Littelfuse (LFUS) 10-Q 31 Jul 19 2019 Q2 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	6 Months Ended
	Jun. 29, 2019	Jul. 26, 2019
Document and Entity Information [Abstract]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Jun. 29, 2019
Document Transition Report	false
Entity File Number	0-20388
Entity Registrant Name	LITTELFUSE INC /DE
Entity Central Index Key	0000889331
Current Fiscal Year End Date	--12-29
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	Q2
Amendment Flag	false
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	36-3795742
Entity Address, Address Line One	8755 West Higgins Road
Entity Address, Address Line Two	Suite 500
Entity Address, City or Town	Chicago
Entity Address, State or Province	IL
Entity Address, Postal Zip Code	60631
City Area Code	773
Local Phone Number	628-1000
Title of 12(b) Security	Common Stock, $0.01 par value
Trading Symbol	LFUS
Security Exchange Name	NASDAQ
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		24,587,591

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Jun. 29, 2019	Dec. 29, 2018
Current assets:
Cash and cash equivalents	$ 474,781	$ 489,733
Short-term investments	34	34
Trade receivables, less allowances of $34,468 and $36,038 at June 29, 2019 and December 29, 2018, respectively	245,723	232,892
Inventories	254,305	258,228
Prepaid income taxes and income taxes receivable	1,374	2,339
Prepaid expenses and other current assets	63,332	49,291
Total current assets	1,039,549	1,032,517
Net property, plant, and equipment	338,500	339,894
Intangible assets, net of amortization	341,174	361,474
Goodwill	826,408	826,715
Investments	25,456	25,405
Deferred income taxes	9,200	7,330
Right of use lease assets, net	23,280
Other assets	18,018	20,971
Total assets	2,621,585	2,614,306
Current liabilities:
Accounts payable	123,058	126,323
Accrued liabilities	111,696	138,405
Accrued income taxes	21,657	20,547
Current portion of long-term debt	10,000	10,000
Total current liabilities	266,411	295,275
Long-term debt, less current portion	676,940	684,730
Deferred income taxes	53,039	51,853
Accrued post-retirement benefits	30,666	31,874
Non-current operating lease liabilities	18,643
Other long-term liabilities	65,944	72,232
Shareholders’ equity:
Common stock, par value $0.01 per share: 34,000,000 shares authorized; shares issued, June 29, 2019–25,786,662; December 29, 2018–25,641,959	255	254
Treasury stock, at cost: 1,157,213 and 868,045 shares, respectively	(166,068)	(116,454)
Additional paid-in capital	855,192	835,828
Accumulated other comprehensive loss	(95,582)	(97,924)
Retained earnings	916,014	856,507
Littelfuse, Inc. shareholders’ equity	1,509,811	1,478,211
Non-controlling interest	131	131
Total equity	1,509,942	1,478,342
Total liabilities and equity	$ 2,621,585	$ 2,614,306

Condensed Consolidated Balanc_2

Condensed Consolidated Balance Sheets (Parentheticals) - USD ($) $ in Thousands	Jun. 29, 2019	Dec. 29, 2018
Statement of Financial Position [Abstract]
Allowance for trade receivables	$ 34,468	$ 36,038
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock authorized (in shares)	34,000,000	34,000,000
Common stock issued (in shares)	25,786,662	25,641,959
Treasury stock (in shares)	1,157,213	868,045

Condensed Consolidated Statemen

Condensed Consolidated Statements of Net Income (Unaudited) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 29, 2019	Jun. 30, 2018	Jun. 29, 2019	Jun. 30, 2018
Income Statement [Abstract]
Net sales	$ 397,879	$ 459,183	$ 803,379	$ 876,996
Cost of sales	256,071	290,196	506,343	558,386
Gross profit	141,808	168,987	297,036	318,610
Selling, general, and administrative expenses	57,666	73,244	120,621	150,758
Research and development expenses	21,458	22,748	42,867	45,288
Amortization of intangibles	10,050	13,373	20,241	25,371
Total operating expenses	89,174	109,365	183,729	221,417
Operating income	52,634	59,622	113,307	97,193
Interest expense	5,589	5,782	11,275	11,205
Foreign exchange (gain) loss	(3,575)	3,200	668	(7,354)
Other (income) expense, net	(2,947)	(1,678)	1,358	(3,621)
Income before income taxes	53,567	52,318	100,006	96,963
Income taxes	9,775	9,992	19,225	18,609
Net income	$ 43,792	$ 42,326	$ 80,781	$ 78,354
Income per share:
Basic (in dollars per share)	$ 1.77	$ 1.69	$ 3.27	$ 3.18
Diluted (in dollars per share)	$ 1.75	$ 1.67	$ 3.23	$ 3.12
Weighted-average shares and equivalent shares outstanding:
Basic (in shares)	24,740	25,004	24,729	24,671
Diluted (in shares)	24,983	25,401	24,998	25,086

Condensed Consolidated Statem_2

Condensed Consolidated Statements of Comprehensive Income (Unaudited) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 29, 2019	Jun. 30, 2018	Jun. 29, 2019	Jun. 30, 2018
Statement of Comprehensive Income [Abstract]
Net income	$ 43,792	$ 42,326	$ 80,781	$ 78,354
Other comprehensive income (loss):
Pension and postemployment adjustment, net of tax	161	766	112	763
Foreign currency translation adjustments	(5,892)	(16,708)	2,230	(16,984)
Comprehensive income	$ 38,061	$ 26,384	$ 83,123	$ 62,133

Condensed Consolidated Statem_3

Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	6 Months Ended
	Jun. 29, 2019	Jun. 30, 2018
OPERATING ACTIVITIES
Net income	$ 80,781	$ 78,354
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation	25,727	24,431
Amortization of intangibles	20,241	25,371
Deferred revenue	0	1,921
Non-cash inventory charges	0	36,927
Impairment charges	0	1,125
Stock-based compensation	12,250	15,883
Loss (gain) on investments and other assets	2,458	(3,311)
Deferred income taxes	(632)	2,434
Other	2,009	778
Changes in operating assets and liabilities:
Trade receivables	(13,242)	(33,481)
Inventories	6,230	(1,502)
Accounts payable	(17,927)	13,684
Accrued liabilities and income taxes	(36,713)	(16,383)
Prepaid expenses and other assets	(1,090)	(5,316)
Net cash provided by operating activities	80,092	140,915
INVESTING ACTIVITIES
Acquisitions of businesses, net of cash acquired	(775)	(310,487)
Purchases of property, plant, and equipment	(25,249)	(40,315)
Net proceeds from sale of property, plant and equipment, and other	6,212	68
Net cash used in investing activities	(19,812)	(350,734)
FINANCING ACTIVITIES
Proceeds of revolving credit facility	0	60,000
Proceeds of term loan	0	75,000
Net proceeds from senior notes payable	0	175,000
Payments of term loan	(7,500)	(40,025)
Payments of revolving credit facility	0	(60,000)
Net proceeds related to stock-based award activities	3,011	5,568
Purchases of common stock	(49,861)	0
Debt issuance costs	0	(878)
Cash dividends paid	(21,274)	(18,458)
Net cash (used in) provided by financing activities	(75,624)	196,207
Effect of exchange rate changes on cash and cash equivalents	392	(7,917)
Decrease in cash and cash equivalents	(14,952)	(21,529)
Cash and cash equivalents at beginning of period	489,733	429,676
Cash and cash equivalents at end of period	$ 474,781	$ 408,147

Condensed Consolidated Statem_4

Condensed Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	Common Stock	Addl. Paid in Capital	Treasury Stock	Accum. Other Comp. Inc. (Loss)	Retained Earnings	Non- controlling Interest
Balance at Dec. 30, 2017	$ 927,556	$ 229	$ 310,012	$ (41,294)	$ (63,668)	$ 722,140	$ 137
Net income	36,029					36,029
Cumulative effect adjustment	0				(9,795)	9,795
Other comprehensive income, net of tax	(279)				(279)
Stock-based compensation	8,714		8,714
Withheld shares on restricted share units for withholding taxes	(2,758)			(2,758)
Stock options exercised	9,609		9,609
Issuance of common stock	472,301	22	472,279
Cash dividends paid	(9,198)					(9,198)
Balance at Mar. 31, 2018	1,441,974	251	800,614	(44,052)	(73,742)	758,766	137
Balance at Dec. 30, 2017	927,556	229	310,012	(41,294)	(63,668)	722,140	137
Net income	78,354
Other comprehensive income, net of tax	(16,221)
Balance at Jun. 30, 2018	1,470,020	253	815,826	(48,336)	(89,684)	791,831	130
Balance at Mar. 31, 2018	1,441,974	251	800,614	(44,052)	(73,742)	758,766	137
Net income	42,326					42,326
Other comprehensive income, net of tax	(15,942)				(15,942)
Stock-based compensation	7,169		7,169
Non-controlling interest	(7)						(7)
Withheld shares on restricted share units for withholding taxes	(4,284)			(4,284)
Stock options exercised	8,045	2	8,043
Cash dividends paid	(9,261)					(9,261)
Balance at Jun. 30, 2018	1,470,020	253	815,826	(48,336)	(89,684)	791,831	130
Balance at Dec. 29, 2018	1,478,342	254	835,828	(116,454)	(97,924)	856,507	131
Net income	36,989					36,989
Other comprehensive income, net of tax	8,073				8,073
Stock-based compensation	3,966		3,966
Withheld shares on restricted share units for withholding taxes	(94)			(94)
Stock options exercised	2,292		2,292
Repurchases of common stock	(13,555)			(13,555)
Cash dividends paid	(10,625)					(10,625)
Balance at Mar. 30, 2019	1,505,388	254	842,086	(130,103)	(89,851)	882,871	131
Balance at Dec. 29, 2018	1,478,342	254	835,828	(116,454)	(97,924)	856,507	131
Net income	80,781
Other comprehensive income, net of tax	2,342
Balance at Jun. 29, 2019	1,509,942	255	855,192	(166,068)	(95,582)	916,014	131
Balance at Mar. 30, 2019	1,505,388	254	842,086	(130,103)	(89,851)	882,871	131
Net income	43,792					43,792
Other comprehensive income, net of tax	(5,731)				(5,731)
Stock-based compensation	8,284		8,284
Withheld shares on restricted share units for withholding taxes	(4,010)			(4,010)
Stock options exercised	4,823	1	4,822
Repurchases of common stock	(31,955)			(31,955)
Cash dividends paid	(10,649)					(10,649)
Balance at Jun. 29, 2019	$ 1,509,942	$ 255	$ 855,192	$ (166,068)	$ (95,582)	$ 916,014	$ 131

Condensed Consolidated Statem_5

Condensed Consolidated Statements of Stockholders' Equity (Parentheticals) - $ / shares	3 Months Ended
	Jun. 29, 2019	Mar. 30, 2019	Jun. 30, 2018	Mar. 31, 2018
Statement of Stockholders' Equity [Abstract]
Cash dividends paid, per share (in dollars per share)	$ 0.43	$ 0.43	$ 0.37	$ 0.37

Summary of Significant Accounti

Summary of Significant Accounting Policies and Other Information	6 Months Ended
	Jun. 29, 2019
Accounting Policies [Abstract]
Summary of Significant Accounting Policies and Other Information	Summary of Significant Accounting Policies and Other Information Nature of Operations Littelfuse, Inc. and subsidiaries (the “Company”) is a global manufacturer of leading technologies in circuit protection, power control and sensing. The Company's products are found in automotive and commercial vehicles, industrial applications, data and telecommunications, medical devices, consumer electronics and appliances. With its broad product portfolio of fuses, semiconductors, polymers, ceramics, relays and sensors, and extensive global infrastructure, the Company’s worldwide associates partner with its customers to design, manufacture and deliver innovative, high-quality solutions for a safer, greener and increasingly connected world. Basis of Presentation The Company’s accompanying unaudited Condensed Consolidated Financial Statements have been prepared in accordance with U.S. Generally Accepted Accounting Principles (“GAAP”) for interim financial information, the instructions to Form 10-Q and Article 10 of Regulation S-X. Accordingly, certain information and disclosures normally included in the consolidated balance sheets, statements of net income and comprehensive income, statements of cash flows, and statement of stockholders' equity prepared in conformity with U.S. GAAP have been condensed or omitted as permitted by such rules and regulations, although the Company believes that the disclosures made are adequate to make the information not misleading. They have been prepared in accordance with accounting policies described in the Company’s Annual Report on Form 10-K for the fiscal year ended December 29, 2018 which should be read in conjunction with the disclosures therein. In the opinion of management, all adjustments considered necessary for a fair presentation have been included and are of a normal, recurring nature. Operating results for interim periods are not necessarily indicative of annual operating results. Revenue Recognition On December 31, 2017, the Company adopted new guidance on revenue from contracts with customers using the modified retrospective method. The adoption did not have a significant impact on the Company’s consolidated financial statements. Revenue Disaggregation The following tables disaggregate the Company’s revenue by primary business units for the three and six months ended June 29, 2019 and June 30, 2018 : Three Months Ended June 29, 2019 Six Months Ended June 29, 2019 (in thousands) Electronics Segment Automotive Segment Industrial Segment Total Electronics Segment Automotive Segment Industrial Segment Total Electronics – Passive Products and Sensors $ 108,481 $ — $ — $ 108,481 $ 216,858 $ — $ — $ 216,858 Electronics – Semiconductor 151,072 — — 151,072 308,089 — — 308,089 Passenger Car Products — 53,916 — 53,916 — 110,459 — 110,459 Automotive Sensors — 24,682 — 24,682 — 50,739 — 50,739 Commercial Vehicle Products — 30,052 — 30,052 — 60,935 — 60,935 Industrial Products — — 29,676 29,676 — — 56,299 56,299 Total $ 259,553 $ 108,650 $ 29,676 $ 397,879 $ 524,947 $ 222,133 $ 56,299 $ 803,379 Three Months Ended June 30, 2018 Six Months Ended June 30, 2018 (in thousands) Electronics Segment Automotive Segment Industrial Segment Total Electronics Segment Automotive Segment Industrial Segment Total Electronics – Passive Products and Sensors $ 128,321 $ — $ — $ 128,321 $ 242,816 $ — $ — $ 242,816 Electronics – Semiconductor 171,036 — — 171,036 320,952 — — 320,952 Passenger Car Products — 63,581 — 63,581 — 127,160 — 127,160 Automotive Sensors — 30,729 — 30,729 — 62,052 — 62,052 Commercial Vehicle Products — 32,862 — 32,862 — 64,090 — 64,090 Industrial Products — — 32,654 32,654 — — 59,926 59,926 Total $ 299,357 $ 127,172 $ 32,654 $ 459,183 $ 563,768 $ 253,302 $ 59,926 $ 876,996 See Note 16, Segment Information for net sales by segment and countries. Revenue Recognition The Company recognizes revenue on product sales in the period in which the Company satisfies its performance obligation and control of the product is transferred to the customer. The Company’s sales arrangements with customers are predominately short term in nature and generally provide for transfer of control at the time of shipment as this is the point at which title and risk of loss of the product transfers to the customer. At the end of each period, for those shipments where title to the products and the risk of loss and rewards of ownership do not transfer until the product has been received by the customer, the Company adjusts revenues and cost of sales for the delay between the time that the products are shipped and when they are received by the customer. The amount of revenue recorded reflects the consideration to which the Company expects to be entitled in exchange for goods and may include adjustments for customer allowance, rebates and price adjustments. The Company’s distribution channels are primarily through direct sales and independent third-party distributors. The Company elected the practical expedient under Accounting Standards Codification ("ASC") 340-40-25-4 to expense commissions when incurred as the amortization period of the commission asset the Company would have otherwise recognized is less than one year. Revenue and Billing The Company generally accepts orders from customers through receipt of purchase orders or electronic data interchange based on written sales agreements and purchasing contracts. Contract pricing and selling agreement terms are based on market factors, costs, and competition. Pricing is often negotiated as an adjustment (premium or discount) from the Company’s published price lists. The customer is invoiced when the Company’s products are shipped to them in accordance with the terms of the sales agreement. As the Company’s standard payment terms are less than one year, the Company elected the practical expedient under ASC 606-10-32-18 to not assess whether a contract has a significant financing component. The Company also elected the practical expedient provided in ASC 606-10-25-18B to treat all product shipping and handling activities as fulfillment activities, and therefore recognize the gross revenue associated with the contract, inclusive of any shipping and handling revenue. This is similar to the Company’s prior practice and therefore the effect of the new guidance is immaterial. Ship and Debit Program Some of the terms of the Company’s sales agreements and normal business conditions provide customers (distributors) the ability to receive price adjustments on products previously shipped and invoiced. This practice is common in the industry and is referred to as a “ship and debit” program. This program allows the distributor to debit the Company for the difference between the distributors’ contracted price and a lower price for specific transactions. Under certain circumstances (usually in a competitive situation or large volume opportunity), a distributor will request authorization for pricing allowances to reduce its price. When the Company approves such a reduction, the distributor is authorized to “debit” its account for the difference between the contracted price and the lower approved price. The Company establishes reserves for this program based on historic activity and actual authorizations for the debit and recognizes these debits as a reduction of revenue. Return to Stock The Company has a return to stock policy whereby certain customers, with prior authorization from Littelfuse management, can return previously purchased goods for full or partial credit. The Company establishes an estimated allowance for these returns based on historic activity. Sales revenue and cost of sales are reduced to anticipate estimated returns. Volume Rebates The Company offers volume based sales incentives to certain customers to encourage greater product sales. If customers achieve their specific quarterly or annual sales targets, they are entitled to rebates. The Company estimates the projected amount of rebates that will be achieved by the customer and recognizes this estimated cost as a reduction to revenue as products are sold. Recently Adopted Accounting Standards In February 2016, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) No. 2016-02, "Leases" (Topic 842), ("ASC 842"). This ASU requires lessees to recognize, on the balance sheet, assets and liabilities for the rights and obligations created by leases of greater than twelve months. The accounting by lessors will remain largely unchanged. The ASU is effective for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2018, with early adoption permitted. Adoption requires using a modified retrospective transition with either 1) periods prior to the adoption date being recast or 2) a cumulative-effect adjustment recognized to the opening balance of retained earnings on the adoption date with prior periods not recast. The Company adopted the standard on December 30, 2018 using alternative modified retrospective transition method provided in ASU No. 2018-11, "Leases (Topic 842): Target Improvements." Under this method, the Company recorded a cumulative-effect adjustment as of December 30, 2018 and did not record any retrospective adjustments to comparative periods to reflect the adoption of ASC 842. The new standard provides a number of optional practical expedients in transition. The Company has elected the ‘package of practical expedients’ which permits us not to reassess under the new standard our prior conclusions about lease identification, lease classification and initial direct costs. The Company has not elected the use-of-hindsight. Adoption of ASC 842 resulted in the recognition of operating lease right-of-use assets ("ROU") net of deferred rent of $26.1 million and lease liabilities of $29.4 million , as of December 30, 2018 for operating leases on its Condensed Consolidated Balance Sheets, with no impact to its Condensed Consolidated Statements of Net Income and no impact on Condensed Consolidated Statements of Cash Flow. See Note 6, Lease Commitments, for further discussion. In February 2018, the FASB issued ASU No. 2018-02 “Income Statement—Reporting Comprehensive Income (Topic 220): Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income,” which permits the reclassification of tax effects stranded in accumulated other comprehensive income to retained earnings as a result of the Tax Act. The standard also requires entities to disclose whether or not they elected to reclassify the tax effects related to the Tax Act as well as their policy for releasing income tax effects from accumulated other comprehensive income. The standard allows the option of applying either a retrospective adoption, meaning the standard is applied to all periods in which the effect of the Tax Act is recognized, or applying the amendments in the period of adoption, meaning an adjustment is made to shareholder’s equity as of the beginning of the reporting period. The Company adopted the new standard on December 30, 2018. The adoption of this guidance did not have a material effect on our Condensed Consolidated Financial Statements.

Acquisitions

Acquisitions	6 Months Ended
	Jun. 29, 2019
Business Combinations [Abstract]
Acquisitions	Acquisitions The Company accounts for acquisitions using the acquisition method in accordance with ASC 805, “Business Combinations,” in which assets acquired and liabilities assumed are recorded at fair value as of the date of acquisition. The operating results of the acquired business are included in the Company’s Consolidated Financial Statements from the date of the acquisition. IXYS Corporation On January 17, 2018, the Company acquired IXYS Corporation (“IXYS”), a global pioneer in the power semiconductor and integrated circuit markets with a focus on medium to high voltage power control semiconductors across the industrial, communications, consumer and medical markets. IXYS has a broad customer base, serving more than 3,500 customers through its direct sales force and global distribution partners. The acquisition of IXYS is expected to accelerate the Company’s growth across the power control market driven by IXYS’s extensive power semiconductor portfolio and technology expertise. With IXYS, the Company will be able to diversify and expand its presence within industrial electronics markets, leveraging the strong IXYS industrial OEM customer base. The Company also expects to increase long-term penetration of its power semiconductor portfolio in automotive markets, expanding its global content per vehicle. Upon completion of the acquisition, at IXYS stockholders’ election and subject to proration, each share of IXYS common stock, par value $0.01 per share, owned immediately prior to the effective time was canceled and extinguished and automatically converted into the right to receive: (i) $23.00 in cash (subject to applicable withholding tax), without interest (referred to as the cash consideration), or (ii) 0.1265 of a share of common stock, par value $0.01 per share, of Littelfuse (referred to as the stock consideration). IXYS stockholders received cash in lieu of any fractional shares of Littelfuse common stock that the IXYS stockholders would otherwise have been entitled to receive. Additionally, each outstanding option to purchase shares of IXYS common stock granted under an IXYS equity plan were assumed by Littelfuse and converted into an option to acquire (i) a number of shares of Littelfuse common stock equal to the number of shares of IXYS common stock subject to such option immediately prior to the effective time multiplied by 0.1265 , rounded down to the nearest whole share, with (ii) an exercise price per share of Littelfuse common stock equal to the exercise price of such IXYS stock option immediately prior to the effective time divided by 0.1265 , rounded up to the nearest whole cent. Based on the $207.5 per share opening price of Littelfuse common stock on January 17, 2018, the consideration IXYS stockholders received in exchange of their IXYS common stock in the acquisition had a value of $814.8 million comprised of $380.6 million of cash and $434.2 million of Littelfuse stock. In addition to the consideration transferred related to IXYS common stock, the value of consideration transferred, and included in the purchase price, related to IXYS stock options that were converted to Littelfuse stock options, or cash settled, had a value of $41.7 million . As a result, total consideration was valued at $856.5 million . The total purchase price of $856.5 million has been allocated to assets acquired and liabilities assumed, as of the completion of the acquisition, based on estimated fair values. The following table summarizes the purchase price allocation of the fair value of assets acquired and liabilities assumed in the IXYS acquisition: (in thousands) Purchase Price Allocation Total purchase consideration: Cash, net of cash acquired $ 302,865 Cash settled stock options 3,622 Littelfuse stock 434,192 Converted stock options 38,109 Total purchase consideration $ 778,788 Allocation of consideration to assets acquired and liabilities assumed: Current assets, net $ 155,930 Property, plant, and equipment 77,442 Intangible assets 212,720 Goodwill 382,360 Other non-current assets 28,706 Other non-current liabilities (78,370 ) $ 778,788 Approximately $49.1 million of net receivables was included in IXYS’s current assets. All IXYS goodwill, other assets and liabilities were recorded in the Electronics segment and primarily reflected in the Americas and European geographic areas. The goodwill resulting from this acquisition consists largely of the Company’s expected future product sales and synergies from combining IXYS’s products and technology with the Company’s existing electronics product portfolio. Goodwill resulting from the IXYS acquisition is not expected to be deductible for tax purposes. Included in the Company’s Condensed Consolidated Statements of Net Income for the three and six months ended June 30, 2018 are net sales of approximately $100.2 million and $186.5 million , respectively, and a loss before income taxes of $13.9 million and $31.7 million , respectively, since the January 17, 2018 acquisition of IXYS. During the three and six months ended June 30, 2018, the Company recognized a charge of $19.0 million and $36.9 million , respectively, for the amortization of the fair value inventory step-up. The step-up was a non-cash charge to cost of goods and reflected as other non-segment costs. The Company recognized approximately $1.6 million and $7.5 million of stock compensation expense related to IXYS stock options converted to Littelfuse stock options during the three and six months ended June 30, 2018, of which $4.5 million was recognized immediately as it related to prior services periods. During the three and six months ended June 30, 2018, the Company incurred approximately $0.8 million and $11.0 million , respectively, of legal and professional fees related to this acquisition which were primarily recognized as selling, general, and administrative expenses . These costs were reflected as other non-segment costs. Pro Forma Results The following table summarizes, on a pro forma basis, the combined results of operations of the Company and IXYS as though the acquisition had occurred as of January 1, 2017. The pro forma amounts presented are not necessarily indicative of either the actual consolidated results had the IXYS acquisition occurred as of January 1, 2017 or of future consolidated operating results. Three Months Ended Six Months Ended (in thousands, except per share amounts) June 30, 2018 June 30, 2018 Net sales $ 459,183 $ 893,709 Income before income taxes 74,857 134,227 Net income 59,283 106,247 Net income per share — basic 2.37 4.26 Net income per share — diluted 2.33 4.22 Pro forma results presented above primarily reflect the following adjustments: Three Months Ended Six Months Ended (in thousands) June 30, 2018 June 30, 2018 Amortization(a) $ 3,298 $ 5,185 Transaction costs(b) — 9,976 Amortization of inventory step-up(c) 19,031 36,927 Stock compensation(d) 210 4,689 Income tax impact of above items (5,582 ) (13,329 ) (a) The amortization adjustment for the three and six months ended June 30, 2018 primarily reflects the reduction of amortization expense in the period related to the Order backlog intangible asset. The Order backlog has a useful life of twelve months and was fully amortized in the fiscal 2017 pro forma results. (b) The transaction cost adjustments reflect the reversal of certain bank and attorney fees from the six months ended June 30, 2018 and recognition of those fees during the six months ended July 1, 2017. (c) The amortization of inventory step-up adjustment reflects the reversal of the amount recognized during the three and six months ended June 30, 2018 and recognition of those costs during the three and six months ended July 1, 2017. The inventory step-up was amortized over five months as the inventory was sold. (d) The stock compensation adjustment reflects the reversal of the portion of stock compensation for IXYS stock options that were converted to Littelfuse stock options and expensed immediately during the six months ended June 30, 2018

Inventories

Inventories	6 Months Ended
	Jun. 29, 2019
Inventory Disclosure [Abstract]
Inventories	Inventories The components of inventories at June 29, 2019 and December 29, 2018 are as follows: (in thousands) June 29, 2019 December 29, 2018 Raw materials $ 75,908 $ 69,883 Work in process 93,523 88,505 Finished goods 84,874 99,840 Total $ 254,305 $ 258,228

Property, Plant, and Equipment

Property, Plant, and Equipment	6 Months Ended
	Jun. 29, 2019
Property, Plant and Equipment [Abstract]
Property, Plant, and Equipment	Property, Plant, and Equipment The components of net property, plant, and equipment at June 29, 2019 and December 29, 2018 are as follows: (in thousands) June 29, 2019 December 29, 2018 Land $ 24,962 $ 25,630 Building 106,962 114,636 Equipment 612,580 583,043 Accumulated depreciation and amortization (406,004 ) (383,415 ) Total $ 338,500 $ 339,894 The Company recorded depreciation expense of $12.6 million and $12.8 million for the three months ended June 29, 2019 and June 30, 2018 , respectively, and $25.7 million and $24.4 million

Goodwill and Other Intangible A

Goodwill and Other Intangible Assets	6 Months Ended
	Jun. 29, 2019
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill and Other Intangible Assets	Goodwill and Other Intangible Assets The amounts for goodwill and changes in the carrying value by segment for the six months ended June 29, 2019 are as follows: (in thousands) Electronics Automotive Industrial Total As of December 29, 2018 $ 656,039 $ 132,332 $ 38,344 $ 826,715 Currency translation (529 ) 89 133 (307 ) As of June 29, 2019 $ 655,510 $ 132,421 $ 38,477 $ 826,408 The components of other intangible assets at June 29, 2019 are as follows: (in thousands) Gross Carrying Value Accumulated Amortization Net Book Value Patents, licenses and software $ 139,415 $ 75,175 $ 64,240 Distribution network 43,900 35,702 8,198 Customer relationships, trademarks, and tradenames 374,658 105,922 268,736 Total $ 557,973 $ 216,799 $ 341,174 During the three months ended June 29, 2019 and June 30, 2018 , the Company recorded amortization expense of $10.1 million and $13.4 million , respectively. During the six months ended June 29, 2019 and June 30, 2018 , the Company recorded amortization expense of $20.2 million and $25.4 million , respectively. Estimated annual amortization expense related to intangible assets with definite lives as of June 29, 2019 is as follows: (in thousands) Amount 2019 $ 40,119 2020 39,458 2021 36,833 2022 36,743 2023 31,524 2024 and thereafter 176,738 Total $ 361,415

Lease Commitments

Lease Commitments	6 Months Ended
	Jun. 29, 2019
Leases [Abstract]
Lease Commitments	Lease Commitments The Company leases office and production space under various non-cancelable operating leases that expire no later than 2025. Certain real estate leases include one or more options to renew. The exercise of lease renewal options is at the Company's sole discretion. Options to extend the lease are included in the lease term when it is reasonably certain the Company will exercise the option. The Company also has production equipment, office equipment and vehicles under operating leases. The depreciable life of assets and leasehold improvements are limited by the expected lease term, unless there is a transfer of title or purchase option that is reasonably certain of exercise. Certain leases include rental payments adjusted periodically for inflation. The lease agreements do not contain any material residual value guarantee or material restrictive covenants. The Company does not have a published credit rating because it has no publicly traded debt; therefore, the Company is generating its incremental borrowing rate (IBR), using a synthetic credit rating model that compares its credit quality to other rated companies based on certain financial metrics and ratios. The reference rate will be based on the yield curve of companies with similar credit quality based on the metrics and adjusted for currency in regions where we have significant operations. All leases with an initial term of 12 months or less that do not include an option to extend or purchase the underlying asset that the Company is reasonably certain to exercise (“short-term leases”) are not recorded on the Condensed Consolidated Balance Sheet. Short-term lease expenses are recognized on a straight-line basis over the lease term. The following table presents the classification of ROU assets and lease liabilities as of June 29, 2019 : Leases (in thousands) Condensed Consolidated Balance Sheet Classification June 29, 2019 Assets Operating ROU assets Right of use lease assets, net $ 23,280 Liabilities Current operating lease liabilities Accrued liabilities $ 7,349 Non-current operating lease liabilities Non-current operating lease liabilities 18,643 Total lease liabilities $ 25,992 The following table represents the lease costs for the three and six months ended June 29, 2019 : Leases cost (in thousands) Condensed Consolidated Statements of Net Income Classification Three Months Ended June 29, 2019 Six Months Ended Short-term lease expenses Cost of sales, SG&A expenses $ 148 $ 301 Variable lease expenses Cost of sales, SG&A expenses 187 381 Operating lease rent expenses Cost of sales, SG&A expenses 2,215 4,408 Total operating lease costs Cost of sales, SG&A expenses $ 2,550 $ 5,090 Maturity of Lease Liabilities as of June 29, 2019 (in thousands) Operating leases 2019 (excluding the six months ended June 29, 2019) $ 4,476 2020 7,594 2021 5,861 2022 4,829 2023 3,190 2024 and thereafter 3,147 Total lease payments $ 29,097 Present value of lease liabilities $ 25,992 Operating Lease Term and Discount Rate June 29, 2019 Weighted-average remaining lease term (years) 4.26 Weighted-average discount rate 5.17 % Other Information (in thousands) Six Months Ended Cash paid for amounts included in the measurement of lease liabilities Operating cash flow payments for operating leases $ (4,463 ) Leased assets obtained in exchange for operating lease liabilities 1,510

Accrued Liabilities

Accrued Liabilities	6 Months Ended
	Jun. 29, 2019
Payables and Accruals [Abstract]
Accrued Liabilities	Accrued Liabilities The components of accrued liabilities at June 29, 2019 and December 29, 2018 are as follows: (in thousands) June 29, 2019 December 29, 2018 Employee-related liabilities $ 36,048 $ 60,640 Other non-income taxes 30,467 21,523 Operating lease liability 7,349 — Professional services 4,595 6,169 Interest 4,366 5,137 Accrued share repurchases — 4,349 Restructuring liability 4,753 3,887 Other 24,118 36,700 Total $ 111,696 $ 138,405 Employee-related liabilities consist primarily of payroll, sales commission, bonus, employee benefit accruals and workers’ compensation. Bonus accruals include amounts earned pursuant to the Company’s primary employee incentive compensation plans. Other accrued liabilities include miscellaneous operating accruals and other client-related liabilities.

Restructuring, Impairment and O

Restructuring, Impairment and Other Charges	6 Months Ended
	Jun. 29, 2019
Restructuring and Related Activities [Abstract]
Restructuring, Impairment and Other Charges	Restructuring, Impairment and Other Charges The Company recorded restructuring, impairment and other charges for the three and six months ended June 29, 2019 and June 30, 2018 as follows: Three months ended June 29, 2019 Six months ended June 29, 2019 (in thousands) Electronics Automotive Industrial Total Electronics Automotive Industrial Total Employee terminations $ 1,698 $ 3,241 $ 674 $ 5,613 $ 3,498 $ 3,846 $ 721 $ 8,065 Other restructuring charges — 70 — 70 13 90 250 353 Total restructuring charges 1,698 3,311 674 5,683 3,511 3,936 971 8,418 Total $ 1,698 $ 3,311 $ 674 $ 5,683 $ 3,511 $ 3,936 $ 971 $ 8,418 Three months ended June 30, 2018 Six months ended June 30, 2018 (in thousands) Electronics Automotive Industrial Total Electronics Automotive Industrial Total Employee terminations $ 2,402 $ — $ 62 $ 2,464 $ 3,079 $ 99 $ 65 $ 3,243 Other restructuring charges 670 — — 670 670 — — 670 Total restructuring charges 3,072 — 62 3,134 3,749 99 65 3,913 Impairment — 88 1,037 1,125 — 88 1,037 1,125 Total $ 3,072 $ 88 $ 1,099 $ 4,259 $ 3,749 $ 187 $ 1,102 $ 5,038 2019 For the three and six months ended June 29, 2019 , the Company recorded total restructuring charges of $5.7 million and $8.4 million , respectively, for employee termination costs and other restructuring charges.These charges primarily related to the reorganization of operations and selling, general and administrative functions as well as the integration of IXYS within the Electronics segment and the reorganization of operations in the automotive sensors and commercial vehicle products businesses within the Automotive segment. In April 2019, we announced the closure of a European manufacturing facility in the automotive sensors business within the Automotive segment. The Company recorded $1.7 million of employee termination costs associated with this plant closure. 2018 For the three and six months ended June 30, 2018, the Company recorded total restructuring charges of $3.1 million and $3.9 million , respectively, for employee termination costs and other restructuring charges related to lease termination and facility closure. These charges primarily related to the integration of IXYS and the reorganization of the IXYS Radio Pulse business within the Electronics segment. For the three and six months ended June 30, 2018, the Company recorded impairment charges of $1.1 million primarily related to the impairment of a building and a trade name associated with the exit of the Custom business within the Industrial segment. The restructuring reserves as of June 29, 2019 and December 29, 2018 are $4.8 million and $3.9 million , respectively. The restructuring reserves are included within accrued liabilities in the Condensed Consolidated Balance Sheets. The Company anticipates the remaining payments associated with employee terminations will primarily be completed by December 2019.

Debt

Debt	6 Months Ended
	Jun. 29, 2019
Debt Disclosure [Abstract]
Debt	Debt The carrying amounts of debt at June 29, 2019 and December 29, 2018 are as follows: (in thousands) June 29, December 29, Term Loan $ 147,500 $ 155,000 Euro Senior Notes, Series A due 2023 132,992 133,417 Euro Senior Notes, Series B due 2028 107,984 108,330 U.S. Senior Notes, Series A due 2022 25,000 25,000 U.S. Senior Notes, Series B due 2027 100,000 100,000 U.S. Senior Notes, Series A due 2025 50,000 50,000 U.S. Senior Notes, Series B due 2030 125,000 125,000 Other 2,619 2,619 Unamortized debt issuance costs (4,155 ) (4,636 ) Total debt 686,940 694,730 Less: Current maturities (10,000 ) (10,000 ) Total long-term debt $ 676,940 $ 684,730 Revolving Credit Facility / Term Loan On March 4, 2016, the Company entered into a five -year credit agreement (“Credit Agreement”) with a group of lenders for up to $700.0 million . The Credit Agreement consisted of an unsecured revolving credit facility (“Revolving Credit Facility”) of $575.0 million and an unsecured term loan credit facility (“Term Loan”) of up to $125.0 million . In addition, the Company had the ability, from time to time, to increase the size of the Revolving Credit Facility and the Term Loan by up to an additional $150.0 million , in the aggregate, in each case in minimum increments of $25.0 million , subject to certain conditions and the agreement of participating lenders. On October 13, 2017, the Company amended the Credit Agreement to increase the Revolving Credit Facility from $575.0 million to $700.0 million and increase the Term Loan from $125.0 million to $200.0 million and to extend the expiration date from March 4, 2021 to October 13, 2022. The Credit Agreement also includes the option for the Company to increase the size of the Revolving Credit Facility and the Term Loan by up to an additional $300.0 million , in the aggregate, subject to the satisfaction of certain conditions set forth in the Credit Agreement. Term Loans may be made in up to two advances. The first advance of $125.0 million occurred on October 13, 2017 and the second advance of $75.0 million occurred on January 16, 2018. For the Term Loan, the Company is required to make quarterly principal payments of 1.25% of the original term loan ( $2.5 million quarterly) through maturity, with the remaining balance due on October 13, 2022. The Company paid quarterly principal payments of $2.5 million and $7.5 million on the term loan during the three and six months ended June 29, 2019 . Outstanding borrowings under the Credit Agreement bear interest, at the Company’s option, at either LIBOR, fixed for interest periods of one , two , three or six -month periods, plus 1.00% to 2.00% , or at the bank’s Base Rate, as defined, plus 0.00% to 1.00% , based upon the Company’s Consolidated Leverage Ratio, as defined. The Company is also required to pay commitment fees on unused portions of the credit agreement ranging from 0.15% to 0.25% , based on the Consolidated Leverage Ratio, as defined in the agreement. The credit agreement includes representations, covenants and events of default that are customary for financing transactions of this nature. The effective interest rate on outstanding borrowings under the credit facility was 3.65% at June 29, 2019 . As of June 29, 2019 , the Company had $0.1 million outstanding in letters of credit and had available $531.1 million of borrowing capacity under the Revolving Credit Facility based on financial covenants. At June 29, 2019 , the Company was in compliance with all covenants under the Credit Agreement. Senior Notes On December 8, 2016, the Company entered into a Note Purchase Agreement, pursuant to which the Company issued and sold €212 million aggregate principal amount of senior notes in two series. The funding date for the Euro denominated senior notes occurred on December 8, 2016 for €117 million in aggregate amount of 1.14% Senior Notes, Series A, due December 8, 2023 (“Euro Senior Notes, Series A due 2023”), and €95 million in aggregate amount of 1.83% Senior Notes, Series B due December 8, 2028 (“Euro Senior Notes, Series B due 2028”) (together, the “Euro Senior Notes”). Interest on the Euro Senior Notes is payable semiannually on June 8 and December 8, commencing June 8, 2017. On December 8, 2016, the Company entered into a Note Purchase Agreement, pursuant to which the Company issued and sold $125 million aggregate principal amount of senior notes in two series. On February 15, 2017, $25 million in aggregate principal amount of 3.03% Senior Notes, Series A, due February 15, 2022 (“U.S. Senior Notes, Series A due 2022”), and $100 million in aggregate principal amount of 3.74% Senior Notes, Series B, due February 15, 2027 (“U.S. Senior Notes, Series B due 2027”) (together, the “U.S. Senior Notes due 2022 and 2027”) were funded. Interest on the U.S. Senior Notes due 2022 and 2027 is payable semiannually on February 15 and August 15, commencing August 15, 2017. On November 15, 2017, the Company entered into a Note Purchase Agreement pursuant to which the Company issued and sold $175 million in aggregate principal amount of senior notes in two series. On January 16, 2018, $50 million aggregate principal amount of 3.48% Senior Notes, Series A, due February 15, 2025 (“U.S. Senior Notes, Series A due 2025”) and $125 million in aggregate principal amount of 3.78% Senior Notes, Series B, due February 15, 2030 (“U.S. Senior Notes, Series B due 2030”) (together the “U.S. Senior Notes due 2025 and 2030” and with the Euro Senior Notes and the U.S. Senior Notes due 2022 and 2027, the “Senior Notes”) were funded. Interest on the U.S. Senior Notes due 2025 and 2030 is payable semiannually on February 15 and August 15, commencing on August 15, 2018. The Senior Notes have not been registered under the Securities Act, or applicable state securities laws. The Senior Notes are general unsecured senior obligations and rank equal in right of payment with all existing and future unsecured unsubordinated indebtedness of the Company. The Senior Notes are subject to certain customary covenants, including limitations on the Company’s ability, with certain exceptions, to engage in mergers, consolidations, asset sales and transactions with affiliates, to engage in any business that would substantially change the general business of the Company, and to incur liens. In addition, the Company is required to satisfy certain financial covenants and tests relating to, among other matters, interest coverage and leverage. At June 29, 2019 , the Company was in compliance with all covenants under the Senior Notes. The Company may redeem the Senior Notes upon the satisfaction of certain conditions and the payment of a make-whole amount to noteholders, and are required to offer to repurchase the Senior Notes at par following certain events, including a change of control. Interest paid on all Company debt was $3.5 million and $3.7 million for the three months ended June 29, 2019 and June 30, 2018 , respectively, and $11.5 million and $7.7 million for the six months ended June 29, 2019 and June 30, 2018 , respectively.

Fair Value of Assets and Liabil

Fair Value of Assets and Liabilities	6 Months Ended
	Jun. 29, 2019
Fair Value Disclosures [Abstract]
Fair Value of Assets and Liabilities	Fair Value of Assets and Liabilities For assets and liabilities measured at fair value on a recurring and nonrecurring basis, a three-level hierarchy of measurements based upon observable and unobservable inputs is used to arrive at fair value. Observable inputs are developed based on market data obtained from independent sources, while unobservable inputs reflect the Company’s assumptions about valuation based on the best information available in the circumstances. Depending on the inputs, the Company classifies each fair value measurement as follows: Level 1 —Valuations based on unadjusted quoted prices for identical assets or liabilities in active markets; Level 2 —Valuations based upon quoted prices for similar instruments, prices for identical or similar instruments in markets that are not active, or model-derived valuations, all of whose significant inputs are observable, and Level 3 —Valuations based upon one or more significant unobservable inputs. Following is a description of the valuation methodologies used for instruments measured at fair value and their classification in the valuation hierarchy. Investments in Equity Securities Investments in equity securities listed on a national market or exchange are valued at the last sales price and classified within Level 1 of the valuation hierarchy and recorded in investments and other assets. The Company has certain convertible debt and convertible preferred stock investments that are accounted for under the cost method reflected in other assets in the Condensed Consolidated Balance Sheets. During the six months ended June 29, 2019 , the Company recorded impairment charges of $2.8 million in Other expense (income), net in the Condensed Consolidated Statements of Net Income to adjust these certain investments to their estimated fair value of $1.2 million . The fair value of these investments are measured on a nonrecurring basis and determined to be Level 3 under the fair value hierarchy. The Company's accounting and finance management determines the valuation policies and procedures for Level 3 fair value measurements and is responsible for the development and determination of unobservable inputs. Mutual Funds The Company has a non-qualified Supplemental Retirement and Savings Plan which provides additional retirement benefits for certain management employees and named executive officers by allowing participants to defer a portion of their annual compensation. The Company maintains accounts for participants through which participants make investment elections. The marketable securities are classified as Level 1 under the fair value hierarchy as they are maintained in mutual funds with readily determinable fair value and recorded in other assets. There were no changes during the quarter ended June 29, 2019 to the Company’s valuation techniques used to measure asset and liability fair values on a recurring basis. As of June 29, 2019 and December 29, 2018 , the Company did not hold any non-financial assets or liabilities that are required to be measured at fair value on a recurring basis. The following table presents assets measured at fair value by classification within the fair value hierarchy as of June 29, 2019 : Fair Value Measurements Using (in thousands) Quoted Prices in Significant Significant Total Investments in equity securities $ 11,161 $ — $ — $ 11,161 Mutual funds 9,619 — — 9,619 The following table presents assets measured at fair value by classification within the fair value hierarchy as of December 29, 2018 : Fair Value Measurements Using (in thousands) Quoted Prices in Significant Significant Total Investments in equity securities $ 10,312 $ — $ — $ 10,312 Mutual funds 9,112 — — 9,112 In addition to the methods and assumptions used for the financial instruments recorded at fair value as discussed above, the following methods and assumptions are used to estimate the fair value of other financial instruments that are not marked to market on a recurring basis. The Company’s other financial instruments include cash and cash equivalents, short-term investments, accounts receivable and its long-term debt. Due to their short-term maturity, the carrying amounts of cash and cash equivalents, short-term investments and accounts receivable approximate their fair values. The Company’s revolving and term loan debt facilities’ fair values approximate book value at June 29, 2019 and December 29, 2018 , as the rates on these borrowings are variable in nature. The carrying value and estimated fair values of the Company’s Euro Senior Notes, Series A and Series B and USD Senior Notes, Series A and Series B, as of June 29, 2019 and December 29, 2018 were as follows: June 29, 2019 December 29, 2018 (in thousands) Carrying Value Estimated Fair Value Carrying Value Estimated Fair Value Euro Senior Notes, Series A due 2023 $ 132,992 $ 136,568 $ 133,417 $ 130,888 Euro Senior Notes, Series B due 2028 107,984 116,210 108,330 103,774 USD Senior Notes, Series A due 2022 25,000 24,781 25,000 24,115 USD Senior Notes, Series B due 2027 100,000 100,440 100,000 94,458 USD Senior Notes, Series A due 2025 50,000 49,884 50,000 47,434 USD Senior Notes, Series B due 2030 125,000 123,756 125,000 114,731

Benefit Plans

Benefit Plans	6 Months Ended
	Jun. 29, 2019
Retirement Benefits [Abstract]
Benefit Plans	Benefit Plans The Company has company-sponsored defined benefit pension plans covering employees in the U.K., Germany, the Philippines, China, Japan, Mexico, Italy and France. The amount of the retirement benefits provided under the plans is based on years of service and final average pay. The Company recognizes interest cost, expected return on plan assets, and amortization of prior service, net within Other expense (income), net in the Condensed Consolidated Statements of Net Income. The components of net periodic benefit cost for the three and six months ended June 29, 2019 and June 30, 2018 were as follows: For the Three Months Ended For the Six Months Ended (in thousands) June 29, 2019 June 30, 2018 June 29, 2019 June 30, 2018 Components of net periodic benefit cost: Service cost $ 514 $ 533 $ 1,014 $ 1,066 Interest cost 813 501 1,597 1,002 Expected return on plan assets (821 ) (540 ) (1,611 ) (1,080 ) Amortization of prior service 62 74 124 148 Net periodic benefit cost $ 568 $ 568 $ 1,124 $ 1,136 The Company expects to make approximately $2.3 million of cash contributions to its pension plans in 2019.

Other Comprehensive Income (Los

Other Comprehensive Income (Loss)	6 Months Ended
	Jun. 29, 2019
Equity [Abstract]
Other Comprehensive Income (Loss)	Other Comprehensive Income (Loss) Changes in other comprehensive (loss) income by component were as follows: (in thousands) Three Months Ended Three Months Ended Pre-tax Tax Net of Tax Pre-tax Tax Net of Tax Defined benefit pension plan adjustments $ 201 $ 40 $ 161 $ 803 $ 37 $ 766 Foreign currency translation adjustments (5,892 ) — (5,892 ) (16,708 ) — (16,708 ) Total change in other comprehensive income (loss) $ (5,691 ) $ 40 $ (5,731 ) $ (15,905 ) $ 37 $ (15,942 ) (in thousands) Six Months Ended Six Months Ended Pre-tax Tax Net of Tax Pre-tax Tax Net of Tax Defined benefit pension plan adjustments $ 123 $ 11 $ 112 $ 734 $ (29 ) $ 763 Foreign currency translation adjustments 2,230 — 2,230 (16,984 ) — (16,984 ) Total change in other comprehensive income (loss) $ 2,353 $ 11 $ 2,342 $ (16,250 ) $ (29 ) $ (16,221 ) The following tables set forth the changes in accumulated other comprehensive (loss) income by component for the six months ended June 29, 2019 and June 30, 2018 : (in thousands) Pension and postretirement liability and reclassification adjustments Foreign currency translation adjustment Accumulated other comprehensive income (loss) Balance at December 29, 2018 $ (9,959 ) $ (87,965 ) $ (97,924 ) Activity in the period 112 2,230 2,342 Balance at June 29, 2019 $ (9,847 ) $ (85,735 ) $ (95,582 ) (in thousands) Pension and postretirement liability and reclassification adjustments Unrealized gain (loss) on investments Foreign currency translation adjustment Accumulated other comprehensive income (loss) Balance at December 30, 2017 $ (10,836 ) $ 9,795 $ (62,627 ) $ (63,668 ) Cumulative effect adjustment (a) — (9,795 ) — (9,795 ) Activity in the period 763 — (16,984 ) (16,221 ) Balance at June 30, 2018 $ (10,073 ) $ — $ (79,611 ) $ (89,684 ) (a)The Company adopted ASU 2016-01 on December 31, 2017 on a modified retrospective basis, recognizing the cumulative effect as a $9.8 million increase to retained earnings. Amounts reclassified from accumulated other comprehensive (loss) income to earnings for the three and six months ended June 29, 2019 and June 30, 2018 were as follows: Three Months Ended Six Months Ended (in thousands) June 29, 2019 June 30, 2018 June 29, 2019 June 30, 2018 Pension and Postemployment plans: Amortization of prior service $ 62 $ 74 $ 124 $ 148 The Company recognizes the amortization of prior service costs in Other (expense) income, net within the Condensed Consolidated Statements of Net Income.

Income Taxes

Income Taxes	6 Months Ended
	Jun. 29, 2019
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes The effective tax rate for the three and six months ended June 29, 2019 was 18.2% and 19.2% respectively, compared to the effective tax rate for the three and six months ended June 30, 2018 of 19.1% and 19.2% respectively. The effective tax rates for both periods were lower than the applicable U.S. statutory tax rate primarily due to income earned in lower tax jurisdictions.

Earnings Per Share

Earnings Per Share	6 Months Ended
	Jun. 29, 2019
Earnings Per Share [Abstract]
Earnings Per Share	Earnings Per Share The following table sets forth the computation of basic and diluted earnings per share: Three Months Ended Six Months Ended (in thousands, except per share amounts) June 29, 2019 June 30, 2018 June 29, 2019 June 30, 2018 Numerator: Net income as reported $ 43,792 $ 42,326 $ 80,781 $ 78,354 Denominator: Weighted average shares outstanding Basic 24,740 25,004 24,729 24,671 Effect of dilutive securities 243 397 269 415 Diluted 24,983 25,401 24,998 25,086 Earnings Per Share: Basic earnings per share $ 1.77 $ 1.69 $ 3.27 $ 3.18 Diluted earnings per share $ 1.75 $ 1.67 $ 3.23 $ 3.12 Potential shares of common stock relating to stock options excluded from the earnings per share calculation because their effect would be anti-dilutive were 167,599 and 47,849 for the three months ended June 29, 2019 and June 30, 2018 , respectively, and 121,326 and 23,659 for the six months ended June 29, 2019 and June 30, 2018 , respectively . Share Repurchase Program The Company’s Board of Directors authorized the repurchase of up to 1,000,000 shares of the Company’s common stock under a program for the period May 1, 2018 to April 30, 2019 ("2018 program"). On April 26, 2019, the Company's Board of Directors authorized a new program to repurchase up to 1,000,000 shares of the Company's common stock for the period May 1, 2019 to April 30, 2020 ("2019 program"). During the three and six months ended June 29, 2019 , the Company repurchased 188,214 and 268,130 shares of its common stock totaling $32.0 million and $45.5 million , respectively. As of July 26, 2019, the Company repurchased 49,816

Related Party Transactions

Related Party Transactions	6 Months Ended
	Jun. 29, 2019
Related Party Transactions [Abstract]
Related Party Transactions	Related Party Transactions As a result of the Company’s acquisition of IXYS, the Company has equity ownership in various investments that are accounted for under the equity method and recorded in investments in the Condensed Consolidated Balance Sheets. The following is a description of the investments and related party transactions. Powersem GmbH: The Company owns 45% of the outstanding equity of Powersem GmbH (“Powersem”), a module manufacturer based in Germany. For the three months ended June 29, 2019 and June 30, 2018 , the Company recorded revenues of $0.1 million and $0.3 million from sales of products to Powersem for use as components in their products, respectively. For the six months ended June 29, 2019 and June 30, 2018 , the Company recorded revenues of $0.2 million and $0.4 million from sales of products to Powersem for use as components in their products, respectively. During the three months ended June 29, 2019 and June 30, 2018 , the Company purchased $0.9 million and $1.0 million of products from Powersem, respectively. During the six months ended June 29, 2019 and June 30, 2018 , the Company purchased $1.7 million and $2.1 million of products from Powersem, respectively. As of June 29, 2019 , the accounts receivable balance from Powersem was $0.1 million and the accounts payable balance to Powersem was $0.1 million . As of December 29, 2018 , the trade receivable balance from Powersem was $0.1 million and the accounts payable balance to Powersem was $0.2 million . EB-Tech Co., Ltd.: The Company owns approximately 19% of the outstanding equity of EB Tech Co., Ltd. (“EB Tech”), a company with expertise in radiation technology based in South Korea. During both the three months ended June 29, 2019 and June 30, 2018 , EB Tech rendered processing services for the Company totaling approximately $0.1 million . During both the six months ended June 29, 2019 and June 30, 2018 , EB Tech rendered processing services for the Company totaling approximately $0.2 million . As of June 29, 2019 and December 29, 2018 , the Company’s accounts payable balance to EB Tech was $0.1 million . Automated Technology (Phil), Inc. : The Company owns approximately 24% of the outstanding common shares of Automated Technology (Phil), Inc. (“ATEC”), a supplier located in the Philippines that provides assembly and test services. During the three months ended June 29, 2019 and June 30, 2018 , ATEC rendered assembly and test services to the Company totaling approximately $2.3 million and $2.8 million , respectively. During the six months ended June 29, 2019 and June 30, 2018 , ATEC rendered assembly and test services to the Company totaling approximately $3.8 million and $5.2 million , respectively. As of June 29, 2019 and December 29, 2018 , the Company’s accounts payable balance to ATEC was $0.5 million . On March 25, 2019, the Company entered into a definitive agreement to sell the assets and liabilities of Microwave Technology, Inc. (“MWT”) resulting in a loss on disposal of $2.6 million reflected in Other income (expense), net in the Condensed Consolidated Statements of Net Income. The operations of Microwave Technology, Inc. were included in the Electronics segment. One member of the Company’s Board of Directors is the co-owner of a company that agreed to purchase MWT. This transaction closed on April 26, 2019.

Segment Information

Segment Information	6 Months Ended
	Jun. 29, 2019
Segment Reporting [Abstract]
Segment Information	Segment Information The Company and its subsidiaries design, manufacture and sell components and modules for circuit protection, power control and sensing throughout the world. The Company reports its operations by the following segments: Electronics, Automotive, and Industrial. An operating segment is defined as a component of an enterprise that engages in business activities from which it may earn revenues and incur expenses, and about which separate financial information is regularly evaluated by the Chief Operating Decision Maker (“CODM”) in deciding how to allocate resources. The CODM is the Company’s President and Chief Executive Officer (“CEO”). The CODM allocates resources to and assesses the performance of each operating segment using information about its revenue and operating income (loss) before interest and taxes, but does not evaluate the operating segments using discrete balance sheet information. Sales, marketing, and research and development expenses are charged directly into each operating segment. Manufacturing, purchasing, logistics, customer service, finance, information technology, and human resources are shared functions that are allocated back to the three operating segments. The Company does not report inter-segment revenue because the operating segments do not record it. Certain expenses, determined by the CODM to be strategic in nature and not directly related to segments current results, are not allocated but identified as “Other”. Additionally, the Company does not allocate interest and other income, interest expense, or taxes to operating segments. These costs are not allocated to the segments, as management excludes such costs when assessing the performance of the segments. Although the CODM uses operating income (loss) to evaluate the segments, operating costs included in one segment may benefit other segments. Except as discussed above, the accounting policies for segment reporting are the same as for the Company as a whole. • Electronics Segment : Consists of one of the broadest product offerings in the industry, including fuses and fuse accessories, positive temperature coefficient (“PTC”) resettable fuses, polymer electrostatic discharge (“ESD”) suppressors, varistors, reed switch based magnetic sensing, gas discharge tubes; semiconductor and power semiconductor products such as discrete transient voltage suppressor (“TVS”) diodes, TVS diode arrays, protection and switching thyristors, silicon carbide, metal-oxide-semiconductor field-effect transistors (“MOSFETs”) and silicon carbide diodes; and insulated gate bipolar transistors (“IGBT”) technologies. The segment covers a broad range of end markets, including industrial and automotive electronics, electric vehicle infrastructure, data and telecommunications, medical devices, LED lighting, consumer electronics and appliances • Automotive Segment: Consists of a wide range of circuit protection, power control and sensing technologies for global original equipment manufacturers (“OEMs”), Tier-I suppliers and parts distributors in passenger car, heavy duty truck, off-road vehicles, material handling, agricultural, construction and other commercial vehicle industries. Passenger car fuse products include fuses and fuse accessories for internal combustion engine vehicles and hybrid and electric vehicles including blade fuses, battery cable protectors, resettable fuses, high-current fuses, and high-voltage fuses. Commercial vehicle products include fuses, switches, relays, and power distribution modules for the commercial vehicle industry. Automotive sensor products include a wide range of automotive and commercial vehicle products designed to monitor the passenger compartment occupants, safety and environment as well as the vehicle’s powertrain, emissions, speed and suspension. • Industrial Segment: Consists of power fuses, protection relays and controls and other circuit protection products for use in various industrial applications such as oil, gas, mining, alternative energy - solar and wind, electric vehicle infrastructure, construction, HVAC systems, elevator and other industrial equipment. Segment information is summarized as follows: Three Months Ended Six Months Ended (in thousands) June 29, 2019 June 30, 2018 June 29, 2019 June 30, 2018 Net sales Electronics $ 259,553 $ 299,357 $ 524,947 $ 563,768 Automotive 108,650 127,172 222,133 253,302 Industrial 29,676 32,654 56,299 59,926 Total net sales $ 397,879 $ 459,183 $ 803,379 $ 876,996 Depreciation and amortization Electronics $ 14,729 $ 15,651 $ 30,071 $ 29,329 Automotive 6,904 5,969 13,781 11,939 Industrial 1,056 1,467 2,116 2,927 Other — 3,103 — 5,607 Total depreciation and amortization $ 22,689 $ 26,190 $ 45,968 $ 49,802 Operating income (loss) Electronics $ 43,630 $ 67,311 $ 92,666 $ 121,275 Automotive 10,349 15,711 23,550 34,102 Industrial 5,831 5,279 9,336 9,988 Other (a) (7,176 ) (28,679 ) (12,245 ) (68,172 ) Total operating income 52,634 59,622 113,307 97,193 Interest expense 5,589 5,782 11,275 11,205 Foreign exchange (gain) loss (3,575 ) 3,200 668 (7,354 ) Other (income) expense, net (2,947 ) (1,678 ) 1,358 (3,621 ) Income before income taxes $ 53,567 $ 52,318 $ 100,006 $ 96,963 (a) Included in “Other” Operating income (loss) for the 2019 second quarter is $1.5 million ( $3.8 million year-to-date) of acquisition related and integration charges primarily related to the IXYS acquisition. In addition, there were $5.7 million ( $8.4 million year-to-date)of restructuring charges primarily related to employee termination costs. See Note 8, Restructuring, Impairment and Other Charges, for further discussion. Included in "Other" Operating income (loss) for the second quarter of 2018 is includes approximately $26.8 million ( $65.4 million year-to-date) of charges primarily related to the IXYS acquisition, which include $19.0 million ( $36.9 million year-to-date) of purchase accounting inventory step-up charges, $2.0 million ( $13.6 million year-to-date) in acquisition-related and integration costs primarily related to legal, accounting and other expenses, $3.1 million ( $5.6 million year-to-date) in backlog amortization costs, $2.7 million of employee termination costs and other restructuring charges, and $4.5 million year-to-date stock compensation expense recognized immediately upon close for converted IXYS options related to prior service periods and $2.1 million year-to-date change in control expense related to IXYS. In addition, there were $0.5 million ( $1.2 million year-to-date) of employee termination costs, other restructuring, impairment charges of $1.1 million associated with the exit of the Custom business in the second quarter, and $0.3 million ( $0.5 million year-to-date) of acquisition-related expenses for other contemplated acquisitions. The Company’s net sales by country were as follows: Three Months Ended Six Months Ended (in thousands) June 29, 2019 June 30, 2018 June 29, 2019 June 30, 2018 Net sales United States $ 115,991 $ 137,236 $ 235,519 $ 261,112 China 107,728 127,776 214,593 234,284 Other countries (a) 174,160 194,171 353,267 381,600 Total net sales $ 397,879 $ 459,183 $ 803,379 $ 876,996 The Company’s long-lived assets by country were as follows: (in thousands) June 29, December 29, Long-lived assets United States $ 58,015 $ 58,691 China 92,621 95,806 Mexico 74,147 70,495 Germany 37,976 36,548 Philippines 37,275 32,459 Other countries (a) 38,466 45,895 Total long-lived assets $ 338,500 $ 339,894 The Company’s additions to long-lived assets by country were as follows: Six Months Ended (in thousands) June 29, 2019 June 30, 2018 Additions to long-lived assets United States $ 3,454 $ 4,234 China 4,958 14,711 Mexico 8,727 8,874 Germany 3,712 5,182 Philippines 6,629 4,241 Other countries (a) 2,378 3,073 Total additions to long-lived assets $ 29,858 $ 40,315 (a) Each country included in other countries are less than 10% of net sales.

Summary of Significant Accoun_2

Summary of Significant Accounting Policies and Other Information (Policies)	6 Months Ended
	Jun. 29, 2019
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The Company’s accompanying unaudited Condensed Consolidated Financial Statements have been prepared in accordance with U.S. Generally Accepted Accounting Principles (“GAAP”) for interim financial information, the instructions to Form 10-Q and Article 10 of Regulation S-X. Accordingly, certain information and disclosures normally included in the consolidated balance sheets, statements of net income and comprehensive income, statements of cash flows, and statement of stockholders' equity prepared in conformity with U.S. GAAP have been condensed or omitted as permitted by such rules and regulations, although the Company believes that the disclosures made are adequate to make the information not misleading. They have been prepared in accordance with accounting policies described in the Company’s Annual Report on Form 10-K for the fiscal year ended December 29, 2018 which should be read in conjunction with the disclosures therein. In the opinion of management, all adjustments considered necessary for a fair presentation have been included and are of a normal, recurring nature. Operating results for interim periods are not necessarily indicative of annual operating results.
Revenue Recognition	Revenue Recognition On December 31, 2017, the Company adopted new guidance on revenue from contracts with customers using the modified retrospective method. The adoption did not have a significant impact on the Company’s consolidated financial statements. Revenue Disaggregation The following tables disaggregate the Company’s revenue by primary business units for the three and six months ended June 29, 2019 and June 30, 2018 : Three Months Ended June 29, 2019 Six Months Ended June 29, 2019 (in thousands) Electronics Segment Automotive Segment Industrial Segment Total Electronics Segment Automotive Segment Industrial Segment Total Electronics – Passive Products and Sensors $ 108,481 $ — $ — $ 108,481 $ 216,858 $ — $ — $ 216,858 Electronics – Semiconductor 151,072 — — 151,072 308,089 — — 308,089 Passenger Car Products — 53,916 — 53,916 — 110,459 — 110,459 Automotive Sensors — 24,682 — 24,682 — 50,739 — 50,739 Commercial Vehicle Products — 30,052 — 30,052 — 60,935 — 60,935 Industrial Products — — 29,676 29,676 — — 56,299 56,299 Total $ 259,553 $ 108,650 $ 29,676 $ 397,879 $ 524,947 $ 222,133 $ 56,299 $ 803,379 Three Months Ended June 30, 2018 Six Months Ended June 30, 2018 (in thousands) Electronics Segment Automotive Segment Industrial Segment Total Electronics Segment Automotive Segment Industrial Segment Total Electronics – Passive Products and Sensors $ 128,321 $ — $ — $ 128,321 $ 242,816 $ — $ — $ 242,816 Electronics – Semiconductor 171,036 — — 171,036 320,952 — — 320,952 Passenger Car Products — 63,581 — 63,581 — 127,160 — 127,160 Automotive Sensors — 30,729 — 30,729 — 62,052 — 62,052 Commercial Vehicle Products — 32,862 — 32,862 — 64,090 — 64,090 Industrial Products — — 32,654 32,654 — — 59,926 59,926 Total $ 299,357 $ 127,172 $ 32,654 $ 459,183 $ 563,768 $ 253,302 $ 59,926 $ 876,996 See Note 16, Segment Information for net sales by segment and countries. Revenue Recognition The Company recognizes revenue on product sales in the period in which the Company satisfies its performance obligation and control of the product is transferred to the customer. The Company’s sales arrangements with customers are predominately short term in nature and generally provide for transfer of control at the time of shipment as this is the point at which title and risk of loss of the product transfers to the customer. At the end of each period, for those shipments where title to the products and the risk of loss and rewards of ownership do not transfer until the product has been received by the customer, the Company adjusts revenues and cost of sales for the delay between the time that the products are shipped and when they are received by the customer. The amount of revenue recorded reflects the consideration to which the Company expects to be entitled in exchange for goods and may include adjustments for customer allowance, rebates and price adjustments. The Company’s distribution channels are primarily through direct sales and independent third-party distributors. The Company elected the practical expedient under Accounting Standards Codification ("ASC") 340-40-25-4 to expense commissions when incurred as the amortization period of the commission asset the Company would have otherwise recognized is less than one year. Revenue and Billing The Company generally accepts orders from customers through receipt of purchase orders or electronic data interchange based on written sales agreements and purchasing contracts. Contract pricing and selling agreement terms are based on market factors, costs, and competition. Pricing is often negotiated as an adjustment (premium or discount) from the Company’s published price lists. The customer is invoiced when the Company’s products are shipped to them in accordance with the terms of the sales agreement. As the Company’s standard payment terms are less than one year, the Company elected the practical expedient under ASC 606-10-32-18 to not assess whether a contract has a significant financing component. The Company also elected the practical expedient provided in ASC 606-10-25-18B to treat all product shipping and handling activities as fulfillment activities, and therefore recognize the gross revenue associated with the contract, inclusive of any shipping and handling revenue. This is similar to the Company’s prior practice and therefore the effect of the new guidance is immaterial. Ship and Debit Program Some of the terms of the Company’s sales agreements and normal business conditions provide customers (distributors) the ability to receive price adjustments on products previously shipped and invoiced. This practice is common in the industry and is referred to as a “ship and debit” program. This program allows the distributor to debit the Company for the difference between the distributors’ contracted price and a lower price for specific transactions. Under certain circumstances (usually in a competitive situation or large volume opportunity), a distributor will request authorization for pricing allowances to reduce its price. When the Company approves such a reduction, the distributor is authorized to “debit” its account for the difference between the contracted price and the lower approved price. The Company establishes reserves for this program based on historic activity and actual authorizations for the debit and recognizes these debits as a reduction of revenue. Return to Stock The Company has a return to stock policy whereby certain customers, with prior authorization from Littelfuse management, can return previously purchased goods for full or partial credit. The Company establishes an estimated allowance for these returns based on historic activity. Sales revenue and cost of sales are reduced to anticipate estimated returns. Volume Rebates The Company offers volume based sales incentives to certain customers to encourage greater product sales. If customers achieve their specific quarterly or annual sales targets, they are entitled to rebates. The Company estimates the projected amount of rebates that will be achieved by the customer and recognizes this estimated cost as a reduction to revenue as products are sold.
Recently Adopted and Issued Accounting Standards	Recently Adopted Accounting Standards In February 2016, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) No. 2016-02, "Leases" (Topic 842), ("ASC 842"). This ASU requires lessees to recognize, on the balance sheet, assets and liabilities for the rights and obligations created by leases of greater than twelve months. The accounting by lessors will remain largely unchanged. The ASU is effective for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2018, with early adoption permitted. Adoption requires using a modified retrospective transition with either 1) periods prior to the adoption date being recast or 2) a cumulative-effect adjustment recognized to the opening balance of retained earnings on the adoption date with prior periods not recast. The Company adopted the standard on December 30, 2018 using alternative modified retrospective transition method provided in ASU No. 2018-11, "Leases (Topic 842): Target Improvements." Under this method, the Company recorded a cumulative-effect adjustment as of December 30, 2018 and did not record any retrospective adjustments to comparative periods to reflect the adoption of ASC 842. The new standard provides a number of optional practical expedients in transition. The Company has elected the ‘package of practical expedients’ which permits us not to reassess under the new standard our prior conclusions about lease identification, lease classification and initial direct costs. The Company has not elected the use-of-hindsight. Adoption of ASC 842 resulted in the recognition of operating lease right-of-use assets ("ROU") net of deferred rent of $26.1 million and lease liabilities of $29.4 million

Summary of Significant Accoun_3

Summary of Significant Accounting Policies and Other Information (Tables)	6 Months Ended
	Jun. 29, 2019
Accounting Policies [Abstract]
Revenue Disaggregation	The following tables disaggregate the Company’s revenue by primary business units for the three and six months ended June 29, 2019 and June 30, 2018 : Three Months Ended June 29, 2019 Six Months Ended June 29, 2019 (in thousands) Electronics Segment Automotive Segment Industrial Segment Total Electronics Segment Automotive Segment Industrial Segment Total Electronics – Passive Products and Sensors $ 108,481 $ — $ — $ 108,481 $ 216,858 $ — $ — $ 216,858 Electronics – Semiconductor 151,072 — — 151,072 308,089 — — 308,089 Passenger Car Products — 53,916 — 53,916 — 110,459 — 110,459 Automotive Sensors — 24,682 — 24,682 — 50,739 — 50,739 Commercial Vehicle Products — 30,052 — 30,052 — 60,935 — 60,935 Industrial Products — — 29,676 29,676 — — 56,299 56,299 Total $ 259,553 $ 108,650 $ 29,676 $ 397,879 $ 524,947 $ 222,133 $ 56,299 $ 803,379 Three Months Ended June 30, 2018 Six Months Ended June 30, 2018 (in thousands) Electronics Segment Automotive Segment Industrial Segment Total Electronics Segment Automotive Segment Industrial Segment Total Electronics – Passive Products and Sensors $ 128,321 $ — $ — $ 128,321 $ 242,816 $ — $ — $ 242,816 Electronics – Semiconductor 171,036 — — 171,036 320,952 — — 320,952 Passenger Car Products — 63,581 — 63,581 — 127,160 — 127,160 Automotive Sensors — 30,729 — 30,729 — 62,052 — 62,052 Commercial Vehicle Products — 32,862 — 32,862 — 64,090 — 64,090 Industrial Products — — 32,654 32,654 — — 59,926 59,926 Total $ 299,357 $ 127,172 $ 32,654 $ 459,183 $ 563,768 $ 253,302 $ 59,926 $ 876,996

Acquisitions (Tables)

Acquisitions (Tables)	6 Months Ended
	Jun. 29, 2019
Business Combinations [Abstract]
Schedule of Recognized Identified Assets Acquired and Liabilities Assumed	The following table summarizes the purchase price allocation of the fair value of assets acquired and liabilities assumed in the IXYS acquisition: (in thousands) Purchase Price Allocation Total purchase consideration: Cash, net of cash acquired $ 302,865 Cash settled stock options 3,622 Littelfuse stock 434,192 Converted stock options 38,109 Total purchase consideration $ 778,788 Allocation of consideration to assets acquired and liabilities assumed: Current assets, net $ 155,930 Property, plant, and equipment 77,442 Intangible assets 212,720 Goodwill 382,360 Other non-current assets 28,706 Other non-current liabilities (78,370 ) $ 778,788
Business Acquisition, Pro Forma Information	The pro forma amounts presented are not necessarily indicative of either the actual consolidated results had the IXYS acquisition occurred as of January 1, 2017 or of future consolidated operating results. Three Months Ended Six Months Ended (in thousands, except per share amounts) June 30, 2018 June 30, 2018 Net sales $ 459,183 $ 893,709 Income before income taxes 74,857 134,227 Net income 59,283 106,247 Net income per share — basic 2.37 4.26 Net income per share — diluted 2.33 4.22
Business Acquisition, Pro Forma Information, Nonrecurring Adjustments	Pro forma results presented above primarily reflect the following adjustments: Three Months Ended Six Months Ended (in thousands) June 30, 2018 June 30, 2018 Amortization(a) $ 3,298 $ 5,185 Transaction costs(b) — 9,976 Amortization of inventory step-up(c) 19,031 36,927 Stock compensation(d) 210 4,689 Income tax impact of above items (5,582 ) (13,329 ) (a) The amortization adjustment for the three and six months ended June 30, 2018 primarily reflects the reduction of amortization expense in the period related to the Order backlog intangible asset. The Order backlog has a useful life of twelve months and was fully amortized in the fiscal 2017 pro forma results. (b) The transaction cost adjustments reflect the reversal of certain bank and attorney fees from the six months ended June 30, 2018 and recognition of those fees during the six months ended July 1, 2017. (c) The amortization of inventory step-up adjustment reflects the reversal of the amount recognized during the three and six months ended June 30, 2018 and recognition of those costs during the three and six months ended July 1, 2017. The inventory step-up was amortized over five months as the inventory was sold. (d) The stock compensation adjustment reflects the reversal of the portion of stock compensation for IXYS stock options that were converted to Littelfuse stock options and expensed immediately during the six months ended June 30, 2018 .

Inventories (Tables)

Inventories (Tables)	6 Months Ended
	Jun. 29, 2019
Inventory Disclosure [Abstract]
Schedule of Inventory	The components of inventories at June 29, 2019 and December 29, 2018 are as follows: (in thousands) June 29, 2019 December 29, 2018 Raw materials $ 75,908 $ 69,883 Work in process 93,523 88,505 Finished goods 84,874 99,840 Total $ 254,305 $ 258,228

Property, Plant, and Equipment

Property, Plant, and Equipment (Tables)	6 Months Ended
	Jun. 29, 2019
Property, Plant and Equipment [Abstract]
Components of net property, plant, and equipment	The components of net property, plant, and equipment at June 29, 2019 and December 29, 2018 are as follows: (in thousands) June 29, 2019 December 29, 2018 Land $ 24,962 $ 25,630 Building 106,962 114,636 Equipment 612,580 583,043 Accumulated depreciation and amortization (406,004 ) (383,415 ) Total $ 338,500 $ 339,894

Goodwill and Other Intangible_2

Goodwill and Other Intangible Assets (Tables)	6 Months Ended
	Jun. 29, 2019
Goodwill and Intangible Assets Disclosure [Abstract]
Schedule of Goodwill	The amounts for goodwill and changes in the carrying value by segment for the six months ended June 29, 2019 are as follows: (in thousands) Electronics Automotive Industrial Total As of December 29, 2018 $ 656,039 $ 132,332 $ 38,344 $ 826,715 Currency translation (529 ) 89 133 (307 ) As of June 29, 2019 $ 655,510 $ 132,421 $ 38,477 $ 826,408
Schedule of Finite-Lived Intangible Assets	The components of other intangible assets at June 29, 2019 are as follows: (in thousands) Gross Carrying Value Accumulated Amortization Net Book Value Patents, licenses and software $ 139,415 $ 75,175 $ 64,240 Distribution network 43,900 35,702 8,198 Customer relationships, trademarks, and tradenames 374,658 105,922 268,736 Total $ 557,973 $ 216,799 $ 341,174
Schedule of Finite-Lived Intangible Assets, Future Amortization Expense	Estimated annual amortization expense related to intangible assets with definite lives as of June 29, 2019 is as follows: (in thousands) Amount 2019 $ 40,119 2020 39,458 2021 36,833 2022 36,743 2023 31,524 2024 and thereafter 176,738 Total $ 361,415

Lease Commitments (Tables)

Lease Commitments (Tables)	6 Months Ended
	Jun. 29, 2019
Leases [Abstract]
Supplemental balance sheet information related to leases	The following table presents the classification of ROU assets and lease liabilities as of June 29, 2019 : Leases (in thousands) Condensed Consolidated Balance Sheet Classification June 29, 2019 Assets Operating ROU assets Right of use lease assets, net $ 23,280 Liabilities Current operating lease liabilities Accrued liabilities $ 7,349 Non-current operating lease liabilities Non-current operating lease liabilities 18,643 Total lease liabilities $ 25,992
Components of lease expense and supplemental cash flow information	Other Information (in thousands) Six Months Ended Cash paid for amounts included in the measurement of lease liabilities Operating cash flow payments for operating leases $ (4,463 ) Leased assets obtained in exchange for operating lease liabilities 1,510 The following table represents the lease costs for the three and six months ended June 29, 2019 : Leases cost (in thousands) Condensed Consolidated Statements of Net Income Classification Three Months Ended June 29, 2019 Six Months Ended Short-term lease expenses Cost of sales, SG&A expenses $ 148 $ 301 Variable lease expenses Cost of sales, SG&A expenses 187 381 Operating lease rent expenses Cost of sales, SG&A expenses 2,215 4,408 Total operating lease costs Cost of sales, SG&A expenses $ 2,550 $ 5,090
Maturities of lease liabilities	Maturity of Lease Liabilities as of June 29, 2019 (in thousands) Operating leases 2019 (excluding the six months ended June 29, 2019) $ 4,476 2020 7,594 2021 5,861 2022 4,829 2023 3,190 2024 and thereafter 3,147 Total lease payments $ 29,097 Present value of lease liabilities $ 25,992
Operating lease term and discount rate	Operating Lease Term and Discount Rate June 29, 2019 Weighted-average remaining lease term (years) 4.26 Weighted-average discount rate 5.17 %

Accrued Liabilities (Tables)

Accrued Liabilities (Tables)	6 Months Ended
	Jun. 29, 2019
Payables and Accruals [Abstract]
Components of accrued liabilities	The components of accrued liabilities at June 29, 2019 and December 29, 2018 are as follows: (in thousands) June 29, 2019 December 29, 2018 Employee-related liabilities $ 36,048 $ 60,640 Other non-income taxes 30,467 21,523 Operating lease liability 7,349 — Professional services 4,595 6,169 Interest 4,366 5,137 Accrued share repurchases — 4,349 Restructuring liability 4,753 3,887 Other 24,118 36,700 Total $ 111,696 $ 138,405

Restructuring, Impairment and_2

Restructuring, Impairment and Other Charges (Tables)	6 Months Ended
	Jun. 29, 2019
Restructuring and Related Activities [Abstract]
Restructuring, impairment and other charges	The Company recorded restructuring, impairment and other charges for the three and six months ended June 29, 2019 and June 30, 2018 as follows: Three months ended June 29, 2019 Six months ended June 29, 2019 (in thousands) Electronics Automotive Industrial Total Electronics Automotive Industrial Total Employee terminations $ 1,698 $ 3,241 $ 674 $ 5,613 $ 3,498 $ 3,846 $ 721 $ 8,065 Other restructuring charges — 70 — 70 13 90 250 353 Total restructuring charges 1,698 3,311 674 5,683 3,511 3,936 971 8,418 Total $ 1,698 $ 3,311 $ 674 $ 5,683 $ 3,511 $ 3,936 $ 971 $ 8,418 Three months ended June 30, 2018 Six months ended June 30, 2018 (in thousands) Electronics Automotive Industrial Total Electronics Automotive Industrial Total Employee terminations $ 2,402 $ — $ 62 $ 2,464 $ 3,079 $ 99 $ 65 $ 3,243 Other restructuring charges 670 — — 670 670 — — 670 Total restructuring charges 3,072 — 62 3,134 3,749 99 65 3,913 Impairment — 88 1,037 1,125 — 88 1,037 1,125 Total $ 3,072 $ 88 $ 1,099 $ 4,259 $ 3,749 $ 187 $ 1,102 $ 5,038

Debt (Tables)

Debt (Tables)	6 Months Ended
	Jun. 29, 2019
Debt Disclosure [Abstract]
Schedule of Long-term Debt Instruments	The carrying amounts of debt at June 29, 2019 and December 29, 2018 are as follows: (in thousands) June 29, December 29, Term Loan $ 147,500 $ 155,000 Euro Senior Notes, Series A due 2023 132,992 133,417 Euro Senior Notes, Series B due 2028 107,984 108,330 U.S. Senior Notes, Series A due 2022 25,000 25,000 U.S. Senior Notes, Series B due 2027 100,000 100,000 U.S. Senior Notes, Series A due 2025 50,000 50,000 U.S. Senior Notes, Series B due 2030 125,000 125,000 Other 2,619 2,619 Unamortized debt issuance costs (4,155 ) (4,636 ) Total debt 686,940 694,730 Less: Current maturities (10,000 ) (10,000 ) Total long-term debt $ 676,940 $ 684,730

Fair Value of Assets and Liab_2

Fair Value of Assets and Liabilities (Tables)	6 Months Ended
	Jun. 29, 2019
Fair Value Disclosures [Abstract]
Fair Value, Assets Measured on Recurring Basis	The following table presents assets measured at fair value by classification within the fair value hierarchy as of June 29, 2019 : Fair Value Measurements Using (in thousands) Quoted Prices in Significant Significant Total Investments in equity securities $ 11,161 $ — $ — $ 11,161 Mutual funds 9,619 — — 9,619 The following table presents assets measured at fair value by classification within the fair value hierarchy as of December 29, 2018 : Fair Value Measurements Using (in thousands) Quoted Prices in Significant Significant Total Investments in equity securities $ 10,312 $ — $ — $ 10,312 Mutual funds 9,112 — — 9,112
Fair Value, by Balance Sheet Grouping	The carrying value and estimated fair values of the Company’s Euro Senior Notes, Series A and Series B and USD Senior Notes, Series A and Series B, as of June 29, 2019 and December 29, 2018 were as follows: June 29, 2019 December 29, 2018 (in thousands) Carrying Value Estimated Fair Value Carrying Value Estimated Fair Value Euro Senior Notes, Series A due 2023 $ 132,992 $ 136,568 $ 133,417 $ 130,888 Euro Senior Notes, Series B due 2028 107,984 116,210 108,330 103,774 USD Senior Notes, Series A due 2022 25,000 24,781 25,000 24,115 USD Senior Notes, Series B due 2027 100,000 100,440 100,000 94,458 USD Senior Notes, Series A due 2025 50,000 49,884 50,000 47,434 USD Senior Notes, Series B due 2030 125,000 123,756 125,000 114,731

Benefit Plans (Tables)

Benefit Plans (Tables)	6 Months Ended
	Jun. 29, 2019
Retirement Benefits [Abstract]
Schedule of Net Benefit Costs	The components of net periodic benefit cost for the three and six months ended June 29, 2019 and June 30, 2018 were as follows: For the Three Months Ended For the Six Months Ended (in thousands) June 29, 2019 June 30, 2018 June 29, 2019 June 30, 2018 Components of net periodic benefit cost: Service cost $ 514 $ 533 $ 1,014 $ 1,066 Interest cost 813 501 1,597 1,002 Expected return on plan assets (821 ) (540 ) (1,611 ) (1,080 ) Amortization of prior service 62 74 124 148 Net periodic benefit cost $ 568 $ 568 $ 1,124 $ 1,136

Other Comprehensive Income (L_2

Other Comprehensive Income (Loss) (Tables)	6 Months Ended
	Jun. 29, 2019
Equity [Abstract]
Schedule of Components of Comprehensive Income (Loss)	Changes in other comprehensive (loss) income by component were as follows: (in thousands) Three Months Ended Three Months Ended Pre-tax Tax Net of Tax Pre-tax Tax Net of Tax Defined benefit pension plan adjustments $ 201 $ 40 $ 161 $ 803 $ 37 $ 766 Foreign currency translation adjustments (5,892 ) — (5,892 ) (16,708 ) — (16,708 ) Total change in other comprehensive income (loss) $ (5,691 ) $ 40 $ (5,731 ) $ (15,905 ) $ 37 $ (15,942 ) (in thousands) Six Months Ended Six Months Ended Pre-tax Tax Net of Tax Pre-tax Tax Net of Tax Defined benefit pension plan adjustments $ 123 $ 11 $ 112 $ 734 $ (29 ) $ 763 Foreign currency translation adjustments 2,230 — 2,230 (16,984 ) — (16,984 ) Total change in other comprehensive income (loss) $ 2,353 $ 11 $ 2,342 $ (16,250 ) $ (29 ) $ (16,221 )
Schedule of Accumulated Other Comprehensive Income (Loss)	The following tables set forth the changes in accumulated other comprehensive (loss) income by component for the six months ended June 29, 2019 and June 30, 2018 : (in thousands) Pension and postretirement liability and reclassification adjustments Foreign currency translation adjustment Accumulated other comprehensive income (loss) Balance at December 29, 2018 $ (9,959 ) $ (87,965 ) $ (97,924 ) Activity in the period 112 2,230 2,342 Balance at June 29, 2019 $ (9,847 ) $ (85,735 ) $ (95,582 ) (in thousands) Pension and postretirement liability and reclassification adjustments Unrealized gain (loss) on investments Foreign currency translation adjustment Accumulated other comprehensive income (loss) Balance at December 30, 2017 $ (10,836 ) $ 9,795 $ (62,627 ) $ (63,668 ) Cumulative effect adjustment (a) — (9,795 ) — (9,795 ) Activity in the period 763 — (16,984 ) (16,221 ) Balance at June 30, 2018 $ (10,073 ) $ — $ (79,611 ) $ (89,684 ) (a)The Company adopted ASU 2016-01 on December 31, 2017 on a modified retrospective basis, recognizing the cumulative effect as a $9.8 million increase to retained earnings.
Reclassification out of Accumulated Other Comprehensive Income	Amounts reclassified from accumulated other comprehensive (loss) income to earnings for the three and six months ended June 29, 2019 and June 30, 2018 were as follows: Three Months Ended Six Months Ended (in thousands) June 29, 2019 June 30, 2018 June 29, 2019 June 30, 2018 Pension and Postemployment plans: Amortization of prior service $ 62 $ 74 $ 124 $ 148

Earnings Per Share (Tables)

Earnings Per Share (Tables)	6 Months Ended
	Jun. 29, 2019
Earnings Per Share [Abstract]
Schedule of Earnings Per Share, Basic and Diluted	The following table sets forth the computation of basic and diluted earnings per share: Three Months Ended Six Months Ended (in thousands, except per share amounts) June 29, 2019 June 30, 2018 June 29, 2019 June 30, 2018 Numerator: Net income as reported $ 43,792 $ 42,326 $ 80,781 $ 78,354 Denominator: Weighted average shares outstanding Basic 24,740 25,004 24,729 24,671 Effect of dilutive securities 243 397 269 415 Diluted 24,983 25,401 24,998 25,086 Earnings Per Share: Basic earnings per share $ 1.77 $ 1.69 $ 3.27 $ 3.18 Diluted earnings per share $ 1.75 $ 1.67 $ 3.23 $ 3.12

Segment Information (Tables)

Segment Information (Tables)	6 Months Ended
	Jun. 29, 2019
Segment Reporting [Abstract]
Schedule of Segment Reporting Information, by Segment	Segment information is summarized as follows: Three Months Ended Six Months Ended (in thousands) June 29, 2019 June 30, 2018 June 29, 2019 June 30, 2018 Net sales Electronics $ 259,553 $ 299,357 $ 524,947 $ 563,768 Automotive 108,650 127,172 222,133 253,302 Industrial 29,676 32,654 56,299 59,926 Total net sales $ 397,879 $ 459,183 $ 803,379 $ 876,996 Depreciation and amortization Electronics $ 14,729 $ 15,651 $ 30,071 $ 29,329 Automotive 6,904 5,969 13,781 11,939 Industrial 1,056 1,467 2,116 2,927 Other — 3,103 — 5,607 Total depreciation and amortization $ 22,689 $ 26,190 $ 45,968 $ 49,802 Operating income (loss) Electronics $ 43,630 $ 67,311 $ 92,666 $ 121,275 Automotive 10,349 15,711 23,550 34,102 Industrial 5,831 5,279 9,336 9,988 Other (a) (7,176 ) (28,679 ) (12,245 ) (68,172 ) Total operating income 52,634 59,622 113,307 97,193 Interest expense 5,589 5,782 11,275 11,205 Foreign exchange (gain) loss (3,575 ) 3,200 668 (7,354 ) Other (income) expense, net (2,947 ) (1,678 ) 1,358 (3,621 ) Income before income taxes $ 53,567 $ 52,318 $ 100,006 $ 96,963 (a) Included in “Other” Operating income (loss) for the 2019 second quarter is $1.5 million ( $3.8 million year-to-date) of acquisition related and integration charges primarily related to the IXYS acquisition. In addition, there were $5.7 million ( $8.4 million year-to-date)of restructuring charges primarily related to employee termination costs. See Note 8, Restructuring, Impairment and Other Charges, for further discussion. Included in "Other" Operating income (loss) for the second quarter of 2018 is includes approximately $26.8 million ( $65.4 million year-to-date) of charges primarily related to the IXYS acquisition, which include $19.0 million ( $36.9 million year-to-date) of purchase accounting inventory step-up charges, $2.0 million ( $13.6 million year-to-date) in acquisition-related and integration costs primarily related to legal, accounting and other expenses, $3.1 million ( $5.6 million year-to-date) in backlog amortization costs, $2.7 million of employee termination costs and other restructuring charges, and $4.5 million year-to-date stock compensation expense recognized immediately upon close for converted IXYS options related to prior service periods and $2.1 million year-to-date change in control expense related to IXYS. In addition, there were $0.5 million ( $1.2 million year-to-date) of employee termination costs, other restructuring, impairment charges of $1.1 million associated with the exit of the Custom business in the second quarter, and $0.3 million ( $0.5 million year-to-date) of acquisition-related expenses for other contemplated acquisitions.
Schedule of Disclosure on Geographic Areas, Long-Lived Assets in Individual Foreign Countries by Country	The Company’s net sales by country were as follows: Three Months Ended Six Months Ended (in thousands) June 29, 2019 June 30, 2018 June 29, 2019 June 30, 2018 Net sales United States $ 115,991 $ 137,236 $ 235,519 $ 261,112 China 107,728 127,776 214,593 234,284 Other countries (a) 174,160 194,171 353,267 381,600 Total net sales $ 397,879 $ 459,183 $ 803,379 $ 876,996 The Company’s long-lived assets by country were as follows: (in thousands) June 29, December 29, Long-lived assets United States $ 58,015 $ 58,691 China 92,621 95,806 Mexico 74,147 70,495 Germany 37,976 36,548 Philippines 37,275 32,459 Other countries (a) 38,466 45,895 Total long-lived assets $ 338,500 $ 339,894 The Company’s additions to long-lived assets by country were as follows: Six Months Ended (in thousands) June 29, 2019 June 30, 2018 Additions to long-lived assets United States $ 3,454 $ 4,234 China 4,958 14,711 Mexico 8,727 8,874 Germany 3,712 5,182 Philippines 6,629 4,241 Other countries (a) 2,378 3,073 Total additions to long-lived assets $ 29,858 $ 40,315 (a) Each country included in other countries are less than 10% of net sales.

Summary of Significant Accoun_4

Summary of Significant Accounting Policies and Other Information (Details Textual) - USD ($) $ in Thousands	Jun. 29, 2019	Dec. 30, 2018
Accounting Policies [Abstract]
Right of use lease assets, net	$ 23,280	$ 26,100
Non-current operating lease liabilities	$ 18,643	$ 29,400

Summary of Significant Accoun_5

Summary of Significant Accounting Policies and Other Information - Revenue Disaggregation (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 29, 2019	Jun. 30, 2018	Jun. 29, 2019	Jun. 30, 2018
Disaggregation of Revenue [Line Items]
Net sales	$ 397,879	$ 459,183	$ 803,379	$ 876,996
Electronics – Passive Products and Sensors
Disaggregation of Revenue [Line Items]
Net sales	108,481	128,321	216,858	242,816
Electronics – Semiconductor
Disaggregation of Revenue [Line Items]
Net sales	151,072	171,036	308,089	320,952
Passenger Car Products
Disaggregation of Revenue [Line Items]
Net sales	53,916	63,581	110,459	127,160
Automotive Sensors
Disaggregation of Revenue [Line Items]
Net sales	24,682	30,729	50,739	62,052
Commercial Vehicle Products
Disaggregation of Revenue [Line Items]
Net sales	30,052	32,862	60,935	64,090
Industrial Products
Disaggregation of Revenue [Line Items]
Net sales	29,676	32,654	56,299	59,926
Electronics Segment
Disaggregation of Revenue [Line Items]
Net sales	259,553	299,357	524,947	563,768
Electronics Segment | Electronics – Passive Products and Sensors
Disaggregation of Revenue [Line Items]
Net sales	108,481	128,321	216,858	242,816
Electronics Segment | Electronics – Semiconductor
Disaggregation of Revenue [Line Items]
Net sales	151,072	171,036	308,089	320,952
Electronics Segment | Passenger Car Products
Disaggregation of Revenue [Line Items]
Net sales	0	0	0	0
Electronics Segment | Automotive Sensors
Disaggregation of Revenue [Line Items]
Net sales	0	0	0	0
Electronics Segment | Commercial Vehicle Products
Disaggregation of Revenue [Line Items]
Net sales	0	0	0	0
Electronics Segment | Industrial Products
Disaggregation of Revenue [Line Items]
Net sales	0	0	0	0
Automotive Segment
Disaggregation of Revenue [Line Items]
Net sales	108,650	127,172	222,133	253,302
Automotive Segment | Electronics – Passive Products and Sensors
Disaggregation of Revenue [Line Items]
Net sales	0	0	0	0
Automotive Segment | Electronics – Semiconductor
Disaggregation of Revenue [Line Items]
Net sales	0	0	0	0
Automotive Segment | Passenger Car Products
Disaggregation of Revenue [Line Items]
Net sales	53,916	63,581	110,459	127,160
Automotive Segment | Automotive Sensors
Disaggregation of Revenue [Line Items]
Net sales	24,682	30,729	50,739	62,052
Automotive Segment | Commercial Vehicle Products
Disaggregation of Revenue [Line Items]
Net sales	30,052	32,862	60,935	64,090
Automotive Segment | Industrial Products
Disaggregation of Revenue [Line Items]
Net sales	0	0	0	0
Industrial Segment
Disaggregation of Revenue [Line Items]
Net sales	29,676	32,654	56,299	59,926
Industrial Segment | Electronics – Passive Products and Sensors
Disaggregation of Revenue [Line Items]
Net sales	0	0	0	0
Industrial Segment | Electronics – Semiconductor
Disaggregation of Revenue [Line Items]
Net sales	0	0	0	0
Industrial Segment | Passenger Car Products
Disaggregation of Revenue [Line Items]
Net sales	0	0	0	0
Industrial Segment | Automotive Sensors
Disaggregation of Revenue [Line Items]
Net sales	0	0	0	0
Industrial Segment | Commercial Vehicle Products
Disaggregation of Revenue [Line Items]
Net sales	0	0	0	0
Industrial Segment | Industrial Products
Disaggregation of Revenue [Line Items]
Net sales	$ 29,676	$ 32,654	$ 56,299	$ 59,926

Acquisitions - Narrative (Detai

Acquisitions - Narrative (Details) $ / shares in Units, $ in Thousands	Jan. 17, 2018USD ($)customer$ / shares	Jun. 30, 2018USD ($)	Jun. 29, 2019USD ($)$ / shares	Jun. 30, 2018USD ($)	Dec. 29, 2018$ / shares
Business Acquisition [Line Items]
Common stock, par value (in dollars per share) | $ / shares			$ 0.01		$ 0.01
Non-cash inventory charges			$ 0	$ 36,927
Cash, net of cash acquired			$ 775	310,487
Inventory amortization period			5 months
IXYS Corporation
Business Acquisition [Line Items]
Number of customers | customer	3,500
Common stock, par value (in dollars per share) | $ / shares	$ 0.01
Share price (in dollars per share) | $ / shares	$ 23
Share exchange ratio	0.1265
Share price (in dollars per share) | $ / shares	$ 207.5
Consideration excluding value of stock options converted	$ 814,800
Cash	380,600
Littelfuse stock	434,192
Value of options converted	41,700
Consideration transferred	856,500
Receivables	49,100
Net sales		$ 100,200		186,500
Loss before income taxes		13,900		31,700
Allocated share based compensation				4,500
Acquisition related costs		800		11,000
Cash, net of cash acquired	$ 302,865
Other | Operating Income (Loss)
Business Acquisition [Line Items]
Acquisition related costs		26,800		65,400
Inventory adjustment		19,000		36,900
Employee Stock Option | IXYS Corporation
Business Acquisition [Line Items]
Allocated share based compensation		$ 1,600		7,500
Employee Stock Option | IXYS Corporation | Selling, General and Administrative Expenses
Business Acquisition [Line Items]
Allocated share based compensation				$ 4,500

Acquisitions - Preliminary Pric

Acquisitions - Preliminary Price Allocation (Details) - USD ($) $ in Thousands	Jan. 17, 2018	Jun. 29, 2019	Jun. 30, 2018	Dec. 29, 2018
Total purchase consideration:
Cash, net of cash acquired		$ 775	$ 310,487
Allocation of consideration to assets acquired and liabilities assumed:
Goodwill		$ 826,408		$ 826,715
IXYS Corporation
Total purchase consideration:
Cash	$ 380,600
Cash, net of cash acquired	302,865
Cash settled stock options	3,622
Littelfuse stock	434,192
Converted stock options	38,109
Total purchase consideration	778,788
Allocation of consideration to assets acquired and liabilities assumed:
Current assets, net	155,930
Property, plant, and equipment	77,442
Intangible assets	212,720
Goodwill	382,360
Other non-current assets	28,706
Other non-current liabilities	(78,370)
Assets acquired and liabilities assumed	$ 778,788

Acquisitions - Business Acquisi

Acquisitions - Business Acquisition Pro Forma Information (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2018
Business Combinations [Abstract]
Net sales	$ 459,183	$ 893,709
Income before income taxes	74,857	134,227
Net income	$ 59,283	$ 106,247
Net income per share — basic (in dollars per share)	$ 2.37	$ 4.26
Net income per share — diluted (in dollars per share)	$ 2.33	$ 4.22

Acquisitions - Pro Forma Inform

Acquisitions - Pro Forma Information Adjustments (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2018
Business Acquisition, Pro Forma Information, Nonrecurring Adjustment [Line Items]
Net income	$ 59,283	$ 106,247
Amortization
Business Acquisition, Pro Forma Information, Nonrecurring Adjustment [Line Items]
Net income	3,298	5,185
Transaction costs
Business Acquisition, Pro Forma Information, Nonrecurring Adjustment [Line Items]
Net income	0	9,976
Amortization of inventory step-up
Business Acquisition, Pro Forma Information, Nonrecurring Adjustment [Line Items]
Net income	19,031	36,927
Stock compensation
Business Acquisition, Pro Forma Information, Nonrecurring Adjustment [Line Items]
Net income	210	4,689
Income tax impact of above items
Business Acquisition, Pro Forma Information, Nonrecurring Adjustment [Line Items]
Net income	$ (5,582)	$ (13,329)

Inventories - Components of Inv

Inventories - Components of Inventories (Details) - USD ($) $ in Thousands	Jun. 29, 2019	Dec. 29, 2018
Inventory Disclosure [Abstract]
Raw materials	$ 75,908	$ 69,883
Work in process	93,523	88,505
Finished goods	84,874	99,840
Total	$ 254,305	$ 258,228

Property, Plant, and Equipmen_2

Property, Plant, and Equipment (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 29, 2019	Jun. 30, 2018	Jun. 29, 2019	Jun. 30, 2018	Dec. 29, 2018
Property, Plant and Equipment [Line Items]
Accumulated depreciation and amortization	$ (406,004)		$ (406,004)		$ (383,415)
Net property, plant, and equipment	338,500		338,500		339,894
Depreciation	12,600	$ 12,800	25,727	$ 24,431
Land
Property, Plant and Equipment [Line Items]
Property, plant, and equipment, gross	24,962		24,962		25,630
Building
Property, Plant and Equipment [Line Items]
Property, plant, and equipment, gross	106,962		106,962		114,636
Equipment
Property, Plant and Equipment [Line Items]
Property, plant, and equipment, gross	$ 612,580		$ 612,580		$ 583,043

Goodwill and Other Intangible_3

Goodwill and Other Intangible Assets - Amounts for Goodwill and Changes in Carrying Value by Operating Segment (Details) $ in Thousands	6 Months Ended
	Jun. 29, 2019USD ($)
Goodwill [Roll Forward]
Balance	$ 826,715
Currency translation	(307)
Balance	826,408
Electronics
Goodwill [Roll Forward]
Balance	656,039
Currency translation	(529)
Balance	655,510
Automotive
Goodwill [Roll Forward]
Balance	132,332
Currency translation	89
Balance	132,421
Industrial
Goodwill [Roll Forward]
Balance	38,344
Currency translation	133
Balance	$ 38,477

Goodwill and Other Intangible_4

Goodwill and Other Intangible Assets - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 29, 2019	Jun. 30, 2018	Jun. 29, 2019	Jun. 30, 2018
Goodwill and Intangible Assets Disclosure [Abstract]
Amortization of intangibles	$ 10,050	$ 13,373	$ 20,241	$ 25,371

Goodwill and Other Intangible_5

Goodwill and Other Intangible Assets - Details of Other Intangible Assets and Related Future Amortization Expense (Details) $ in Thousands	Jun. 29, 2019USD ($)
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Value	$ 557,973
Accumulated Amortization	216,799
Net Book Value	341,174
Patents, licenses and software
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Value	139,415
Accumulated Amortization	75,175
Net Book Value	64,240
Distribution network
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Value	43,900
Accumulated Amortization	35,702
Net Book Value	8,198
Customer relationships, trademarks, and tradenames
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Value	374,658
Accumulated Amortization	105,922
Net Book Value	$ 268,736

Goodwill and Other Intangible_6

Goodwill and Other Intangible Assets - Estimated Amortization Expense Related to Intangible Assets with Definite Lives (Details) $ in Thousands	Jun. 29, 2019USD ($)
Goodwill and Intangible Assets Disclosure [Abstract]
2019	$ 40,119
2020	39,458
2021	36,833
2022	36,743
2023	31,524
2024 and thereafter	176,738
Total	$ 361,415

Lease Commitments - Balance She

Lease Commitments - Balance Sheet, Operating Lease Term and Discount Rate (Details) - USD ($) $ in Thousands	Jun. 29, 2019	Dec. 30, 2018	Dec. 29, 2018
Leases [Abstract]
Operating ROU assets	$ 23,280	$ 26,100
Current operating lease liabilities	7,349		$ 0
Non-current operating lease liabilities	18,643	$ 29,400
Total lease liabilities	$ 25,992
Weighted-average remaining lease term (years)	4 years 3 months 3 days
Weighted-average discount rate	5.17%

Lease Commitments - Lease Cost

Lease Commitments - Lease Cost (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
	Jun. 29, 2019	Jun. 29, 2019
Leases [Abstract]
Short-term lease expenses	$ 148	$ 301
Variable lease expenses	187	381
Operating lease rent expenses	2,215	4,408
Total operating lease costs	$ 2,550	$ 5,090

Lease Commitments - Maturities

Lease Commitments - Maturities of Lease Liabilities (Details) $ in Thousands	Jun. 29, 2019USD ($)
Operating Leases
2019 (excluding the six months ended June 29, 2019)	$ 4,476
2020	7,594
2021	5,861
2022	4,829
2023	3,190
2024 and thereafter	3,147
Total lease payments	29,097
Present value of lease liabilities	$ 25,992

Lease Commitments - Supplementa

Lease Commitments - Supplemental Cash Flow Information (Details) $ in Thousands	6 Months Ended
	Jun. 29, 2019USD ($)
Cash paid for amounts included in the measurement of lease liabilities
Operating cash flow payments for operating leases	$ (4,463)
Leased assets obtained in exchange for operating lease liabilities	$ 1,510

Accrued Liabilities (Details)

Accrued Liabilities (Details) - USD ($) $ in Thousands	Jun. 29, 2019	Dec. 29, 2018
Payables and Accruals [Abstract]
Employee-related liabilities	$ 36,048	$ 60,640
Other non-income taxes	30,467	21,523
Operating lease liability	7,349	0
Professional services	4,595	6,169
Interest	4,366	5,137
Accrued share repurchases	0	4,349
Restructuring liability	4,753	3,887
Other	24,118	36,700
Total	$ 111,696	$ 138,405

Restructuring, Impairment and_3

Restructuring, Impairment and Other Charges (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 29, 2019	Jun. 30, 2018	Jun. 29, 2019	Jun. 30, 2018	Apr. 30, 2019	Dec. 29, 2018
Restructuring Cost and Reserve [Line Items]
Total restructuring charges	$ 5,683	$ 3,134	$ 8,418	$ 3,913
Impairment charges		1,125		1,125
Restructuring costs	5,683	4,259	8,418	5,038
Restructuring reserves	4,800		4,800			$ 3,900
Employee terminations
Restructuring Cost and Reserve [Line Items]
Total restructuring charges	5,613	2,464	8,065	3,243
Other restructuring charges
Restructuring Cost and Reserve [Line Items]
Total restructuring charges	70	670	353	670
Facility closing | Minimum
Restructuring Cost and Reserve [Line Items]
Expected restructuring cost					$ 1,700
Electronics
Restructuring Cost and Reserve [Line Items]
Total restructuring charges	1,698	3,072	3,511	3,749
Impairment charges		0		0
Restructuring costs	1,698	3,072	3,511	3,749
Electronics | Employee terminations
Restructuring Cost and Reserve [Line Items]
Total restructuring charges	1,698	2,402	3,498	3,079
Electronics | Other restructuring charges
Restructuring Cost and Reserve [Line Items]
Total restructuring charges	0	670	13	670
Automotive
Restructuring Cost and Reserve [Line Items]
Total restructuring charges	3,311	0	3,936	99
Impairment charges		88		88
Restructuring costs	3,311	88	3,936	187
Automotive | Employee terminations
Restructuring Cost and Reserve [Line Items]
Total restructuring charges	3,241	0	3,846	99
Automotive | Other restructuring charges
Restructuring Cost and Reserve [Line Items]
Total restructuring charges	70	0	90	0
Industrial
Restructuring Cost and Reserve [Line Items]
Total restructuring charges	674	62	971	65
Impairment charges		1,037		1,037
Restructuring costs	674	1,099	971	1,102
Industrial | Employee terminations
Restructuring Cost and Reserve [Line Items]
Total restructuring charges	674	62	721	65
Industrial | Other restructuring charges
Restructuring Cost and Reserve [Line Items]
Total restructuring charges	$ 0	$ 0	$ 250	$ 0

Debt - Carrying Amounts of Long

Debt - Carrying Amounts of Long-term Debt (Details) - USD ($) $ in Thousands	Jun. 29, 2019	Dec. 29, 2018
Debt Instrument [Line Items]
Unamortized debt issuance costs	$ (4,155)	$ (4,636)
Total debt	686,940	694,730
Less: Current maturities	(10,000)	(10,000)
Total long-term debt	676,940	684,730
Term Loan
Debt Instrument [Line Items]
Long-term debt, gross	147,500	155,000
Euro Senior Notes, Series A due 2023
Debt Instrument [Line Items]
Long-term debt, gross	132,992	133,417
Euro Senior Notes, Series B due 2028
Debt Instrument [Line Items]
Long-term debt, gross	107,984	108,330
U.S. Senior Notes, Series A due 2022
Debt Instrument [Line Items]
Long-term debt, gross	25,000	25,000
U.S. Senior Notes, Series B due 2027
Debt Instrument [Line Items]
Long-term debt, gross	100,000	100,000
U.S. Senior Notes, Series A due 2025
Debt Instrument [Line Items]
Long-term debt, gross	50,000	50,000
U.S. Senior Notes, Series B due 2030
Debt Instrument [Line Items]
Long-term debt, gross	125,000	125,000
Other
Debt Instrument [Line Items]
Long-term debt, gross	$ 2,619	$ 2,619

Debt - Narrative (Details)

Debt - Narrative (Details)

Jan. 16, 2018USD ($)

Oct. 13, 2017USD ($)advance

Mar. 04, 2016USD ($)

Jun. 29, 2019USD ($)

Jun. 30, 2018USD ($)

Jun. 29, 2019USD ($)

Jun. 30, 2018USD ($)

Dec. 29, 2018

Nov. 15, 2017USD ($)series

Oct. 12, 2017USD ($)

Feb. 15, 2017USD ($)

Dec. 08, 2016EUR (€)series

Dec. 08, 2016USD ($)series

Debt Instrument [Line Items]

Interest paid

$ 3,500,000

$ 3,700,000

$ 11,500,000

$ 7,700,000

Credit Agreement

Debt Instrument [Line Items]

Debt term

5 years

Maximum borrowing capacity

$ 700,000,000

Additional uncommitted borrowing capacity

$ 300,000,000

150,000,000

Additional uncommitted borrowing capacity, minimum increments

$ 25,000,000

Number of advances | advance

2

Effective interest rate

3.65%

3.65%

Letter of credit outstanding

$ 100,000

$ 100,000

Credit Agreement | Minimum

Debt Instrument [Line Items]

Commitment fee

0.15%

Credit Agreement | Maximum

Debt Instrument [Line Items]

Commitment fee

0.25%

Credit Agreement | LIBOR | Minimum

Debt Instrument [Line Items]

Basis spread on variable rate

1.00%

Credit Agreement | LIBOR | Maximum

Debt Instrument [Line Items]

Basis spread on variable rate

2.00%

Credit Agreement | Base Rate | Minimum

Debt Instrument [Line Items]

Basis spread on variable rate

0.00%

Credit Agreement | Base Rate | Maximum

Debt Instrument [Line Items]

Basis spread on variable rate

1.00%

Credit Agreement | Revolving Credit Facility

Debt Instrument [Line Items]

Maximum borrowing capacity

$ 700,000,000

$ 575,000,000

$ 575,000,000

Remaining borrowing capacity

531,100,000

531,100,000

Credit Agreement | Term Loan Credit Facility

Debt Instrument [Line Items]

Maximum borrowing capacity, credit facility

200,000,000

$ 125,000,000

Proceeds from issuance of debt

$ 75,000,000

$ 125,000,000

Quarterly payments, percentage of loan

1.25%

Periodic payment

2,500,000

Repayments of debt

$ 2,500,000

$ 7,500,000

Euro Senior Notes, Series A and B

Debt Instrument [Line Items]

Face amount of debt | €

€ 212,000,000

Number of series | series

2

2

2

Euro Senior Notes, Series A due 2023

Debt Instrument [Line Items]

Face amount of debt | €

€ 117,000,000

Stated interest rate

1.14%

1.14%

Euro Senior Notes, Series B due 2028

Debt Instrument [Line Items]

Face amount of debt | €

€ 95,000,000

Stated interest rate

1.83%

1.83%

U.S. Senior Notes, Series A and B

Debt Instrument [Line Items]

Face amount of debt

$ 125,000,000

U.S. Senior Notes, Series A

Debt Instrument [Line Items]

Face amount of debt

$ 25,000,000

Stated interest rate

3.03%

U.S. Senior Notes, Series B

Debt Instrument [Line Items]

Face amount of debt

$ 100,000,000

Stated interest rate

3.74%

US Senior Notes A and B Due 2025 and 2030

Debt Instrument [Line Items]

Face amount of debt

$ 175,000,000

U.S. Senior Notes, Series A due 2025

Debt Instrument [Line Items]

Face amount of debt

$ 50,000,000

Stated interest rate

3.48%

U.S. Senior Notes, Series B due 2030

Debt Instrument [Line Items]

Face amount of debt

$ 125,000,000

Stated interest rate

3.78%

Fair Value of Assets and Liab_3

Fair Value of Assets and Liabilities - Assets Measured at Fair Value (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 29, 2019	Jun. 30, 2018	Dec. 29, 2018
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impairment charges	$ 0	$ 1,125
Investments in equity securities	11,161		$ 10,312
Mutual funds	9,619		9,112
Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments in equity securities	11,161		10,312
Mutual funds	9,619		9,112
Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments in equity securities	0		0
Mutual funds	0		0
Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments in equity securities	0		0
Mutual funds	0		$ 0
Other Expense (Income)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impairment charges	2,800
Investments in equity securities	$ 1,200

Fair Value of Assets and Liab_4

Fair Value of Assets and Liabilities - Carrying Value and Estimated Fair Value of Senior Notes (Details) - USD ($) $ in Thousands	Jun. 29, 2019	Dec. 29, 2018
Carrying Value | Euro Senior Notes, Series A due 2023
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt fair value	$ 132,992	$ 133,417
Carrying Value | Euro Senior Notes, Series B due 2028
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt fair value	107,984	108,330
Carrying Value | U.S. Senior Notes, Series A due 2022
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt fair value	25,000	25,000
Carrying Value | U.S. Senior Notes, Series B due 2027
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt fair value	100,000	100,000
Carrying Value | U.S. Senior Notes, Series A due 2025
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt fair value	50,000	50,000
Carrying Value | U.S. Senior Notes, Series B due 2030
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt fair value	125,000	125,000
Estimated Fair Value | Euro Senior Notes, Series A due 2023
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt fair value	136,568	130,888
Estimated Fair Value | Euro Senior Notes, Series B due 2028
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt fair value	116,210	103,774
Estimated Fair Value | U.S. Senior Notes, Series A due 2022
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt fair value	24,781	24,115
Estimated Fair Value | U.S. Senior Notes, Series B due 2027
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt fair value	100,440	94,458
Estimated Fair Value | U.S. Senior Notes, Series A due 2025
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt fair value	49,884	47,434
Estimated Fair Value | U.S. Senior Notes, Series B due 2030
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt fair value	$ 123,756	$ 114,731

Benefit Plans - Narrative (Deta

Benefit Plans - Narrative (Details) $ in Millions	Jun. 29, 2019USD ($)
Retirement Benefits [Abstract]
Contributions expected	$ 2.3

Benefit Plans - Benefit Plan Ex

Benefit Plans - Benefit Plan Expenses (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 29, 2019	Jun. 30, 2018	Jun. 29, 2019	Jun. 30, 2018
Retirement Benefits [Abstract]
Service cost	$ 514	$ 533	$ 1,014	$ 1,066
Interest cost	813	501	1,597	1,002
Expected return on plan assets	(821)	(540)	(1,611)	(1,080)
Amortization of prior service	62	74	124	148
Net periodic benefit cost	$ 568	$ 568	$ 1,124	$ 1,136

Other Comprehensive Income (L_3

Other Comprehensive Income (Loss) - Schedule of Components of Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	3 Months Ended				6 Months Ended
	Jun. 29, 2019	Mar. 30, 2019	Jun. 30, 2018	Mar. 31, 2018	Jun. 29, 2019	Jun. 30, 2018
Other Comprehensive Income (Loss) [Line Items]
Pre-tax	$ (5,691)		$ (15,905)		$ 2,353	$ (16,250)
Tax	40		37		11	(29)
Total change in other comprehensive income (loss)	(5,731)	$ 8,073	(15,942)	$ (279)	2,342	(16,221)
Pension and postretirement liability and reclassification adjustments
Other Comprehensive Income (Loss) [Line Items]
Pre-tax	201		803		123	734
Tax	40		37		11	(29)
Total change in other comprehensive income (loss)	161		766		112	763
Foreign currency translation adjustment
Other Comprehensive Income (Loss) [Line Items]
Pre-tax	(5,892)		(16,708)		2,230	(16,984)
Tax	$ 0		0		0	0
Total change in other comprehensive income (loss)		$ (5,892)	$ (16,708)		$ 2,230	(16,984)
Unrealized gain (loss) on investments
Other Comprehensive Income (Loss) [Line Items]
Total change in other comprehensive income (loss)						$ 0

Other Comprehensive Income (L_4

Other Comprehensive Income (Loss) - Schedule of Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	3 Months Ended				6 Months Ended
	Jun. 29, 2019	Mar. 30, 2019	Jun. 30, 2018	Mar. 31, 2018	Jun. 29, 2019	Jun. 30, 2018
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance	$ 1,505,388	$ 1,478,342	$ 1,441,974	$ 927,556	$ 1,478,342	$ 927,556
Activity in the period	(5,731)	8,073	(15,942)	(279)	2,342	(16,221)
Balance	1,509,942	1,505,388	1,470,020	1,441,974	1,509,942	1,470,020
Pension and postretirement liability and reclassification adjustments
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance		(9,959)		(10,836)	(9,959)	(10,836)
Cumulative effect adjustment						0
Activity in the period	161		766		112	763
Balance	(9,847)		(10,073)		(9,847)	(10,073)
Unrealized gain (loss) on investments
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance				9,795		9,795
Cumulative effect adjustment						(9,795)
Activity in the period						0
Balance			0			0
Foreign currency translation adjustment
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance		(87,965)		(62,627)	(87,965)	(62,627)
Cumulative effect adjustment						0
Activity in the period		(5,892)	(16,708)		2,230	(16,984)
Balance	(85,735)		(79,611)		(85,735)	(79,611)
Accumulated other comprehensive income (loss)
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance		$ (97,924)		$ (63,668)	(97,924)	(63,668)
Cumulative effect adjustment						(9,795)
Activity in the period					2,342	(16,221)
Balance	$ (95,582)		$ (89,684)		$ (95,582)	$ (89,684)

Other Comprehensive Income (L_5

Other Comprehensive Income (Loss) - Reclassification out of Accumulated Other Comprehensive Income (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 29, 2019	Jun. 30, 2018	Jun. 29, 2019	Jun. 30, 2018
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Amortization of prior service	$ 256,071	$ 290,196	$ 506,343	$ 558,386
Amortization of prior service | Reclassification out of Accumulated Other Comprehensive Income
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Amortization of prior service	$ 62	$ 74	$ 124	$ 148

Income Taxes (Details Textual)

Income Taxes (Details Textual)	3 Months Ended		6 Months Ended
	Jun. 29, 2019	Jun. 30, 2018	Jun. 29, 2019	Jun. 30, 2018
Income Tax Disclosure [Abstract]
Effective tax rate	18.20%	19.10%	19.20%	19.20%

Earnings Per Share - Narrative

Earnings Per Share - Narrative (Details) - USD ($) $ in Thousands	1 Months Ended	3 Months Ended			6 Months Ended
	Jul. 26, 2019	Jun. 29, 2019	Mar. 30, 2019	Jun. 30, 2018	Jun. 29, 2019	Jun. 30, 2018
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Repurchases of common stock		$ (31,955)	$ (13,555)
Share Repurchase Program
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Repurchase authorized (in shares)		1,000,000		1,000,000	1,000,000	1,000,000
Shares repurchased (in shares)		188,214			268,130
Repurchases of common stock		$ (32,000)			$ (45,500)
Employee Stock Option
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded (in shares)		167,599		47,849	121,326	23,659
Subsequent Event | Share Repurchase Program
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Shares repurchased (in shares)	49,816

Earnings Per Share - Computatio

Earnings Per Share - Computation of Basic and Diluted Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended				6 Months Ended
	Jun. 29, 2019	Mar. 30, 2019	Jun. 30, 2018	Mar. 31, 2018	Jun. 29, 2019	Jun. 30, 2018
Numerator:
Net income as reported	$ 43,792	$ 36,989	$ 42,326	$ 36,029	$ 80,781	$ 78,354
Weighted average shares outstanding
Basic (in shares)	24,740		25,004		24,729	24,671
Effect of dilutive securities (in shares)	243		397		269	415
Diluted (in shares)	24,983		25,401		24,998	25,086
Earnings Per Share:
Basic earnings per share (in dollars per share)	$ 1.77		$ 1.69		$ 3.27	$ 3.18
Diluted earnings per share (in dollars per share)	$ 1.75		$ 1.67		$ 3.23	$ 3.12

Related Party Transactions (Det

Related Party Transactions (Details) - USD ($) $ in Millions	Mar. 25, 2019	Jun. 29, 2019	Jun. 30, 2018	Jun. 29, 2019	Jun. 30, 2018	Dec. 29, 2018
Powersem
Related Party Transaction [Line Items]
Revenue from related parties		$ 0.1	$ 0.3	$ 0.2	$ 0.4
Purchase from related party		0.9	1	1.7	2.1
Receivable from related parties		0.1		0.1		$ 0.1
Payables to related parties		0.1		0.1		0.2
EB Tech
Related Party Transaction [Line Items]
Payables to related parties						0.1
Amount of transaction		0.1		0.2
ATEC
Related Party Transaction [Line Items]
Payables to related parties						$ 0.5
Amount of transaction		$ 2.3	$ 2.8	$ 3.8	$ 5.2
MWT
Related Party Transaction [Line Items]
Loss on disposal	$ 2.6
Powersem
Related Party Transaction [Line Items]
Ownership percentage		45.00%		45.00%
EB Tech
Related Party Transaction [Line Items]
Ownership percentage		19.00%		19.00%
ATEC
Related Party Transaction [Line Items]
Ownership percentage		24.00%		24.00%

Segment Information - Segment I

Segment Information - Segment Information (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 29, 2019	Jun. 30, 2018	Jun. 29, 2019	Jun. 30, 2018
Segment Reporting Information [Line Items]
Net sales	$ 397,879	$ 459,183	$ 803,379	$ 876,996
Depreciation and amortization	22,689	26,190	45,968	49,802
Operating income (loss)	52,634	59,622	113,307	97,193
Interest expense	5,589	5,782	11,275	11,205
Foreign exchange (gain) loss	(3,575)	3,200	668	(7,354)
Other (income) expense, net	(2,947)	(1,678)	1,358	(3,621)
Income before income taxes	53,567	52,318	100,006	96,963
Electronics
Segment Reporting Information [Line Items]
Net sales	259,553	299,357	524,947	563,768
Depreciation and amortization	14,729	15,651	30,071	29,329
Operating income (loss)	43,630	67,311	92,666	121,275
Automotive
Segment Reporting Information [Line Items]
Net sales	108,650	127,172	222,133	253,302
Depreciation and amortization	6,904	5,969	13,781	11,939
Operating income (loss)	10,349	15,711	23,550	34,102
Industrial
Segment Reporting Information [Line Items]
Net sales	29,676	32,654	56,299	59,926
Depreciation and amortization	1,056	1,467	2,116	2,927
Operating income (loss)	5,831	5,279	9,336	9,988
Other
Segment Reporting Information [Line Items]
Depreciation and amortization	0	3,103	0	5,607
Operating income (loss)	$ (7,176)	$ (28,679)	$ (12,245)	$ (68,172)

Segment Information - Narrative

Segment Information - Narrative (Details) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 29, 2019USD ($)	Jun. 30, 2018USD ($)	Jun. 29, 2019USD ($)segment	Jun. 30, 2018USD ($)
Segment Reporting Information [Line Items]
Number of operating segments | segment			3
Restructuring charges	$ 5,683	$ 3,134	$ 8,418	$ 3,913
Impairment charges			$ 0	1,125
Impairment charges		1,125		1,125
Net sales | Geographic Concentration Risk | Other countries(a)
Segment Reporting Information [Line Items]
Concentration risk (less than)			10.00%
Other | Operating Income (Loss)
Segment Reporting Information [Line Items]
Acquisition related costs		26,800		65,400
Inventory adjustment		19,000		36,900
Legal, accounting and other expenses	1,500	2,000	$ 3,800	13,600
Backlog amortization costs		3,100		5,600
Change in control expense		2,100
Restructuring charges	$ 5,700		$ 8,400
Impairment charges		500		1,200
Other restructuring		1,100
Impairment charges		300		500
IXYS Corporation
Segment Reporting Information [Line Items]
Acquisition related costs		800		11,000
Allocated share based compensation				4,500
Employee Stock Option | IXYS Corporation
Segment Reporting Information [Line Items]
Allocated share based compensation		$ 1,600		7,500
Restructuring charges				$ 2,700

Segment Information - Revenues

Segment Information - Revenues and Long-lived Assets by Geographical Area (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 29, 2019	Jun. 30, 2018	Jun. 29, 2019	Jun. 30, 2018	Dec. 29, 2018
Segment Reporting Information [Line Items]
Net sales	$ 397,879	$ 459,183	$ 803,379	$ 876,996
Long-lived assets	338,500		338,500		$ 339,894
Additions to long-lived assets			29,858	40,315
United States
Segment Reporting Information [Line Items]
Net sales	115,991	137,236	235,519	261,112
Long-lived assets	58,015		58,015		58,691
Additions to long-lived assets			3,454	4,234
China
Segment Reporting Information [Line Items]
Net sales	107,728	127,776	214,593	234,284
Long-lived assets	92,621		92,621		95,806
Additions to long-lived assets			4,958	14,711
Mexico
Segment Reporting Information [Line Items]
Long-lived assets	74,147		74,147		70,495
Additions to long-lived assets			8,727	8,874
Germany
Segment Reporting Information [Line Items]
Long-lived assets	37,976		37,976		36,548
Additions to long-lived assets			3,712	5,182
Philippines
Segment Reporting Information [Line Items]
Long-lived assets	37,275		37,275		32,459
Additions to long-lived assets			6,629	4,241
Other countries(a)
Segment Reporting Information [Line Items]
Net sales	174,160	$ 194,171	353,267	381,600
Long-lived assets	$ 38,466		38,466		$ 45,895
Additions to long-lived assets			$ 2,378	$ 3,073