Monolithic Power Systems (MPWR) 10-Q1 Nov 192019 Q3 Quarterly reportFinancial data

Company Profile

Document And Entity Information

Document And Entity Information - shares	9 Months Ended
Document And Entity Information - shares	Sep. 30, 2019	Oct. 28, 2019
Document Information [Line Items]
Entity Central Index Key	0001280452
Entity Registrant Name	MONOLITHIC POWER SYSTEMS INC
Amendment Flag	false
Current Fiscal Year End Date	--12-31
Document Fiscal Period Focus	Q3
Document Fiscal Year Focus	2019
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Sep. 30, 2019
Document Transition Report	false
Entity File Number	000-51026
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	77-0466789
Entity Address, Address Line One	4040 Lake Washington Blvd. NE, Suite 201
Entity Address, City or Town	Kirkland
Entity Address, State or Province	WA
Entity Address, Postal Zip Code	98033
City Area Code	425
Local Phone Number	296-9956
Title of 12(b) Security	Common Stock, par value $0.001 per share
Trading Symbol	MPWR
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		43,439,000

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets (Current Period Unaudited) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Current assets:
Cash and cash equivalents	$ 205,229	$ 172,704
Short-term investments	213,511	204,577
Accounts receivable, net	58,261	55,214
Inventories	135,634	136,384
Other current assets	16,660	11,931
Total current assets	629,295	580,810
Property and equipment, net	217,043	150,001
Long-term investments	3,264	3,241
Goodwill	6,571	6,571
Deferred tax assets, net	16,619	16,830
Other long-term assets	43,343	35,979
Total assets	916,135	793,432
Current liabilities:
Accounts payable	30,318	22,678
Accrued compensation and related benefits	28,724	18,799
Other accrued liabilities	45,984	38,962
Total current liabilities	105,026	80,439
Income tax liabilities	32,402	34,375
Other long-term liabilities	44,279	38,525
Total liabilities	181,707	153,339
Commitments and contingencies
Stockholders’ equity:
Common stock and additional paid-in capital: $0.001 par value; shares authorized: 150,000; shares issued and outstanding: 43,435 and 42,505, respectively	528,775	450,908
Retained earnings	215,692	194,728
Accumulated other comprehensive loss	(10,039)	(5,543)
Total stockholders’ equity	734,428	640,093
Total liabilities and stockholders’ equity	$ 916,135	$ 793,432

Condensed Consolidated Balanc_2

Condensed Consolidated Balance Sheets (Current Period Unaudited) (Parentheticals) - $ / shares shares in Thousands	Sep. 30, 2019	Dec. 31, 2018
Common stock, par value (in dollars per share)	$ 0.001	$ 0.001
Common stock, shares authorized (in shares)	150,000	150,000
Common stock, shares issued (in shares)	43,435	42,505
Common stock, shares outstanding (in shares)	43,435	42,505

Condensed Consolidated Statemen

Condensed Consolidated Statements of Operations (Unaudited) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Revenue	$ 168,813	$ 159,975	$ 461,183	$ 428,885
Cost of revenue	75,655	70,957	206,794	190,810
Gross profit	93,158	89,018	254,389	238,075
Operating expenses:
Research and development	27,742	25,630	80,746	70,720
Selling, general and administrative	34,692	29,552	100,302	85,431
Litigation expense	692	343	1,473	1,513
Total operating expenses	63,126	55,525	182,521	157,664
Income from operations	30,032	33,493	71,868	80,411
Interest and other income, net	2,257	2,714	7,827	5,387
Income before income taxes	32,289	36,207	79,695	85,798
Income tax expense	2,761	4,639	3,293	8,168
Net income	$ 29,528	$ 31,568	$ 76,402	$ 77,630
Net income per share
Basic (in dollars per share)	$ 0.68	$ 0.75	$ 1.77	$ 1.84
Diluted (in dollars per share)	$ 0.64	$ 0.71	$ 1.68	$ 1.75
Weighted-average shares outstanding:
Basic (in shares)	43,308	42,362	43,055	42,173
Diluted (in shares)	45,833	44,669	45,516	44,450

Condensed Consolidated Statem_2

Condensed Consolidated Statements of Comprehensive Income (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Net income	$ 29,528	$ 31,568	$ 76,402	$ 77,630
Other comprehensive loss, net of tax:
Foreign currency translation adjustments	(6,135)	(4,526)	(6,167)	(6,999)
Change in unrealized gain (loss) on available-for-sale securities, net of tax of $(38), $241, $(200) and $241, respectively	234	491	1,671	(554)
Other comprehensive loss, net of tax	(5,901)	(4,035)	(4,496)	(7,553)
Comprehensive income	$ 23,627	$ 27,533	$ 71,906	$ 70,077

Condensed Consolidated Statem_3

Condensed Consolidated Statements of Comprehensive Income (Unaudited) (Parentheticals) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Change in unrealized gain (loss) on available-for-sale securities, tax	$ (38)	$ 241	$ (200)	$ 241

Condensed Consolidated Statem_4

Condensed Consolidated Statements of Stockholders' Equity (Unaudited) - USD ($) shares in Thousands, $ in Thousands	Common Stock Including Additional Paid in Capital [Member]	Retained Earnings [Member]	AOCI Attributable to Parent [Member]	Total
Balance (in shares) at Dec. 31, 2017	41,614
Balance at Dec. 31, 2017	$ 376,586	$ 143,608	$ 1,813	$ 522,007
Net income	0	77,630	0	77,630
Other comprehensive loss	0	0	(7,553)	(7,553)
Dividends and dividend equivalents declared	$ 0	(40,798)	0	(40,798)
Common stock issued under employee equity incentive plans (in shares)	761
Common stock issued under employee equity incentive plans	$ 9,684	0	0	9,684
Common stock issued under employee stock purchase plan (in shares)	33
Common stock issued under employee stock purchase plan	$ 3,028	0	0	3,028
Stock-based compensation expense	45,787	0	0	45,787
Cumulative effect of a change in accounting principles at Sep. 30, 2018	$ 0	379	0	379
Balance (in shares) at Sep. 30, 2018	42,408
Balance at Sep. 30, 2018	$ 435,085	180,819	(5,740)	610,164
Balance (in shares) at Jun. 30, 2018	42,285
Balance at Jun. 30, 2018	$ 417,866	162,859	(1,705)	579,020
Net income	0	31,568	0	31,568
Other comprehensive loss	0	0	(4,035)	(4,035)
Dividends and dividend equivalents declared	$ 0	(13,608)	0	(13,608)
Common stock issued under employee equity incentive plans (in shares)	108
Common stock issued under employee equity incentive plans	$ 1,465	0	0	1,465
Common stock issued under employee stock purchase plan (in shares)	15
Common stock issued under employee stock purchase plan	$ 916	0	0	916
Stock-based compensation expense	14,838	0	0	14,838
Cumulative effect of a change in accounting principles at Sep. 30, 2018	$ 0	379	0	379
Balance (in shares) at Sep. 30, 2018	42,408
Balance at Sep. 30, 2018	$ 435,085	180,819	(5,740)	$ 610,164
Balance (in shares) at Dec. 31, 2018	42,505			42,505
Balance at Dec. 31, 2018	$ 450,908	194,728	(5,543)	$ 640,093
Net income	0	76,402	0	76,402
Other comprehensive loss	0	0	(4,496)	(4,496)
Dividends and dividend equivalents declared	$ 0	(55,438)	0	(55,438)
Common stock issued under employee equity incentive plans (in shares)	902
Common stock issued under employee equity incentive plans	$ 14,561	0	0	14,561
Common stock issued under employee stock purchase plan (in shares)	28
Common stock issued under employee stock purchase plan	$ 3,277	0	0	3,277
Stock-based compensation expense	$ 60,029	0	0	$ 60,029
Balance (in shares) at Sep. 30, 2019	43,435			43,435
Balance at Sep. 30, 2019	$ 528,775	215,692	(10,039)	$ 734,428
Balance (in shares) at Jun. 30, 2019	43,234
Balance at Jun. 30, 2019	$ 503,759	204,533	(4,138)	704,154
Net income	0	29,528	0	29,528
Other comprehensive loss	0	0	(5,901)	(5,901)
Dividends and dividend equivalents declared	$ 0	(18,369)	0	(18,369)
Common stock issued under employee equity incentive plans (in shares)	187
Common stock issued under employee equity incentive plans	$ 2,090	0	0	2,090
Common stock issued under employee stock purchase plan (in shares)	14
Common stock issued under employee stock purchase plan	$ 1,650	0	0	1,650
Stock-based compensation expense	$ 21,276	0	0	$ 21,276
Balance (in shares) at Sep. 30, 2019	43,435			43,435
Balance at Sep. 30, 2019	$ 528,775	$ 215,692	$ (10,039)	$ 734,428

Condensed Consolidated Statem_5

Condensed Consolidated Statements of Stockholders' Equity (Unaudited) (Parentheticals) - $ / shares	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Retained Earnings [Member]
Dividends and dividend equivalents declared per share (in dollars per share)	$ 0.40	$ 0.30	$ 1.20	$ 0.90
Dividends and dividend equivalents declared per share (in dollars per share)	$ 0.40	$ 0.30	$ 1.20	$ 0.90

Condensed Consolidated Statem_6

Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018
Cash flows from operating activities:
Net income	$ 76,402	$ 77,630
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	10,817	9,058
Gain on disposal and sale of property and equipment, net	(282)	0
Amortization of premium on available-for-sale securities	384	1,122
Gain on deferred compensation plan investments	(2,630)	(949)
Deferred taxes, net	(18)	3,169
Stock-based compensation expense	60,019	45,765
Changes in operating assets and liabilities:
Accounts receivable	(3,048)	(22,752)
Inventories	754	(37,496)
Other assets	(5,849)	(665)
Accounts payable	7,173	5,978
Accrued compensation and related benefits	10,328	7,838
Other accrued liabilities	7,453	4,635
Income tax liabilities	(6,186)	528
Net cash provided by operating activities	155,317	93,861
Cash flows from investing activities:
Purchases of property and equipment	(87,129)	(18,057)
Acquisition of in-place leases	(981)	0
Purchases of short-term investments	(106,409)	(86,021)
Proceeds from maturities and sales of short-term investments	98,814	83,679
Proceeds from sales of long-term investments	125	0
Proceeds from sales of property and equipment	9,268	0
Contributions to deferred compensation plan, net	(1,797)	(1,396)
Net cash used in investing activities	(88,109)	(21,795)
Cash flows from financing activities:
Property and equipment purchased on extended payment terms	(204)	0
Proceeds from common stock issued under employee equity incentive plans	14,561	9,684
Proceeds from common stock issued under employee stock purchase plan	3,277	3,028
Dividends and dividend equivalents paid	(48,641)	(34,381)
Net cash used in financing activities	(31,007)	(21,669)
Effect of change in exchange rates	(2,516)	(2,062)
Net increase in cash, cash equivalents and restricted cash	33,685	48,335
Cash, cash equivalents and restricted cash, beginning of period	172,818	82,874
Cash, cash equivalents and restricted cash, end of period	206,503	131,209
Supplemental disclosures for cash flow information:
Cash paid for taxes	9,472	6,388
Non-cash investing and financing activities:
Liability accrued for property and equipment purchases	4,969	1,563
Liability accrued for dividends and dividend equivalents	$ 20,866	$ 15,397

Note 1 - Basis of Presentation

Note 1 - Basis of Presentation	9 Months Ended
Note 1 - Basis of Presentation	Sep. 30, 2019
Notes to Financial Statements
Organization, Consolidation and Presentation of Financial Statements Disclosure [Text Block]	1. The accompanying unaudited condensed consolidated financial statements have been prepared by Monolithic Power Systems, Inc. (the “Company” or “MPS”) in accordance with the rules and regulations of the Securities and Exchange Commission (the “SEC”). Certain information and disclosures normally included in financial statements prepared in accordance with accounting principles generally accepted in the United States (“GAAP”) have been condensed or omitted in accordance with these accounting principles, rules and regulations. The information in this report should be read in conjunction with the Company’s audited consolidated financial statements and notes thereto included in the Annual Report on Form 10 December 31, 2018, March 1, 2019. In the opinion of management, the accompanying unaudited condensed consolidated financial statements reflect all adjustments (consisting only of normal recurring adjustments) necessary to present fairly the Company’s financial position, results of operations and cash flows for the interim periods presented. The financial statements contained in this Form 10 not may December 31, 2019 Summary of Significant Accounting Policies Except for the changes related to leases discussed in Note 6, no three nine September 30, 2019, 10 December 31, 2018. Recently Adopted Accounting Pronouncement In February 2016, No. 2016 02, Leases (Topic 842 12 January 1, 2019 not not January 1, 2019. Upon adoption, the Company recognized ROU assets and lease liabilities of its outstanding operating leases on the Condensed Consolidated Balance Sheets, primarily related to real estate. The adoption did not 6 Recent Accounting Pronounce ments Not September 30, 2019 In August 2018, No. 2018 13, Fair Value Measurement (Topic 820 3 December 15, 2019. not In January 2017, No. 2017 04, Intangibles – Goodwill and Other (Topic 350 two not December 15, 2019. not In June 2016, No. 2016 13, Financial Instruments – Credit Losses (Topic 326 December 15, 2019, December 15, 2018. not

Note 2 - Revenue Recognition

Note 2 - Revenue Recognition	9 Months Ended
Note 2 - Revenue Recognition	Sep. 30, 2019
Notes to Financial Statements
Revenue from Contract with Customer [Text Block]	2. Revenue from Product Sales The Company generates revenue primarily from product sales, which include assembled and tested integrated circuits, as well as dies in wafer form. These product sales were 99% and 98% of the Company’s total revenue for the three September 30, 2019 2018, nine September 30, 2019 2018, third not 8 The Company sells its products primarily through third three September 30, 2019 2018, nine September 30, 2019 2018, not The Company recognizes revenue when it satisfies a performance obligation by transferring control of the promised goods or services to its customers, in an amount that reflects the consideration the Company expects to be entitled to in exchange for those goods or services. The Company excludes taxes assessed by government authorities, such as sales taxes, from revenue. Product sales consist of a single performance obligation that the Company satisfies at a point in time. The Company recognizes product revenue from distributors and direct end customers when the following events have occurred: (a) the Company has transferred physical possession of the products, (b) the Company has a present right to payment, (c) the customer has legal title to the products, and (d) the customer bears significant risks and rewards of ownership of the products. In accordance with the shipping terms specified in the contracts, these criteria are generally met when the products are shipped from the Company’s facilities (such as the “Ex Works” shipping term) or delivered to the customers’ locations (such as the “Delivered Duty Paid” shipping term). Under certain consignment agreements, revenue is not not Variable Consideration The Company accounts for price adjustment and stock rotation rights as variable consideration that reduces the transaction price, and recognizes that reduction in the same period the associated revenue is recognized. Three U.S.-based distributors have price adjustment rights when they sell the Company’s products to their end customers at a price that is lower than the distribution price invoiced by the Company. When the Company receives claims from the distributors that products have been sold to the end customers at the lower price, the Company issues the distributors credit memos for the price adjustments. The Company estimates the price adjustments using the expected value method based on an analysis of historical claims, at both the distributor and product level, as well as an assessment of any known trends of product sales mix. Other U.S. distributors and non-U.S. distributors, which make up the majority of the Company’s total sales to distributors, do not Certain distributors have limited stock rotation rights that permit the return of a small percentage of the previous six Contract Balances The Company records a receivable when it has an unconditional right to receive consideration after the performance obligations are satisfied. As of September 30, 2019 December 31, 2018, not September 30, 2019 December 31, 2018. For certain customers located in Asia, the Company requires cash payments two September 30, 2019 December 31, 2018, nine September 30, 2019 nine September 30, 2019, December 31, 2018. Practical Expedients The Company has elected the practical expedient to expense sales commissions as incurred because the amortization period would have been one The Company’s standard payment terms generally require customers to pay 30 to 60 days after the Company satisfies the performance obligations. For those customers who are required to pay in advance, the Company satisfies the performance obligations generally within two not The Company’s unsatisfied performance obligations primarily include products held in consignment arrangements and customer purchase orders for products that the Company has not one not

Note 3 - Stock-based Compensati

Note 3 - Stock-based Compensation	9 Months Ended
Note 3 - Stock-based Compensation	Sep. 30, 2019
Notes to Financial Statements
Share-based Payment Arrangement [Text Block]	3. 2014 “2014 The Board of Directors adopted the 2014 April 2013, June 2013. October 2014, 2014 2014 November 13, 2014 2014 November 13, 2024. September 30, 2019, 2014 Stock-Based Compensation Expense The Company recognized stock-based compensation expenses as follows (in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2019 2018 2019 2018 Cost of revenue $ 641 $ 471 $ 1,834 $ 1,384 Research and development 4,960 3,979 14,801 12,168 Selling, general and administrative 15,699 10,393 43,384 32,213 Total stock-based compensation expense $ 21,300 $ 14,843 $ 60,019 $ 45,765 Tax benefit related to stock-based compensation $ 595 $ 764 $ 2,139 $ 2,723 Restricted Stock Units (“RSUs”) The Company’s RSUs include time-based RSUs, RSUs with performance conditions (“PSUs”), RSUs with market conditions (“MSUs”), and RSUs with both market and performance conditions (“MPSUs”). Vesting of awards with performance conditions or market conditions is subject to the achievement of pre-determined performance goals and the approval of such achievement by the Compensation Committee of the Board of Directors (the “Compensation Committee”). All awards include service conditions which require continued employment with the Company. A summary of RSU activity is presented in the table below (in thousands, except per-share amounts): Time-Based RSUs PSUs and MPSUs MSUs Total Number of Shares Weighted- Average Grant Date Fair Value Per Share Number of Shares Weighted- Average Grant Date Fair Value Per Share Number of Shares Weighted- Average Grant Date Fair Value Per Share Number of Shares Weighted- Average Grant Date Fair Value Per Share Outstanding at January 1, 2019 240 $ 95.38 2,174 $ 61.61 2,219 $ 35.69 4,633 $ 50.94 Granted 47 $ 141.03 535 (1) $ 98.45 - $ - 582 $ 101.89 Vested (88 ) $ 79.91 (571 ) $ 54.41 (243 ) $ 23.57 (902 ) $ 48.61 Forfeited (6 ) $ 110.23 (43 ) $ 42.72 (7 ) $ 68.48 (56 ) $ 53.06 Outstanding at September 30, 2019 193 $ 113.22 2,095 $ 73.37 1,969 $ 37.08 4,257 $ 58.38 ( 1 Amount reflects the number of PSUs that may The intrinsic value related to vested RSUs was $26.1 million and $13.9 million for the three September 30, 2019 2018, nine September 30, 2019 2018, September 30, 2019, September 30, 2019, Cash proceeds from vested PSUs with a purchase price totaled $14.6 million and $9.6 million for the nine September 30, 2019 2018, Time-Based RSUs: For the nine September 30, 2019, four one 2019 In February 2019, two 2019 2020 two “2019 2019 2019 first 2021 2019 two 2019 The 2019 not not 2019 2004 For the three September 30, 2019 2018, nine September 30, 2019 2018, September 30, 2019, The intrinsic value of the shares issued was $0.4 million and $0.6 million for the three September 30, 2019 2018, nine September 30, 2019 2018, September 30, 2019, first 2020. Three Months Ended September 30, Nine Months Ended September 30, 2019 2018 2019 2018 Expected term (in years) 0.5 0.5 0.5 0.5 Expected volatility 36.7 % 30.8 % 37.0 % 29.5 % Risk-free interest rate 1.9 % 2.2 % 2.2 % 2.0 % Dividend yield 1.1 % 0.9 % 1.1 % 1.0 % Cash proceeds from the shares issued under the ESPP were $3.3 million and $3.0 million for the nine September 30, 2019 2018,

Note 4 - Balance Sheet Componen

Note 4 - Balance Sheet Components	9 Months Ended
Note 4 - Balance Sheet Components	Sep. 30, 2019
Notes to Financial Statements
Supplemental Balance Sheet Disclosures [Text Block]	4. Inventories Inventories consist of the following (in thousands): September 30, December 31, 2019 2018 Raw materials $ 27,001 $ 43,017 Work in process 43,076 38,674 Finished goods 65,557 54,693 Total $ 135,634 $ 136,384 Other Current Assets Other current assets consist of the following (in thousands): September 30, December 31, 2019 2018 RSU tax withholding proceeds receivable $ 5,331 $ 39 Prepaid expense 4,024 3,425 Assets for product returns 2,261 1,602 Interest receivable 1,869 1,441 Value-added tax receivable 628 423 Prepaid wafer refund receivable - 4,297 Other 2,547 704 Total $ 16,660 $ 11,931 Other Long-Term Assets Other long-term assets consist of the following (in thousands): September 30, December 31, 2019 2018 Deferred compensation plan assets $ 36,397 $ 31,970 Operating lease ROU assets 3,102 - Prepaid expense 2,274 2,713 Other 1,570 1,296 Total $ 43,343 $ 35,979 Other Accrued Liabilities Other accrued liabilities consist of the following (in thousands): September 30, December 31, 2019 2018 Dividends and dividend equivalents $ 21,895 $ 15,044 Stock rotation and sales returns 7,884 5,363 Customer prepayments 4,160 2,520 Income tax payable 2,778 7,018 Operating lease liabilities 1,318 - Warranty 1,267 4,564 Commissions 976 1,369 Other 5,706 3,084 Total $ 45,984 $ 38,962 Other Long-Term Liabilities Other long-term liabilities consist of the following (in thousands): September 30, December 31, 2019 2018 Deferred compensation plan liabilities $ 36,968 $ 32,283 Dividend equivalents 6,091 6,145 Operating lease liabilities 1,190 - Other 30 97 Total $ 44,279 $ 38,525

Note 5 - Real Estate Transactio

Note 5 - Real Estate Transaction	9 Months Ended
Note 5 - Real Estate Transaction	Sep. 30, 2019
Notes to Financial Statements
Real Estate Transaction [Text Block]	5. In March 2019, The purchase price allocation was as follows (in thousands): Building $ 30,078 Land 22,254 In-place leases 981 Total $ 53,313 The fair value of the building was determined based on the income approach, which considered the discounted cash flows and direct capitalization analysis, and the sales comparison approach. The fair value of land was determined based on the sales comparison approach. The fair value of the in-place leases was determined primarily based on the analysis of the economic benefits of certain cost savings attributable to the leases. The building is depreciated over a useful life of 40 years and the in-place leases are amortized over the average remaining lease terms of 3.5 years. Land is not

Note 6 - Leases

Note 6 - Leases	9 Months Ended
Note 6 - Leases	Sep. 30, 2019
Notes to Financial Statements
Leases Disclosure [Text Block]	6. Lessee The Company has operating leases primarily for administrative and sales and marketing offices, manufacturing operations and research and development facilities, employee housing units, and certain equipment. These leases have remaining lease terms from less than a year to four five not Operating lease ROU assets and liabilities are recognized at the commencement date based on the present value of lease payments over the lease term. ROU assets also include any initial direct costs incurred and prepaid lease payments, less lease incentives received. As of September 30, 2019, As permitted by Topic 842, not 12 not The following tables summarize certain information related to the leases (in thousands, except percentages): Three Months Ended Nine Months Ended September 30, 2019 September 30, 2019 Lease costs: Operating lease costs $ 377 $ 1,013 Short-term and other lease costs 102 394 Total lease costs $ 479 $ 1,407 Three Months Ended Nine Months Ended September 30, 2019 September 30, 2019 Cash paid for amounts included in the measurement of lease liabilities: Operating cash flows from operating leases $ 299 $ 1,026 ROU assets obtained in exchange for operating lease liabilities (1) $ 869 $ 3,450 September 30, 2019 Weighted-average remaining lease term (in years) 2.3 Weighted-average discount rate 3.9 % ( 1 For the nine September 30, 2019, January 1, 2019. As of September 30, 2019, 2019 (remaining three months) $ 364 2020 1,241 2021 634 2022 379 2023 22 Total remaining lease payments 2,640 Less: imputed interest (132 ) Total lease liabilities $ 2,508 Reported as: Current liabilities $ 1,318 Long-term liabilities $ 1,190 Lessor The Company owns certain office buildings and leases a portion of these properties to third two five five For the three nine September 30, 2019, September 30, 2019, 2019 (remaining three months) $ 279 2020 1,539 2021 1,384 2022 1,136 2023 602 2024 and beyond 597 Total $ 5,537

Note 7 - Net Income Per Share

Note 7 - Net Income Per Share	9 Months Ended
Note 7 - Net Income Per Share	Sep. 30, 2019
Notes to Financial Statements
Earnings Per Share [Text Block]	7. Basic net income per share is computed by dividing net income by the weighted-average number of common shares outstanding for the period. Diluted net income per share reflects the potential dilution that would occur if outstanding securities or other contracts to issue common stock were exercised or converted into common shares, and calculated using the treasury stock method. Contingently issuable shares, including equity awards with performance conditions or market conditions, are considered outstanding common shares and included in the basic net income per share as of the date that all necessary conditions to earn the awards have been satisfied. Prior to the end of the contingency period, the number of contingently issuable shares included in the diluted net income per share is based on the number of shares, if any, that would be issuable under the terms of the arrangement at the end of the reporting period. The Company’s outstanding RSUs contain forfeitable rights to receive cash dividend equivalents, which are accumulated and paid to the employees when the underlying RSUs vest. Dividend equivalents accumulated on the underlying RSUs are forfeited if the employees do not not not The following table sets forth the computation of basic and diluted net income per share (in thousands, except per-share amounts): Three Months Ended September 30, Nine Months Ended September 30, 2019 2018 2019 2018 Numerator: Net income $ 29,528 $ 31,568 $ 76,402 $ 77,630 Denominator: Weighted-average outstanding shares - basic 43,308 42,362 43,055 42,173 Effect of dilutive securities 2,525 2,307 2,461 2,277 Weighted-average outstanding shares - diluted 45,833 44,669 45,516 44,450 Net income per share: Basic $ 0.68 $ 0.75 $ 1.77 $ 1.84 Diluted $ 0.64 $ 0.71 $ 1.68 $ 1.75

Note 8 - Segment and Geographic

Note 8 - Segment and Geographic Information	9 Months Ended
Note 8 - Segment and Geographic Information	Sep. 30, 2019
Notes to Financial Statements
Segment Reporting Disclosure [Text Block]	8. The Company operates in one reportable segment that includes the design, development, marketing and sale of high-performance analog solutions for the computing and storage, automotive, industrial, communications and consumer markets. The Company’s chief operating decision maker is its Chief Executive Officer, who reviews financial information presented on a consolidated basis for purposes of allocating resources and evaluating financial performance. The Company derives a majority of its revenue from sales to customers located outside North America, with geographic revenue based on the customers’ ship-to locations. The Company sells its products primarily through third 10% 10% Revenue Accounts Receivable Three Months Ended September 30, Nine Months Ended September 30, September 30, December 31, Customer 2019 2018 2019 2018 2019 2018 Company A (distributor) 24 % 23 % 23 % 21 % 25 % 25 % Company B (distributor) * 10 % * 10 % 12 % 16 % Company A (value-added reseller) * * * * 10 % * * Represents less than 10%. The Company’s agreements with these third may may not The following is a summary of revenue by geographic regions (in thousands): Three Months Ended September 30, Nine Months Ended September 30, Country or Region 2019 2018 2019 2018 China $ 105,857 $ 91,509 $ 276,892 $ 245,580 Taiwan 18,547 20,774 55,912 55,315 Europe 12,047 12,579 38,071 36,696 Korea 11,990 11,406 31,224 30,046 Southeast Asia 7,904 11,259 23,698 28,261 Japan 8,150 6,895 21,084 18,994 United States 4,225 5,375 14,044 13,404 Other 93 178 258 589 Total $ 168,813 $ 159,975 $ 461,183 $ 428,885 The following is a summary of revenue by product family (in thousands): Three Months Ended September 30, Nine Months Ended September 30, Product Family 2019 2018 2019 2018 DC to DC $ 159,723 $ 147,727 $ 432,125 $ 394,492 Lighting Control 9,090 12,248 29,058 34,393 Total $ 168,813 $ 159,975 $ 461,183 $ 428,885 The following is a summary of property and equipment, net, by geographic regions (in thousands): September 30, December 31, Country 2019 2018 China $ 105,030 $ 93,096 United States 93,967 39,054 Taiwan 16,750 16,972 Other 1,296 879 Total $ 217,043 $ 150,001

Note 9 - Commitments and Contin

Note 9 - Commitments and Contingencies	9 Months Ended
Note 9 - Commitments and Contingencies	Sep. 30, 2019
Notes to Financial Statements
Commitments and Contingencies Disclosure [Text Block]	9. Product Warranties The following table presents changes in the warranty reserve (in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2019 2018 2019 2018 Balance at beginning of period $ 1,748 $ 3,951 $ 4,564 $ 2,416 Warranty provision for product sales 92 3,840 671 5,654 Settlements made (326 ) (36 ) (2,625 ) (100 ) Unused warranty provision (247 ) (2,821 ) (1,343 ) (3,036 ) Balance at end of period $ 1,267 $ 4,934 $ 1,267 $ 4,934 Purchase Commitments The Company has outstanding purchase commitments with its suppliers and other parties that require the future purchase of goods or services, which primarily consist of wafer purchases, assembly and other manufacturing services, construction services and license arrangements. As of September 30, 2019, Litigation The Company is a party to actions and proceedings in the ordinary course of business, including potential litigation initiated by its stockholders, challenges to the enforceability or validity of its intellectual property, claims that the Company’s products infringe on the intellectual property rights of others, and employment matters. These proceedings often involve complex questions of fact and law and may September 30, 2019, no

Note 10 - Cash, Cash Equivalent

Note 10 - Cash, Cash Equivalents, Investments and Restricted Cash	9 Months Ended
	Sep. 30, 2019
Notes to Financial Statements
Financial Instruments Disclosure [Text Block]	10. The following is a summary of the Company’s cash, cash equivalents and investments (in thousands): September 30, December 31, 2019 2018 Cash, cash equivalents and investments: Cash $ 162,741 $ 131,569 Money market funds 39,982 41,135 Corporate debt securities 195,667 170,909 U.S. treasuries and government agency bonds 20,350 32,068 Certificates of deposit - 1,600 Auction-rate securities backed by student-loan notes 3,264 3,241 Total $ 422,004 $ 380,522 September 30, December 31, 2019 2018 Reported as: Cash and cash equivalents $ 205,229 $ 172,704 Short-term investments 213,511 204,577 Long-term investments 3,264 3,241 Total $ 422,004 $ 380,522 The contractual maturities of the Company’s short-term and long-term available-for-sale investments are as follows (in thousands): September 30, December 31, 2019 2018 Due in less than 1 year $ 142,336 $ 125,845 Due in 1 - 5 years 71,175 78,732 Due in greater than 5 years 3,264 3,241 Total $ 216,775 $ 207,818 The following tables summarize the unrealized gain and loss positions related to the Company’s available-for sale investments (in thousands): September 30, 2019 Amortized Cost Unrealized Gains Unrealized Losses Total Fair Value Fair Value of Investments in Unrealized Loss Position Money market funds $ 39,982 $ - $ - $ 39,982 $ - Corporate debt securities 195,471 324 (128 ) 195,667 83,247 U.S. treasuries and government agency bonds 20,341 11 (2 ) 20,350 7,998 Auction-rate securities backed by student-loan notes 3,445 - (181 ) 3,264 3,264 Total $ 259,239 $ 335 $ (311 ) $ 259,263 $ 94,509 December 31, 2018 Amortized Cost Unrealized Gains Unrealized Losses Total Fair Value Fair Value of Investments in Unrealized Loss Position Money market funds $ 41,135 $ - $ - $ 41,135 $ - Corporate debt securities 172,288 7 (1,386 ) 170,909 166,204 U.S. treasuries and government agency bonds 32,207 2 (141 ) 32,068 28,507 Certificates of deposit 1,600 - - 1,600 - Auction-rate securities backed by student-loan notes 3,570 - (329 ) 3,241 3,241 Total $ 250,800 $ 9 $ (1,856 ) $ 248,953 $ 197,952 As of September 30, 2019 December 31, 2018, 12 September 30, 2019, not Restricted Cash The following table provides a reconciliation of cash, cash equivalents and restricted cash reported on the Condensed Consolidated Balance Sheets to the amounts reported on the Condensed Consolidated Statements of Cash Flows (in thousands): September 30, December 31, 2019 2018 Cash and cash equivalents $ 205,229 $ 172,704 Restricted cash included in other current assets 1,161 - Restricted cash included in other long-term assets 113 114 Total cash, cash equivalents and restricted cash reported on the Condensed Consolidated Statements of Cash Flows $ 206,503 $ 172,818 As of September 30, 2019, September 30, 2019 December 31, 2018,

Note 11 - Fair Value Measuremen

Note 11 - Fair Value Measurements	9 Months Ended
Note 11 - Fair Value Measurements	Sep. 30, 2019
Notes to Financial Statements
Fair Value Disclosures [Text Block]	11. The following tables summarize the fair value measurement of the financial assets (in thousands): Fair Value Measurement at September 30, 2019 Total Level 1 Level 2 Level 3 Money market funds $ 39,982 $ 39,982 $ - $ - Corporate debt securities 195,667 - 195,667 - U.S. treasuries and government agency bonds 20,350 - 20,350 - Auction-rate securities backed by student-loan notes 3,264 - - 3,264 Mutual funds and money market funds under deferred compensation plan 19,968 19,968 - - Total $ 279,231 $ 59,950 $ 216,017 $ 3,264 Fair Value Measurement at December 31, 2018 Total Level 1 Level 2 Level 3 Money market funds $ 41,135 $ 41,135 $ - $ - Corporate debt securities 170,909 - 170,909 - U.S. treasuries and government agency bonds 32,068 - 32,068 - Certificates of deposit 1,600 - 1,600 - Auction-rate securities backed by student-loan notes 3,241 - - 3,241 Mutual funds and money market funds under deferred compensation plan 18,867 18,867 - - Total $ 267,820 $ 60,002 $ 204,577 $ 3,241 ● Level 1—includes ● Level 2—includes may third ● Level 3—includes The Company’s level 3 Balance at January 1, 2019 $ 3,241 Change in unrealized gain included in other comprehensive income 148 Sale and settlement at par (125 ) Balance at September 30, 2019 $ 3,264 The Company determined the fair value of the auction-rate securities using a discounted cash flow model with the following assumptions: September 30, December 31, 2019 2018 Time-to-liquidity (in years) 2 - 3 2 - 3 Discount rate 3.7% - 7.9% 4.9% - 10.1%

Note 12 - Deferred Compensation

Note 12 - Deferred Compensation Plan	9 Months Ended
Note 12 - Deferred Compensation Plan	Sep. 30, 2019
Notes to Financial Statements
Compensation and Employee Benefit Plans [Text Block]	12. The following table summarizes the deferred compensation plan balances on the Condensed Consolidated Balance Sheets (in thousands): September 30, December 31, 2019 2018 Deferred compensation plan asset components: Cash surrender value of corporate-owned life insurance policies $ 16,429 $ 13,103 Fair value of mutual funds and money market funds 19,968 18,867 Total $ 36,397 $ 31,970 Deferred compensation plan assets reported in: Other long-term assets $ 36,397 $ 31,970 Deferred compensation plan liabilities reported in: Accrued compensation and related benefits (short-term) $ 425 $ 447 Other long-term liabilities 36,968 32,283 Total $ 37,393 $ 32,730

Note 13 - Interest and Other In

Note 13 - Interest and Other Income, Net	9 Months Ended
Note 13 - Interest and Other Income, Net	Sep. 30, 2019
Notes to Financial Statements
Other Nonoperating Income and Expense [Text Block]	13. The components of interest and other income, net, are as follows (in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2019 2018 2019 2018 Interest income $ 1,850 $ 1,583 $ 5,207 $ 4,606 Amortization of premium on available-for-sale securities (168 ) (314 ) (384 ) (1,122 ) Gain on deferred compensation plan investments 74 717 2,630 949 Foreign currency exchange gain 175 700 47 915 Other 326 28 327 39 Total $ 2,257 $ 2,714 $ 7,827 $ 5,387 For the three nine September 30, 2019,

Note 14 - Income Taxes

Note 14 - Income Taxes	9 Months Ended
Note 14 - Income Taxes	Sep. 30, 2019
Notes to Financial Statements
Income Tax Disclosure [Text Block]	14. The income tax provision for interim periods is generally determined using an estimate of the Company’s annual effective tax rate and adjusted for discrete items, if any, in the relevant period. Each quarter the estimate of the annual effective tax rate is updated, and if the Company’s estimated tax rate changes, a cumulative adjustment is made. The income tax expense for the three September 30, 2019 nine September 30, 2019 The income tax provision for the three September 30, 2018 nine September 30, 2018 For the three nine September 30, 2019, three nine September 30, 2018, The Company’s uncertain tax positions relate to the allocation of income and deductions between the Company’s global entities and to the determination of the research and development tax credit. It is reasonably possible that over the next twelve may not July 2015, Altera Corp. v. Commissioner, December 2015, June 2016. June 2019, July 2019, not September 30, 2019.

Note 15 - Accumulated Other Com

Note 15 - Accumulated Other Comprehensive Loss	9 Months Ended
Note 15 - Accumulated Other Comprehensive Loss	Sep. 30, 2019
Notes to Financial Statements
Comprehensive Income (Loss) Note [Text Block]	15. The following table summarizes the changes in accumulated other comprehensive loss (in thousands): Unrealized Gains (Losses) on Available-for-Sale Securities Foreign Currency Translation Adjustments Total Balance as of January 1, 2019 $ (1,638 ) $ (3,905 ) $ (5,543 ) Other comprehensive income before reclassifications 924 3,677 4,601 Tax effect (98 ) - (98 ) Other comprehensive income 826 3,677 4,503 Balance as of March 31, 2019 (812 ) (228 ) (1,040 ) Other comprehensive income (loss) before reclassifications 675 (3,709 ) (3,034 ) Tax effect (64 ) - (64 ) Other comprehensive income (loss) 611 (3,709 ) (3,098 ) Balance as of June 30, 2019 (201 ) (3,937 ) (4,138 ) Other comprehensive income (loss) before reclassifications 272 (6,135 ) (5,863 ) Tax effect (38 ) - (38 ) Other comprehensive income (loss) 234 (6,135 ) (5,901 ) Balance as of September 30, 2019 $ 33 $ (10,072 ) $ (10,039 )

Note 16 - Dividends and Dividen

Note 16 - Dividends and Dividend Equivalents	9 Months Ended
Note 16 - Dividends and Dividend Equivalents	Sep. 30, 2019
Notes to Financial Statements
Dividends And Dividend Equivalents [Text Block]	16. Cash Dividend Program In June 2014, Three Months Ended September 30, Nine Months Ended September 30, 2019 2018 2019 2018 Dividend declared per share $ 0.40 $ 0.30 $ 1.20 $ 0.90 Total amount $ 17,341 $ 12,722 $ 51,782 $ 38,052 As of September 30, 2019 December 31, 2018, The declaration of any future cash dividends is at the discretion of the Board of Directors and will depend on, among other things, the Company’s financial condition, results of operations, capital requirements, business conditions, and other factors that the Board of Directors may The Company anticipates that cash used for future dividend payments will come from its domestic cash, cash generated from ongoing U.S. operations, and cash repatriated from its Bermuda subsidiary. Earnings from other foreign subsidiaries will continue to be indefinitely reinvested. Cash Dividend Equivalent Rights Under the Company’s stock plans, outstanding RSUs contain rights to receive cash dividend equivalents, which entitle employees who hold RSUs to the same dividend value per share as holders of common stock. The dividend equivalents are accumulated and paid to the employees when the underlying RSUs vest. Dividend equivalents accumulated on the underlying RSUs are forfeited if the employees do not not September 30, 2019 December 31, 2018,

Significant Accounting Policies

Significant Accounting Policies (Policies)	9 Months Ended
Significant Accounting Policies (Policies)	Sep. 30, 2019
Accounting Policies [Abstract]
Basis of Accounting, Policy [Policy Text Block]	The accompanying unaudited condensed consolidated financial statements have been prepared by Monolithic Power Systems, Inc. (the “Company” or “MPS”) in accordance with the rules and regulations of the Securities and Exchange Commission (the “SEC”). Certain information and disclosures normally included in financial statements prepared in accordance with accounting principles generally accepted in the United States (“GAAP”) have been condensed or omitted in accordance with these accounting principles, rules and regulations. The information in this report should be read in conjunction with the Company’s audited consolidated financial statements and notes thereto included in the Annual Report on Form 10 December 31, 2018, March 1, 2019. In the opinion of management, the accompanying unaudited condensed consolidated financial statements reflect all adjustments (consisting only of normal recurring adjustments) necessary to present fairly the Company’s financial position, results of operations and cash flows for the interim periods presented. The financial statements contained in this Form 10 not may December 31, 2019
New Accounting Pronouncements, Policy [Policy Text Block]	Recently Adopted Accounting Pronouncement In February 2016, No. 2016 02, Leases (Topic 842 12 January 1, 2019 not not January 1, 2019. Upon adoption, the Company recognized ROU assets and lease liabilities of its outstanding operating leases on the Condensed Consolidated Balance Sheets, primarily related to real estate. The adoption did not 6 Recent Accounting Pronounce ments Not September 30, 2019 In August 2018, No. 2018 13, Fair Value Measurement (Topic 820 3 December 15, 2019. not In January 2017, No. 2017 04, Intangibles – Goodwill and Other (Topic 350 two not December 15, 2019. not In June 2016, No. 2016 13, Financial Instruments – Credit Losses (Topic 326 December 15, 2019, December 15, 2018. not

Note 3 - Stock-based Compensa_2

Note 3 - Stock-based Compensation (Tables)	9 Months Ended
Note 3 - Stock-based Compensation (Tables)	Sep. 30, 2019
Notes Tables
Share-based Payment Arrangement, Cost by Plan [Table Text Block]	Three Months Ended September 30, Nine Months Ended September 30, 2019 2018 2019 2018 Cost of revenue $ 641 $ 471 $ 1,834 $ 1,384 Research and development 4,960 3,979 14,801 12,168 Selling, general and administrative 15,699 10,393 43,384 32,213 Total stock-based compensation expense $ 21,300 $ 14,843 $ 60,019 $ 45,765 Tax benefit related to stock-based compensation $ 595 $ 764 $ 2,139 $ 2,723
Share-based Payment Arrangement, Restricted Stock and Restricted Stock Unit, Activity [Table Text Block]	Time-Based RSUs PSUs and MPSUs MSUs Total Number of Shares Weighted- Average Grant Date Fair Value Per Share Number of Shares Weighted- Average Grant Date Fair Value Per Share Number of Shares Weighted- Average Grant Date Fair Value Per Share Number of Shares Weighted- Average Grant Date Fair Value Per Share Outstanding at January 1, 2019 240 $ 95.38 2,174 $ 61.61 2,219 $ 35.69 4,633 $ 50.94 Granted 47 $ 141.03 535 (1) $ 98.45 - $ - 582 $ 101.89 Vested (88 ) $ 79.91 (571 ) $ 54.41 (243 ) $ 23.57 (902 ) $ 48.61 Forfeited (6 ) $ 110.23 (43 ) $ 42.72 (7 ) $ 68.48 (56 ) $ 53.06 Outstanding at September 30, 2019 193 $ 113.22 2,095 $ 73.37 1,969 $ 37.08 4,257 $ 58.38
Schedule of Share-based Payment Award, Employee Stock Purchase Plan, Valuation Assumptions [Table Text Block]	Three Months Ended September 30, Nine Months Ended September 30, 2019 2018 2019 2018 Expected term (in years) 0.5 0.5 0.5 0.5 Expected volatility 36.7 % 30.8 % 37.0 % 29.5 % Risk-free interest rate 1.9 % 2.2 % 2.2 % 2.0 % Dividend yield 1.1 % 0.9 % 1.1 % 1.0 %

Note 4 - Balance Sheet Compon_2

Note 4 - Balance Sheet Components (Tables)	9 Months Ended
Note 4 - Balance Sheet Components (Tables)	Sep. 30, 2019
Notes Tables
Schedule of Inventory, Current [Table Text Block]	September 30, December 31, 2019 2018 Raw materials $ 27,001 $ 43,017 Work in process 43,076 38,674 Finished goods 65,557 54,693 Total $ 135,634 $ 136,384
Schedule of Other Current Assets [Table Text Block]	September 30, December 31, 2019 2018 RSU tax withholding proceeds receivable $ 5,331 $ 39 Prepaid expense 4,024 3,425 Assets for product returns 2,261 1,602 Interest receivable 1,869 1,441 Value-added tax receivable 628 423 Prepaid wafer refund receivable - 4,297 Other 2,547 704 Total $ 16,660 $ 11,931
Schedule of Other Assets, Noncurrent [Table Text Block]	September 30, December 31, 2019 2018 Deferred compensation plan assets $ 36,397 $ 31,970 Operating lease ROU assets 3,102 - Prepaid expense 2,274 2,713 Other 1,570 1,296 Total $ 43,343 $ 35,979
Schedule of Accrued Liabilities [Table Text Block]	September 30, December 31, 2019 2018 Dividends and dividend equivalents $ 21,895 $ 15,044 Stock rotation and sales returns 7,884 5,363 Customer prepayments 4,160 2,520 Income tax payable 2,778 7,018 Operating lease liabilities 1,318 - Warranty 1,267 4,564 Commissions 976 1,369 Other 5,706 3,084 Total $ 45,984 $ 38,962
Other Noncurrent Liabilities [Table Text Block]	September 30, December 31, 2019 2018 Deferred compensation plan liabilities $ 36,968 $ 32,283 Dividend equivalents 6,091 6,145 Operating lease liabilities 1,190 - Other 30 97 Total $ 44,279 $ 38,525

Note 5 - Real Estate Transact_2

Note 5 - Real Estate Transaction (Tables)	9 Months Ended
Note 5 - Real Estate Transaction (Tables)	Sep. 30, 2019
Notes Tables
Asset Acquisition, Allocation of Consideration [Table Text Block]	Building $ 30,078 Land 22,254 In-place leases 981 Total $ 53,313

Note 6 - Leases (Tables)

Note 6 - Leases (Tables)	9 Months Ended
Note 6 - Leases (Tables)	Sep. 30, 2019
Notes Tables
Lease, Cost [Table Text Block]	Three Months Ended Nine Months Ended September 30, 2019 September 30, 2019 Lease costs: Operating lease costs $ 377 $ 1,013 Short-term and other lease costs 102 394 Total lease costs $ 479 $ 1,407 Three Months Ended Nine Months Ended September 30, 2019 September 30, 2019 Cash paid for amounts included in the measurement of lease liabilities: Operating cash flows from operating leases $ 299 $ 1,026 ROU assets obtained in exchange for operating lease liabilities (1) $ 869 $ 3,450 September 30, 2019 Weighted-average remaining lease term (in years) 2.3 Weighted-average discount rate 3.9 %
Lessee, Operating Lease, Liability, Maturity [Table Text Block]	2019 (remaining three months) $ 364 2020 1,241 2021 634 2022 379 2023 22 Total remaining lease payments 2,640 Less: imputed interest (132 ) Total lease liabilities $ 2,508 Reported as: Current liabilities $ 1,318 Long-term liabilities $ 1,190
Lessor, Operating Lease, Payments to be Received, Maturity [Table Text Block]	2019 (remaining three months) $ 279 2020 1,539 2021 1,384 2022 1,136 2023 602 2024 and beyond 597 Total $ 5,537

Note 7 - Net Income Per Share (

Note 7 - Net Income Per Share (Tables)	9 Months Ended
Note 7 - Net Income Per Share (Tables)	Sep. 30, 2019
Notes Tables
Schedule of Earnings Per Share, Basic and Diluted [Table Text Block]	Three Months Ended September 30, Nine Months Ended September 30, 2019 2018 2019 2018 Numerator: Net income $ 29,528 $ 31,568 $ 76,402 $ 77,630 Denominator: Weighted-average outstanding shares - basic 43,308 42,362 43,055 42,173 Effect of dilutive securities 2,525 2,307 2,461 2,277 Weighted-average outstanding shares - diluted 45,833 44,669 45,516 44,450 Net income per share: Basic $ 0.68 $ 0.75 $ 1.77 $ 1.84 Diluted $ 0.64 $ 0.71 $ 1.68 $ 1.75

Note 8 - Segment and Geograph_2

Note 8 - Segment and Geographic Information (Tables)	9 Months Ended
Note 8 - Segment and Geographic Information (Tables)	Sep. 30, 2019
Notes Tables
Schedules of Concentration of Risk, by Risk Factor [Table Text Block]	Revenue Accounts Receivable Three Months Ended September 30, Nine Months Ended September 30, September 30, December 31, Customer 2019 2018 2019 2018 2019 2018 Company A (distributor) 24 % 23 % 23 % 21 % 25 % 25 % Company B (distributor) * 10 % * 10 % 12 % 16 % Company A (value-added reseller) * * * * 10 % *
Schedule of Revenue from External Customers Attributed to Foreign Countries by Geographic Area [Table Text Block]	Three Months Ended September 30, Nine Months Ended September 30, Country or Region 2019 2018 2019 2018 China $ 105,857 $ 91,509 $ 276,892 $ 245,580 Taiwan 18,547 20,774 55,912 55,315 Europe 12,047 12,579 38,071 36,696 Korea 11,990 11,406 31,224 30,046 Southeast Asia 7,904 11,259 23,698 28,261 Japan 8,150 6,895 21,084 18,994 United States 4,225 5,375 14,044 13,404 Other 93 178 258 589 Total $ 168,813 $ 159,975 $ 461,183 $ 428,885
Revenue from External Customers by Products and Services [Table Text Block]	Three Months Ended September 30, Nine Months Ended September 30, Product Family 2019 2018 2019 2018 DC to DC $ 159,723 $ 147,727 $ 432,125 $ 394,492 Lighting Control 9,090 12,248 29,058 34,393 Total $ 168,813 $ 159,975 $ 461,183 $ 428,885
Schedule of Disclosure on Geographic Areas, Long-Lived Assets in Individual Foreign Countries by Country [Table Text Block]	September 30, December 31, Country 2019 2018 China $ 105,030 $ 93,096 United States 93,967 39,054 Taiwan 16,750 16,972 Other 1,296 879 Total $ 217,043 $ 150,001

Note 9 - Commitments and Cont_2

Note 9 - Commitments and Contingencies (Tables)	9 Months Ended
Note 9 - Commitments and Contingencies (Tables)	Sep. 30, 2019
Notes Tables
Schedule of Product Warranty Liability [Table Text Block]	Three Months Ended September 30, Nine Months Ended September 30, 2019 2018 2019 2018 Balance at beginning of period $ 1,748 $ 3,951 $ 4,564 $ 2,416 Warranty provision for product sales 92 3,840 671 5,654 Settlements made (326 ) (36 ) (2,625 ) (100 ) Unused warranty provision (247 ) (2,821 ) (1,343 ) (3,036 ) Balance at end of period $ 1,267 $ 4,934 $ 1,267 $ 4,934

Note 10 - Cash, Cash Equivale_2

Note 10 - Cash, Cash Equivalents, Investments and Restricted Cash (Tables)	9 Months Ended
	Sep. 30, 2019
Notes Tables
Fair Value, by Balance Sheet Grouping [Table Text Block]	September 30, December 31, 2019 2018 Cash, cash equivalents and investments: Cash $ 162,741 $ 131,569 Money market funds 39,982 41,135 Corporate debt securities 195,667 170,909 U.S. treasuries and government agency bonds 20,350 32,068 Certificates of deposit - 1,600 Auction-rate securities backed by student-loan notes 3,264 3,241 Total $ 422,004 $ 380,522 September 30, December 31, 2019 2018 Reported as: Cash and cash equivalents $ 205,229 $ 172,704 Short-term investments 213,511 204,577 Long-term investments 3,264 3,241 Total $ 422,004 $ 380,522
Investments Classified by Contractual Maturity Date [Table Text Block]	September 30, December 31, 2019 2018 Due in less than 1 year $ 142,336 $ 125,845 Due in 1 - 5 years 71,175 78,732 Due in greater than 5 years 3,264 3,241 Total $ 216,775 $ 207,818
Unrealized Gain (Loss) on Investments [Table Text Block]	September 30, 2019 Amortized Cost Unrealized Gains Unrealized Losses Total Fair Value Fair Value of Investments in Unrealized Loss Position Money market funds $ 39,982 $ - $ - $ 39,982 $ - Corporate debt securities 195,471 324 (128 ) 195,667 83,247 U.S. treasuries and government agency bonds 20,341 11 (2 ) 20,350 7,998 Auction-rate securities backed by student-loan notes 3,445 - (181 ) 3,264 3,264 Total $ 259,239 $ 335 $ (311 ) $ 259,263 $ 94,509 December 31, 2018 Amortized Cost Unrealized Gains Unrealized Losses Total Fair Value Fair Value of Investments in Unrealized Loss Position Money market funds $ 41,135 $ - $ - $ 41,135 $ - Corporate debt securities 172,288 7 (1,386 ) 170,909 166,204 U.S. treasuries and government agency bonds 32,207 2 (141 ) 32,068 28,507 Certificates of deposit 1,600 - - 1,600 - Auction-rate securities backed by student-loan notes 3,570 - (329 ) 3,241 3,241 Total $ 250,800 $ 9 $ (1,856 ) $ 248,953 $ 197,952
Restrictions on Cash and Cash Equivalents [Table Text Block]	September 30, December 31, 2019 2018 Cash and cash equivalents $ 205,229 $ 172,704 Restricted cash included in other current assets 1,161 - Restricted cash included in other long-term assets 113 114 Total cash, cash equivalents and restricted cash reported on the Condensed Consolidated Statements of Cash Flows $ 206,503 $ 172,818

Note 11 - Fair Value Measurem_2

Note 11 - Fair Value Measurements (Tables)	9 Months Ended
Note 11 - Fair Value Measurements (Tables)	Sep. 30, 2019
Notes Tables
Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis [Table Text Block]	Fair Value Measurement at September 30, 2019 Total Level 1 Level 2 Level 3 Money market funds $ 39,982 $ 39,982 $ - $ - Corporate debt securities 195,667 - 195,667 - U.S. treasuries and government agency bonds 20,350 - 20,350 - Auction-rate securities backed by student-loan notes 3,264 - - 3,264 Mutual funds and money market funds under deferred compensation plan 19,968 19,968 - - Total $ 279,231 $ 59,950 $ 216,017 $ 3,264 Fair Value Measurement at December 31, 2018 Total Level 1 Level 2 Level 3 Money market funds $ 41,135 $ 41,135 $ - $ - Corporate debt securities 170,909 - 170,909 - U.S. treasuries and government agency bonds 32,068 - 32,068 - Certificates of deposit 1,600 - 1,600 - Auction-rate securities backed by student-loan notes 3,241 - - 3,241 Mutual funds and money market funds under deferred compensation plan 18,867 18,867 - - Total $ 267,820 $ 60,002 $ 204,577 $ 3,241
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Table Text Block]	Balance at January 1, 2019 $ 3,241 Change in unrealized gain included in other comprehensive income 148 Sale and settlement at par (125 ) Balance at September 30, 2019 $ 3,264
Schedule Of Level 3 Assumptions [Table Text Block]	September 30, December 31, 2019 2018 Time-to-liquidity (in years) 2 - 3 2 - 3 Discount rate 3.7% - 7.9% 4.9% - 10.1%

Note 12 - Deferred Compensati_2

Note 12 - Deferred Compensation Plan (Tables)	9 Months Ended
Note 12 - Deferred Compensation Plan (Tables)	Sep. 30, 2019
Notes Tables
Schedule of Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits by Title of Individual and Type of Deferred Compensation [Table Text Block]	September 30, December 31, 2019 2018 Deferred compensation plan asset components: Cash surrender value of corporate-owned life insurance policies $ 16,429 $ 13,103 Fair value of mutual funds and money market funds 19,968 18,867 Total $ 36,397 $ 31,970 Deferred compensation plan assets reported in: Other long-term assets $ 36,397 $ 31,970 Deferred compensation plan liabilities reported in: Accrued compensation and related benefits (short-term) $ 425 $ 447 Other long-term liabilities 36,968 32,283 Total $ 37,393 $ 32,730

Note 13 - Interest and Other _2

Note 13 - Interest and Other Income, Net (Tables)	9 Months Ended
Note 13 - Interest and Other Income, Net (Tables)	Sep. 30, 2019
Notes Tables
Schedule of Other Nonoperating Income (Expense) [Table Text Block]	Three Months Ended September 30, Nine Months Ended September 30, 2019 2018 2019 2018 Interest income $ 1,850 $ 1,583 $ 5,207 $ 4,606 Amortization of premium on available-for-sale securities (168 ) (314 ) (384 ) (1,122 ) Gain on deferred compensation plan investments 74 717 2,630 949 Foreign currency exchange gain 175 700 47 915 Other 326 28 327 39 Total $ 2,257 $ 2,714 $ 7,827 $ 5,387

Note 15 - Accumulated Other C_2

Note 15 - Accumulated Other Comprehensive Loss (Tables)	9 Months Ended
Note 15 - Accumulated Other Comprehensive Loss (Tables)	Sep. 30, 2019
Notes Tables
Schedule of Accumulated Other Comprehensive Income (Loss) [Table Text Block]	Unrealized Gains (Losses) on Available-for-Sale Securities Foreign Currency Translation Adjustments Total Balance as of January 1, 2019 $ (1,638 ) $ (3,905 ) $ (5,543 ) Other comprehensive income before reclassifications 924 3,677 4,601 Tax effect (98 ) - (98 ) Other comprehensive income 826 3,677 4,503 Balance as of March 31, 2019 (812 ) (228 ) (1,040 ) Other comprehensive income (loss) before reclassifications 675 (3,709 ) (3,034 ) Tax effect (64 ) - (64 ) Other comprehensive income (loss) 611 (3,709 ) (3,098 ) Balance as of June 30, 2019 (201 ) (3,937 ) (4,138 ) Other comprehensive income (loss) before reclassifications 272 (6,135 ) (5,863 ) Tax effect (38 ) - (38 ) Other comprehensive income (loss) 234 (6,135 ) (5,901 ) Balance as of September 30, 2019 $ 33 $ (10,072 ) $ (10,039 )

Note 16 - Dividends and Divid_2

Note 16 - Dividends and Dividend Equivalents (Tables)	9 Months Ended
Note 16 - Dividends and Dividend Equivalents (Tables)	Sep. 30, 2019
Notes Tables
Dividends Declared [Table Text Block]	Three Months Ended September 30, Nine Months Ended September 30, 2019 2018 2019 2018 Dividend declared per share $ 0.40 $ 0.30 $ 1.20 $ 0.90 Total amount $ 17,341 $ 12,722 $ 51,782 $ 38,052

Note 2 - Revenue Recognition (D

Note 2 - Revenue Recognition (Details Textual) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Lapse Period for Consignment			60 days
Accounts Receivable, after Allowance for Credit Loss, Current, Total	$ 58,261		$ 58,261		$ 55,214
Accounts Receivable, Allowance for Credit Loss, Writeoff			0		0
Contract with Customer, Liability, Current	4,160		$ 4,160		2,520
Revenue, Performance Obligation, Performance Period Following Prepayment			14 days
Minimum [Member]
Contract with Customer, Payment Term			30 days
Maximum [Member]
Contract with Customer, Payment Term			60 days
Certain Customers in China [Member]
Contract with Customer, Payment Term Required Prior to Shipping Products			14 days
Contract with Customer, Liability, Revenue Recognized			$ 2,500
Certain Customers in China [Member] \| Accrued Liabilities, Current [Member]
Contract with Customer, Liability, Current	$ 4,200		$ 4,200		$ 2,500
Customer Concentration Risk [Member] \| Revenue Benchmark [Member] \| Distributor Sales [Member]
Concentration Risk, Percentage	88.00%	87.00%	83.00%	87.00%
Product [Member]
Percentage of Revenue	99.00%	98.00%	99.00%	98.00%

Note 3 - Stock-based Compensa_3

Note 3 - Stock-based Compensation (Details Textual) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended	3 Months Ended		9 Months Ended
	Feb. 28, 2019	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Nov. 13, 2014
Proceeds, Issuance of Shares, Share-based Payment Arrangement, Excluding Option Exercised				$ 14,561	$ 9,684
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period				582,000
Proceeds from Stock Plans				$ 3,277	3,028
Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Aggregate Intrinsic Value, Vested		$ 26,100	$ 13,900	110,100	79,000
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Aggregate Intrinsic Value, Outstanding		$ 617,600		$ 617,600
Share Price		$ 155.63		$ 155.63
Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Amount, Total		$ 120,500		$ 120,500
Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Period for Recognition				3 years 4 months 24 days
Performance-based RSUs (PSUs) [Member]
Proceeds, Issuance of Shares, Share-based Payment Arrangement, Excluding Option Exercised				$ 14,600	$ 9,600
Time-Based RSUs [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period				47,000
Time-Based RSUs [Member] \| Non-executive Employees and Non-employer Directors [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period				88,000
Time-Based RSUs [Member] \| Employees [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period				4 years
Time-Based RSUs [Member] \| Director [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period				1 year
PSU 2019 [Member] \| Executive Officer [Member]
Share Price	$ 130.67
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period	151,000
Share-based Compensation Arrangement by Share-based Payment Award, Vesting, Measurement Period of Relative Revenue Growth Rate to Industry Average	2 years
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Maximum Percentage Allowed	300.00%
Maximum Stock Compensation Costs	$ 46,600
Share-based Compensation Arrangement by Share-based Payment Award, Price Per Share Payable Upon Vesting of Equity Instruments Other than Options	$ 30
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Term	2 years 7 months 6 days
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Volatility Rate	29.00%
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Risk Free Interest Rate	2.50%
PSU 2019 [Member] \| Executive Officer [Member] \| Share-based Payment Arrangement, Tranche One [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Rights, Percentage	50.00%
PSU 2019 [Member] \| Executive Officer [Member] \| Share-based Payment Arrangement, Tranche Two [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period	2 years
The2014 Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized						5,500,000
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant		1,600,000		1,600,000
Employee Stock Purchase Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant		4,500,000		4,500,000
Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Amount, Total		$ 400		$ 400
Stock Issued During Period, Shares, Employee Stock Purchase Plans		14,000	15,000	28,000	33,000
Employee Stock Purchase Plan Shares Issued, Intrinsic Value		$ 400	$ 600	$ 700	$ 1,100
Proceeds from Stock Plans				$ 3,300	$ 3,000

Note 3 - Stock-based Compensa_4

Note 3 - Stock-based Compensation - Stock-based Compensation Plan Expenses (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Share based compensation expense	$ 21,300	$ 14,843	$ 60,019	$ 45,765
Tax benefit related to stock-based compensation	595	764	2,139	2,723
Cost of Sales [Member]
Share based compensation expense	641	471	1,834	1,384
Research and Development Expense [Member]
Share based compensation expense	4,960	3,979	14,801	12,168
Selling, General and Administrative Expenses [Member]
Share based compensation expense	$ 15,699	$ 10,393	$ 43,384	$ 32,213

Note 3 - Stock-based Compensa_5

Note 3 - Stock-based Compensation - RSU Summary (Details) shares in Thousands	9 Months Ended
	Sep. 30, 2019$ / sharesshares
Beginning balance (in shares) \| shares	4,633
Weighted-Average Grant Date Fair Value Per Share, beginning balance (in dollars per share) \| $ / shares	$ 50.94
Granted (in shares) \| shares	582
Weighted-Average Grant Date Fair Value Per Share, granted (in dollars per share) \| $ / shares	$ 101.89
Vested (in shares) \| shares	(902)
Weighted-Average Grant Date Fair Value Per Share, vested (in dollars per share) \| $ / shares	$ 48.61
Forfeited (in shares) \| shares	(56)
Weighted-Average Grant Date Fair Value Per Share, forfeited (in dollars per share) \| $ / shares	$ 53.06
Ending balance (in shares) \| shares	4,257
Weighted-Average Grant Date Fair Value Per Share, ending balance (in dollars per share) \| $ / shares	$ 58.38
Time-Based RSUs [Member]
Beginning balance (in shares) \| shares	240
Weighted-Average Grant Date Fair Value Per Share, beginning balance (in dollars per share) \| $ / shares	$ 95.38
Granted (in shares) \| shares	47
Weighted-Average Grant Date Fair Value Per Share, granted (in dollars per share) \| $ / shares	$ 141.03
Vested (in shares) \| shares	(88)
Weighted-Average Grant Date Fair Value Per Share, vested (in dollars per share) \| $ / shares	$ 79.91
Forfeited (in shares) \| shares	(6)
Weighted-Average Grant Date Fair Value Per Share, forfeited (in dollars per share) \| $ / shares	$ 110.23
Ending balance (in shares) \| shares	193
Weighted-Average Grant Date Fair Value Per Share, ending balance (in dollars per share) \| $ / shares	$ 113.22
PSUs and MPSUs [Member]
Beginning balance (in shares) \| shares	2,174
Weighted-Average Grant Date Fair Value Per Share, beginning balance (in dollars per share) \| $ / shares	$ 61.61
Granted (in shares) \| shares	535	[1]
Weighted-Average Grant Date Fair Value Per Share, granted (in dollars per share) \| $ / shares	$ 98.45
Vested (in shares) \| shares	(571)
Weighted-Average Grant Date Fair Value Per Share, vested (in dollars per share) \| $ / shares	$ 54.41
Forfeited (in shares) \| shares	(43)
Weighted-Average Grant Date Fair Value Per Share, forfeited (in dollars per share) \| $ / shares	$ 42.72
Ending balance (in shares) \| shares	2,095
Weighted-Average Grant Date Fair Value Per Share, ending balance (in dollars per share) \| $ / shares	$ 73.37
MSUs [Member]
Beginning balance (in shares) \| shares	2,219
Weighted-Average Grant Date Fair Value Per Share, beginning balance (in dollars per share) \| $ / shares	$ 35.69
Granted (in shares) \| shares	0
Weighted-Average Grant Date Fair Value Per Share, granted (in dollars per share) \| $ / shares	$ 0
Vested (in shares) \| shares	(243)
Weighted-Average Grant Date Fair Value Per Share, vested (in dollars per share) \| $ / shares	$ 23.57
Forfeited (in shares) \| shares	(7)
Weighted-Average Grant Date Fair Value Per Share, forfeited (in dollars per share) \| $ / shares	$ 68.48
Ending balance (in shares) \| shares	1,969
Weighted-Average Grant Date Fair Value Per Share, ending balance (in dollars per share) \| $ / shares	$ 37.08

[1]	Amount reflects the number of PSUs that may ultimately be earned based on managements probability assessment of the achievement of performance conditions at each reporting period.

Note 3 - Stock-based Compensa_6

Note 3 - Stock-based Compensation - Valuation Assumptions (Details) - 2004 Employee Stock Plan [Member] - Employee Stock Purchase Plan [Member]	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Expected term (in years) (Year)	6 months	6 months	6 months	6 months
Expected volatility	36.70%	30.80%	37.00%	29.50%
Risk-free interest rate	1.90%	2.20%	2.20%	2.00%
Dividend yield	1.10%	0.90%	1.10%	1.00%

Note 4 - Balance Sheet Compon_3

Note 4 - Balance Sheet Components - Inventories (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Raw materials	$ 27,001	$ 43,017
Work in process	43,076	38,674
Finished goods	65,557	54,693
Total	$ 135,634	$ 136,384

Note 4 - Balance Sheet Compon_4

Note 4 - Balance Sheet Components - Other Current Assets (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
RSU tax withholding proceeds receivable	$ 5,331	$ 39
Prepaid expense	4,024	3,425
Assets for product returns	2,261	1,602
Interest receivable	1,869	1,441
Value-added tax receivable	628	423
Prepaid wafer refund receivable	0	4,297
Other	2,547	704
Total	$ 16,660	$ 11,931

Note 4 - Balance Sheet Compon_5

Note 4 - Balance Sheet Components - Other Long-term Assets (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Deferred compensation plan assets	$ 36,397	$ 31,970
Operating lease ROU assets	3,102	0
Prepaid expense	2,274	2,713
Other	1,570	1,296
Total	$ 43,343	$ 35,979

Note 4 - Balance Sheet Compon_6

Note 4 - Balance Sheet Components - Accrued Liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Dividends and dividend equivalents	$ 21,895	$ 15,044
Stock rotation and sales returns	7,884	5,363
Customer prepayments	4,160	2,520
Income tax payable	2,778	7,018
Operating lease liabilities	1,318	0
Warranty	1,267	4,564
Commissions	976	1,369
Other	5,706	3,084
Total	$ 45,984	$ 38,962

Note 4 - Balance Sheet Compon_7

Note 4 - Balance Sheet Components - Long-term Liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Deferred compensation plan liabilities	$ 36,968	$ 32,283
Dividend equivalents	6,091	6,145
Operating lease liabilities	1,190	0
Other	30	97
Total	$ 44,279	$ 38,525

Note 5 - Real Estate Transact_3

Note 5 - Real Estate Transaction (Details Textual) $ in Millions	1 Months Ended
	Mar. 31, 2019USD ($)
Payments to Acquire Real Estate, Total	$ 52.9
Real Estate, Capitalized Transaction Costs	$ 0.4
Leases, Acquired-in-Place [Member]
Finite-Lived Intangible Asset, Useful Life	3 years 6 months
Building [Member]
Property, Plant and Equipment, Useful Life	40 years

Note 5 - Real Estate Transact_4

Note 5 - Real Estate Transaction - Allocation of Consideration (Details) - Property in Kirkland, Washington [Member] $ in Thousands	Sep. 30, 2019USD ($)
Building	$ 30,078
Land	22,254
In-place leases	981
Total	$ 53,313

Note 6 - Leases (Details Textua

Note 6 - Leases (Details Textual) - USD ($) $ in Thousands	Jan. 01, 2019	Sep. 30, 2019		Sep. 30, 2019		Dec. 31, 2018
Operating Lease, Right-of-Use Asset		$ 3,102		$ 3,102		$ 0
Operating Lease, Liability, Total		2,508		2,508
Right-of-Use Asset Obtained in Exchange for Operating Lease Liability	$ 2,200	$ 869	[1]	$ 3,450	[1]
Operating Lease, Weighted Average Remaining Lease Term		2 years 3 months 18 days		2 years 3 months 18 days
Operating Lease, Lease Income, Lease Payments		$ 500		$ 1,300
Maximum [Member]
Lessee, Operating Lease, Term of Contract		4 years		4 years
Lessee, Operating Lease, Renewal Term		5 years		5 years
Operating Lease, Weighted Average Remaining Lease Term		5 years		5 years
Lessor, Operating Lease, Renewal Term		5 years		5 years
Minimum [Member]
Operating Lease, Weighted Average Remaining Lease Term		2 years		2 years

[1]	For the nine months ended September 30, 2019, the amount includes $2.2 million for operating leases existing on January 1, 2019.

Note 6 - Leases - Leases Cost (

Note 6 - Leases - Leases Cost (Details) - USD ($) $ in Thousands	Jan. 01, 2019	Sep. 30, 2019		Sep. 30, 2019
Operating lease costs		$ 377		$ 1,013
Short-term and other lease costs		102		394
Total lease costs		479		1,407
Operating cash flows from operating leases		299		1,026
ROU assets obtained in exchange for operating lease liabilities (1)	$ 2,200	$ 869	[1]	$ 3,450	[1]
Weighted-average remaining lease term (in years) (Year)		2 years 3 months 18 days		2 years 3 months 18 days
Weighted-average discount rate		3.90%		3.90%

[1]	For the nine months ended September 30, 2019, the amount includes $2.2 million for operating leases existing on January 1, 2019.

Note 6 - Leases - Maturities of

Note 6 - Leases - Maturities of Lease Liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
2019 (remaining three months)	$ 364
2020	1,241
2021	634
2022	379
2023	22
Total remaining lease payments	2,640
Less: imputed interest	(132)
Total lease liabilities	2,508
Current liabilities	1,318	$ 0
Long-term liabilities	$ 1,190	$ 0

Note 6 - Leases - Maturities _2

Note 6 - Leases - Maturities of Income Related to Lease Payments (Details) $ in Thousands	Sep. 30, 2019USD ($)
2019 (remaining three months)	$ 279
2020	1,539
2021	1,384
2022	1,136
2023	602
2024 and beyond	597
Total	$ 5,537

Note 7 - Net Income Per Share -

Note 7 - Net Income Per Share - Net Income Per Share Basic and Diluted (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Numerator:
Net income	$ 29,528	$ 31,568	$ 76,402	$ 77,630
Denominator:
Weighted-average outstanding shares - basic (in shares)	43,308	42,362	43,055	42,173
Effect of dilutive securities (in shares)	2,525	2,307	2,461	2,277
Weighted-average outstanding shares - diluted (in shares)	45,833	44,669	45,516	44,450
Net income per share:
Earnings per share, basic (in dollars per share)	$ 0.68	$ 0.75	$ 1.77	$ 1.84
Earnings per share, diluted (in dollars per share)	$ 0.64	$ 0.71	$ 1.68	$ 1.75

Note 8 - Segment and Geograph_3

Note 8 - Segment and Geographic Information (Details Textual)	9 Months Ended
	Sep. 30, 2019
Number of Reportable Segments	1

Note 8 - Segment and Geograph_4

Note 8 - Segment and Geographic Information - Customers with Sales and Accounts Receivable Greater Than 10% (Details) - Customer Concentration Risk [Member]		3 Months Ended		9 Months Ended		12 Months Ended
		Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Revenue Benchmark [Member] \| Distributor A [Member]
Concentration risk		24.00%	23.00%	23.00%	21.00%
Revenue Benchmark [Member] \| Distributor B [Member]
Concentration risk	[1]		10.00%		10.00%
Accounts Receivable [Member] \| Distributor A [Member]
Concentration risk				25.00%		25.00%
Accounts Receivable [Member] \| Distributor B [Member]
Concentration risk	[1]			12.00%		16.00%
Accounts Receivable [Member] \| End Customer [Member]
Concentration risk				10.00%

[1]	Represents less than 10%.

Note 8 - Segment and Geograph_5

Note 8 - Segment and Geographic Information - Revenue by Region (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Revenue	$ 168,813	$ 159,975	$ 461,183	$ 428,885
CHINA
Revenue	105,857	91,509	276,892	245,580
TAIWAN, PROVINCE OF CHINA
Revenue	18,547	20,774	55,912	55,315
Europe [Member]
Revenue	12,047	12,579	38,071	36,696
KOREA, REPUBLIC OF
Revenue	11,990	11,406	31,224	30,046
South East Asia [Member]
Revenue	7,904	11,259	23,698	28,261
JAPAN
Revenue	8,150	6,895	21,084	18,994
UNITED STATES
Revenue	4,225	5,375	14,044	13,404
Other Region [Member]
Revenue	$ 93	$ 178	$ 258	$ 589

Note 8 - Segment and Geograph_6

Note 8 - Segment and Geographic Information - Revenue by Product Family (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Revenue	$ 168,813	$ 159,975	$ 461,183	$ 428,885
DC To DC Products [Member]
Revenue	159,723	147,727	432,125	394,492
Lighting Control Products [Member]
Revenue	$ 9,090	$ 12,248	$ 29,058	$ 34,393

Note 8 - Segment and Geograph_7

Note 8 - Segment and Geographic Information - Long Lived Assets by Geographic Region (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Long lived assets by region	$ 217,043	$ 150,001
CHINA
Long lived assets by region	105,030	93,096
UNITED STATES
Long lived assets by region	93,967	39,054
TAIWAN, PROVINCE OF CHINA
Long lived assets by region	16,750	16,972
Other Region [Member]
Long lived assets by region	$ 1,296	$ 879

Note 9 - Commitments and Cont_3

Note 9 - Commitments and Contingencies (Details Textual) $ in Millions	Sep. 30, 2019USD ($)
Purchase Obligation, Total	$ 70.9

Note 9 - Commitments and Cont_4

Note 9 - Commitments and Contingencies - Changes in Warranty Reserve (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Balance	$ 1,748	$ 3,951	$ 4,564	$ 2,416
Warranty provision for product sales	92	3,840	671	5,654
Settlements made	(326)	(36)	(2,625)	(100)
Unused warranty provision	(247)	(2,821)	(1,343)	(3,036)
Balance	$ 1,267	$ 4,934	$ 1,267	$ 4,934

Note 10 - Cash, Cash Equivale_3

Note 10 - Cash, Cash Equivalents, Investments and Restricted Cash (Details Textual) - USD ($) $ in Millions	Sep. 30, 2019	Dec. 31, 2018
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	$ 0.3	$ 1.6

Note 10 - Cash, Cash Equivale_4

Note 10 - Cash, Cash Equivalents, Investments and Restricted Cash - Cash Equivalents, Short-term and Long-term Investments (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Cash	$ 162,741	$ 131,569
Money market funds	39,982	41,135
U.S. treasuries and government agency bonds	20,350	32,068
Certificates of deposit		1,600
Total	422,004	380,522
Cash and cash equivalents	205,229	172,704
Short-term investments	213,511	204,577
Long-term investments	3,264	3,241
Corporate Debt Securities [Member]
Available-for-sale securities	195,667	170,909
Auction Rate Securities [Member]
Available-for-sale securities	$ 3,264	$ 3,241

Note 10 - Cash, Cash Equivale_5

Note 10 - Cash, Cash Equivalents, Investments and Restricted Cash - Investment Maturity Classification (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Due in less than 1 year	$ 142,336	$ 125,845
Due in 1 - 5 years	71,175	78,732
Due in greater than 5 years	3,264	3,241
Total	$ 216,775	$ 207,818

Note 10- Cash, Cash Equivalents

Note 10- Cash, Cash Equivalents, Investments and Restricted Cash - Unrealized Gains and Losses on Investments (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Adjusted Cost	$ 259,239	$ 250,800
Total Fair Value	259,263	248,953
Unrealized Gains	335	9
Unrealized Losses	(311)	(1,856)
Fair Value of Investments in Unrealized Loss Position	94,509	197,952
Money Market Funds [Member]
Adjusted Cost	39,982	41,135
Total Fair Value	39,982	41,135
Corporate Debt Securities [Member]
Adjusted Cost	195,471	172,288
Total Fair Value	195,667	170,909
Unrealized Gains	324	7
Unrealized Losses	(128)	(1,386)
Fair Value of Investments in Unrealized Loss Position	83,247	166,204
US Government Agencies Short-term Debt Securities [Member]
Adjusted Cost	20,341	32,207
Total Fair Value	20,350	32,068
Unrealized Gains	11	2
Unrealized Losses	(2)	(141)
Fair Value of Investments in Unrealized Loss Position	7,998	28,507
Auction Rate Securities [Member]
Adjusted Cost	3,445	3,570
Total Fair Value	3,264	3,241
Unrealized Losses	(181)	(329)
Fair Value of Investments in Unrealized Loss Position	$ 3,264	3,241
Certificates of Deposit [Member]
Adjusted Cost		1,600
Total Fair Value		$ 1,600

Note 10 - Cash, Cash Equivale_6

Note 10 - Cash, Cash Equivalents, Investments and Restricted Cash - Restricted Cash (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018	Sep. 30, 2018	Dec. 31, 2017
Cash and cash equivalents	$ 205,229	$ 172,704
Restricted cash included in other current assets	1,161	0
Restricted cash included in other long-term assets	113	114
Total cash, cash equivalents and restricted cash reported on the Condensed Consolidated Statements of Cash Flows	$ 206,503	$ 172,818	$ 131,209	$ 82,874

Note 11 - Fair Value Measurem_3

Note 11 - Fair Value Measurements - Financial Assets and Liabilities, Fair Value (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Total Fair Value	$ 259,263	$ 248,953
Assets, fair value	279,231	267,820
Fair Value, Inputs, Level 1 [Member]
Assets, fair value	59,950	60,002
Fair Value, Inputs, Level 2 [Member]
Assets, fair value	216,017	204,577
Fair Value, Inputs, Level 3 [Member]
Assets, fair value	3,264	3,241
Money Market Funds [Member]
Total Fair Value	39,982	41,135
Money Market Funds [Member] \| Fair Value, Inputs, Level 1 [Member]
Total Fair Value	39,982	41,135
Money Market Funds [Member] \| Fair Value, Inputs, Level 2 [Member]
Total Fair Value		0
Money Market Funds [Member] \| Fair Value, Inputs, Level 3 [Member]
Total Fair Value		0
Corporate Debt Securities [Member]
Total Fair Value	195,667	170,909
Corporate Debt Securities [Member] \| Fair Value, Inputs, Level 1 [Member]
Total Fair Value		0
Corporate Debt Securities [Member] \| Fair Value, Inputs, Level 2 [Member]
Total Fair Value	195,667	170,909
Corporate Debt Securities [Member] \| Fair Value, Inputs, Level 3 [Member]
Total Fair Value		0
US Government Agencies Short-term Debt Securities [Member]
Total Fair Value	20,350	32,068
US Government Agencies Short-term Debt Securities [Member] \| Fair Value, Inputs, Level 1 [Member]
Total Fair Value		0
US Government Agencies Short-term Debt Securities [Member] \| Fair Value, Inputs, Level 2 [Member]
Total Fair Value	20,350	32,068
US Government Agencies Short-term Debt Securities [Member] \| Fair Value, Inputs, Level 3 [Member]
Total Fair Value		0
Auction Rate Securities [Member]
Total Fair Value	3,264	3,241
Auction Rate Securities [Member] \| Fair Value, Inputs, Level 1 [Member]
Total Fair Value		0
Auction Rate Securities [Member] \| Fair Value, Inputs, Level 2 [Member]
Total Fair Value		0
Auction Rate Securities [Member] \| Fair Value, Inputs, Level 3 [Member]
Total Fair Value	3,264	3,241
Certificates of Deposit [Member]
Total Fair Value		1,600
Certificates of Deposit [Member] \| Fair Value, Inputs, Level 1 [Member]
Total Fair Value		0
Certificates of Deposit [Member] \| Fair Value, Inputs, Level 2 [Member]
Total Fair Value		1,600
Certificates of Deposit [Member] \| Fair Value, Inputs, Level 3 [Member]
Total Fair Value		0
Mutual Fund [Member]
Total Fair Value	19,968	18,867
Mutual Fund [Member] \| Fair Value, Inputs, Level 1 [Member]
Total Fair Value	$ 19,968	18,867
Mutual Fund [Member] \| Fair Value, Inputs, Level 2 [Member]
Total Fair Value		0
Mutual Fund [Member] \| Fair Value, Inputs, Level 3 [Member]
Total Fair Value		$ 0

Note 11 - Fair Value Measurem_4

Note 11 - Fair Value Measurements - Level 3 Investments (Details) - Auction Rate Securities [Member] $ in Thousands	9 Months Ended
	Sep. 30, 2019USD ($)
Balance, auction rate securities	$ 3,241
Change in unrealized gain included in other comprehensive income	148
Sale and settlement at par	(125)
Balance, auction rate securities	$ 3,264

Note 11 - Fair Value Measurem_5

Note 11 - Fair Value Measurements - Discounted Cash Flow Assumptions (Details)	9 Months Ended	12 Months Ended
	Sep. 30, 2019	Dec. 31, 2018
Minimum [Member]
Time-to-liquidity (Year)	2 years	2 years
Discount rate	3.70%	4.90%
Maximum [Member]
Time-to-liquidity (Year)	3 years	3 years
Discount rate	7.90%	10.10%

Note 12 - Deferred Compensati_3

Note 12 - Deferred Compensation Plan - Summary of Deferred Compensation Plan (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Deferred compensation plan assets	$ 36,397	$ 31,970
Deferred compensation plan assets reported in:
Deferred compensation plan assets	36,397	31,970
Deferred compensation plan liabilities reported in:
Deferred compensation plan liabilities	37,393	32,730
Other Long-term Assets [Member]
Deferred compensation plan assets	36,397	31,970
Deferred compensation plan assets reported in:
Deferred compensation plan assets	36,397	31,970
Accrued Compensation and Related Benefits [Member]
Deferred compensation plan liabilities reported in:
Deferred compensation plan liabilities	425	447
Other Long-term Liabilities [Member]
Deferred compensation plan liabilities reported in:
Deferred compensation plan liabilities	36,968	32,283
Cash Surrender Value [Member]
Deferred compensation plan assets	16,429	13,103
Deferred compensation plan assets reported in:
Deferred compensation plan assets	16,429	13,103
Mutual Funds and Money Market Funds, Fair Value [Member]
Deferred compensation plan assets	19,968	18,867
Deferred compensation plan assets reported in:
Deferred compensation plan assets	$ 19,968	$ 18,867

Note 13 - Interest and Other _3

Note 13 - Interest and Other Income, Net (Details Textual) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2019
Other Nonoperating Income (Expense) [Member] \| Land [Member]
Gain (Loss) on Disposition of Property Plant Equipment, Excluding Oil and Gas Property and Timber Property	$ 0.7	$ 0.7

Note 13 - Interest and Other _4

Note 13 - Interest and Other Income, Net - Interest and Other Income Components (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Interest income	$ 1,850	$ 1,583	$ 5,207	$ 4,606
Amortization of premium on available-for-sale securities	(168)	(314)	(384)	(1,122)
Gain on deferred compensation plan investments	74	717	2,630	949
Foreign currency exchange gain	175	700	47	915
Other	326	28	327	39
Total	$ 2,257	$ 2,714	$ 7,827	$ 5,387

Note 14 - Income Taxes (Details

Note 14 - Income Taxes (Details Textual) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Income Tax Expense (Benefit), Total	$ 2,761	$ 4,639	$ 3,293	$ 8,168
Effective Income Tax Rate Reconciliation, Percent, Total	8.60%	12.80%	4.10%	9.50%
GILTI Income	$ 13,000	$ 18,400	$ 38,500	$ 46,200

Note 15 - Accumulated Other C_3

Note 15 - Accumulated Other Comprehensive Loss - Changes in Accumulated Other Comprehensive Income (Details) - USD ($) $ in Thousands	3 Months Ended
	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019
Balance	$ 704,154		$ 640,093
Balance	734,428	$ 704,154
AOCI, Accumulated Gain (Loss), Debt Securities, Available-for-sale, Parent [Member]
Balance	(201)	(812)	(1,638)
Other comprehensive income before reclassifications	272	675	924
Tax effect	(38)	(64)	(98)
Other comprehensive income	234	611	826
Balance	33	(201)	(812)
Accumulated Foreign Currency Adjustment Attributable to Parent [Member]
Balance	(3,937)	(228)	(3,905)
Other comprehensive income before reclassifications	(6,135)	(3,709)	3,677
Other comprehensive income	(6,135)	(3,709)	3,677
Balance	(10,072)	(3,937)	(228)
AOCI Attributable to Parent [Member]
Balance	(4,138)	(1,040)	(5,543)
Other comprehensive income before reclassifications	(5,863)	(3,034)	4,601
Tax effect	(38)	(64)	(98)
Other comprehensive income	(5,901)	(3,098)	4,503
Balance	$ (10,039)	$ (4,138)	$ (1,040)

Note 16 - Dividends and Divid_3

Note 16 - Dividends and Dividend Equivalents (Details Textual) - USD ($) $ in Millions	Sep. 30, 2019	Dec. 31, 2018
Dividends Payable, Current	$ 17.3	$ 12.8
Accrued Dividend Equivalents	$ 10.6	$ 8.4

Note 16 - Dividends and Divid_4

Note 16 - Dividends and Dividend Equivalents - Cash Dividends (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Dividend declared per share (in dollars per share)	$ 0.40	$ 0.30	$ 1.20	$ 0.90
Total amount	$ 17,341	$ 12,722	$ 51,782	$ 38,052