ON Semiconductor (ON) 10-Q 3 May 21 2021 Q1 Quarterly report Financial data

Cover Page

Cover Page - shares	3 Months Ended
	Apr. 02, 2021	Apr. 28, 2021
Document Information [Line Items]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Apr. 2, 2021
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 Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		427,008,100
Central Index Key	0001097864
Current Fiscal Year End	--12-31
Document Fiscal Period	Q1
Document Fiscal Year	2021
Amendment	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
No Trading Symbol Flag	true
Security Exchange Name	NASDAQ

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Millions	Apr. 02, 2021	Dec. 31, 2020
Assets
Cash and cash equivalents	$ 1,042.5	$ 1,080.7
Receivables, net	683.6	676
Inventories	1,295.5	1,251.4
Other current assets	166	176
Total current assets	3,187.6	3,184.1
Property, plant and equipment, net	2,489.4	2,512.3
Goodwill	1,663.4	1,663.4
Intangible assets, net	441.1	469
Deferred tax assets	447.2	429
Other assets	401.7	410.2
Total assets	8,630.4	8,668
Liabilities, Non-Controlling Interest and Stockholders’ Equity
Accounts payable	605	572.9
Accrued expenses and other current liabilities	588.3	570
Current portion of long-term debt	536.7	531.6
Total current liabilities	1,730	1,674.5
Long-term debt	2,806.9	2,959.7
Deferred tax liabilities	53.9	57.3
Other long-term liabilities	390	418.4
Total liabilities	4,980.8	5,109.9
Commitments and contingencies (Note 9)
ON Semiconductor Corporation stockholders’ equity:
Common stock ($0.01 par value, 1,250,000,000 shares authorized, 579,553,444 and 570,766,439 issued, 419,896,411 and 411,842,629 outstanding, respectively)	5.8	5.7
Additional paid-in capital	4,161	4,133.1
Accumulated other comprehensive loss	(55.9)	(57.6)
Accumulated earnings	1,515.4	1,425.5
Less: Treasury stock, at cost: 159,657,033 and 158,923,810 shares, respectively	(1,996.7)	(1,968.2)
Total ON Semiconductor Corporation stockholders’ equity	3,629.6	3,538.5
Non-controlling interest	20	19.6
Total stockholders' equity	3,649.6	3,558.1
Total liabilities and stockholders' equity	$ 8,630.4	$ 8,668

Consolidated Balance Sheets - P

Consolidated Balance Sheets - Parenthetical - $ / shares	Apr. 02, 2021	Dec. 31, 2020
Statement of Financial Position [Abstract]
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)	579,553,444	570,766,439
Common stock, shares outstanding (in shares)	419,896,411	411,842,629
Treasury stock, shares (in shares)	159,657,033	158,923,810

Consolidated Statements of Oper

Consolidated Statements of Operations and Comprehensive Income - USD ($) shares in Millions, $ in Millions	3 Months Ended
	Apr. 02, 2021	Apr. 03, 2020
Income Statement [Abstract]
Revenue	$ 1,481.7	$ 1,277.9
Cost of revenue (exclusive of amortization shown below)	960.5	875.2
Gross profit	521.2	402.7
Operating expenses:
Research and development	173.6	171
Selling and marketing	78.9	76.8
General and administrative	72.4	71.2
Amortization of acquisition-related intangible assets	25	32.3
Restructuring, asset impairments and other charges, net	42.5	32.8
Intangible asset impairment	2.9	0
Total operating expenses	395.3	384.1
Operating income	125.9	18.6
Other income (expense), net:
Interest expense	(33.4)	(42.5)
Interest income	0.4	1.9
Other income	4.5	0.1
Other income (expense), net	(28.5)	(40.5)
Income (loss) before income taxes	97.4	(21.9)
Income tax (provision) benefit	(7.1)	8.2
Net income (loss)	90.3	(13.7)
Less: Net income attributable to non-controlling interest	(0.4)	(0.3)
Net income (loss) attributable to ON Semiconductor Corporation	89.9	(14)
Comprehensive income (loss), net of tax:
Net income (loss)	90.3	(13.7)
Foreign currency translation adjustments	(2.3)	0.6
Effects of cash flow hedges	4	(12.8)
Other comprehensive income (loss), net of tax	1.7	(12.2)
Comprehensive income (loss)	92	(25.9)
Comprehensive income attributable to non-controlling interest	(0.4)	(0.3)
Comprehensive income (loss) attributable to ON Semiconductor Corporation	$ 91.6	$ (26.2)
Net income (loss) per share of common stock attributable to ON Semiconductor Corporation:
Basic (in dollars per share)	$ 0.22	$ (0.03)
Diluted (in dollars per share)	$ 0.20	$ (0.03)
Weighted-average shares of common stock outstanding:
Basic (in shares)	413.4	410.6
Diluted (in shares)	445.4	410.6

Consolidated Statements of Stoc

Consolidated Statements of Stockholders' Equity - USD ($) $ in Millions	Total	Common Stock	Additional Paid-in Capital	Accumulated Other Comprehensive Loss	Accumulated Earnings	Treasury Stock	Non-Controlling Interest
Balance, beginning (in shares) at Dec. 31, 2019		565,562,607				(154,249,943)
Balance, beginning 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]
Shares issued pursuant to the ESPP (in shares)		487,438
Shares issued pursuant to the ESPP	5.1		5.1
RSUs and stock grant awards issued (in shares)		2,724,497
RSUs and stock grant awards issued	0	$ 0
Payment of tax withholding for RSUs (in shares)						(908,620)
Payment of tax withholding for RSUs	(16)					$ (16)
Share-based compensation	15.7		15.7
Repurchase of common stock (in shares)						(3,611,413)
Repurchase of common stock	(65.4)					$ (65.4)
Comprehensive (loss) income	(25.9)			(12.2)	(14)		0.3
Balance, ending (in shares) at Apr. 03, 2020		568,774,542				(158,769,976)
Balance, ending at Apr. 03, 2020	3,237.6	$ 5.7	3,830.3	(66.5)	1,177.3	$ (1,731.9)	22.7
Balance, beginning (in shares) at Dec. 31, 2020		570,766,439				(158,923,810)
Balance, beginning at Dec. 31, 2020	3,558.1	$ 5.7	4,133.1	(57.6)	1,425.5	$ (1,968.2)	19.6
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares issued pursuant to the ESPP (in shares)		204,415
Shares issued pursuant to the ESPP	5.7		5.7
RSUs and stock grant awards issued (in shares)		2,269,328
RSUs and stock grant awards issued	0
Shares issued upon exercise of warrants for 1.00% Notes (in shares)		6,313,262
Shares issued upon exercise of warrants for 1.00% Notes	0	$ 0.1	(0.1)
Payment of tax withholding for RSUs (in shares)						(733,223)
Payment of tax withholding for RSUs	(28.5)					$ (28.5)
Share-based compensation	22.3		22.3
Comprehensive (loss) income	92			1.7	89.9		0.4
Balance, ending (in shares) at Apr. 02, 2021		579,553,444				(159,657,033)
Balance, ending at Apr. 02, 2021	$ 3,649.6	$ 5.8	$ 4,161	$ (55.9)	$ 1,515.4	$ (1,996.7)	$ 20

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Millions	3 Months Ended
	Apr. 02, 2021	Apr. 03, 2020
Cash flows from operating activities:
Net income (loss)	$ 90.3	$ (13.7)
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Depreciation and amortization	153.4	161.2
Loss on sale or disposal of fixed assets	0.3	0.2
Amortization of debt discount and issuance costs	2.4	3
Share-based compensation	22.3	15.7
Non-cash interest on convertible notes	4.6	9.5
Non-cash asset impairment charges	6.1	1.4
Change in deferred tax balances	(23.2)	(19)
Other	(2)	0
Changes in assets and liabilities:
Receivables	(9.9)	52.7
Inventories	(42)	(19.5)
Other assets	9.9	5.9
Accounts payable	8.9	(12.4)
Accrued expenses and other current liabilities	12.8	(17.6)
Other long-term liabilities	(15.4)	(1.4)
Net cash provided by operating activities	218.5	166
Cash flows from investing activities:
Purchase of property, plant and equipment	(77)	(132.3)
Proceeds from sale of property, plant and equipment	0.2	0
Deposits utilized (made) for purchase of property, plant and equipment	(0.4)	2.2
Purchase of business, net of cash acquired	0	(4.5)
Settlement of purchase price from previous acquisition	0	26
Net cash used in investing activities	(77.2)	(108.6)
Cash flows from financing activities:
Proceeds for the issuance of common stock under the ESPP	6.6	7.5
Payment of tax withholding for RSUs	(28.5)	(16)
Repurchase of common stock	0	(65.4)
Issuance and borrowings under debt agreements	0	1,165
Repayment of borrowings under debt agreements	(154.1)	(56)
Payments related to prior acquisition	(2.1)	(4.9)
Net cash provided by (used in) financing activities	(178.1)	1,030.2
Effect of exchange rate changes on cash, cash equivalents and restricted cash	(0.8)	0.2
Net increase (decrease) in cash, cash equivalents and restricted cash	(37.6)	1,087.8
Cash, cash equivalents and restricted cash, beginning of period	1,081.5	894.2
Cash, cash equivalents and restricted cash, end of period	$ 1,043.9	$ 1,982

Background and Basis of Present

Background and Basis of Presentation	3 Months Ended
	Apr. 02, 2021
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 ("ON Semiconductor," "we," “us,” “our,” or the "Company"), uses a thirteen-week fiscal quarter accounting period for the first three fiscal quarters of each year, with the first quarter of 2021 having ended on April 2, 2021 and each fiscal year ending on December 31. The quarters ended April 2, 2021 and April 3, 2020 contained 92 and 94 days, respectively. As of April 2, 2021, the Company was organized into the following three operating and reportable segments: the Power Solutions Group ("PSG"), the Advanced Solutions Group ("ASG") and the Intelligent Sensing Group ("ISG"). The accompanying unaudited financial statements as of and for the quarter ended April 2, 2021 have been prepared in accordance with generally accepted accounting principles in the United States of America ("GAAP") for unaudited interim financial information. Accordingly, the unaudited financial statements do not include all of the information and footnotes required by GAAP for audited financial statements. The balance sheet as of December 31, 2020 was derived from the Company's audited financial statements, but does not include all disclosures required by GAAP for audited financial statements. In the opinion of the Company's management, the interim information includes all adjustments, which include normal recurring adjustments, necessary for a fair statement of the results for the interim periods. Certain reclassifications have been made to prior period amounts to conform to current-period presentation. The footnote disclosures related to the interim financial information included herein are also unaudited. Such financial information should be read in conjunction with the consolidated financial statements and related notes thereto for the year ended December 31, 2020 included in the Company's Annual Report on Form 10-K for the year ended December 31, 2020, which was filed with the SEC on February 16, 2021 (the “2020 Form 10-K”). 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 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.

Revenue and Segment Information

Revenue and Segment Information	3 Months Ended
	Apr. 02, 2021
Segment Reporting [Abstract]
Revenue and Segment Information	Note 2: Revenue and Segment Information The Company is organized into three operating and reportable segments consisting of PSG, ASG and ISG. These segments represent the Company’s view of the business, and its gross profit is used to evaluate the performance of the Company’s segments, the progress of major initiatives and the allocation of resources. Gross profit is exclusive of the amortization of acquisition-related intangible assets. Depreciation expense is included in segment gross profit. Revenue and gross profit for the Company’s operating and reportable segments are as follows (in millions): PSG ASG ISG Total For the quarter ended April 2, 2021: Revenue from external customers $ 747.0 $ 531.5 $ 203.2 $ 1,481.7 Gross profit $ 246.5 $ 206.8 $ 67.9 $ 521.2 For the quarter ended April 3, 2020: Revenue from external customers $ 623.9 $ 467.1 $ 186.9 $ 1,277.9 Gross profit (1) $ 182.6 $ 157.8 $ 62.3 $ 402.7 (1) Beginning in the first quarter of 2021, the Company started including unallocated manufacturing costs as part of segment operating results to determine segment gross profit. As a result, the prior-period amounts have been reclassified to conform to current-period presentation. The Company had one customer, a distributor, whose revenue accounted for approximately 10.6% of the total revenue for the quarter ended April 2, 2021. 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): Quarter Ended April 2, 2021 PSG ASG ISG Total Geographic Location Singapore $ 274.5 $ 201.7 $ 32.8 $ 509.0 Hong Kong 196.1 100.5 45.6 342.2 United Kingdom 142.7 82.6 43.6 268.9 United States 75.3 70.2 38.8 184.3 Other 58.4 76.5 42.4 177.3 Total $ 747.0 $ 531.5 $ 203.2 $ 1,481.7 Sales Channel Distributors $ 523.9 $ 288.9 $ 121.2 $ 934.0 Direct Customers 223.1 242.6 82.0 547.7 Total $ 747.0 $ 531.5 $ 203.2 $ 1,481.7 Quarter Ended April 3, 2020 PSG ASG ISG Total Geographic Location Singapore $ 194.3 $ 172.6 $ 41.4 $ 408.3 Hong Kong 192.0 91.9 32.3 316.2 United Kingdom 105.1 76.8 45.1 227.0 United States 72.7 77.3 34.5 184.5 Other 59.8 48.5 33.6 141.9 Total $ 623.9 $ 467.1 $ 186.9 $ 1,277.9 Sales Channel Distributors $ 386.3 $ 213.6 $ 103.4 $ 703.3 Direct Customers 237.6 253.5 83.5 574.6 Total $ 623.9 $ 467.1 $ 186.9 $ 1,277.9 The Company operates in various geographic locations. Sales to unaffiliated customers have little correlation with the location of manufacturers. Accordingly, the Company does not 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, is summarized as follows (in millions): As of April 2, 2021 December 31, 2020 United States $ 690.8 $ 686.6 South Korea 446.0 455.5 Philippines 376.4 386.6 China 224.5 229.6 Czech Republic 211.3 216.1 Japan 216.1 209.3 Malaysia 188.3 190.2 Other 136.0 138.4 Total $ 2,489.4 $ 2,512.3

Recent Accounting Pronouncement

Recent Accounting Pronouncements	3 Months Ended
	Apr. 02, 2021
Accounting Changes and Error Corrections [Abstract]
Recent Accounting Pronouncements	Note 3: Recent Accounting Pronouncements 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 the purpose of 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. As required, the Company plans to adopt ASU

Restructuring, Asset Impairment

Restructuring, Asset Impairments and Other, Net	3 Months Ended
	Apr. 02, 2021
Restructuring Charges [Abstract]
Restructuring, Asset Impairments and Other, Net	Note 4: Restructuring, Asset Impairments and Other, Net Details of restructuring, asset impairments and other charges, net are as follows (in millions): Restructuring Asset Impairments Other Total Quarter ended April 2, 2021 2021 Involuntary Separation Program $ 33.0 $ — $ — $ 33.0 Other — 3.2 6.3 9.5 Total $ 33.0 $ 3.2 $ 6.3 $ 42.5 A summary of changes in accrued restructuring from December 31, 2020 to April 2, 2021 is as follows (in millions): As of As of December 31, 2020 Charges Usage April 2, 2021 Employee separation charges $ 6.2 $ 33.0 $ (11.4) $ 27.8 Total $ 6.2 $ 33.0 $ (11.4) $ 27.8 2021 Involuntary Separation Program On March 4, 2021, as part of its ongoing efforts to realign its investments to focus on growth drivers and key markets and to streamline its operations, the Company announced its plans to implement certain employee terminations during the first half of 2021 (the "ISP"). Under the ISP, the Company expects to terminate the employment of approximately 740 employees and incur severance costs and other benefits between $58 million and $62 million. During the quarter ended April 2, 2021, the Company notified approximately 500 employees of their employment termination, and incurred severance costs and other benefits amounting to $33.0 million, pursuant to the ISP. As of April 2, 2021, $26.5 million of such severance costs and benefits remained accrued and, based on the exit dates of the notified employees, is expected to be paid during the second quarter of 2021. The remaining employees are expected to be notified, and the corresponding severance costs will be incurred, during the second quarter of 2021.

Balance Sheet Information and O

Balance Sheet Information and Other	3 Months Ended
	Apr. 02, 2021
Balance Sheet Related Disclosures [Abstract]
Balance Sheet Information and Other	Note 5: Balance Sheet Information and Other Goodwill There was no change in the balance of goodwill from December 31, 2020 to April 2, 2021. Goodwill is tested for impairment annually on the first day of the fourth quarter or more frequently if events or changes in circumstances (each, a "triggering event") would more likely than not reduce the carrying value of goodwill below its fair value. Management did not identify any triggering events during the quarter ended April 2, 2021 that would require an interim impairment analysis. Inventory Details of Inventory included in the Company’s Consolidated Balance Sheets are as follows (in millions): As of April 2, 2021 December 31, 2020 Inventories: Raw materials $ 139.0 $ 135.7 Work in process 834.4 829.7 Finished goods 322.1 286.0 $ 1,295.5 $ 1,251.4 Defined Benefit Plans The Company recognizes the aggregate amount of all overfunded plans as assets and the aggregate amount of all underfunded plans as liabilities in its financial statements. As of April 2, 2021, the net assets for the overfunded plans totaled $8.5 million. The total accrued pension liability for underfunded plans was $147.9 million, of which the current portion of $0.4 million was classified as accrued expenses and other current liabilities. As of December 31, 2020, the net funded status for all the plans was a liability of $141.9 million, of which the current portion of $0.3 million was classified as accrued expenses and other current liabilities. The components of the net periodic pension expense were as follows (in millions): Quarters Ended April 2, 2021 April 3, 2020 Service cost $ 3.1 $ 2.7 Interest cost 1.1 1.1 Expected return on plan assets (1.7) (1.5) Curtailment loss 1.9 — Total net periodic pension cost $ 4.4 $ 2.3 Leases Operating lease arrangements are comprised primarily of real estate and equipment agreements. The components of lease expense were as follows (in millions): Quarters Ended April 2, 2021 April 3, 2020 Operating lease $ 9.9 $ 9.1 Variable lease 1.0 1.1 Short-term lease 0.7 1.1 Total lease expense $ 11.6 $ 11.3 The lease liabilities recognized in the Consolidated Balance Sheets are as follows (in millions): As of April 2, 2021 December 31, 2020 Accrued expenses and other current liabilities $ 32.9 $ 32.2 Other long-term liabilities 108.8 115.7 Total lease liabilities $ 141.7 $ 147.9 Operating Right-of-use ("ROU") assets as of April 2, 2021 and December 31, 2020 amounted to $133.8 million and $136.3 million, respectively, and are included in other assets in the Consolidated Balance Sheets. As of April 2, 2021, the weighted-average remaining lease-term was 6.7 years years and the weighted-average discount rate was 4.8%. Supplemental Disclosure of Cash Flow Information Certain of the Company's cash and non-cash activities were as follows (in millions): Quarters Ended April 2, 2021 April 3, 2020 Non-cash investing activities: Capital expenditures in accounts payable and other long-term liabilities $ 180.9 $ 123.5 ROU assets obtained in exchange of lease liabilities 7.1 8.8 Non-cash financing activity: Liability incurred for purchase of business $ — $ 7.7 Cash paid for: Interest expense $ 31.4 $ 24.5 Income taxes 20.9 9.9 Operating lease payments in operating cash flows 10.3 8.2 Reconciliation of the captions in the Consolidated Balance Sheets to the Consolidated Statements of Cash Flows (in millions): As of April 2, 2021 December 31, 2020 April 3, 2020 December 31, 2019 Consolidated Balance Sheets: Cash and cash equivalents $ 1,042.5 $ 1,080.7 $ 1,982.0 $ 894.2 Restricted cash (included in other current assets) 1.4 0.8 — — Cash, cash equivalents and restricted cash in Consolidated Statements of Cash Flows $ 1,043.9 $ 1,081.5 $ 1,982.0 $ 894.2

Long-Term Debt

Long-Term Debt	3 Months Ended
	Apr. 02, 2021
Debt Disclosure [Abstract]
Long-Term Debt	Note 6: Long-Term Debt The Company's long-term debt consists of the following (annualized interest rates, in millions): As of April 2, 2021 December 31, 2020 Amended Credit Agreement: Revolving Credit Facility due 2024, interest payable monthly at 1.61% and 1.90%, respectively $ 550.0 $ 700.0 Term Loan “B” Facility due 2026, interest payable monthly at 2.11% and 2.15%, respectively 1,610.4 1,614.5 3.875% Notes due 2028 (1) 700.0 700.0 1.625% Notes due 2023 (2) 575.0 575.0 Gross long-term debt, including current portion $ 3,435.4 $ 3,589.5 Less: Debt discount (3) (64.7) (69.7) Less: Debt issuance costs (4) (27.1) (28.5) Net long-term debt, including current portion $ 3,343.6 $ 3,491.3 Less: Current portion of long-term debt (536.7) (531.6) Net long-term debt $ 2,806.9 $ 2,959.7 (1) Interest is payable on March 1 and September 1 of each year at 3.875% annually. (2) Interest is payable on April 15 and October 15 of each year at 1.625% annually. (3) Debt discount of $6.4 million and $6.5 million for the 3.875% Notes, $49.6 million and $54.2 million for the 1.625% Notes and $8.7 million and $9.0 million for the Term Loan "B" Facility, in each case as of April 2, 2021 and December 31, 2020, respectively. (4) Debt issuance costs of $2.2 million and $2.3 million for the 3.875% Notes, $4.8 million and $5.2 million for the 1.625% Notes and $20.1 million and $21.0 million for the Term Loan "B" Facility, in each case as of April 2, 2021 and December 31, 2020, respectively. Expected maturities of gross long-term debt (including current portion - see 1.625% Notes section below) as of April 2, 2021 were as follows (in millions): Period Expected Maturities Remainder of 2021 $ 587.3 2022 16.3 2023 16.3 2024 566.4 2025 16.3 Thereafter 2,232.8 Total $ 3,435.4 The Company was in compliance with its covenants under all debt agreements as of April 2, 2021. Revolving Credit Facility During the quarter ended April 2, 2021, the Company repaid $150.0 million of the outstanding balance under the Revolving Credit Facility using the cash generated from its operations. As a result, as of April 2, 2021, the Company had approximately $1,419.0 million available for future borrowings under the Revolving Credit Facility. 1.625% Notes due 2023

Earnings Per Share and Equity

Earnings Per Share and Equity	3 Months Ended
	Apr. 02, 2021
Earnings Per Share [Abstract]
Earnings Per Share and Equity	Note 7: Earnings Per Share and Equity Earnings Per Share Net income (loss) per share of common stock attributable to ON Semiconductor Corporation is calculated as follows (in millions, except per share data): Quarters Ended April 2, 2021 April 3, 2020 Net income (loss) attributable to ON Semiconductor Corporation $ 89.9 $ (14.0) Basic weighted-average shares of common stock outstanding 413.4 410.6 Dilutive effect of share-based awards 2.7 — Dilutive effect of convertible notes and warrants 29.3 — Diluted weighted-average shares of common stock outstanding 445.4 410.6 Net income (loss) per share of common stock attributable to ON Semiconductor Corporation: Basic $ 0.22 $ (0.03) Diluted $ 0.20 $ (0.03) Basic income (loss) per share of common stock is computed by dividing net income (loss) 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 0.7 million and 2.6 million for the quarters ended April 2, 2021 and April 3, 2020, respectively, were excluded as the impact was considered anti-dilutive. The dilutive impact related to the 1.625% Notes has been determined in accordance with the net share settlement requirements, under which the 1.625% Notes are assumed to be convertible into cash up to the par value, with the excess over par value being convertible into common stock. 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. The dilutive impact of the warrants issued concurrently with the issuance of the 1.00% Notes and 1.625% Notes, with exercise prices of $25.96 and $30.70, respectively, has been included in the calculation of diluted weighted-average common shares outstanding. Approximately half of the warrants issued in connection with the 1.00% Notes were settled during the quarter ended April 2, 2021. Equity Warrants Settlement At the time of issuance of the 1.00% Notes, the Company sold 37.3 million warrants to bank counterparties whereby the holders of the warrants had 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 beginning in March 2021. The bank counterparties exercised 18.7 million warrants during the quarter ended April 2, 2021, and the Company settled them by issuing 6.3 million shares of common stock on a net-share basis based on the average stock price on the day of exercise. Subsequent to the end of the first quarter, the warrant holders exercised the remaining 18.6 million warrants and the Company settled them by issuing 7.1 million shares of common stock. Share Repurchase Program There were no repurchases during the quarter ended April 2, 2021 under the share repurchase program announced on November 15, 2018 (the “Share Repurchase Program”), as compared to $65.3 million in share repurchases made by the Company under the Share Repurchase Program during the quarter ended April 3, 2020. As of April 2, 2021, the authorized amount remaining under the Share Repurchase Program was $1,295.8 million. Activity under the Share Repurchase Program during the quarters ended April 2, 2021 and April 3, 2020 was as follows (in millions, except per share data): Quarters Ended April 2, 2021 April 3, 2020 Number of repurchased shares (1) — 3.6 Aggregate purchase price $ — $ 65.3 Fees, commissions and other expenses — 0.1 Total cash used for share repurchases $ — $ 65.4 Weighted-average purchase price per share (2) $ — $ 18.08 (1) None of these shares had been reissued or retired as of April 2, 2021, but may be reissued or retired at a later date. (2) Exclusive of fees, commissions and other expenses. Shares for Restricted Stock Units Tax Withholding The amounts remitted for employee withholding taxes during the quarters ended April 2, 2021 and April 3, 2020 were $28.5 million and $16.0 million, respectively, for which the Company withheld approximately 0.7 million and approximately 0.9 million shares of common stock, respectively, that were underlying the RSUs that vested. None of these shares had been reissued or retired as of April 2, 2021, but may be reissued or retired by the Company at a later date. Non-Controlling Interest in Leshan-Phoenix Semiconductor Company Limited (“Leshan”) The results of Leshan have been consolidated in the Company's financial statements. As of December 31, 2020, the non-controlling interest balance was $19.6 million and along with the $0.4 million share of the earnings for the quarter ended April 2, 2021, increased to $20.0 million as of April 2, 2021.

Share-Based Compensation

Share-Based Compensation	3 Months Ended
	Apr. 02, 2021
Share-based Payment Arrangement [Abstract]
Share-Based Compensation	Note 8: Share-Based Compensation Total share-based compensation expense related to the Company's RSUs, stock grant awards and the ESPP was recorded within the Consolidated Statements of Operations and Comprehensive Income as follows (in millions): Quarters Ended April 2, 2021 April 3, 2020 Cost of revenue $ 3.3 $ 2.5 Research and development 5.7 4.1 Selling and marketing 4.3 2.9 General and administrative 9.0 6.2 Share-based compensation expense $ 22.3 $ 15.7 Income tax benefit (4.7) (3.3) Share-based compensation expense, net of taxes $ 17.6 $ 12.4 As of April 2, 2021, total unrecognized expected share-based compensation expense, net of estimated forfeitures, related to non-vested RSUs with service, performance and market conditions was $142.7 million, which is expected to be recognized over a weighted-average period of 1.8 years. There were no stock options exercised during the quarter ended April 2, 2021. 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. The annualized pre-vesting forfeiture rate for RSUs was estimated to be 5% for each of the quarters ended April 2, 2021 and April 3, 2020. Shares Available As of April 2, 2021 and December 31, 2020, there was an aggregate of 17.6 million and 16.5 million shares of common stock, respectively, available for grant under the Amended and Restated SIP. The increase in available shares is attributable to the forfeiture of certain awards granted in 2019 due to the non-achievement of the performance criteria. As of April 2, 2021 and December 31, 2020, there was an aggregate of 2.7 million and 3.0 million shares of common stock, respectively, available for issuance under the ESPP. Restricted Stock Units RSUs generally vest ratably over three years for awards with service conditions and over two Number of Shares Weighted-Average Grant Date Fair Value Per Share Non-vested RSUs at December 31, 2020 11.3 $ 20.73 Granted 2.1 41.19 Released (2.3) 21.97 Forfeited (2.8) 21.63 Non-vested RSUs at April 2, 2021 8.3 25.38

Commitments and Contingencies

Commitments and Contingencies	3 Months Ended
	Apr. 02, 2021
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Note 9: Commitments and Contingencies Environmental Contingencies There are no new material environmental contingencies subsequent to the filing of the 2020 Form 10-K. 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 April 2, 2021, the Company's Revolving Credit Facility included $15.0 million available for the issuance of letters of credit. There were $0.9 million in letters of credit outstanding under the Revolving Credit Facility as of April 2, 2021, which reduced the Company's borrowing capacity. As of April 2, 2021, the Company also had outstanding guarantees and letters of credit outside of its Revolving Credit Facility totaling $8.6 million. 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 April 2, 2021. 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 There are no new material indemnification contingencies subsequent to the filing of the 2020 Form 10-K. Legal Matters The Company is currently involved in a variety of legal matters that arise in the ordinary course of business. Based on information currently available, 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. 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	3 Months Ended
	Apr. 02, 2021
Fair Value Disclosures [Abstract]
Fair Value Measurements	Note 10: 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): As of Fair Value Hierarchy Description April 2, 2021 Level 1 Level 2 Level 3 Assets: Cash and cash equivalents: Demand and time deposits $ 8.5 $ 8.5 $ — $ — As of Fair Value Hierarchy Description December 31, 2020 Level 1 Level 2 Level 3 Assets: Cash and cash equivalents: Demand and time deposits $ 8.5 $ 8.5 $ — $ — 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 values of the Company’s long-term borrowings were as follows (in millions): As of April 2, 2021 December 31, 2020 Carrying Fair Value Carrying Fair Value Long-term debt, including current portion (1) Convertible notes $ 520.6 $ 1,214.0 $ 515.6 $ 967.1 Other long-term debt 2,823.0 2,781.4 2,975.7 2,966.8 (1) Carrying amounts shown are net of debt discount and debt issuance costs. The fair values of the 3.875% Notes and the 1.625% Notes 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).

Financial Instruments

Financial Instruments	3 Months Ended
	Apr. 02, 2021
Investments, All Other Investments [Abstract]
Financial Instruments	Note 11: 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 April 2, 2021 and December 31, 2020, the Company had net outstanding foreign exchange contracts with notional amounts of $281.7 million and $263.4 million, respectively. Such contracts were obtained through financial institutions and were scheduled to mature within one The following summarizes the Company’s net foreign exchange positions in U.S. Dollars (in millions): As of April 2, 2021 December 31, 2020 Buy (Sell) Notional Amount Buy (Sell) Notional Amount Japanese Yen 81.2 81.2 71.2 71.2 Philippine Peso 65.1 65.1 57.2 57.2 Euro 50.7 50.7 47.7 47.7 Korean Won 36.9 36.9 34.4 34.4 Chinese Yuan 13.3 13.3 17.7 17.7 Malaysian Ringgit 11.9 11.9 11.7 11.7 Other Currencies - Buy 17.3 17.3 12.4 12.4 Other Currencies - Sell (5.3) 5.3 (11.1) 11.1 $ 271.1 $ 281.7 $ 241.2 $ 263.4 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. During the quarters ended April 2, 2021 and April 3, 2020, realized and unrealized foreign currency transactions totaled a gain of $4.0 million and a loss of $0.2 million, respectively, and 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 Company’s Consolidated Balance Sheets at their fair value and classified based on the applicable instrument's maturity date. Foreign Currency Risk The purpose of the 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. For the quarters ended April 2, 2021 and April 3, 2020, the Company did not have outstanding derivatives for its foreign currency exposure designated as cash flow hedges. Interest Rate Risk The Company uses interest rate swap contracts to mitigate its exposure to interest rate fluctuations. The Company did not identify any ineffectiveness with respect to the notional amounts of the interest rate swap contracts effective as of April 2, 2021 and April 3, 2020, amounting to $1.5 billion and $1.0 billion, respectively. Other As of April 2, 2021, the Company had no outstanding commodity derivatives, currency swaps or options relating to either its debt instruments or investments. The Company does not hedge the value of its equity investments in its subsidiaries or affiliated companies. The Company is exposed to credit-related losses if counterparties to hedge contracts fail to perform their obligations. As of April 2, 2021, the counterparties to the Company’s hedge contracts were held at financial institutions that the Company believes to be highly-rated, and no credit-related losses are anticipated.

Income Taxes

Income Taxes	3 Months Ended
	Apr. 02, 2021
Income Tax Disclosure [Abstract]
Income Taxes	Note 12: Income Taxes The Company recognizes interest and penalties related to uncertain tax positions in tax expense on the Company's Consolidated Statements of Operations and Comprehensive Income. The Company had approximately $3.0 million and $5.2 million of net interest and penalties accrued as of April 2, 2021 and April 3, 2020, respectively. It is reasonably possible that $42.3 million of its uncertain tax positions will be reduced in the next 12 months due to settlement with tax authorities or expiration of the applicable statute of limitations. The Company maintains a partial valuation allowance on its U.S. state deferred tax assets and a valuation allowance on foreign net operating losses and tax credits in certain foreign jurisdictions, a substantial portion of which relate to Japan net operating losses, which are projected to expire prior to utilization. Tax years prior to 2017 are generally not subject to examination by the United States Internal Revenue Service (the “IRS”) except for items involving tax attributes that have been carried forward to tax years with statutes of limitations that remain open. The Company is currently under IRS examination for the 2017 tax year. For state tax returns, the Company is generally not subject to income tax examinations for tax years prior to 2016. The Company is also subject to routine examinations by various foreign tax jurisdictions in which it operates. With respect to jurisdictions outside the United States, the Company is generally not subject to examination for tax years prior to 2010. The Company believes that adequate provisions have been made for any adjustments that may result from tax examinations. However, the outcome of tax audits cannot be predicted with certainty. If any issues addressed in the Company’s tax audits are resolved in a manner not consistent with the Company's expectations, the Company could be required to adjust its provision for income taxes in the period such resolution occurs.

Changes in Accumulated Other Co

Changes in Accumulated Other Comprehensive Loss	3 Months Ended
	Apr. 02, 2021
Equity [Abstract]
Changes in Accumulated Other Comprehensive Loss	Note 13: 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 as of December 31, 2020 $ (40.6) $ (17.0) $ (57.6) Other comprehensive income (loss) prior to reclassifications (2.3) 8.6 6.3 Amounts reclassified from accumulated other comprehensive loss — (4.6) (4.6) Net current period other comprehensive income (loss) (1) (2.3) 4.0 1.7 Balance as of April 2, 2021 $ (42.9) $ (13.0) $ (55.9) (1) Effects of cash flow hedges are net of tax expense of $1.2 million for the quarter ended April 2, 2021. Amounts reclassified from accumulated other comprehensive loss to the specific caption within Consolidated Statements of Operations and Comprehensive Income were as follows: Amounts Reclassified from Accumulated Other Comprehensive Loss Quarters Ended April 2, 2021 April 3, 2020 To caption Interest rate swaps $ 4.6 $ 1.9 Interest expense Total reclassifications $ 4.6 $ 1.9

Background and Basis of Prese_2

Background and Basis of Presentation (Policies)	3 Months Ended
	Apr. 02, 2021
Organization, Consolidation and Presentation of Financial Statements [Abstract]
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 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.
Recent Accounting Pronouncements	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 the purpose of 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. As required, the Company plans to adopt ASU

Revenue and Segment Informati_2

Revenue and Segment Information (Tables)	3 Months Ended
	Apr. 02, 2021
Segment Reporting [Abstract]
Revenues 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 the quarter ended April 2, 2021: Revenue from external customers $ 747.0 $ 531.5 $ 203.2 $ 1,481.7 Gross profit $ 246.5 $ 206.8 $ 67.9 $ 521.2 For the quarter ended April 3, 2020: Revenue from external customers $ 623.9 $ 467.1 $ 186.9 $ 1,277.9 Gross profit (1) $ 182.6 $ 157.8 $ 62.3 $ 402.7 (1) Beginning in the first quarter of 2021, the Company started including unallocated manufacturing costs as part of segment operating results to determine segment gross profit. As a result, the prior-period amounts have been reclassified to conform to current-period presentation.
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): Quarter Ended April 2, 2021 PSG ASG ISG Total Geographic Location Singapore $ 274.5 $ 201.7 $ 32.8 $ 509.0 Hong Kong 196.1 100.5 45.6 342.2 United Kingdom 142.7 82.6 43.6 268.9 United States 75.3 70.2 38.8 184.3 Other 58.4 76.5 42.4 177.3 Total $ 747.0 $ 531.5 $ 203.2 $ 1,481.7 Sales Channel Distributors $ 523.9 $ 288.9 $ 121.2 $ 934.0 Direct Customers 223.1 242.6 82.0 547.7 Total $ 747.0 $ 531.5 $ 203.2 $ 1,481.7 Quarter Ended April 3, 2020 PSG ASG ISG Total Geographic Location Singapore $ 194.3 $ 172.6 $ 41.4 $ 408.3 Hong Kong 192.0 91.9 32.3 316.2 United Kingdom 105.1 76.8 45.1 227.0 United States 72.7 77.3 34.5 184.5 Other 59.8 48.5 33.6 141.9 Total $ 623.9 $ 467.1 $ 186.9 $ 1,277.9 Sales Channel Distributors $ 386.3 $ 213.6 $ 103.4 $ 703.3 Direct Customers 237.6 253.5 83.5 574.6 Total $ 623.9 $ 467.1 $ 186.9 $ 1,277.9
Summary of Property, Plant and Equipment by Geographic Location	Property, plant and equipment, net, by geographic location, is summarized as follows (in millions): As of April 2, 2021 December 31, 2020 United States $ 690.8 $ 686.6 South Korea 446.0 455.5 Philippines 376.4 386.6 China 224.5 229.6 Czech Republic 211.3 216.1 Japan 216.1 209.3 Malaysia 188.3 190.2 Other 136.0 138.4 Total $ 2,489.4 $ 2,512.3

Restructuring, Asset Impairme_2

Restructuring, Asset Impairments and Other, Net - (Tables)	3 Months Ended
	Apr. 02, 2021
Restructuring Charges [Abstract]
Schedule of Activity Included in Restructuring, Asset Impairments, and Other, Net	Details of restructuring, asset impairments and other charges, net are as follows (in millions): Restructuring Asset Impairments Other Total Quarter ended April 2, 2021 2021 Involuntary Separation Program $ 33.0 $ — $ — $ 33.0 Other — 3.2 6.3 9.5 Total $ 33.0 $ 3.2 $ 6.3 $ 42.5
Schedule of Changes in Accrued Restructuring Reserve	A summary of changes in accrued restructuring from December 31, 2020 to April 2, 2021 is as follows (in millions): As of As of December 31, 2020 Charges Usage April 2, 2021 Employee separation charges $ 6.2 $ 33.0 $ (11.4) $ 27.8 Total $ 6.2 $ 33.0 $ (11.4) $ 27.8

Balance Sheet Information and_2

Balance Sheet Information and Other - (Tables)	3 Months Ended
	Apr. 02, 2021
Balance Sheet Related Disclosures [Abstract]
Schedule of Inventory	Details of Inventory included in the Company’s Consolidated Balance Sheets are as follows (in millions): As of April 2, 2021 December 31, 2020 Inventories: Raw materials $ 139.0 $ 135.7 Work in process 834.4 829.7 Finished goods 322.1 286.0 $ 1,295.5 $ 1,251.4
Schedule of Net Periodic Pension Expense	The components of the net periodic pension expense were as follows (in millions): Quarters Ended April 2, 2021 April 3, 2020 Service cost $ 3.1 $ 2.7 Interest cost 1.1 1.1 Expected return on plan assets (1.7) (1.5) Curtailment loss 1.9 — Total net periodic pension cost $ 4.4 $ 2.3
Schedule of Components of Lease Expense	The components of lease expense were as follows (in millions): Quarters Ended April 2, 2021 April 3, 2020 Operating lease $ 9.9 $ 9.1 Variable lease 1.0 1.1 Short-term lease 0.7 1.1 Total lease expense $ 11.6 $ 11.3 The lease liabilities recognized in the Consolidated Balance Sheets are as follows (in millions): As of April 2, 2021 December 31, 2020 Accrued expenses and other current liabilities $ 32.9 $ 32.2 Other long-term liabilities 108.8 115.7 Total lease liabilities $ 141.7 $ 147.9
Schedule of Cash and Non-cash Activities	Certain of the Company's cash and non-cash activities were as follows (in millions): Quarters Ended April 2, 2021 April 3, 2020 Non-cash investing activities: Capital expenditures in accounts payable and other long-term liabilities $ 180.9 $ 123.5 ROU assets obtained in exchange of lease liabilities 7.1 8.8 Non-cash financing activity: Liability incurred for purchase of business $ — $ 7.7 Cash paid for: Interest expense $ 31.4 $ 24.5 Income taxes 20.9 9.9 Operating lease payments in operating cash flows 10.3 8.2
Schedule of Cash and Cash Equivalents	Reconciliation of the captions in the Consolidated Balance Sheets to the Consolidated Statements of Cash Flows (in millions): As of April 2, 2021 December 31, 2020 April 3, 2020 December 31, 2019 Consolidated Balance Sheets: Cash and cash equivalents $ 1,042.5 $ 1,080.7 $ 1,982.0 $ 894.2 Restricted cash (included in other current assets) 1.4 0.8 — — Cash, cash equivalents and restricted cash in Consolidated Statements of Cash Flows $ 1,043.9 $ 1,081.5 $ 1,982.0 $ 894.2
Schedule of Restrictions on Cash and Cash Equivalents	Reconciliation of the captions in the Consolidated Balance Sheets to the Consolidated Statements of Cash Flows (in millions): As of April 2, 2021 December 31, 2020 April 3, 2020 December 31, 2019 Consolidated Balance Sheets: Cash and cash equivalents $ 1,042.5 $ 1,080.7 $ 1,982.0 $ 894.2 Restricted cash (included in other current assets) 1.4 0.8 — — Cash, cash equivalents and restricted cash in Consolidated Statements of Cash Flows $ 1,043.9 $ 1,081.5 $ 1,982.0 $ 894.2

Long-Term Debt - (Tables)

Long-Term Debt - (Tables)	3 Months Ended
	Apr. 02, 2021
Debt Disclosure [Abstract]
Schedule of Long-Term Debt	The Company's long-term debt consists of the following (annualized interest rates, in millions): As of April 2, 2021 December 31, 2020 Amended Credit Agreement: Revolving Credit Facility due 2024, interest payable monthly at 1.61% and 1.90%, respectively $ 550.0 $ 700.0 Term Loan “B” Facility due 2026, interest payable monthly at 2.11% and 2.15%, respectively 1,610.4 1,614.5 3.875% Notes due 2028 (1) 700.0 700.0 1.625% Notes due 2023 (2) 575.0 575.0 Gross long-term debt, including current portion $ 3,435.4 $ 3,589.5 Less: Debt discount (3) (64.7) (69.7) Less: Debt issuance costs (4) (27.1) (28.5) Net long-term debt, including current portion $ 3,343.6 $ 3,491.3 Less: Current portion of long-term debt (536.7) (531.6) Net long-term debt $ 2,806.9 $ 2,959.7 (1) Interest is payable on March 1 and September 1 of each year at 3.875% annually. (2) Interest is payable on April 15 and October 15 of each year at 1.625% annually. (3) Debt discount of $6.4 million and $6.5 million for the 3.875% Notes, $49.6 million and $54.2 million for the 1.625% Notes and $8.7 million and $9.0 million for the Term Loan "B" Facility, in each case as of April 2, 2021 and December 31, 2020, respectively. (4) Debt issuance costs of $2.2 million and $2.3 million for the 3.875% Notes, $4.8 million and $5.2 million for the 1.625% Notes and $20.1 million and $21.0 million for the Term Loan "B" Facility, in each case as of April 2, 2021 and December 31, 2020, respectively.
Schedule of Annual Maturities Relating To Long-Term Debt	Expected maturities of gross long-term debt (including current portion - see 1.625% Notes section below) as of April 2, 2021 were as follows (in millions): Period Expected Maturities Remainder of 2021 $ 587.3 2022 16.3 2023 16.3 2024 566.4 2025 16.3 Thereafter 2,232.8 Total $ 3,435.4

Earnings Per Share and Equity -

Earnings Per Share and Equity - (Tables)	3 Months Ended
	Apr. 02, 2021
Earnings Per Share [Abstract]
Summary of Earnings Per Share	Net income (loss) per share of common stock attributable to ON Semiconductor Corporation is calculated as follows (in millions, except per share data): Quarters Ended April 2, 2021 April 3, 2020 Net income (loss) attributable to ON Semiconductor Corporation $ 89.9 $ (14.0) Basic weighted-average shares of common stock outstanding 413.4 410.6 Dilutive effect of share-based awards 2.7 — Dilutive effect of convertible notes and warrants 29.3 — Diluted weighted-average shares of common stock outstanding 445.4 410.6 Net income (loss) per share of common stock attributable to ON Semiconductor Corporation: Basic $ 0.22 $ (0.03) Diluted $ 0.20 $ (0.03)
Schedule of Share Repurchase Program	Activity under the Share Repurchase Program during the quarters ended April 2, 2021 and April 3, 2020 was as follows (in millions, except per share data): Quarters Ended April 2, 2021 April 3, 2020 Number of repurchased shares (1) — 3.6 Aggregate purchase price $ — $ 65.3 Fees, commissions and other expenses — 0.1 Total cash used for share repurchases $ — $ 65.4 Weighted-average purchase price per share (2) $ — $ 18.08 (1) None of these shares had been reissued or retired as of April 2, 2021, but may be reissued or retired at a later date. (2) Exclusive of fees, commissions and other expenses.

Share-Based Compensation - (Tab

Share-Based Compensation - (Tables)	3 Months Ended
	Apr. 02, 2021
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 the ESPP was recorded within the Consolidated Statements of Operations and Comprehensive Income as follows (in millions): Quarters Ended April 2, 2021 April 3, 2020 Cost of revenue $ 3.3 $ 2.5 Research and development 5.7 4.1 Selling and marketing 4.3 2.9 General and administrative 9.0 6.2 Share-based compensation expense $ 22.3 $ 15.7 Income tax benefit (4.7) (3.3) Share-based compensation expense, net of taxes $ 17.6 $ 12.4
Summary Of Restricted Stock Units Transactions	A summary of the RSU transactions for the quarter ended April 2, 2021 is as follows (in millions, except per share data): Number of Shares Weighted-Average Grant Date Fair Value Per Share Non-vested RSUs at December 31, 2020 11.3 $ 20.73 Granted 2.1 41.19 Released (2.3) 21.97 Forfeited (2.8) 21.63 Non-vested RSUs at April 2, 2021 8.3 25.38

Fair Value Measurements - (Tabl

Fair Value Measurements - (Tables)	3 Months Ended
	Apr. 02, 2021
Fair Value Disclosures [Abstract]
Summary of Fair Value of Assets and Liabilities	The following table summarizes the Company's financial assets and liabilities, excluding pension assets, measured at fair value on a recurring basis (in millions): As of Fair Value Hierarchy Description April 2, 2021 Level 1 Level 2 Level 3 Assets: Cash and cash equivalents: Demand and time deposits $ 8.5 $ 8.5 $ — $ — As of Fair Value Hierarchy Description December 31, 2020 Level 1 Level 2 Level 3 Assets: Cash and cash equivalents: Demand and time deposits $ 8.5 $ 8.5 $ — $ —
Summary of Fair Value, by Balance Sheet Grouping	The carrying amounts and fair values of the Company’s long-term borrowings were as follows (in millions): As of April 2, 2021 December 31, 2020 Carrying Fair Value Carrying Fair Value Long-term debt, including current portion (1) Convertible notes $ 520.6 $ 1,214.0 $ 515.6 $ 967.1 Other long-term debt 2,823.0 2,781.4 2,975.7 2,966.8 (1) Carrying amounts shown are net of debt discount and debt issuance costs.

Financial Instruments - (Tables

Financial Instruments - (Tables)	3 Months Ended
	Apr. 02, 2021
Investments, All Other Investments [Abstract]
Schedule of Net Foreign Exchange Positions	The following summarizes the Company’s net foreign exchange positions in U.S. Dollars (in millions): As of April 2, 2021 December 31, 2020 Buy (Sell) Notional Amount Buy (Sell) Notional Amount Japanese Yen 81.2 81.2 71.2 71.2 Philippine Peso 65.1 65.1 57.2 57.2 Euro 50.7 50.7 47.7 47.7 Korean Won 36.9 36.9 34.4 34.4 Chinese Yuan 13.3 13.3 17.7 17.7 Malaysian Ringgit 11.9 11.9 11.7 11.7 Other Currencies - Buy 17.3 17.3 12.4 12.4 Other Currencies - Sell (5.3) 5.3 (11.1) 11.1 $ 271.1 $ 281.7 $ 241.2 $ 263.4

Changes in Accumulated Other _2

Changes in Accumulated Other Comprehensive Loss - (Tables)	3 Months Ended
	Apr. 02, 2021
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 as of December 31, 2020 $ (40.6) $ (17.0) $ (57.6) Other comprehensive income (loss) prior to reclassifications (2.3) 8.6 6.3 Amounts reclassified from accumulated other comprehensive loss — (4.6) (4.6) Net current period other comprehensive income (loss) (1) (2.3) 4.0 1.7 Balance as of April 2, 2021 $ (42.9) $ (13.0) $ (55.9) (1) Effects of cash flow hedges are net of tax expense of $1.2 million for the quarter ended April 2, 2021. Amounts reclassified from accumulated other comprehensive loss to the specific caption within Consolidated Statements of Operations and Comprehensive Income were as follows: Amounts Reclassified from Accumulated Other Comprehensive Loss Quarters Ended April 2, 2021 April 3, 2020 To caption Interest rate swaps $ 4.6 $ 1.9 Interest expense Total reclassifications $ 4.6 $ 1.9

Background and Basis of Prese_3

Background and Basis of Presentation (Details) - segment	3 Months Ended
	Apr. 02, 2021	Apr. 03, 2020
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Fiscal period duration	92 days	94 days
Number of operating segments	3
Number of reportable segments	3

Revenue and Segment Informati_3

Revenue and Segment Information Additional Information (Details)	3 Months Ended
	Apr. 02, 2021segment
Segment Reporting Information [Line Items]
Number of operating segments	3
Number of reportable segments	3
One Customer | Revenue from Contract with Customer Benchmark | Customer Concentration Risk
Segment Reporting Information [Line Items]
Concentration risk, percentage	10.60%

Revenue and Segment Informati_4

Revenue and Segment Information - Segment Information Of Revenues, Gross Profit And Operating Income (Details) - USD ($) $ in Millions	3 Months Ended
	Apr. 02, 2021	Apr. 03, 2020
Segment Reporting Information [Line Items]
Revenue	$ 1,481.7	$ 1,277.9
Gross profit	521.2	402.7
PSG
Segment Reporting Information [Line Items]
Revenue	747	623.9
Gross profit	246.5	182.6
ASG
Segment Reporting Information [Line Items]
Revenue	531.5	467.1
Gross profit	206.8	157.8
ISG
Segment Reporting Information [Line Items]
Revenue	203.2	186.9
Gross profit	$ 67.9	$ 62.3

Revenue and Segment Informati_5

Revenue and Segment Information - Disaggregation of Revenue (Details) - USD ($) $ in Millions	3 Months Ended
	Apr. 02, 2021	Apr. 03, 2020
Segment Reporting Information [Line Items]
Revenue	$ 1,481.7	$ 1,277.9
Distributors
Segment Reporting Information [Line Items]
Revenue	934	703.3
Direct Customers
Segment Reporting Information [Line Items]
Revenue	547.7	574.6
Singapore
Segment Reporting Information [Line Items]
Revenue	509	408.3
Hong Kong
Segment Reporting Information [Line Items]
Revenue	342.2	316.2
United Kingdom
Segment Reporting Information [Line Items]
Revenue	268.9	227
United States
Segment Reporting Information [Line Items]
Revenue	184.3	184.5
Other
Segment Reporting Information [Line Items]
Revenue	177.3	141.9
PSG
Segment Reporting Information [Line Items]
Revenue	747	623.9
PSG | Distributors
Segment Reporting Information [Line Items]
Revenue	523.9	386.3
PSG | Direct Customers
Segment Reporting Information [Line Items]
Revenue	223.1	237.6
PSG | Singapore
Segment Reporting Information [Line Items]
Revenue	274.5	194.3
PSG | Hong Kong
Segment Reporting Information [Line Items]
Revenue	196.1	192
PSG | United Kingdom
Segment Reporting Information [Line Items]
Revenue	142.7	105.1
PSG | United States
Segment Reporting Information [Line Items]
Revenue	75.3	72.7
PSG | Other
Segment Reporting Information [Line Items]
Revenue	58.4	59.8
ASG
Segment Reporting Information [Line Items]
Revenue	531.5	467.1
ASG | Distributors
Segment Reporting Information [Line Items]
Revenue	288.9	213.6
ASG | Direct Customers
Segment Reporting Information [Line Items]
Revenue	242.6	253.5
ASG | Singapore
Segment Reporting Information [Line Items]
Revenue	201.7	172.6
ASG | Hong Kong
Segment Reporting Information [Line Items]
Revenue	100.5	91.9
ASG | United Kingdom
Segment Reporting Information [Line Items]
Revenue	82.6	76.8
ASG | United States
Segment Reporting Information [Line Items]
Revenue	70.2	77.3
ASG | Other
Segment Reporting Information [Line Items]
Revenue	76.5	48.5
ISG
Segment Reporting Information [Line Items]
Revenue	203.2	186.9
ISG | Distributors
Segment Reporting Information [Line Items]
Revenue	121.2	103.4
ISG | Direct Customers
Segment Reporting Information [Line Items]
Revenue	82	83.5
ISG | Singapore
Segment Reporting Information [Line Items]
Revenue	32.8	41.4
ISG | Hong Kong
Segment Reporting Information [Line Items]
Revenue	45.6	32.3
ISG | United Kingdom
Segment Reporting Information [Line Items]
Revenue	43.6	45.1
ISG | United States
Segment Reporting Information [Line Items]
Revenue	38.8	34.5
ISG | Other
Segment Reporting Information [Line Items]
Revenue	$ 42.4	$ 33.6

Revenue and Segment Informati_6

Revenue and Segment Information - Summary of Property, Plant and Equipment by Geographic Location (Details) - USD ($) $ in Millions	Apr. 02, 2021	Dec. 31, 2020
Revenues from External Customers and Long-Lived Assets [Line Items]
Property, plant and equipment, net	$ 2,489.4	$ 2,512.3
United States
Revenues from External Customers and Long-Lived Assets [Line Items]
Property, plant and equipment, net	690.8	686.6
South Korea
Revenues from External Customers and Long-Lived Assets [Line Items]
Property, plant and equipment, net	446	455.5
Philippines
Revenues from External Customers and Long-Lived Assets [Line Items]
Property, plant and equipment, net	376.4	386.6
China
Revenues from External Customers and Long-Lived Assets [Line Items]
Property, plant and equipment, net	224.5	229.6
Czech Republic
Revenues from External Customers and Long-Lived Assets [Line Items]
Property, plant and equipment, net	211.3	216.1
Japan
Revenues from External Customers and Long-Lived Assets [Line Items]
Property, plant and equipment, net	216.1	209.3
Malaysia
Revenues from External Customers and Long-Lived Assets [Line Items]
Property, plant and equipment, net	188.3	190.2
Other
Revenues from External Customers and Long-Lived Assets [Line Items]
Property, plant and equipment, net	$ 136	$ 138.4

Restructuring, Asset Impairme_3

Restructuring, Asset Impairments and Other, Net - Schedule of Activity Included in Restructuring, Asset Impairments, and Other, Net (Details) - USD ($) $ in Millions	3 Months Ended
	Apr. 02, 2021	Apr. 03, 2020
Restructuring Cost and Reserve [Line Items]
Restructuring	$ 33
Asset Impairments	3.2
Other	6.3
Total	42.5	$ 32.8
Other
Restructuring Cost and Reserve [Line Items]
Restructuring	0
Asset Impairments	3.2
Other	6.3
Total	9.5
2021 Involuntary Separation Program
Restructuring Cost and Reserve [Line Items]
Restructuring	33
Asset Impairments	0
Other	0
Total	$ 33

Restructuring, Asset Impairme_4

Restructuring, Asset Impairments and Other, Net - Summary of Changes in Accrued Restructuring Charges (Details) $ in Millions	3 Months Ended
	Apr. 02, 2021USD ($)
Restructuring Reserve [Roll Forward]
Balance at Beginning of Period	$ 6.2
Charges	33
Usage	(11.4)
Balance at End of Period	27.8
Employee separation charges
Restructuring Reserve [Roll Forward]
Balance at Beginning of Period	6.2
Charges	33
Usage	(11.4)
Balance at End of Period	$ 27.8

Restructuring, Asset Impairme_5

Restructuring, Asset Impairments and Other, Net - Narrative (Details) $ in Millions	Mar. 04, 2021USD ($)employee	Apr. 02, 2021USD ($)employee	Dec. 31, 2020USD ($)
Restructuring Cost and Reserve [Line Items]
Restructuring reserve accrued		$ 27.8	$ 6.2
2021 Involuntary Separation Program
Restructuring Cost and Reserve [Line Items]
Expected number of positions eliminated | employee	740
Number of positions eliminated | employee		500
Severance costs		$ 33
Restructuring reserve accrued		$ 26.5
2021 Involuntary Separation Program | Minimum
Restructuring Cost and Reserve [Line Items]
Expected restructuring cost	$ 58
2021 Involuntary Separation Program | Maximum
Restructuring Cost and Reserve [Line Items]
Expected restructuring cost	$ 62

Balance Sheet Information and_3

Balance Sheet Information and Other - Narrative (Details) - USD ($)	3 Months Ended	12 Months Ended
	Apr. 02, 2021	Dec. 31, 2020
Balance Sheet Related Disclosures [Abstract]
Changes in goodwill	$ 0	$ 0
Net assets for overfunded plans	8,500,000
Accrued pension liability	147,900,000	141,900,000
Current portion accrued pension liability	400,000	300,000
Operating ROU assets	$ 133,800,000	$ 136,300,000
Remaining Lease Term (in years)	6 years 8 months 12 days
Discount Rate (as a percent)	4.80%

Balance Sheet Information and_4

Balance Sheet Information and Other - Inventory (Details) - USD ($) $ in Millions	Apr. 02, 2021	Dec. 31, 2020
Inventories:
Raw materials	$ 139	$ 135.7
Work in process	834.4	829.7
Finished goods	322.1	286
Inventories	$ 1,295.5	$ 1,251.4

Balance Sheet Information and_5

Balance Sheet Information and Other - Pension Expense (Details) - USD ($) $ in Millions	3 Months Ended
	Apr. 02, 2021	Apr. 03, 2020
Balance Sheet Related Disclosures [Abstract]
Service cost	$ 3.1	$ 2.7
Interest cost	1.1	1.1
Expected return on plan assets	(1.7)	(1.5)
Curtailment loss	1.9	0
Total net periodic pension cost	$ 4.4	$ 2.3

Balance Sheet Information and_6

Balance Sheet Information and Other - Lease Expense (Details) - USD ($) $ in Millions	3 Months Ended
	Apr. 02, 2021	Apr. 03, 2020	Dec. 31, 2020
Balance Sheet Related Disclosures [Abstract]
Operating lease	$ 9.9	$ 9.1
Variable lease	1	1.1
Short-term lease	0.7	1.1
Total lease expense	11.6	$ 11.3
Accrued expenses and other current liabilities	32.9		$ 32.2
Other long-term liabilities	108.8		115.7
Total lease liabilities	$ 141.7		$ 147.9
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]	Other long-term liabilities		Other long-term liabilities

Balance Sheet Information and_7

Balance Sheet Information and Other - Cash and Non-cash Activity (Details) - USD ($) $ in Millions	3 Months Ended
	Apr. 02, 2021	Apr. 03, 2020
Non-cash investing activities:
Capital expenditures in accounts payable and other long-term liabilities	$ 180.9	$ 123.5
ROU assets obtained in exchange of lease liabilities	7.1	8.8
Non-cash financing activity:
Liability incurred for purchase of business	0	7.7
Cash paid for:
Interest expense	31.4	24.5
Income taxes	20.9	9.9
Operating lease payments in operating cash flows	$ 10.3	$ 8.2

Balance Sheet Information and_8

Balance Sheet Information and Other - Summary of Cash and Cash Equivalents (Details) - USD ($) $ in Millions	Apr. 02, 2021	Dec. 31, 2020	Apr. 03, 2020	Dec. 31, 2019
Balance Sheet Related Disclosures [Abstract]
Cash and cash equivalents	$ 1,042.5	$ 1,080.7	$ 1,982	$ 894.2
Restricted cash (included in other current assets)	1.4	0.8	0	0
Cash, cash equivalents and restricted cash in Consolidated Statements of Cash Flows	$ 1,043.9	$ 1,081.5	$ 1,982	$ 894.2

Long-Term Debt - Schedule of Lo

Long-Term Debt - Schedule of Long-Term Debt (Details) - USD ($) $ in Millions	Apr. 02, 2021	Dec. 31, 2020
Debt Instrument [Line Items]
Long-term debt	$ 3,435.4	$ 3,589.5
Less: Debt discount	(64.7)	(69.7)
Less: Debt issuance costs	(27.1)	(28.5)
Net long-term debt, including current portion	3,343.6	3,491.3
Less: Current portion of long-term debt	(536.7)	(531.6)
Net long-term debt	2,806.9	2,959.7
Senior Revolving Credit Facility
Debt Instrument [Line Items]
Long-term debt	$ 550	$ 700
Debt instrument, interest rate (as a percent)	1.61%	1.90%
Term Loan B Facility
Debt Instrument [Line Items]
Long-term debt	$ 1,610.4	$ 1,614.5
Less: Debt discount	(8.7)	(9)
Less: Debt issuance costs	$ (20.1)	$ (21)
Debt instrument, interest rate (as a percent)	2.11%	2.15%
3.875% Notes | Notes Payable
Debt Instrument [Line Items]
Long-term debt	$ 700	$ 700
Less: Debt discount	(6.4)	(6.5)
Less: Debt issuance costs	$ (2.2)	(2.3)
Debt instrument, interest rate (as a percent)	3.875%
1.625% Notes | Convertible Debt
Debt Instrument [Line Items]
Long-term debt	$ 575	575
Less: Debt discount	(49.6)	(54.2)
Less: Debt issuance costs	(4.8)	$ (5.2)
Less: Current portion of long-term debt	$ (520.6)
Debt instrument, interest rate (as a percent)	1.625%

Long-Term Debt - Annual Maturit

Long-Term Debt - Annual Maturities Relating To Long-Term Debt (Details) $ in Millions	Apr. 02, 2021USD ($)
Long-term Debt, Fiscal Year Maturity [Abstract]
Remainder of 2021	$ 587.3
2022	16.3
2023	16.3
2024	566.4
2025	16.3
Thereafter	2,232.8
Total	$ 3,435.4

Long-Term Debt - Revolving Cred

Long-Term Debt - Revolving Credit Facility and 1.625% Notes due 2023 (Details)	Apr. 02, 2021USD ($)$ / shares	Mar. 31, 2021day	Apr. 02, 2021USD ($)	Dec. 31, 2020USD ($)
Debt Instrument [Line Items]
Current portion of long-term debt	$ 536,700,000		$ 536,700,000	$ 531,600,000
Senior Revolving Credit Facility
Debt Instrument [Line Items]
Debt instrument, interest rate (as a percent)	1.61%		1.61%	1.90%
Repayments of revolving credit facility			$ 150,000,000
Remaining borrowing capacity	$ 1,419,000,000		$ 1,419,000,000
1.625% Notes | Convertible Debt
Debt Instrument [Line Items]
Debt instrument, interest rate (as a percent)	1.625%		1.625%
Threshold trading days | day		20
Threshold consecutive trading days | day		30
Stock price trigger (in dollars per share) | $ / shares	$ 26.94
Threshold percentage of stock price trigger (greater than or equal to)	130.00%
Current portion of long-term debt	$ 520,600,000		$ 520,600,000
Minimum denomination of principal	$ 1,000		$ 1,000

Earnings Per Share and Equity_2

Earnings Per Share and Equity - Summary of earnings per share (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended
	Apr. 02, 2021	Apr. 03, 2020
Earnings Per Share [Abstract]
Net income (loss) attributable to ON Semiconductor Corporation	$ 89.9	$ (14)
Basic weighted average shares of common stock outstanding (in shares)	413.4	410.6
Dilutive effect of share-based awards (in shares)	2.7	0
Dilutive effect of convertible notes (in shares)	29.3	0
Diluted weighted-average shares of common stock outstanding (in shares)	445.4	410.6
Net income (loss) per share of common stock attributable to ON Semiconductor Corporation:
Basic (in dollars per share)	$ 0.22	$ (0.03)
Diluted (in dollars per share)	$ 0.20	$ (0.03)

Earnings Per Share and Equity_3

Earnings Per Share and Equity - Narrative (Details) - USD ($) $ / shares in Units, $ in Millions	1 Months Ended	3 Months Ended
	May 03, 2021	Apr. 02, 2021	Apr. 03, 2020	Dec. 31, 2020
Dividends Payable [Line Items]
Anti-dilutive shares		700,000	2,600,000
Aggregate purchase price		$ 0	$ 65.4
Payments of tax withholding for restricted shares		$ 28.5	$ 16
Common stock withheld underlying restricted stock units (in shares)		700,000	900,000
Treasury shares reissued or retired during period		0
Non-controlling interest		$ 20		$ 19.6
Non-controlling interest share of earnings		$ 0.4	$ 0.3
1.00% Notes Warrants
Dividends Payable [Line Items]
Price per unit (in dollars per unit)		$ 25.96
Warrants settled, percent		50.00%
Number of warrants (in shares)		37,300,000
Warrants exercised (in shares)		18,700,000
Stock issued for settlement of warrants (in shares)		6,300,000
1.00% Notes Warrants | Subsequent Event
Dividends Payable [Line Items]
Warrants exercised (in shares)	18,600,000
Stock issued for settlement of warrants (in shares)	7,100,000
Convertible Debt | 1.625% Notes
Dividends Payable [Line Items]
Debt instrument, interest rate (as a percent)		1.625%
Conversion price per share (in dollars per share)		$ 20.72
Price per unit (in dollars per unit)		$ 30.70
Convertible Debt | 1.00% Notes
Dividends Payable [Line Items]
Debt instrument, interest rate (as a percent)		1.00%
Price per unit (in dollars per unit)		$ 25.96
Share Repurchase Program
Dividends Payable [Line Items]
Number of repurchased shares		0	3,600,000
Aggregate purchase price		$ 0	$ 65.3
Remaining authorized amount available for repurchase		$ 1,295.8

Earnings Per Share and Equity_4

Earnings Per Share and Equity - Schedule of Share Repurchase Program (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended
	Apr. 02, 2021	Apr. 03, 2020
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Aggregate purchase price	$ 0	$ 65.4
Fees, commissions and other expenses	0	0.1
Total cash used for share repurchases	$ 0	$ 65.4
Treasury shares reissued or retired during period	0
Share Repurchase Program
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of repurchased shares	0	3,600,000
Aggregate purchase price	$ 0	$ 65.3
Weighted-average purchase price per share (in dollars per share )	$ 0	$ 18.08

Share-Based Compensation - Summ

Share-Based Compensation - Summary Of Share-Based Compensation (Details) - USD ($) $ in Millions	3 Months Ended
	Apr. 02, 2021	Apr. 03, 2020
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Share-based compensation expense	$ 22.3	$ 15.7
Income tax benefit	(4.7)	(3.3)
Share-based compensation expense, net of taxes	17.6	12.4
Cost of revenue
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Share-based compensation expense	3.3	2.5
Research and development
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Share-based compensation expense	5.7	4.1
Selling and marketing
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Share-based compensation expense	4.3	2.9
General and administrative
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Share-based compensation expense	$ 9	$ 6.2

Share-Based Compensation - Narr

Share-Based Compensation - Narrative (Details) - USD ($) shares in Millions, $ in Millions	3 Months Ended
	Apr. 02, 2021	Apr. 03, 2020	Dec. 31, 2020
Amended And Restated Stock Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Aggregate of common stock available for grant (in shares)	17.6		16.5
Restricted Stock Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized share-based compensation expense on non-vested stock options	$ 142.7
Period For Recognition (in years)	1 year 9 months 18 days
Options pre-vesting forfeitures estimated	5.00%	5.00%
Service Based Restricted Stock Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Maximum award vesting period (in years)	3 years
Performance or Market Based Restricted Stock Units | Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Maximum award vesting period (in years)	2 years
Performance or Market Based Restricted Stock Units | Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Maximum award vesting period (in years)	3 years
Employee Stock Purchase Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Aggregate of common stock available for grant (in shares)	2.7		3

Share-Based Compensation - Su_2

Share-Based Compensation - Summary Of Restricted Stock Units Transactions (Details) - Restricted Stock Units shares in Millions	3 Months Ended
	Apr. 02, 2021$ / sharesshares
Number of Shares
Nonvested shares restricted stock units, beginning (in shares) | shares	11.3
Restricted stock units granted (in shares) | shares	2.1
Restricted stock units released (in shares) | shares	(2.3)
Restricted stock units forfeited (in shares) | shares	(2.8)
Nonvested shares restricted stock units, ending (in shares) | shares	8.3
Weighted-Average Grant Date Fair Value Per Share
Weighted Average Grant Date Fair Value, Nonvested, beginning (in dollars per share) | $ / shares	$ 20.73
Weighted Average Grant Date Fair Value, Granted (in dollars per share) | $ / shares	41.19
Weighted-Average Grant Date Fair Value, Released (in dollars per share) | $ / shares	21.97
Weighted Average Grant Date Fair Value, Forfeited (in dollars per share) | $ / shares	21.63
Weighted Average Grant Date Fair Value, Nonvested, ending (in dollars per share) | $ / shares	$ 25.38

Commitments and Contingencies -

Commitments and Contingencies - Narrative (Details) $ in Millions	Apr. 02, 2021USD ($)
Loss Contingencies [Line Items]
Outstanding guarantees and letters of credit	$ 8.6
Guarantees	0.9
Revolving Credit Facility | Senior Revolving Credit Facility
Loss Contingencies [Line Items]
Current borrowing capacity	15
Letter of Credit | Senior Revolving Credit Facility
Loss Contingencies [Line Items]
Credit commitment outstanding	$ 0.9

Fair Value Measurements - Summa

Fair Value Measurements - Summary of Fair Value of Assets and Liabilities (Details) - Fair Value, Measurements, Recurring - Demand and time deposits - USD ($) $ in Millions	Apr. 02, 2021	Dec. 31, 2020
Level 1
Assets:
Cash and cash equivalents	$ 8.5	$ 8.5
Level 2
Assets:
Cash and cash equivalents	0	0
Level 3
Assets:
Cash and cash equivalents	0	0
Estimate of Fair Value
Assets:
Cash and cash equivalents	$ 8.5	$ 8.5

Fair Value Measurements - Sum_2

Fair Value Measurements - Summary of Fair Value, by Balance Sheet Grouping (Details) - USD ($) $ in Millions	Apr. 02, 2021	Dec. 31, 2020
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying Amount	$ 3,435.4	$ 3,589.5
Convertible notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying Amount	520.6	515.6
Fair Value	1,214	967.1
Other long-term debt
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying Amount	2,823	2,975.7
Fair Value	$ 2,781.4	$ 2,966.8

Fair Value Measurements - Narra

Fair Value Measurements - Narrative (Details)	Apr. 02, 2021
Notes Payable | 3.875% Notes
Debt Instrument [Line Items]
Debt instrument, interest rate (as a percent)	3.875%
Convertible Debt | 1.625% Notes
Debt Instrument [Line Items]
Debt instrument, interest rate (as a percent)	1.625%

Financial Instruments - Narrati

Financial Instruments - Narrative (Details) - USD ($)	3 Months Ended
	Apr. 02, 2021	Apr. 03, 2020	Dec. 31, 2020
Derivatives, Fair Value [Line Items]
Foreign currency transaction gain (loss) realized	$ 4,000,000	$ (200,000)
Foreign currency exchange contracts
Derivatives, Fair Value [Line Items]
Notional Amount	$ 281,700,000		$ 263,400,000
Foreign currency exchange contracts | Minimum
Derivatives, Fair Value [Line Items]
Derivative, term of contract (in months)	1 month
Foreign currency exchange contracts | Maximum
Derivatives, Fair Value [Line Items]
Derivative, term of contract (in months)	3 months
Interest Rate Swap
Derivatives, Fair Value [Line Items]
Notional Amount	$ 1,500,000,000	$ 1,000,000,000

Financial Instruments - Schedul

Financial Instruments - Schedule of Net Foreign Exchange Positions (Details) - Foreign currency exchange contracts - USD ($) $ in Millions	Apr. 02, 2021	Dec. 31, 2020
Derivatives, Fair Value [Line Items]
Buy (Sell)	$ 271.1	$ 241.2
Notional Amount	281.7	263.4
Other Currencies - Buy
Derivatives, Fair Value [Line Items]
Buy (Sell)	17.3	12.4
Notional Amount	17.3	12.4
Other Currencies - Sell
Derivatives, Fair Value [Line Items]
Buy (Sell)	(5.3)	(11.1)
Notional Amount	5.3	11.1
Japanese Yen
Derivatives, Fair Value [Line Items]
Buy (Sell)	81.2	71.2
Notional Amount	81.2	71.2
Philippine Peso
Derivatives, Fair Value [Line Items]
Buy (Sell)	65.1	57.2
Notional Amount	65.1	57.2
Euro
Derivatives, Fair Value [Line Items]
Buy (Sell)	50.7	47.7
Notional Amount	50.7	47.7
Korean Won
Derivatives, Fair Value [Line Items]
Buy (Sell)	36.9	34.4
Notional Amount	36.9	34.4
Chinese Yuan
Derivatives, Fair Value [Line Items]
Buy (Sell)	13.3	17.7
Notional Amount	13.3	17.7
Malaysian Ringgit
Derivatives, Fair Value [Line Items]
Buy (Sell)	11.9	11.7
Notional Amount	$ 11.9	$ 11.7

Income Taxes - Additional Infor

Income Taxes - Additional Information (Details) - USD ($) $ in Millions	Apr. 02, 2021	Apr. 03, 2020
Income Tax Disclosure [Abstract]
Unrecognized tax benefits, income tax penalties and interest accrued	$ 3	$ 5.2
Possible reduction in unrecognized tax benefits in next twelve months	$ 42.3

Changes in Accumulated Other _3

Changes in Accumulated Other Comprehensive Loss - Schedule of Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Millions	3 Months Ended
	Apr. 02, 2021	Apr. 03, 2020
Accumulated Other Comprehensive Income [Roll Forward]
Balance, beginning	$ 3,558.1	$ 3,324.1
Other comprehensive income (loss) prior to reclassifications	6.3
Amounts reclassified from accumulated other comprehensive loss	(4.6)
Other comprehensive income (loss), net of tax	1.7	(12.2)
Balance, ending	3,649.6	3,237.6
Cash flow hedge, tax	1.2
Currency Translation Adjustments
Accumulated Other Comprehensive Income [Roll Forward]
Balance, beginning	(40.6)
Other comprehensive income (loss) prior to reclassifications	(2.3)
Amounts reclassified from accumulated other comprehensive loss	0
Other comprehensive income (loss), net of tax	(2.3)
Balance, ending	(42.9)
Effects of Cash Flow Hedges
Accumulated Other Comprehensive Income [Roll Forward]
Balance, beginning	(17)
Other comprehensive income (loss) prior to reclassifications	8.6
Amounts reclassified from accumulated other comprehensive loss	(4.6)
Other comprehensive income (loss), net of tax	4
Balance, ending	(13)
Accumulated Other Comprehensive Loss
Accumulated Other Comprehensive Income [Roll Forward]
Balance, beginning	(57.6)	(54.3)
Balance, ending	$ (55.9)	$ (66.5)

Changes in Accumulated Other _4

Changes in Accumulated Other Comprehensive Loss - Reclassifications from Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Millions	3 Months Ended
	Apr. 02, 2021	Apr. 03, 2020
Accumulated Other Comprehensive Income (Loss) [Line Items]
Interest expense	$ 4.5	$ 0.1
Net income (loss)	90.3	(13.7)
Interest rate swaps
Accumulated Other Comprehensive Income (Loss) [Line Items]
Net income (loss)	4.6	1.9
Effects of Cash Flow Hedges | Interest rate swaps
Accumulated Other Comprehensive Income (Loss) [Line Items]
Interest expense	$ 4.6	$ 1.9