2018 Share Repurchase Program $ 1,295.8 $ 1,361.1 $ 1,500.0 _______________________ (1) None of these shares had been reissued or retired as of December 31, 2020, but may be reissued or retired later.

Share-Based Compensation (Table

Share-Based Compensation (Tables)	12 Months Ended
	Dec. 31, 2020
Share-based Payment Arrangement [Abstract]
Summary of Share-Based Compensation Expense	Total share-based compensation expense related to the Company's RSUs, stock grant awards and ESPP were recorded within the Consolidated Statements of Operations and Comprehensive Income as follows (in millions): Year Ended December 31, 2020 2019 2018 Cost of revenue $ 11.5 $ 10.6 $ 7.0 Research and development 18.2 17.0 14.3 Selling and marketing 12.9 14.8 14.1 General and administrative 25.1 37.0 42.9 Share-based compensation expense 67.7 79.4 78.3 Income tax benefit (14.2) (16.7) (16.4) Share-based compensation expense, net of taxes $ 53.5 $ 62.7 $ 61.9
Summary of Restricted Stock Units Transactions	A roll forward of the beginning to ending balance of RSUs outstanding as of December 31, 2020 is as follows (number of shares in millions): Number of Shares Weighted-Average Grant Date Fair Value Nonvested shares of RSUs at December 31, 2019 8.9 $ 20.84 Granted 6.5 19.50 Released (3.3) 18.57 Canceled (0.8) 20.86 Nonvested shares of RSUs at December 31, 2020 11.3 20.73

Employee Benefit Plans (Tables)

Employee Benefit Plans (Tables)	12 Months Ended
	Dec. 31, 2020
Defined Benefit Plans and Other Postretirement Benefit Plans Disclosures [Abstract]
Summary of Net Periodic Pension Cost	Following is a summary of the status of the Company's foreign defined benefit pension plans and the net periodic pension cost (amounts in millions): Year Ended December 31, 2020 2019 2018 Service cost $ 10.9 $ 9.4 $ 9.6 Interest cost 4.7 5.0 4.7 Expected return on plan assets (6.3) (6.0) (6.1) Curtailment gain (1.6) — (0.3) Actuarial losses 4.0 15.6 6.1 Total net periodic pension cost $ 11.7 $ 24.0 $ 14.0 Weighted average assumptions Discount rate used for net periodic pension costs 1.43 % 1.74 % 1.66 % Discount rate used for pension benefit obligations 1.31 % 1.43 % 1.74 % Expected return on plan assets 3.06 % 3.23 % 3.18 % Rate of compensation increase 3.26 % 3.07 % 3.22 %
Summary of Status Of Foreign Pension Plans	2020 2019 Change in projected benefit obligation (PBO) Projected benefit obligation at the beginning of the year $ 322.9 $ 290.8 Service cost 10.9 9.4 Interest cost 4.7 5.0 Net actuarial loss 8.1 25.8 Benefits paid by plan assets (8.9) (5.7) Benefits paid by the Company (7.4) (3.8) Curtailments and settlements (1.6) (0.2) Translation and other loss 22.5 1.6 Projected benefit obligation at the end of the year $ 351.2 $ 322.9 Accumulated benefit obligation at the end of the year $ 288.3 $ 258.8 Change in plan assets Fair value of plan assets at the beginning of the year $ 190.2 $ 174.9 Actual return on plan assets 10.4 16.2 Benefits paid from plan assets (8.9) (5.7) Employer contributions 4.3 4.6 Settlements — (0.2) Translation and other gain 13.3 0.4 Fair value of plan assets at the end of the year $ 209.3 $ 190.2 As of December 31, 2020 2019 Plans with underfunded or non-funded projected benefit obligation (1) Projected benefit obligation $ 248.7 $ 314.7 Fair value of plan assets 97.7 180.5 Plans with underfunded or non-funded accumulated benefit obligation Accumulated benefit obligation $ 189.4 $ 193.6 Fair value of plan assets 97.7 115.2 Amounts recognized in the balance sheet consist of Non-current assets $ 9.0 $ — Current liabilities (0.3) (0.3) Non-current liabilities (150.6) (132.4) Funded status $ (141.9) $ (132.7)
Fair Value Measurement of Plan Assets	The following table sets forth, by level within the fair value hierarchy, a summary of investments measured at fair value and the asset allocations of the plan assets in the Company's foreign pension plans (in millions): As of December, 31, 2020 Allocation Total Level 1 Level 2 Level 3 Asset Category Cash/Money Markets 2 % $ 4.1 $ 4.1 $ — $ — Foreign Government/Treasury Securities (1) 10 % 21.4 21.4 — — Corporate Bonds, Debentures (2) 18 % 36.9 — 36.9 — Equity Securities (3) 23 % 48.5 — 48.5 — Mutual Funds 5 % 9.5 — 9.5 — Investment and Insurance Contracts (4) 42 % 88.9 — 31.4 57.5 100 % $ 209.3 $ 25.5 $ 126.3 $ 57.5 As of December, 31, 2019 Allocation Total Level 1 Level 2 Level 3 Asset Category Cash/Money Markets 3 % $ 4.5 $ 4.5 $ — $ — Foreign Government/Treasury Securities (1) 10 % 19.4 19.4 — — Corporate Bonds, Debentures (2) 19 % 35.3 — 35.3 — Equity Securities (3) 21 % 40.4 — 40.4 — Mutual Funds 4 % 8.0 — 8.0 — Investment and Insurance Contracts (4) 43 % 82.6 — 30.6 52.0 100 % $ 190.2 $ 23.9 $ 114.3 $ 52.0 _______________________ (1) Includes investments primarily in guaranteed return securities. (2) Includes investments in government bonds and corporate bonds of developed countries, emerging market government bonds, emerging market corporate bonds and convertible bonds. (3) Includes investments in equity securities of developed countries and emerging markets. (4) Includes certain investments with insurance companies that guarantee a minimum rate of return on the investment.
Activity of Plan Assets With Fair Value Measurement Using Significant Unobservable Inputs	Activity during the years ended December 31, 2020 and 2019, respectively, for plan assets with fair value measurement using significant unobservable inputs (Level 3) were as follows (in millions): Investment and Insurance Contracts Balance at December 31, 2018 $ 50.6 Actual return on plan assets 3.3 Purchase, sales and settlements. net (0.9) Foreign currency impact (1.0) Balance at December 31, 2019 $ 52.0 Actual return on plan assets 0.8 Purchase, sales and settlements, net (0.3) Foreign currency impact 5.0 Balance at December 31, 2020 $ 57.5
Expected Benefit Payments	The expected benefit payments from the Company's defined benefit plans from 2021 through 2025 and the five years thereafter are as follows (in millions): 2021 $ 7.0 2022 10.6 2023 14.0 2024 15.8 2025 17.9 Five years thereafter 114.3 Total $ 179.6

Commitments and Contingencies (

Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2020
Commitments and Contingencies Disclosure [Abstract]
Future Minimum Purchase Obligations Under Non-cancelable Agreements	The following is a schedule by year of future minimum purchase obligations under non-cancelable arrangements entered into during the ordinary course of business as of December 31, 2020 (in millions): Year Ending December 31, 2021 $ 524.9 2022 (1) 598.9 2023 259.5 2024 248.0 2025 3.5 Thereafter 3.5 Total $ 1,638.3 (1) During 2019, the Company incurred additional commitments related to the pending acquisition of a manufacturing facility, of which $70.0 million and $100.0 million were deposited with the seller during the years ended December 31, 2019 and 2020, respectively. The remaining commitment of $230.0 million will be owed on or around December 31, 2022.

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	12 Months Ended
	Dec. 31, 2020
Fair Value Disclosures [Abstract]
Fair Value Of Assets And Liabilities Measured On Recurring Basis	The following table summarizes the Company's financial assets and liabilities, excluding pension assets, measured at fair value on a recurring basis (in millions): Fair Value Hierarchy Description As of December, 31, 2020 Level 1 Level 2 Level 3 Assets: Cash, cash equivalents: Demand and time deposits $ 8.5 $ 8.5 — — Fair Value Hierarchy Description As of December, 31, 2019 Level 1 Level 2 Level 3 Assets: Cash, cash equivalents: Demand and time deposits $ 28.2 $ 28.2 — —
Fair Value, by Balance Sheet Grouping	The carrying amounts and fair value of the Company’s long-term borrowings are as follows (in millions): As of December 31, 2020 2019 Carrying Amount Fair Value Carrying Amount Fair Value Long-term debt, including current portion (1) Convertible notes $ 515.6 $ 967.1 $ 1,163.1 $ 1,730.2 Long-term debt 2,975.7 2,966.8 2,449.3 2,427.8 _______________________ (1) Long-term debt is carried on the Consolidated Balance Sheets at historical cost net of debt discount and issuance costs.
Fair Value Measurements, Nonrecurring	The following table shows the adjustments to fair value of certain of the Company's non-financial assets that had an impact on the Company's results of operations (in millions): Year Ended December 31, 2020 2019 2018 Nonrecurring fair value measurements Asset impairments (Level 3) $ 17.5 $ 3.4 $ 2.4 Goodwill and IPRD impairments (Level 3) 1.3 1.6 6.8 $ 18.8 $ 5.0 $ 9.2

Financial Instruments (Tables)

Financial Instruments (Tables)	12 Months Ended
	Dec. 31, 2020
Investments, All Other Investments [Abstract]
Schedule of Net Foreign Exchange Positions	The following schedule summarizes the Company's net foreign exchange positions in U.S. dollars (in millions): As of December 31, 2020 2019 Buy (Sell) Notional Amount Buy (Sell) Notional Amount Japanese Yen $ 71.2 $ 71.2 $ 49.8 $ 49.8 Philippine Peso 57.2 57.2 36.4 36.4 Euro 47.7 47.7 — — Korean Won 34.4 34.4 18.1 18.1 Chinese Yuan 17.7 17.7 20.2 20.2 Malaysian Ringgit 11.7 11.7 20.4 20.4 Czech Koruna — — 11.9 11.9 Other currencies - Buy 12.4 12.4 21.9 21.9 Other currencies - Sell (11.1) 11.1 (4.6) 4.6 $ 241.2 263.4 $ 174.1 $ 183.3

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2020
Income Tax Disclosure [Abstract]
Income (Loss) Before Income Taxes And Minority Interests	The Company's geographic sources of income (loss) before income taxes and non-controlling interest are as follows (in millions): Year ended December 31, 2020 2019 2018 United States $ (181.2) $ (308.2) $ (181.8) Foreign 357.8 584.8 936.8 Income before income taxes $ 176.6 $ 276.6 $ 755.0
Provision (Benefit) For Income Taxes	The Company's provision (benefit) for income taxes is as follows (in millions): Year ended December 31, 2020 2019 2018 Current: Federal $ 0.6 $ 1.2 $ (2.0) State and local 0.1 — (2.2) Foreign 54.0 48.5 55.3 54.7 49.7 51.1 Deferred: Federal (69.2) (5.0) 99.4 State and local (66.4) — — Foreign 21.1 18.0 (25.4) (114.5) 13.0 74.0 Total provision (benefit) $ (59.8) $ 62.7 $ 125.1
Reconciliation Of The U.S. Federal Statutory Income Tax Rate	A reconciliation of the U.S. federal statutory income tax rate to the Company's effective income tax rate is as follows: Year ended December 31, 2020 2019 2018 U.S. federal statutory rate 21.0 % 21.0 % 21.0 % Increase (decrease) resulting from: State and local taxes, net of federal tax benefit (1.4) (2.6) (1.0) Impact of U.S. Tax Reform and related effects (1) — — 4.7 Impact of foreign operations 7.6 3.8 (1.2) Impact of U.S. tax method changes (2) — — (6.4) Impact of the Domestication (3) (35.7) — — Change in valuation allowance and related effects (4) (24.4) 1.8 0.6 Non-deductible share-based compensation costs 1.7 (0.5) (0.5) U.S. federal R&D credit (3.6) (3.7) (1.1) Nondeductible officer compensation 1.1 1.5 0.4 Other (0.1) 1.4 0.1 Total (33.8) % 22.7 % 16.6 % (1) For the year ended December 31, 2018, this primarily included expense of (i) $31.8 million, or 4.2%, related to the recognition of deferred tax liability for undistributed prior years' earnings of the foreign subsidiaries, (ii) $1.8 million, or 0.3% related to the limitation on deductibility of prior years’ executive compensation, and (iii) $1.5 million, or 0.2% related to the impact of the mandatory repatriation tax. These adjustments were made pursuant to SAB 118. (2) For the year ended December 31, 2018, this included a one-time benefit of $48.2 million, or 6.4%, related to U.S. tax method changes made during the year that impacted the Company’s GILTI inclusion. (3) On July 6, 2020, the Company completed a simplification of its corporate structure by repatriating the economic rights of its non-U.S. IP to the United States via domestication of certain foreign subsidiaries (the "Domestication"). The Domestication more closely aligns the Company's corporate structure with its operating structure in accordance with the OECD’s BEPS conclusions and changes to U.S. and European tax laws. The impact of the Domestication, which is regarded as a change in tax status, resulted in a benefit primarily from recognizing certain deferred tax assets, net of deferred tax liabilities, of $63.0 million, or 35.7%.
Tax Effects Of Temporary Differences	The tax effects of temporary differences in the recognition of income and expense for tax and financial reporting purposes that give rise to significant portions of the net deferred tax asset (liability) are as follows (in millions): As of December 31, 2020 2019 NOL and tax credit carryforwards $ 471.6 $ 612.9 163 (j) interest expense carryforward 65.7 49.3 Lease liabilities (1) 32.5 22.1 ROU asset (1) (32.5) (22.1) Tax-deductible goodwill and amortizable intangibles (38.0) (48.6) Capitalization of research and development expenses 90.7 42.7 Reserves and accruals 68.4 27.5 Property, plant and equipment (95.8) (81.2) Inventories 84.3 22.0 Undistributed earnings of foreign subsidiaries (57.5) (63.7) Share-based compensation 7.7 10.3 Pension 21.2 26.3 Other 3.2 8.0 Deferred tax assets and liabilities before valuation allowance 621.5 605.5 Valuation allowance (249.9) (357.9) Net deferred tax asset $ 371.6 $ 247.6
Activity For Unrecognized Gross Tax Benefits	The activity for unrecognized gross tax benefits is as follows (in millions): 2020 2019 2018 Balance at beginning of year $ 130.0 $ 112.2 $ 114.8 Acquired balances — 15.5 — Additions for tax benefits related to the current year 11.9 9.4 7.4 Additions for tax benefits of prior years 12.3 8.0 2.8 Reductions for tax benefits of prior years (1.4) (0.2) (1.9) Lapse of statute (1.3) (8.2) (10.9) Settlements (0.5) (6.7) — Balance at end of year $ 151.0 $ 130.0 $ 112.2

Changes in Accumulated Other _2

Changes in Accumulated Other Comprehensive Loss (Tables)	12 Months Ended
	Dec. 31, 2020
Equity [Abstract]
Schedule of Accumulated Other Comprehensive Loss	Amounts comprising the Company's accumulated other comprehensive loss and reclassifications are as follows (in millions): Currency Translation Adjustments Effects of Cash Flow Hedges Total Balance December 31, 2018 $ (42.5) 4.6 $ (37.9) Other comprehensive income (loss) prior to reclassifications 0.1 (19.6) (19.5) Amounts reclassified from accumulated other comprehensive loss — 3.1 3.1 Net current period other comprehensive income (loss) (1) 0.1 (16.5) (16.4) Balance December 31, 2019 (42.4) (11.9) (54.3) Other comprehensive income prior to reclassifications 1.8 14.9 16.7 Amounts reclassified from accumulated other comprehensive loss — (20.0) (20.0) Net current period other comprehensive income (loss) (1) 1.8 (5.1) (3.3) Balance December 31, 2020 $ (40.6) $ (17.0) $ (57.6) _______________________ (1) Effects of cash flow hedges are net of tax benefit of $1.7 million and $4.4 million for the years ended December 31, 2020 and December 31, 2019, respectively.
Schedule of Reclassifications from Accumulated Other Comprehensive Loss	Amounts reclassified from accumulated other comprehensive loss to the specific caption within the Consolidated Statements of Operations and Comprehensive Income were as follows: Year Ended December 31, To caption 2020 2019 Interest rate swaps $ 20.0 $ (3.1) Interest expense Total reclassifications $ 20.0 $ (3.1)

Supplemental Disclosures (Table

Supplemental Disclosures (Tables)	12 Months Ended
	Dec. 31, 2020
Supplemental Cash Flow Elements [Abstract]
Schedule of Cash Flow, Supplemental Disclosures	Certain of the Company's cash and non-cash activities were as follows (in millions): Year ended December 31, 2020 2019 2018 Non-cash investing activities: Capital expenditures in accounts payable and other long-term liabilities $ 162.5 $ 155.3 $ 233.9 Sale of property in exchange of note receivable 7.2 — — Right-of-use assets obtained in exchange of lease liabilities (1) 58.2 17.5 Non-cash financing activities: Liability incurred for purchase of business $ — $ 12.7 $ — Debt assumed through purchase of equity interest and assets — — 50.6 Cash paid for: Interest expense $ 109.1 $ 97.2 $ 80.0 Income taxes 52.5 62.9 53.2 Operating lease payments in operating cash flows (1) 36.9 37.6 (1) These disclosures are not applicable for the year ended December 31, 2018 due to the method of adoption of the New Leasing Standard.
Schedule of Cash and Cash Equivalents	Following is a reconciliation of the captions in the Consolidated Balance Sheets to the Consolidated Statements of Cash Flows (in millions): As of December 31, 2020 2019 2018 Consolidated Balance Sheets: Cash and cash equivalents $ 1,080.7 $ 894.2 $ 1,069.6 Restricted cash (included in other current assets) 0.8 — 17.5 Cash, cash equivalents and restricted cash in Consolidated Statements of Cash Flows $ 1,081.5 $ 894.2 $ 1,087.1

Supplementary Financial Infor_2

Supplementary Financial Information - Selected Quarterly Financial Data (Unaudited) (Tables)	12 Months Ended
	Dec. 31, 2020
Quarterly Financial Information Disclosure [Abstract]
Schedule of Quarterly Financial Information	Consolidated unaudited quarterly financial information is as follows (in millions, except per share data): Quarters ended in 2020 April 3 July 3 October 2 December 31 Revenue $ 1,277.9 $ 1,213.5 $ 1,317.3 $ 1,446.3 Gross Profit (exclusive of the amortization of acquisition-related intangible assets) 402.7 374.3 441.2 497.6 Net income (loss) attributable to ON Semiconductor Corporation (14.0) (1.4) 160.6 89.0 Diluted net income (loss) per common share attributable to ON Semiconductor Corporation (0.03) 0.00 0.38 0.21 Quarters ended in 2019 March 29 June 28 September 27 (1) December 31 Revenue $ 1,386.6 $ 1,347.7 $ 1,381.8 $ 1,401.8 Gross Profit (exclusive of the amortization of acquisition-related intangible assets) 513.7 499.0 475.2 485.7 Net income (loss) attributable to ON Semiconductor Corporation 114.1 101.8 (60.7) 56.5 Diluted net income (loss) per common share attributable to ON Semiconductor Corporation 0.27 0.24 (0.15) 0.14 (1) The net loss for the quarter ended September 27, 2019 was primarily due to the expensing of $169.5 million relating to the settlement of litigation with PI.

Background and Basis of Prese_2

Background and Basis of Presentation (Details)	12 Months Ended
	Dec. 31, 2020segment
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Number of operating segments	3
Number of reportable segments	3

Significant Accounting Polici_3

Significant Accounting Policies (Details)	12 Months Ended
	Dec. 31, 2020
Significant Accounting Policies [Line Items]
Description of payment terms	Although payment terms vary, most distributor agreements require payment within 30 days
Payment period to receive cash discount	10 days
Standard product warranty, period from the date of delivery	2 years
ISG
Significant Accounting Policies [Line Items]
Standard product warranty, period from the date of delivery	1 year
Minimum | Buildings
Significant Accounting Policies [Line Items]
Estimated useful lives of property, plant and equipment (in years)	30 years
Minimum | Computers, machinery and equipment
Significant Accounting Policies [Line Items]
Estimated useful lives of property, plant and equipment (in years)	3 years
Maximum | Buildings
Significant Accounting Policies [Line Items]
Estimated useful lives of property, plant and equipment (in years)	50 years
Maximum | Computers, machinery and equipment
Significant Accounting Policies [Line Items]
Estimated useful lives of property, plant and equipment (in years)	10 years

Revenue and Segment Informati_2

Revenue and Segment Information - Narrative (Details) $ in Millions	12 Months Ended
	Dec. 31, 2020USD ($)segment	Dec. 31, 2019USD ($)	Dec. 31, 2018USD ($)
Segment Reporting Information [Line Items]
Revenue	$ 5,255	$ 5,517.9	$ 5,878.3
Number of operating segments | segment	3
Number of reportable segments | segment	3
One Customer | Revenue from Contract with Customer Benchmark | Customer Concentration Risk
Segment Reporting Information [Line Items]
Concentration risk, percentage	11.00%
Product [Member]
Segment Reporting Information [Line Items]
Revenue	$ 5,227.8	5,492	5,849
Product development agreements
Segment Reporting Information [Line Items]
Revenue	$ 27.2	$ 25.9	$ 29.3

Revenue and Segment Informati_3

Revenue and Segment Information - Segment Information Of Revenues, Gross Profit And Operating Income (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Segment Reporting Information [Line Items]
Revenue from external customers	$ 5,255	$ 5,517.9	$ 5,878.3
Segment gross profit	1,769.9	2,046.2	2,305.5
PSG
Segment Reporting Information [Line Items]
Revenue from external customers	2,606.1	2,788.3	3,038.2
Segment gross profit	801.7	976	1,110.1
ASG
Segment Reporting Information [Line Items]
Revenue from external customers	1,910.4	1,972.3	2,071.2
Segment gross profit	730.5	794.8	878.3
ISG
Segment Reporting Information [Line Items]
Revenue from external customers	738.5	757.3	768.9
Segment gross profit	$ 237.7	$ 275.4	$ 317.1

Revenue and Segment Informati_4

Revenue and Segment Information - Reconciliation Of Operating Profit (Loss) From Segments To Consolidated (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Oct. 02, 2020	Jul. 03, 2020	Apr. 03, 2020	Dec. 31, 2019	Sep. 27, 2019	Jun. 28, 2019	Mar. 29, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Segment Reporting Information [Line Items]
Gross profit for reportable segments									$ 1,769.9	$ 2,046.2	$ 2,305.5
Gross profit	$ 497.6	$ 441.2	$ 374.3	$ 402.7	$ 485.7	$ 475.2	$ 499	$ 513.7	1,715.8	1,973.6	2,238.7
Operating Segments
Segment Reporting Information [Line Items]
Gross profit for reportable segments									1,769.9	2,046.2	2,305.5
Segment Reconciling Items
Segment Reporting Information [Line Items]
Less: unallocated manufacturing costs									$ (54.1)	$ (72.6)	$ (66.8)

Revenue and Segment Informati_5

Revenue and Segment Information - Revenues by Geographic Location Including Local Sales and Exports (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Segment Reporting Information [Line Items]
Revenue from external customers	$ 5,255	$ 5,517.9	$ 5,878.3
Distributors
Segment Reporting Information [Line Items]
Revenue from external customers	3,169.6	3,173.1	3,541.7
OEM
Segment Reporting Information [Line Items]
Revenue from external customers	1,765.7	1,976.6	1,970.9
Electronic Manufacturing Service Providers
Segment Reporting Information [Line Items]
Revenue from external customers	319.7	368.2	365.7
Singapore
Segment Reporting Information [Line Items]
Revenue from external customers	1,799.5	1,713.1	1,955
Hong Kong
Segment Reporting Information [Line Items]
Revenue from external customers	1,311.6	1,417.3	1,489.1
United Kingdom
Segment Reporting Information [Line Items]
Revenue from external customers	805.9	921.6	946.5
United States
Segment Reporting Information [Line Items]
Revenue from external customers	728.6	810.3	862.7
Other
Segment Reporting Information [Line Items]
Revenue from external customers	609.4	655.6	625
PSG
Segment Reporting Information [Line Items]
Revenue from external customers	2,606.1	2,788.3	3,038.2
PSG | Distributors
Segment Reporting Information [Line Items]
Revenue from external customers	1,776.4	1,740.6	2,011.1
PSG | OEM
Segment Reporting Information [Line Items]
Revenue from external customers	673.6	857.5	846.8
PSG | Electronic Manufacturing Service Providers
Segment Reporting Information [Line Items]
Revenue from external customers	156.1	190.2	180.3
PSG | Singapore
Segment Reporting Information [Line Items]
Revenue from external customers	978	864.7	1,086.6
PSG | Hong Kong
Segment Reporting Information [Line Items]
Revenue from external customers	723.2	843.5	847.9
PSG | United Kingdom
Segment Reporting Information [Line Items]
Revenue from external customers	395.7	467.1	488.5
PSG | United States
Segment Reporting Information [Line Items]
Revenue from external customers	282.8	356.3	398.5
PSG | Other
Segment Reporting Information [Line Items]
Revenue from external customers	226.4	256.7	216.7
ASG
Segment Reporting Information [Line Items]
Revenue from external customers	1,910.4	1,972.3	2,071.2
ASG | Distributors
Segment Reporting Information [Line Items]
Revenue from external customers	986.4	971.5	1,066.4
ASG | OEM
Segment Reporting Information [Line Items]
Revenue from external customers	794.6	860.3	860.7
ASG | Electronic Manufacturing Service Providers
Segment Reporting Information [Line Items]
Revenue from external customers	129.4	140.5	144.1
ASG | Singapore
Segment Reporting Information [Line Items]
Revenue from external customers	695	679.7	704.2
ASG | Hong Kong
Segment Reporting Information [Line Items]
Revenue from external customers	410.6	436.8	496.5
ASG | United Kingdom
Segment Reporting Information [Line Items]
Revenue from external customers	264.5	303.5	319.8
ASG | United States
Segment Reporting Information [Line Items]
Revenue from external customers	282	332.6	339.2
ASG | Other
Segment Reporting Information [Line Items]
Revenue from external customers	258.3	219.7	211.5
ISG
Segment Reporting Information [Line Items]
Revenue from external customers	738.5	757.3	768.9
ISG | Distributors
Segment Reporting Information [Line Items]
Revenue from external customers	406.8	461	464.2
ISG | OEM
Segment Reporting Information [Line Items]
Revenue from external customers	297.5	258.8	263.4
ISG | Electronic Manufacturing Service Providers
Segment Reporting Information [Line Items]
Revenue from external customers	34.2	37.5	41.3
ISG | Singapore
Segment Reporting Information [Line Items]
Revenue from external customers	126.5	168.7	164.2
ISG | Hong Kong
Segment Reporting Information [Line Items]
Revenue from external customers	177.8	137	144.7
ISG | United Kingdom
Segment Reporting Information [Line Items]
Revenue from external customers	145.7	151	138.2
ISG | United States
Segment Reporting Information [Line Items]
Revenue from external customers	163.8	121.4	125
ISG | Other
Segment Reporting Information [Line Items]
Revenue from external customers	$ 124.7	$ 179.2	$ 196.8

Revenue and Segment Informati_6

Revenue and Segment Information - Summary of Property, Plant and Equipment by Geographic Location (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Segment Reporting Information [Line Items]
Property, plant and equipment, net	$ 2,512.3	$ 2,591.6
United States
Segment Reporting Information [Line Items]
Property, plant and equipment, net	686.6	616.7
South Korea
Segment Reporting Information [Line Items]
Property, plant and equipment, net	455.5	485.4
Philippines
Segment Reporting Information [Line Items]
Property, plant and equipment, net	386.6	433.5
China
Segment Reporting Information [Line Items]
Property, plant and equipment, net	229.6	243.6
Japan
Segment Reporting Information [Line Items]
Property, plant and equipment, net	209.3	218.1
Czech Republic
Segment Reporting Information [Line Items]
Property, plant and equipment, net	216.1	213.4
Malaysia
Segment Reporting Information [Line Items]
Property, plant and equipment, net	190.2	204.4
Other
Segment Reporting Information [Line Items]
Property, plant and equipment, net	$ 138.4	$ 176.5

Recent Accounting Pronounceme_2

Recent Accounting Pronouncements (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019	Jan. 01, 2019	Mar. 31, 2017
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Right-of-use assets	$ 136.3	$ 110.2
Total lease liabilities	$ 147.9	$ 114
Cumulative Effect, Period of Adoption, Adjustment
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Right-of-use assets			$ 112.3
Deferred rent liabilities			5.1
Total lease liabilities			$ 117.4
1.625% Notes | Convertible Debt
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Debt instrument, interest rate	1.625%	1.625%		1.625%

Acquisitions, Divestitures an_3

Acquisitions, Divestitures and Licensing Transactions - 2019 Acquisition and Pending Acquisition (Details) - USD ($) $ in Millions	Oct. 05, 2020	Jun. 19, 2019	Apr. 22, 2019	Dec. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Business Acquisition [Line Items]
Acquisition-related costs					$ 1	$ 11.3
Discount rate				12.00%		12.00%
Goodwill				$ 1,659.2	1,663.4	$ 1,659.2	$ 932.5
GFUS
Business Acquisition [Line Items]
Purchase price consideration			$ 400
Non-refundable deposit	$ 100		70		100	70
License fee			$ 30
Contingent consideration					$ 230
Quantenna
Business Acquisition [Line Items]
Purchase price consideration		$ 1,039.3
Percent of shares acquired		100.00%
Proceeds from lines of credit		$ 900
Business combination, revenue recognized				84.8
Business combination, net loss				39.3
Intangible assets acquired				110.9		110.9
Developed technology				58.3		58.3
Goodwill				$ 726.7		$ 726.7
Developed technology | Quantenna
Business Acquisition [Line Items]
Weighted average useful life (in years)						8 years
Intangible Assets, Amortization Period | Quantenna
Business Acquisition [Line Items]
Weighted average useful life (in years)						8 years

Acquisitions - Allocation of th

Acquisitions - Allocation of the Purchase Price of Quantenna (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Business Acquisition [Line Items]
Goodwill	$ 1,663.4	$ 1,659.2	$ 932.5
Quantenna
Business Acquisition [Line Items]
Cash and cash equivalents		133.4
Receivables		22.2
Inventories		41.8
Other current assets		4.3
Property, plant and equipment		16.9
Goodwill		726.7
Intangible assets (excluding IPRD)		87.1
IPRD		23.8
Deferred tax assets		29.2
Other non-current assets		12.7
Total assets acquired		1,098.1
Accounts payable		22.6
Other current liabilities		17.5
Deferred tax liabilities		3.3
Other non-current liabilities		15.4
Total liabilities assumed		58.8
Net assets acquired/purchase price		$ 1,039.3

Acquisitions - Pro Forma Inform

Acquisitions - Pro Forma Information (Details) - Quantenna - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Business Acquisition, Pro Forma Information, Nonrecurring Adjustment [Line Items]
Revenue	$ 5,613.2	$ 6,098.8
Net income	218.2	567.2
Net income attributable to ON Semiconductor Corporation	$ 216	$ 564.7
Basic (in dollars per share)	$ 0.53	$ 1.33
Diluted (in dollars per share)	$ 0.52	$ 1.30

Acquisitions, Divestitures an_4

Acquisitions, Divestitures and Licensing Transactions - 2018 Acquisition, Divestitures and Licensing Transactions (Details) - USD ($) $ in Millions	Jun. 25, 2018	May 08, 2018	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Business Acquisition [Line Items]
Goodwill			$ 1,663.4	$ 1,659.2	$ 932.5
Proceeds from divestiture of business			0	5.2	8.4
Gain on divestiture of business			0	0	5
Revenue from external customers			$ 5,255	$ 5,517.9	5,878.3
Disposal Group, Disposed of by Sale, Not Discontinued Operations
Business Acquisition [Line Items]
Gain on divestiture of business					5
Disposal Group, Disposed of by Sale, Not Discontinued Operations | Transient Voltage Suppressing Diodes
Business Acquisition [Line Items]
Proceeds from divestiture of business	$ 5.6
Gain on divestiture of business	$ 4.6
HIDM
Business Acquisition [Line Items]
Licensing income					10
QST Co. | License
Business Acquisition [Line Items]
Revenue from external customers					$ 22.7
SensL Technologies, Ltd.
Business Acquisition [Line Items]
Amount of outstanding shares acquired in the period		100.00%
Cash paid for acquisition		$ 71.6
Intangible assets acquired		31.4
Developed technology		$ 30
Weighted average useful life (in years)		7 years
Goodwill		$ 18.9
SensL Technologies, Ltd. | Developed technology
Business Acquisition [Line Items]
Weighted average useful life (in years)		7 years
SensL Technologies, Ltd. | IPRD
Business Acquisition [Line Items]
Discount rate (as a percent)		30.00%

Acquisitions, Divestitures an_5

Acquisitions, Divestitures and Licensing Transactions - Allocation of the Purchase Price of SensL (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	May 08, 2018
Business Acquisition [Line Items]
Goodwill	$ 1,663.4	$ 1,659.2	$ 932.5
SensL Technologies, Ltd.
Business Acquisition [Line Items]
Current assets				$ 4.2
Cash and cash equivalents				0.7
Property, plant and equipment and other non-current assets				1.8
Goodwill				18.9
Intangible assets (excluding IPRD)				31.4
IPRD				20
Total assets acquired				76.3
Current liabilities				0.7
Other non-current liabilities				4
Total liabilities assumed				4.7
Net assets acquired/purchase price				$ 71.6

Goodwill and Intangible Asset_2

Goodwill and Intangible Assets - Summary of Goodwill by Operating Segment (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Goodwill [Line Items]
Goodwill	$ 2,114.2	$ 2,110	$ 1,383.3
Accumulated Impairment Losses	(450.8)	(450.8)	(450.8)
Carrying Value	1,663.4	1,659.2	932.5
ASG
Goodwill [Line Items]
Goodwill	1,566.3	1,563.4	836.7
Accumulated Impairment Losses	(418.9)	(418.9)	(418.9)
Carrying Value	1,147.4	1,144.5	417.8
ISG
Goodwill [Line Items]
Goodwill	114.7	114.4	114.4
Accumulated Impairment Losses	0	0	0
Carrying Value	114.7	114.4	114.4
PSG
Goodwill [Line Items]
Goodwill	433.2	432.2	432.2
Accumulated Impairment Losses	(31.9)	(31.9)	(31.9)
Carrying Value	$ 401.3	$ 400.3	$ 400.3

Goodwill and Intangible Asset_3

Goodwill and Intangible Assets - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Finite-Lived Intangible Assets [Line Items]
Goodwill impairment			$ 3.3
Amortization of acquisition-related intangible assets	$ 120.3	$ 115.2	111.7
Intangible assets, net	469	590.5
IPRD
Finite-Lived Intangible Assets [Line Items]
IPRD projects reclassified to developed technology	15.2	23.2
Intangible assets, net	$ 24.1	$ 40.6
IPRD | ISG
Finite-Lived Intangible Assets [Line Items]
Impairment of intangible assets			$ 3.5

Goodwill and Intangible Asset_4

Goodwill and Intangible Assets - Summary of Change in Goodwill (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Goodwill [Roll Forward]
Goodwill, beginning balance	$ 1,659.2	$ 932.5
Addition due to business combination	4.2	726.7
Goodwill, ending balance	$ 1,663.4	$ 1,659.2

Goodwill and Intangible Asset_5

Goodwill and Intangible Assets - Summary of Intangible Assets, Net (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Finite-Lived Intangible Assets [Line Items]
Original Cost	$ 1,535	$ 1,538.7
Accumulated Amortization	(1,005.2)	(886.2)
Accumulated Impairment Losses	(60.8)	(62)
Carrying Value	469	590.5
Customer relationships
Finite-Lived Intangible Assets [Line Items]
Original Cost	581.5	585.2
Accumulated Amortization	(411.7)	(386.8)
Accumulated Impairment Losses	(17.6)	(20.1)
Carrying Value	152.2	178.3
Developed technology
Finite-Lived Intangible Assets [Line Items]
Original Cost	794.7	779.5
Accumulated Amortization	(532.9)	(440.3)
Accumulated Impairment Losses	(2.6)	(2.6)
Carrying Value	259.2	336.6
IPRD
Finite-Lived Intangible Assets [Line Items]
Original Cost	49.5	64.7
Accumulated Amortization	0	0
Accumulated Impairment Losses	(25.4)	(24.1)
Carrying Value	24.1	40.6
Licenses
Finite-Lived Intangible Assets [Line Items]
Original Cost	30	30
Accumulated Amortization	0	0
Accumulated Impairment Losses	0	0
Carrying Value	30	30
Other intangibles
Finite-Lived Intangible Assets [Line Items]
Original Cost	79.3	79.3
Accumulated Amortization	(60.6)	(59.1)
Accumulated Impairment Losses	(15.2)	(15.2)
Carrying Value	$ 3.5	$ 5

Goodwill and Intangible Asset_6

Goodwill and Intangible Assets - Summary of Amortization Expense (Details) $ in Millions	Dec. 31, 2020USD ($)
Goodwill and Intangible Assets Disclosure [Abstract]
2021	$ 99.2
2022	83.8
2023	65.9
2024	54.1
2025	41.1
Thereafter	100.8
Total estimated amortization expense	$ 444.9

Restructuring, Asset Impairme_3

Restructuring, Asset Impairments and Other Charges, net - Summary of Restructuring, Asset Impairments and Other, Net (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Apr. 03, 2020	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Restructuring Cost and Reserve [Line Items]
Restructuring		$ 51.6	$ 24.9	$ 3.9
Asset Impairments		17.5	3.4	4.6
Other		(3.9)	0.4	(4.2)
Total		65.2	28.7	4.3
Property, plant and equipment impairment		9.1
Impairment of investments		7
Impairment charges for ROU assets		1.4
Other
Restructuring Cost and Reserve [Line Items]
Restructuring		0	0.8	3.9
Asset Impairments		17.5	3.4	4.6
Other		(3.9)	0.4	(4.2)
Total		13.6	4.6	$ 4.3
Voluntary separation program | Workforce Reduction
Restructuring Cost and Reserve [Line Items]
Restructuring		27.5
Asset Impairments		0
Other		0
Total	$ 27.5	27.5
2020 Involuntary separation program | Workforce Reduction
Restructuring Cost and Reserve [Line Items]
Restructuring		11.8
Asset Impairments		0
Other		0
Total		11.8
General workforce reduction | Workforce Reduction
Restructuring Cost and Reserve [Line Items]
Restructuring		12.3	8.4
Asset Impairments		0	0
Other		0	0
Total		$ 12.3	8.4
Post-Quantenna acquisition restructuring
Restructuring Cost and Reserve [Line Items]
Restructuring			15.7
Asset Impairments			0
Other			0
Total			$ 15.7

Restructuring, Asset Impairme_4

Restructuring, Asset Impairments and Other Charges, net - Rollforward of Accrued Restructuring Charges (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Restructuring Reserve [Roll Forward]
Balance at Beginning of Period	$ 0.2	$ 0.5
Charges	51.6	24.9
Usage	(45.6)	(25.2)
Balance at End of Period	6.2	0.2
Estimated employee separation charges
Restructuring Reserve [Roll Forward]
Balance at Beginning of Period	0.1	0.3
Charges	51.6	24.9
Usage	(45.5)	(25.1)
Balance at End of Period	6.2	0.1
Estimated costs to exit
Restructuring Reserve [Roll Forward]
Balance at Beginning of Period	0.1	0.2
Charges	0	0
Usage	(0.1)	(0.1)
Balance at End of Period	$ 0	$ 0.1

Restructuring, Asset Impairme_5

Restructuring, Asset Impairments and Other Charges, net - Narrative (Details) $ in Millions	Dec. 31, 2020USD ($)employees	Dec. 31, 2020USD ($)employees	Jul. 03, 2020USD ($)segment	Apr. 03, 2020USD ($)employee	Jun. 28, 2019employee	Oct. 02, 2020USD ($)employees	Dec. 31, 2020USD ($)	Dec. 31, 2019USD ($)employee	Dec. 31, 2018USD ($)
Restructuring Cost and Reserve [Line Items]
Restructuring, asset impairments and other charges, net							$ 65.2	$ 28.7	$ 4.3
Accrued liabilities	$ 6.2	$ 6.2					6.2	0.2	$ 0.5
Charges							51.6	24.9
Voluntary separation program | Workforce Reduction
Restructuring Cost and Reserve [Line Items]
Number of positions eliminated | employee				243
Restructuring, asset impairments and other charges, net				$ 27.5			27.5
2020 Involuntary separation program
Restructuring Cost and Reserve [Line Items]
Number of positions eliminated | segment			191
Severance Costs			$ 11.8
2020 Involuntary separation program | Workforce Reduction
Restructuring Cost and Reserve [Line Items]
Restructuring, asset impairments and other charges, net							11.8
General workforce reduction
Restructuring Cost and Reserve [Line Items]
Number of positions eliminated | employees	67	106				153
Severance Costs		$ 6.1				$ 6.2
Accrued liabilities	$ 5.3	$ 5.3					5.3
General workforce reduction | Workforce Reduction
Restructuring Cost and Reserve [Line Items]
Restructuring, asset impairments and other charges, net							12.3	$ 8.4
General workforce reduction | Employee Severance
Restructuring Cost and Reserve [Line Items]
Number of positions eliminated | employee								143
Charges							$ 8.4
Post-Quantenna acquisition restructuring
Restructuring Cost and Reserve [Line Items]
Restructuring, asset impairments and other charges, net								$ 15.7
Charges								$ 15.7
Post-Quantenna acquisition restructuring | Employee Severance
Restructuring Cost and Reserve [Line Items]
Number of positions eliminated | employee					8			10

Balance Sheet Information - Sup

Balance Sheet Information - Supplemental Balance Sheet Information (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Inventories:
Raw materials	$ 135.7	$ 138.4
Work in process	829.7	772.9
Finished goods	286	321.1
Inventories, net	1,251.4	1,232.4
Property, plant and equipment, net:
Property, plant and equipment, gross	5,507.7	5,261
Less: Accumulated depreciation	(2,995.4)	(2,669.4)
Property, plant and equipment, net	2,512.3	2,591.6
Accrued expenses:
Accrued payroll and related benefits	166.8	153.4
Sales related reserves	233.3	247.3
Income taxes payable	25.5	22.5
Other	144.4	115.6
Accrued expenses	570	538.8
Land
Property, plant and equipment, net:
Property, plant and equipment, gross	119.7	125.2
Buildings
Property, plant and equipment, net:
Property, plant and equipment, gross	850	860.6
Machinery and equipment
Property, plant and equipment, net:
Property, plant and equipment, gross	$ 4,538	$ 4,275.2

Balance Sheet Information - Nar

Balance Sheet Information - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Balance Sheet Related Disclosures [Abstract]
Carrying value of assets classified as held-for-sale	$ 7.4
Depreciation expense for property, plant and equipment	444.1	$ 409.7	$ 359.3
Ship and credit reserves	180.2	178.7
Operating lease assets	$ 136.3	$ 110.2
Weighted average remaining lease term	6 years 10 months 24 days
Weighted average discount rate	4.90%
Total rent expense			$ 43.6

Balance Sheet Information - Lea

Balance Sheet Information - Lease expense (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Balance Sheet Related Disclosures [Abstract]
Operating lease	$ 38.2	$ 35
Variable lease	4.2	4
Short-term lease	4.1	2.6
Total lease expense	46.5	41.6
Accrued expenses and other current liabilities	32.2	26.1
Other long-term liabilities	115.7	87.9
Lease liabilities	$ 147.9	$ 114
Operating Lease, Liability, Current, Statement of Financial Position [Extensible List]	us-gaap:AccruedLiabilitiesCurrent	us-gaap:AccruedLiabilitiesCurrent
Operating Lease, Liability, Noncurrent, Statement of Financial Position [Extensible List]	us-gaap:OtherLiabilitiesNoncurrent	us-gaap:OtherLiabilitiesNoncurrent

Balance Sheet Information - Sum

Balance Sheet Information - Summary of Operating Leases Maturity and Future Minimum Payments (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Operating Leases, Income Statement [Abstract]
2021	$ 36.5
2022	30.1
2023	23.1
2024	20.8
2025	14.2
Thereafter	49.9
Total lease payments	174.6
Less: Interest	(26.7)
Total lease liabilities	$ 147.9	$ 114

Long-Term Debt - Schedule of Lo

Long-Term Debt - Schedule of Long-Term Debt (Details) - USD ($)	Dec. 31, 2020	Aug. 21, 2020	Dec. 31, 2019	Mar. 31, 2017
Debt Instrument [Line Items]
Long-term debt	$ 3,589,500,000		$ 3,749,200,000
Less: Debt discount	(69,700,000)		(102,700,000)
Less: Debt issuance costs	(28,500,000)		(34,000,000)
Net long-term debt, including current maturities	3,491,300,000		3,612,500,000
Less: Current maturities	(531,600,000)		(736,000,000)
Net long-term debt	2,959,700,000		2,876,500,000
Senior Revolving Credit Facility
Debt Instrument [Line Items]
Long-term debt	$ 700,000,000		$ 800,000,000
Debt instrument, interest rate	1.90%		3.30%
Term Loan B Facility
Debt Instrument [Line Items]
Long-term debt	$ 1,614,500,000		$ 1,630,900,000
Less: Debt discount	(9,000,000)		(10,500,000)
Less: Debt issuance costs	$ (21,000,000)		$ (24,300,000)
Debt instrument, interest rate	2.15%		3.80%
Other long-term debt
Debt Instrument [Line Items]
Long-term debt	$ 0		$ 53,300,000
3.875% Notes | Notes Payable
Debt Instrument [Line Items]
Long-term debt	700,000,000		0
Less: Debt discount	(6,500,000)		0
Less: Debt issuance costs	$ (2,300,000)		0
Debt instrument, interest rate	3.875%	3.875%
1.00% Notes | Convertible Debt
Debt Instrument [Line Items]
Long-term debt	$ 0		690,000,000
Less: Debt discount	0		(20,400,000)
Less: Debt issuance costs	$ 0		(2,800,000)
Debt instrument, interest rate	1.00%
1.625% Notes | Convertible Debt
Debt Instrument [Line Items]
Long-term debt	$ 575,000,000		575,000,000
Less: Debt discount	(54,200,000)		(71,800,000)
Less: Debt issuance costs	(5,200,000)		$ (6,900,000)
Less: Current maturities	$ (515,600,000)
Debt instrument, interest rate	1.625%		1.625%	1.625%
Minimum | Other long-term debt
Debt Instrument [Line Items]
Debt instrument, interest rate	1.00%
Maximum | Other long-term debt
Debt Instrument [Line Items]
Debt instrument, interest rate	1.48%

Long-Term Debt - Schedule of An

Long-Term Debt - Schedule of Annual Maturities Relating to Long-Term Debt (Details) $ in Millions	Dec. 31, 2020USD ($)
Debt Disclosure [Abstract]
2021	$ 591.4
2022	16.3
2023	16.3
2024	716.4
2025	16.3
Thereafter	2,232.8
Total	$ 3,589.5

Long-Term Debt - Amended Credit

Long-Term Debt - Amended Credit Agreement (Details) - USD ($)	Dec. 31, 2020	Apr. 15, 2016
Debt Instrument [Line Items]
Long-term debt	$ 3,589,500,000
Term Loan B Facility
Debt Instrument [Line Items]
Long-term debt		$ 2,400,000,000
Revolving Credit Facility
Debt Instrument [Line Items]
Credit facility, maximum borrowing capacity		$ 1,970,000,000

Long-Term Debt - Amendments to

Long-Term Debt - Amendments to the Credit Agreement (Details) $ in Millions	12 Months Ended			48 Months Ended
	Dec. 31, 2020USD ($)	Dec. 31, 2019USD ($)	Dec. 31, 2018USD ($)	Dec. 31, 2019amendment
Debt Instrument [Line Items]
Number of amendments to credit agreement | amendment				7
Additional proceeds under term loan	$ 1,858	$ 1,404.8	$ 15.3
Revolving Credit Facility
Debt Instrument [Line Items]
Repayments of Revolving Credit Facility		500
Term Loan B Facility
Debt Instrument [Line Items]
Additional proceeds under term loan		$ 500

Long-Term Debt - Debt Refinanci

Long-Term Debt - Debt Refinancing and Prepayments (Details) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Debt Instrument [Line Items]
Debt issuance costs	$ 28,500,000	$ 34,000,000
Loss on debt refinancing and extinguishment	0	0	$ (1,100,000)
Loss on debt refinancing and prepayment	$ 0	6,200,000	$ 4,600,000
2019 Amendment One
Debt Instrument [Line Items]
Debt issuance costs		17,500,000
Loss on debt refinancing and extinguishment		5,800,000
2019 Amendment Two
Debt Instrument [Line Items]
Debt issuance costs		6,600,000
Loss on debt refinancing and extinguishment		$ 400,000

Long-Term Debt - Borrowing and

Long-Term Debt - Borrowing and repayment under the Revolving Credit Facility (Details) - USD ($) $ in Millions	Dec. 31, 2020	Aug. 21, 2020	Mar. 24, 2020	Dec. 31, 2019
Senior Revolving Credit Facility
Debt Instrument [Line Items]
Debt instrument, interest rate	1.90%			3.30%
Notes Payable | 3.875% Notes
Debt Instrument [Line Items]
Debt instrument, interest rate	3.875%	3.875%
Revolving Credit Facility
Debt Instrument [Line Items]
Repayments of Revolving Credit Facility				$ 500
Revolving Credit Facility | Senior Revolving Credit Facility
Debt Instrument [Line Items]
Borrowings used to enter into convertible note hedge and warrant transactions			$ 1,165
Repayments of Revolving Credit Facility	$ 65	$ 1,200
Remaining borrowing capacity	$ 1,269

Long-Term Debt - 3.875% Notes (

Long-Term Debt - 3.875% Notes (Details) - USD ($)	Dec. 31, 2020	Aug. 21, 2020	Dec. 31, 2019	Mar. 31, 2017
3.875% Notes | Notes Payable
Debt Instrument [Line Items]
Debt instrument, interest rate	3.875%	3.875%
Principal amount of debt		$ 700,000,000
Debt discount and issuance costs		$ 9,400,000
1.625% Notes | Convertible Debt
Debt Instrument [Line Items]
Debt instrument, interest rate	1.625%		1.625%	1.625%
Principal amount of debt				$ 575,000,000

Long-Term Debt - Maturity and S

Long-Term Debt - Maturity and Settlement of 1.00% Notes (Details) - USD ($)	Dec. 01, 2020	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Debt Instrument [Line Items]
Shares issued to settle excess over principal for 1.00% Notes	$ 88,700,000	$ 0
Share repurchased value	321,000,000	$ 65,400,000	$ 139,000,000	$ 315,300,000
Convertible Debt | 1.00% Notes
Debt Instrument [Line Items]
Debt instrument, interest rate		1.00%
Principal amount of debt	$ 690,000,000
Share repurchased value		$ 0
Exercise price, warrants (in dollars per share)		$ 25.96
Convertible Debt | 1.00% Notes | Embedded Derivative Financial Instruments
Debt Instrument [Line Items]
Number of convertible shares (in shares)		37,300,000

Long-Term Debt - 1.625% Notes d

Long-Term Debt - 1.625% Notes due 2023 (Details)	Dec. 31, 2020USD ($)$ / shares	Dec. 01, 2020trading_day	Mar. 31, 2017USD ($)trading_dayd$ / sharesRate	Dec. 31, 2019USD ($)
Debt Instrument [Line Items]
Current portion of long-term debt | $	$ 531,600,000			$ 736,000,000
1.625% Notes | Convertible Debt
Debt Instrument [Line Items]
Debt instrument, interest rate (as a percent)	1.625%		1.625%	1.625%
Principal amount of debt | $			$ 575,000,000
Conversion rate | Rate			4.82567%
Conversion price per share (in dollars per share) | $ / shares	$ 20.72		$ 20.72
Threshold trading days		20
Threshold consecutive trading days		30
Threshold percentage of stock price trigger (greater than or equal to)	130.00%
Stock price trigger (in dollars per share) | $ / shares	$ 26.94
Current portion of long-term debt | $	$ 515,600,000
Debt Conversion One | 1.625% Notes | Convertible Debt
Debt Instrument [Line Items]
Threshold trading days			20
Threshold consecutive trading days			30
Threshold percentage of stock price trigger (greater than or equal to)			130.00%
Debt Conversion Two | 1.625% Notes | Convertible Debt
Debt Instrument [Line Items]
Threshold consecutive trading days | d			5
Period immediately following consecutive trading days (in business days)			5 days
Ratio of trading price per 1000 principal amount (as a percent) (less than)			0.98

Long-Term Debt - Fujiitsu Note

Long-Term Debt - Fujiitsu Note Payable (Details) - USD ($)	Dec. 31, 2020	Dec. 31, 2018	Oct. 01, 2018
OSA
Debt Instrument [Line Items]
Ownership percentage	100.00%	60.00%
Fujitsu Semiconductor Limited | Loans Payable
Debt Instrument [Line Items]
Principal amount of debt			$ 50,600,000

Earnings Per Share and Equity -

Earnings Per Share and Equity - Schedule of Net Income Per Share (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Oct. 02, 2020	Jul. 03, 2020	Apr. 03, 2020	Dec. 31, 2019	Sep. 27, 2019	Jun. 28, 2019	Mar. 29, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Equity [Abstract]
Net income (loss) attributable to ON Semiconductor Corporation	$ 89	$ 160.6	$ (1.4)	$ (14)	$ 56.5	$ (60.7)	$ 101.8	$ 114.1	$ 234.2	$ 211.7	$ 627.4
Basic weighted average shares of common stock outstanding (in shares)									410.7	410.9	423.8
Add: Incremental shares for:
Dilutive effect of share-based awards (in shares)									1.9	1.9	4.3
Dilutive effect of convertible notes and warrants (in shares)									6.2	3.2	7.8
Diluted weighted average shares of common stock outstanding (in shares)									418.8	416	435.9
Net income per share of common stock attributable to ON Semiconductor Corporation:
Basic (in dollars per share)									$ 0.57	$ 0.52	$ 1.48
Diluted (in dollars per share)	$ 0.21	$ 0.38	$ 0	$ (0.03)	$ 0.14	$ (0.15)	$ 0.24	$ 0.27	$ 0.56	$ 0.51	$ 1.44

Earnings Per Share and Equity_2

Earnings Per Share and Equity - Narrative (Details) - USD ($)	Dec. 01, 2014	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Jun. 07, 2020	Nov. 30, 2018	Nov. 15, 2018	Mar. 31, 2017
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Anti-dilutive shares (in shares)		800,000	800,000	600,000
Amount remaining to be repurchased under the stock repurchase program		$ 1,295,800,000	$ 1,361,100,000	$ 1,500,000,000
Common stock repurchased		65,300,000	138,900,000	315,000,000
Payments of tax withholding for restricted shares		$ 20,000,000	33,500,000	31,600,000
Shares reissued or retired (in shares)		0
Noncontrolling interest balance		$ 19,600,000	22,400,000
Income attributable to non-controlling interests		2,200,000	2,200,000	2,500,000
Dividend to non-controlling shareholder		$ 5,000,000	$ 2,300,000	$ 2,200,000
Rights Agreement | Series B Preferred Stock
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Exercise price, warrants (in dollars per share)					$ 100.80
Dividend declared (in shares)					1
Preferred stock par value (in dollars per share)					$ 0.01
Minimum beneficial ownership to trigger exercise option					15.00%
Leshan
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Ownership percentage		80.00%
Noncontrolling interest balance		$ 19,600,000
OSA
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Ownership percentage		100.00%		60.00%
Additional ownership percentage acquired		40.00%		50.00%
Equity interest value				$ 24,600,000
Settlement of purchase price		$ 26,000,000
Treasury Stock
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Shares withheld for payment of taxes (in shares)		1,062,377	1,620,543	1,343,961
Noncontrolling Interest
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Dividend to non-controlling shareholder		$ 5,000,000	$ 2,300,000	$ 2,200,000
2014 Program
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Cash allocation policy, target percentage to return to shareholders	80.00%
Authorized repurchases	$ 1,000,000,000
Period in which the company intends to repurchase the shares	4 years
Amount remaining to be repurchased under the stock repurchase program						$ 288,200,000
Common stock repurchased				$ 315,000,000
2018 Program
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Authorized repurchases							$ 1,500,000,000
Amount remaining to be repurchased under the stock repurchase program		1,295,800,000
Common stock repurchased		$ 65,300,000	$ 138,900,000
1.00% Notes | Convertible Debt
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Debt instrument, interest rate		1.00%
Exercise price, warrants (in dollars per share)		$ 25.96
1.625% Notes | Convertible Debt
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Debt instrument, interest rate		1.625%	1.625%					1.625%
Exercise price, warrants (in dollars per share)		$ 30.70
Conversion price per share (in dollars per share)		$ 20.72						$ 20.72

Earnings Per Share and Equity_3

Earnings Per Share and Equity - Schedule of Share Repurchase Program (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Equity [Abstract]
Number of repurchased shares (in shares)	3,600,000	7,800,000	16,800,000
Aggregate purchase price	$ 65.3	$ 138.9	$ 315
Fees, commissions and other expenses	0.1	0.1	0.3
Total cash used for share repurchases	$ 65.4	$ 139	$ 315.3
Weighted-average purchase price per share (in dollars per share)	$ 18.08	$ 17.89	$ 18.78
Available under the 2018 Share Repurchase Program	$ 1,295.8	$ 1,361.1	$ 1,500
Treasury shares reissued or retired (in shares)	0

Share-Based Compensation - Summ

Share-Based Compensation - Summary of Share-Based Compensation Expense (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Share-based compensation expense	$ 67.7	$ 79.4	$ 78.3
Income tax benefit	(14.2)	(16.7)	(16.4)
Share-based compensation expense, net of taxes	53.5	62.7	61.9
Cost of revenue
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Share-based compensation expense	11.5	10.6	7
Research and development
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Share-based compensation expense	18.2	17	14.3
Selling and marketing
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Share-based compensation expense	12.9	14.8	14.1
General and administrative
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Share-based compensation expense	$ 25.1	$ 37	$ 42.9

Share-Based Compensation - Narr

Share-Based Compensation - Narrative (Details) - USD ($)	May 15, 2012	Feb. 17, 2000	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	May 17, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Employee stock options granted in period (in shares)			0	0	0
Share-based compensation expense			$ 67,700,000	$ 79,400,000	$ 78,300,000
Amended And Restated Stock Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares available for issuance under the plan (in shares)	33,000,000					27,900,000
Common stock reserved and available for grant (in shares)						87,000,000
Aggregate of common stock available for grant (in shares)			16,500,000
Time Based Restricted Stock Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized share-based compensation expense on non-vested restricted stock units			$ 74,500,000
Compensation expense recognized on restricted stock units			$ 52,500,000
Restricted Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Recognition period for compensation expense (in years)			1 year 7 months 6 days
Restricted Stock | Director
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Equity awards granted in period (in shares)			100,000
Weighted average grant date fair value (In dollars per share)			$ 18.19
Employee Stock Purchase Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Aggregate of common stock available for grant (in shares)			3,000,000			28,500,000
Share-based compensation expense			$ 8,100,000
Maximum employee subscription rate for the ESPP (as a percent)		10.00%
Discount rate from market value paid by participants for shares under the plan (as a percent)		85.00%
Maximum annual amount of purchases per employee under the plan		$ 25,000
Shares authorized for purchase per employee per quarter (in shares)		500
Maximum fair value of shares employee may purchase in a quarter		$ 6,250
Shares issued pursuant to the employee stock purchase plan (in shares)			1,800,000	1,700,000	1,500,000
Employee Stock Purchase Plan | Director
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation expense			$ 1,500,000
Restricted Stock Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Pre-vesting forfeitures (as a percent)			5.00%	5.00%	5.00%
Equity awards granted in period (in shares)			6,500,000
Compensation expense recognized on restricted stock units			$ 58,100,000
Weighted average grant date fair value (In dollars per share)			$ 19.50
Restricted Stock Units | Officers And Employees
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Equity awards granted in period (in shares)			2,700,000
Service Based Restricted Stock Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized share-based compensation expense on non-vested restricted stock units			$ 69,700,000
Service Based Restricted Stock Units | Amended And Restated Stock Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period (in years)	3 years
Performance And Market Based Restricted Stock Units | Amended And Restated Stock Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period (in years)	2 years
Performance Based Restricted Stock Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized share-based compensation expense on non-vested restricted stock units			800,000
Market Based Restricted Stock Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized share-based compensation expense on non-vested restricted stock units			$ 4,000,000

Share-Based Compensation - Su_2

Share-Based Compensation - Summary of Restricted Stock Units Transactions (Details) - Restricted Stock Units shares in Millions	12 Months Ended
	Dec. 31, 2020$ / sharesshares
Number of Shares
Nonvested shares of restricted stock units beginning (in shares) | shares	8.9
Granted (in shares) | shares	6.5
Released (in shares) | shares	(3.3)
Canceled (in shares) | shares	(0.8)
Nonvested shares of restricted stock units ending (in shares) | shares	11.3
Weighted-Average Grant Date Fair Value
Nonvested shares of restricted stock units beginning (in dollars per share) | $ / shares	$ 20.84
Granted (in dollars per share) | $ / shares	19.50
Released (in dollars per share) | $ / shares	18.57
Canceled (in dollars per share) | $ / shares	20.86
Nonvested shares of restricted stock units ending (in dollars per share) | $ / shares	$ 20.73

Employee Benefit Plans - Narrat

Employee Benefit Plans - Narrative (Details) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items]
Actuarial loss	$ 4,000,000	$ 15,600,000	$ 6,100,000
Net actuarial loss	8,100,000	25,800,000
Total underfunded status	141,900,000
Expected company contribution in the current period	$ 22,100,000
Employer contribution as percentage of employee contribution	100.00%
Annual contribution limit per employee	$ 11,400
Foreign Plan
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items]
Actuarial loss	4,000,000	15,600,000	6,100,000
Net actuarial loss	8,100,000
Better than expected return on plan assets	4,100,000
Compensation expense recognized	21,800,000	20,600,000	20,500,000
United States
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items]
Compensation expense recognized	$ 19,400,000	$ 18,100,000	$ 19,200,000
Minimum
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items]
Percentage of employee contribution, basis for employer contribution	0.00%
Maximum
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items]
Percentage of employee contribution, basis for employer contribution	4.00%

Employee Benefit Plans - Summar

Employee Benefit Plans - Summary of Net Periodic Pension Cost (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Defined Benefit Plans and Other Postretirement Benefit Plans Disclosures [Abstract]
Service cost	$ 10.9	$ 9.4	$ 9.6
Interest cost	4.7	5	4.7
Expected return on plan assets	(6.3)	(6)	(6.1)
Curtailment gain	(1.6)	0	(0.3)
Actuarial losses	4	15.6	6.1
Total net periodic pension cost	$ 11.7	$ 24	$ 14
Discount rate used for net periodic pension costs	1.43%	1.74%	1.66%
Discount rate used for pension benefit obligations	1.31%	1.43%	1.74%
Expected return on plan assets	3.06%	3.23%	3.18%
Rate of compensation increase	3.26%	3.07%	3.22%

Employee Benefit Plans - Summ_2

Employee Benefit Plans - Summary of Status Of Foreign Pension Plans (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Defined Benefit Plans and Other Postretirement Benefit Plans Disclosures [Abstract]
Projected benefit obligation at the beginning of the year	$ 322.9	$ 290.8
Change in projected benefit obligation (PBO)
Service cost	10.9	9.4	$ 9.6
Interest cost	4.7	5	4.7
Net actuarial loss	8.1	25.8
Benefits paid by plan assets	(8.9)	(5.7)
Benefits paid by the Company	(7.4)	(3.8)
Curtailments and settlements	(1.6)	(0.2)
Translation and other loss	22.5	1.6
Projected benefit obligation at the end of the year	351.2	322.9	290.8
Accumulated benefit obligation at the end of the year	288.3	258.8
Change in plan assets
Fair value of plan assets at the beginning of the year	190.2	174.9
Actual return on plan assets	10.4	16.2
Benefits paid from plan assets	(8.9)	(5.7)
Employer contributions	4.3	4.6
Settlements	0	(0.2)
Translation and other gain	13.3	0.4
Fair value of plan assets at the end of the year	209.3	190.2	$ 174.9
Plans with underfunded or non-funded projected benefit obligation (1)
Projected benefit obligation	248.7	314.7
Fair value of plan assets	97.7	180.5
Plans with underfunded or non-funded accumulated benefit obligation
Accumulated benefit obligation	189.4	193.6
Fair value of plan assets	97.7	115.2
Amounts recognized in the balance sheet consist of
Non-current assets	9	0
Current liabilities	(0.3)	(0.3)
Non-current liabilities	(150.6)	(132.4)
Funded status	$ (141.9)	$ (132.7)

Employee Benefit Plans - Fair V

Employee Benefit Plans - Fair Value Measurement of Plan Assets (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Defined Benefit Plan Disclosure [Line Items]
Allocation	100.00%	100.00%
Plan assets	$ 209.3	$ 190.2	$ 174.9
Cash/Money Markets
Defined Benefit Plan Disclosure [Line Items]
Allocation	2.00%	3.00%
Plan assets	$ 4.1	$ 4.5
Foreign Government/Treasury Securities
Defined Benefit Plan Disclosure [Line Items]
Allocation	10.00%	10.00%
Plan assets	$ 21.4	$ 19.4
Corporate Bonds, Debentures
Defined Benefit Plan Disclosure [Line Items]
Allocation	18.00%	19.00%
Plan assets	$ 36.9	$ 35.3
Equity Securities
Defined Benefit Plan Disclosure [Line Items]
Allocation	23.00%	21.00%
Plan assets	$ 48.5	$ 40.4
Mutual Funds
Defined Benefit Plan Disclosure [Line Items]
Allocation	5.00%	4.00%
Plan assets	$ 9.5	$ 8
Investment and Insurance Contracts
Defined Benefit Plan Disclosure [Line Items]
Allocation	42.00%	43.00%
Plan assets	$ 88.9	$ 82.6
Level 1
Defined Benefit Plan Disclosure [Line Items]
Plan assets	25.5	23.9
Level 1 | Cash/Money Markets
Defined Benefit Plan Disclosure [Line Items]
Plan assets	4.1	4.5
Level 1 | Foreign Government/Treasury Securities
Defined Benefit Plan Disclosure [Line Items]
Plan assets	21.4	19.4
Level 1 | Corporate Bonds, Debentures
Defined Benefit Plan Disclosure [Line Items]
Plan assets	0	0
Level 1 | Equity Securities
Defined Benefit Plan Disclosure [Line Items]
Plan assets	0	0
Level 1 | Mutual Funds
Defined Benefit Plan Disclosure [Line Items]
Plan assets	0	0
Level 1 | Investment and Insurance Contracts
Defined Benefit Plan Disclosure [Line Items]
Plan assets	0	0
Level 2
Defined Benefit Plan Disclosure [Line Items]
Plan assets	126.3	114.3
Level 2 | Cash/Money Markets
Defined Benefit Plan Disclosure [Line Items]
Plan assets	0	0
Level 2 | Foreign Government/Treasury Securities
Defined Benefit Plan Disclosure [Line Items]
Plan assets	0	0
Level 2 | Corporate Bonds, Debentures
Defined Benefit Plan Disclosure [Line Items]
Plan assets	36.9	35.3
Level 2 | Equity Securities
Defined Benefit Plan Disclosure [Line Items]
Plan assets	48.5	40.4
Level 2 | Mutual Funds
Defined Benefit Plan Disclosure [Line Items]
Plan assets	9.5	8
Level 2 | Investment and Insurance Contracts
Defined Benefit Plan Disclosure [Line Items]
Plan assets	31.4	30.6
Level 3
Defined Benefit Plan Disclosure [Line Items]
Plan assets	57.5	52
Level 3 | Cash/Money Markets
Defined Benefit Plan Disclosure [Line Items]
Plan assets	0	0
Level 3 | Foreign Government/Treasury Securities
Defined Benefit Plan Disclosure [Line Items]
Plan assets	0	0
Level 3 | Corporate Bonds, Debentures
Defined Benefit Plan Disclosure [Line Items]
Plan assets	0	0
Level 3 | Equity Securities
Defined Benefit Plan Disclosure [Line Items]
Plan assets	0	0
Level 3 | Mutual Funds
Defined Benefit Plan Disclosure [Line Items]
Plan assets	0	0
Level 3 | Investment and Insurance Contracts
Defined Benefit Plan Disclosure [Line Items]
Plan assets	$ 57.5	$ 52	$ 50.6

Employee Benefit Plans - Activi

Employee Benefit Plans - Activity of Plan Assets With Fair Value Measurement Using Significant Unobservable Inputs (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value of plan assets at the beginning of the year	$ 190.2	$ 174.9
Foreign currency impact	13.3	0.4
Fair value of plan assets at the end of the year	209.3	190.2
Investment and Insurance Contracts
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value of plan assets at the beginning of the year	82.6
Fair value of plan assets at the end of the year	88.9	82.6
Level 3
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value of plan assets at the beginning of the year	52
Fair value of plan assets at the end of the year	57.5	52
Level 3 | Investment and Insurance Contracts
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value of plan assets at the beginning of the year	52	50.6
Actual return on plan assets	0.8	3.3
Purchase, sales and settlements. net	(0.3)	(0.9)
Foreign currency impact	5	(1)
Fair value of plan assets at the end of the year	$ 57.5	$ 52

Employee Benefit Plans - Expect

Employee Benefit Plans - Expected Benefit Payments (Details) $ in Millions	Dec. 31, 2020USD ($)
Defined Benefit Plans and Other Postretirement Benefit Plans Disclosures [Abstract]
2021	$ 7
2022	10.6
2023	14
2024	15.8
2025	17.9
Five years thereafter	114.3
Total	$ 179.6

Commitments and Contingencies -

Commitments and Contingencies - Future Minimum Purchase Obligations Under Non-cancelable Agreements (Details) - USD ($) $ in Millions	Oct. 05, 2020	Apr. 22, 2019	Dec. 31, 2020	Dec. 31, 2019
Long-term Purchase Commitment [Line Items]
2021			$ 524.9
2022			598.9
2023			259.5
2024			248
2025			3.5
Thereafter			3.5
Total			1,638.3
GFUS
Long-term Purchase Commitment [Line Items]
Commitments related to pending acquisition			230
Non-refundable deposit	$ 100	$ 70	$ 100	$ 70

Commitments and Contingencies_2

Commitments and Contingencies - Narrative (Details) - USD ($) $ in Millions	Aug. 06, 2020	Oct. 22, 2019	Jun. 19, 2019	Sep. 19, 2016	Dec. 31, 2020
Loss Contingencies [Line Items]
Availability under senior revolving credit facility					$ 15
Outstanding guarantees and letters of credit					9.7
Guarantees related subsidiaries' finance lease obligations, and line of credit					0.9
Fairchild
Loss Contingencies [Line Items]
Maximum remediation cost recoveries receivable					150
Power Integrations, Inc.
Loss Contingencies [Line Items]
Cash paid for legal settlements		$ 175
AcBel Polytech, Inc.
Loss Contingencies [Line Items]
Cash paid for legal settlements	$ 6
Letter of Credit | Senior Revolving Credit Facility
Loss Contingencies [Line Items]
Credit commitment outstanding					$ 0.9
Fairchild
Loss Contingencies [Line Items]
Business acquisition, maximum indemnification period				6 years
Quantenna
Loss Contingencies [Line Items]
Business acquisition, maximum indemnification period			6 years

Fair Value Measurements - Fair

Fair Value Measurements - Fair Value of Assets and Liabilities Measured on Recurring Basis (Details) - Fair Value, Measurements, Recurring - Demand and time deposits - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Quoted Prices in Active Markets (Level 1)
Assets:
Cash and cash equivalents	$ 8.5	$ 28.2
Level 2
Assets:
Cash and cash equivalents	0	0
Fair Value Inputs (Level 3)
Assets:
Cash and cash equivalents	0	0
Estimate of Fair Value Measurement
Assets:
Cash and cash equivalents	$ 8.5	$ 28.2

Fair Value Measurements - Narra

Fair Value Measurements - Narrative (Details) - USD ($)	Dec. 31, 2020	Aug. 21, 2020	Dec. 31, 2019	Mar. 31, 2017
Non-financial Assets | Fair Value, Measurements, Nonrecurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Non-financial assets	$ 0		$ 0
Notes Payable | 3.875% Notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt instrument, interest rate	3.875%	3.875%
Convertible Debt | 1.00% Notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt instrument, interest rate	1.00%
Convertible Debt | 1.625% Notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt instrument, interest rate	1.625%		1.625%	1.625%

Fair Value Measurements - Fai_2

Fair Value Measurements - Fair Value of Long-Term Debt, Including Current Portion (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term debt, including current portion, carrying amount	$ 3,589.5	$ 3,749.2
Convertible Notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term debt, including current portion, carrying amount	515.6	1,163.1
Long-term debt, including current portion, fair value	967.1	1,730.2
Long-term Debt
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term debt, including current portion, carrying amount	2,975.7	2,449.3
Long-term debt, including current portion, fair value	$ 2,966.8	$ 2,427.8

Fair Value Measurements - Adjus

Fair Value Measurements - Adjustments to Fair Value of Non-Financial Assets (Details) - Fair Value, Measurements, Nonrecurring - Fair Value Inputs (Level 3) - Changes Measurement - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Asset impairments (Level 3)	$ 17.5	$ 3.4	$ 2.4
Goodwill and IPRD impairments (Level 3)	1.3	1.6	6.8
Total assets	$ 18.8	$ 5	$ 9.2

Financial Instruments - Narrati

Financial Instruments - Narrative (Details) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Apr. 17, 2020	Mar. 31, 2017
Foreign exchange contract
Derivatives, Fair Value [Line Items]
Notional amount	$ 263,400,000	$ 183,300,000
Realized and unrealized foreign currency transaction loss	6,200,000	5,000,000	$ 8,000,000
Interest Rate Swap
Derivatives, Fair Value [Line Items]
Notional amount	$ 1,500,000,000	$ 1,000,000,000
Interest rate swap agreement 1
Derivatives, Fair Value [Line Items]
Notional amount				$ 1,250,000,000
Interest rate swap agreement 2
Derivatives, Fair Value [Line Items]
Notional amount				750,000,000
Interest rate swap agreement 3
Derivatives, Fair Value [Line Items]
Notional amount				$ 750,000,000
Convertible Debt | 1.00% Notes
Derivatives, Fair Value [Line Items]
Debt instrument, interest rate	1.00%
Convertible Debt | 1.625% Notes
Derivatives, Fair Value [Line Items]
Debt instrument, interest rate	1.625%	1.625%			1.625%

Financial Instruments - Schedul

Financial Instruments - Schedule of Net Foreign Exchange Positions (Details) - Foreign exchange contract - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Financial Instruments [Line Items]
Buy (Sell)	$ 241.2	$ 174.1
Notional Amount	263.4	183.3
Other currencies - Buy
Financial Instruments [Line Items]
Buy (Sell)	12.4	21.9
Notional Amount	12.4	21.9
Other currencies - Sell
Financial Instruments [Line Items]
Buy (Sell)	(11.1)	(4.6)
Notional Amount	11.1	4.6
Japanese Yen
Financial Instruments [Line Items]
Buy (Sell)	71.2	49.8
Notional Amount	71.2	49.8
Philippine Peso
Financial Instruments [Line Items]
Buy (Sell)	57.2	36.4
Notional Amount	57.2	36.4
Euro
Financial Instruments [Line Items]
Buy (Sell)	47.7	0
Notional Amount	47.7	0
Korean Won
Financial Instruments [Line Items]
Buy (Sell)	34.4	18.1
Notional Amount	34.4	18.1
Chinese Yuan
Financial Instruments [Line Items]
Buy (Sell)	17.7	20.2
Notional Amount	17.7	20.2
Malaysian Ringgit
Financial Instruments [Line Items]
Buy (Sell)	11.7	20.4
Notional Amount	11.7	20.4
Czech Koruna
Financial Instruments [Line Items]
Buy (Sell)	0	11.9
Notional Amount	$ 0	$ 11.9

Income Taxes - Income (Loss) Be

Income Taxes - Income (Loss) Before Income Taxes and Non-controlling Interests (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Income Tax Disclosure [Abstract]
United States	$ (181.2)	$ (308.2)	$ (181.8)
Foreign	357.8	584.8	936.8
Income before income taxes	$ 176.6	$ 276.6	$ 755

Income Taxes - Provision (Benef

Income Taxes - Provision (Benefit) For Income Taxes (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Current:
Federal	$ 0.6	$ 1.2	$ (2)
State and local	0.1	0	(2.2)
Foreign	54	48.5	55.3
Current, Provision (benefit) for income taxes	54.7	49.7	51.1
Deferred:
Federal	(69.2)	(5)	99.4
State and local	(66.4)	0	0
Foreign	21.1	18	(25.4)
Deferred, Provision (benefit) for income taxes	(114.5)	13	74
Total provision (benefit)	$ (59.8)	$ 62.7	$ 125.1

Income Taxes - Narrative (Detai

Income Taxes - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Taxes [Line Items]
Effective income tax rate (benefit) (as a percent)	(33.80%)	22.70%	16.60%
Deferred tax assets, valuation allowance	$ 249.9	$ 357.9
Balance of unrecognized tax benefit	151	130	$ 112.2	$ 114.8
Unrecognized tax position, that would affect the annual effective tax rate	116
Unrecognized Tax Benefits that would impact Deferred Taxes	35
Estimate of decrease in unrecognized tax positions	48.8
Interest and penalties tax expense	0.2
Accrued interest and penalties	5.3	5.1	$ 5.1
Federal
Income Taxes [Line Items]
Net operating loss carryforwards	99	521.9
Tax credit carryforwards	153.4	134.5
State
Income Taxes [Line Items]
Net operating loss carryforwards	741.3	825.8
Tax credit carryforwards	141.1	138.6
Deferred tax assets, valuation allowance	72.5
Foreign
Income Taxes [Line Items]
Net operating loss carryforwards	581.6	757.1
Tax credit carryforwards	69.4	$ 76.8
National Tax Agency, Japan
Income Taxes [Line Items]
Valuation allowance	$ 128.5

Income Taxes - Reconciliation O

Income Taxes - Reconciliation Of The U.S. Federal Statutory Income Tax Rate (Details) - USD ($) $ in Millions	Jul. 06, 2020	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Income Taxes [Line Items]
U.S. federal statutory rate (as a percent)		21.00%	21.00%	21.00%
Increase (decrease) resulting from:
State and local taxes, net of federal tax benefit		(1.40%)	(2.60%)	(1.00%)
Impact of U.S. Tax Reform and related effects		0	0	0.047
Impact of foreign operations		7.60%	3.80%	(1.20%)
Impact of U.S. tax method changes		0.00%	0.00%	(6.40%)
Impact of the Domestication	(35.70%)	(35.70%)	0.00%	0.00%
Change in valuation allowance and related effects		(24.40%)	1.80%	0.60%
Non-deductible share-based compensation costs		1.70%	(0.50%)	(0.50%)
U.S. federal R&D credit		(3.60%)	(3.70%)	(1.10%)
Nondeductible officer compensation		1.10%	1.50%	0.40%
Other		(0.10%)	1.40%	0.10%
Total		(33.80%)	22.70%	16.60%
Expense (benefit) for reduction in deferred tax liability for undistributed foreign earnings, amount				$ 31.8
Expense (benefit) for reduction in deferred tax liability for undistributed foreign earnings, percent				4.20%
Executive compensation deduction				$ 1.8
Executive compensation deduction, percent				0.30%
Expense for mandatory repatriation tax, amount				$ 1.5
Expense for mandatory repatriation tax, percent				0.002
Impact of U.S. tax method changes				$ 48.2
Recognition of deferred tax assets, net	$ 63
Change in valuation allowance, benefit		$ 49.4
Change in valuation allowance, benefit, percent		28.00%
Foreign
Increase (decrease) resulting from:
Change in valuation allowance, benefit		$ 61.8	$ 11.2	$ 135.2
Change in valuation allowance, benefit, percent		35.00%	4.00%	17.90%
Change in valuation allowance, expense		$ 61.8	$ 11.2	$ 135.2
Change in valuation allowance, expense, percent		35.00%	4.00%	17.90%

Income Taxes - Tax Effects Of T

Income Taxes - Tax Effects Of Temporary Differences (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Income Tax Disclosure [Abstract]
NOL and tax credit carryforwards	$ 471.6	$ 612.9
163 (j) interest expense carryforward	65.7	49.3
Lease liabilities	32.5	22.1
ROU asset	(32.5)	(22.1)
Tax-deductible goodwill and amortizable intangibles	(38)	(48.6)
Capitalization of research and development expenses	90.7	42.7
Reserves and accruals	68.4	27.5
Property, plant and equipment	(95.8)	(81.2)
Inventories	84.3	22
Undistributed earnings of foreign subsidiaries	(57.5)	(63.7)
Share-based compensation	7.7	10.3
Pension	21.2	26.3
Other	3.2	8
Deferred tax assets and liabilities before valuation allowance	621.5	605.5
Valuation allowance	(249.9)	(357.9)
Net deferred tax asset	$ 371.6	$ 247.6

Income Taxes - Activity for Unr

Income Taxes - Activity for Unrecognized Gross Tax Benefits (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Unrecognized Gross Tax Benefits
Balance at beginning of year	$ 130	$ 112.2	$ 114.8
Acquired balances	0	15.5	0
Additions for tax benefits related to the current year	11.9	9.4	7.4
Additions for tax benefits of prior years	12.3	8	2.8
Reductions for tax benefits of prior years	(1.4)	(0.2)	(1.9)
Lapse of statute	(1.3)	(8.2)	(10.9)
Settlements	(0.5)	(6.7)	0
Balance at end of year	$ 151	$ 130	$ 112.2

Changes in Accumulated Other _3

Changes in Accumulated Other Comprehensive Loss - Schedule of Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balance, beginning	$ 3,324.1	$ 3,194.1	$ 2,801
Other comprehensive income (loss) prior to reclassifications	16.7	(19.5)
Amounts reclassified from accumulated other comprehensive loss	(20)	3.1
Other comprehensive income (loss), net of tax	(3.3)	(16.4)	2.7
Balance, ending	3,558.1	3,324.1	3,194.1
Effects of cash flow hedges, tax amount	1.7	4.4
Currency Translation Adjustments
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balance, beginning	(42.4)	(42.5)
Other comprehensive income (loss) prior to reclassifications	1.8	0.1
Amounts reclassified from accumulated other comprehensive loss	0	0
Other comprehensive income (loss), net of tax	1.8	0.1
Balance, ending	(40.6)	(42.4)	(42.5)
Effects of Cash Flow Hedges
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balance, beginning	(11.9)	4.6
Other comprehensive income (loss) prior to reclassifications	14.9	(19.6)
Amounts reclassified from accumulated other comprehensive loss	(20)	3.1
Other comprehensive income (loss), net of tax	(5.1)	(16.5)
Balance, ending	(17)	(11.9)	4.6
Accumulated Other Comprehensive Loss
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balance, beginning	(54.3)	(37.9)	(40.6)
Balance, ending	$ (57.6)	$ (54.3)	$ (37.9)

Changes in Accumulated Other _4

Changes in Accumulated Other Comprehensive Loss - Schedule of Reclassifications from Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Interest expense	$ (8.6)	$ (11.8)	$ (7.1)
Total reclassifications	236.4	213.9	$ 629.9
Reclassification out of Accumulated Other Comprehensive Income
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Total reclassifications	20	(3.1)
Effects of Cash Flow Hedges | Reclassification out of Accumulated Other Comprehensive Income
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Interest expense	$ 20	$ (3.1)

Supplemental Disclosures - Sche

Supplemental Disclosures - Schedule of Cash Flow, Supplemental Disclosures and Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Non-cash investing activities:
Capital expenditures in accounts payable and other long-term liabilities	$ 162.5	$ 155.3	$ 233.9
Sale of property in exchange of note receivable	7.2	0	0
Right-of-use assets obtained in exchange of lease liabilities	58.2	17.5
Non-cash financing activities:
Liability incurred for purchase of business	0	12.7	0
Debt assumed through purchase of equity interest and assets	0	0	50.6
Cash paid for:
Interest expense	109.1	97.2	80
Income taxes	52.5	62.9	53.2
Operating lease payments in operating cash flows	36.9	37.6
Reconciliation of balance sheet to cash flow
Cash and cash equivalents	1,080.7	894.2	1,069.6
Restricted cash (included in other current assets)	0.8	0	17.5
Cash, cash equivalents and restricted cash in Consolidated Statements of Cash Flows	$ 1,081.5	$ 894.2	$ 1,087.1	$ 966.6
1.00% Notes | Convertible Debt
Debt Instrument [Line Items]
Debt instrument, interest rate	1.00%

Supplementary Financial Infor_3

Supplementary Financial Information - Selected Quarterly Financial Data (Unaudited) - Schedule of Quarterly Financial Information (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Oct. 02, 2020	Jul. 03, 2020	Apr. 03, 2020	Dec. 31, 2019	Sep. 27, 2019	Jun. 28, 2019	Mar. 29, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Quarterly Financial Information Disclosure [Abstract]
Revenue	$ 1,446.3	$ 1,317.3	$ 1,213.5	$ 1,277.9	$ 1,401.8	$ 1,381.8	$ 1,347.7	$ 1,386.6
Gross Profit (exclusive of the amortization of acquisition-related intangible assets)	497.6	441.2	374.3	402.7	485.7	475.2	499	513.7	$ 1,715.8	$ 1,973.6	$ 2,238.7
Net income (loss) attributable to ON Semiconductor Corporation	$ 89	$ 160.6	$ (1.4)	$ (14)	$ 56.5	$ (60.7)	$ 101.8	$ 114.1	$ 234.2	$ 211.7	$ 627.4
Diluted net income (loss) per common share attributable to ON Semiconductor Corporation (in dollars per share)	$ 0.21	$ 0.38	$ 0	$ (0.03)	$ 0.14	$ (0.15)	$ 0.24	$ 0.27	$ 0.56	$ 0.51	$ 1.44
Litigation settlement						$ 169.5			$ 0	$ 169.5	$ 0

Schedule II - Valuation and Q_2

Schedule II - Valuation and Qualifying Accounts (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Quantenna
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Charged to Other Accounts		$ 14
Valuation Allowance of Deferred Tax Assets
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Period	$ 357.9	347.5	$ 462.3
Charged (Credited) to Costs and Expenses	(43.1)	5	4.6
Charged to Other Accounts	11	16.6	15.8
Deductions/Write-offs	(75.9)	(11.2)	(135.2)
Balance at End of Period	$ 249.9	$ 357.9	$ 347.5