Vicor (VICR) 10-K 28 Feb 19 2018 FY Annual report Financial data

Document And Entity Information

Document And Entity Information - USD ($)	12 Months Ended
	Dec. 31, 2018	Feb. 21, 2019	Jun. 30, 2018
Document Information [Line Items]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2018
Document Fiscal Year Focus	2,018
Document Fiscal Period Focus	FY
Entity Registrant Name	VICOR CORP
Entity Central Index Key	751,978
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Filer Category	Large Accelerated Filer
Entity Public Float			$ 750,683,000
Trading Symbol	VICR
Entity Shell Company	false
Entity Emerging Growth Company	false
Entity Small Business	false
Class A Common Stock [Member]
Document Information [Line Items]
Entity Common Stock, Shares Outstanding		28,453,729
Class B Common Stock [Member]
Document Information [Line Items]
Entity Common Stock, Shares Outstanding		11,758,218

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Current assets:
Cash and cash equivalents	$ 70,557	$ 44,230
Accounts receivable, less allowance of $224 in 2018 and $159 in 2017	43,673	34,487
Inventories, net	47,370	36,499
Other current assets	3,460	3,616
Total current assets	165,060	118,832
Long-term deferred tax assets	265	210
Long-term investment, net	2,526	2,525
Property, plant and equipment, net	50,432	41,356
Other assets	2,785	2,801
Total assets	221,068	165,724
Current liabilities:
Accounts payable	16,149	9,065
Accrued compensation and benefits	10,657	9,891
Accrued expenses	2,631	2,989
Sales allowances	548
Accrued severance and other charges	234
Income taxes payable	710	300
Deferred revenue	5,069	5,791
Total current liabilities	35,998	28,036
Long-term deferred revenue	232	303
Contingent consideration obligations	408	678
Long-term income taxes payable	238	195
Other long-term liabilities	102	93
Total liabilities	36,978	29,305
Commitments and contingencies (Note 15)
Vicor Corporation stockholders' equity:
Additional paid-in capital	193,457	181,395
Retained earnings	129,000	93,605
Accumulated other comprehensive loss	(394)	(478)
Treasury stock at cost: 11,635,739 shares in 2018 and 11,671,486 shares in 2017	(138,927)	(138,927)
Total Vicor Corporation stockholders' equity	183,656	136,114
Noncontrolling interest	434	305
Total equity	184,090	136,419
Total liabilities and equity	221,068	165,724
Class B Common Stock [Member]
Vicor Corporation stockholders' equity:
Common Stock	118	118
Total equity	118	118
Common Stock [Member]
Vicor Corporation stockholders' equity:
Common Stock	$ 402	$ 401

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) $ in Thousands	Dec. 31, 2018USD ($)Vote$ / sharesshares	Dec. 31, 2017USD ($)Vote$ / sharesshares
Accounts receivable, allowance | $	$ 224	$ 159
Treasury stock, shares	11,635,739	11,671,486
Class B Common Stock [Member]
Common Stock, votes per share | Vote	10	10
Common Stock, par value | $ / shares	$ 0.01	$ 0.01
Common Stock, shares authorized	14,000,000	14,000,000
Common Stock, shares issued	11,758,218	11,758,218
Common Stock, shares outstanding	11,758,218	11,758,218
Common Stock [Member]
Common Stock, votes per share | Vote	1	1
Common Stock, par value | $ / shares	$ 0.01	$ 0.01
Common Stock, shares authorized	62,000,000	62,000,000
Common Stock, shares issued	40,066,710	39,324,029
Common Stock, shares outstanding	28,430,971	27,652,543

Consolidated Statements of Oper

Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Statement [Abstract]
Net revenues	$ 291,220	$ 227,830	$ 200,280
Cost of revenues	152,249	126,174	109,071
Gross margin	138,971	101,656	91,209
Operating expenses:
Selling, general and administrative	62,224	58,092	55,675
Research and development	44,286	44,924	41,848
Severance and other charges	402
Total operating expenses	106,912	103,016	97,523
Income (loss) from operations	32,059	(1,360)	(6,314)
Other income (expense), net:
Total unrealized gains (losses) on available-for-sale securities, net	1	17	(18)
Portion of losses (gains) recognized in other comprehensive income (loss)	6	(6)	31
Net credit gains recognized in earnings	7	11	13
Other income (expense), net	867	1,251	271
Total other income (expense), net	874	1,262	284
Income (loss) before income taxes	32,933	(98)	(6,030)
Less: Provision (benefit) for income taxes	1,087	(356)	231
Consolidated net income (loss)	31,846	258	(6,261)
Less: Net income (loss) attributable to noncontrolling interest	121	91	(14)
Net income (loss) attributable to Vicor Corporation	$ 31,725	$ 167	$ (6,247)
Net income (loss) per common share attributable to Vicor Corporation:
Basic	$ 0.80	$ 0	$ (0.16)
Diluted	$ 0.78	$ 0	$ (0.16)
Shares used to compute net income (loss) per common share attributable to Vicor Corporation:
Basic	39,872	39,228	38,842
Diluted	40,729	39,933	38,842

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income (Loss) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Statement of Comprehensive Income [Abstract]
Consolidated net income (loss)		$ 31,846	$ 258	$ (6,261)
Foreign currency translation gains, net of tax benefit	[1]	98	83	52
Unrealized (losses) gains on available-for-sale securities, net of tax	[1]	(6)	6	(31)
Other comprehensive income		92	89	21
Consolidated comprehensive income (loss)		31,938	347	(6,240)
Less: Comprehensive income (loss) attributable to noncontrolling interest		129	97	(9)
Comprehensive income (loss) attributable to Vicor Corporation		$ 31,809	$ 250	$ (6,231)
[1]	The deferred tax assets associated with cumulative foreign currency translation gains and cumulative unrealized gains (losses) on available for sale securities are completely offset by a tax valuation allowance as of December 31, 2018, 2017, and 2016. Therefore, there is no income tax benefit (provision) recognized in any of the three years ended December 31, 2018.

Consolidated Statements of Co_2

Consolidated Statements of Comprehensive Income (Loss) (Parenthetical) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Statement of Comprehensive Income [Abstract]
Recognized income tax benefit (provision)	$ 0	$ 0	$ 0

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Operating activities:
Consolidated net income (loss)	$ 31,846	$ 258	$ (6,261)
Adjustments to reconcile consolidated net income (loss) to net cash provided by (used for) operating activities:
Depreciation and amortization	9,254	8,893	8,438
Stock-based compensation expense	3,396	1,735	506
Increase (decrease) in long-term income taxes payable	43	(1)	4
Deferred income taxes	(55)	(172)	(78)
Decrease in long-term deferred revenue	(71)	(71)	(94)
Increase in other long-term liabilities	9	93
(Gain) loss on disposal of equipment	(57)	(14)	4
Provision (benefit) for doubtful accounts	65	6	(22)
Credit gain on available-for-sale securities	(7)	(11)	(13)
Increase in refundable income taxes		(736)
Increase in contingent consideration obligations		650
Increase in other assets			(505)
Change in current assets and liabilities, net	(8,252)	(13,094)	(1,435)
Net cash provided by (used for) operating activities	36,171	(2,464)	544
Investing activities:
Additions to property, plant and equipment	(18,211)	(12,545)	(8,428)
Proceeds from sale of equipment	57	14	2
(Decrease) increase in other assets	(85)	5	(93)
Net cash used for investing activities	(18,239)	(12,526)	(8,519)
Financing activities:
Proceeds from issuance of Common Stock	8,656	3,300	1,584
Payment of contingent consideration obligations	(270)	(225)	(99)
Deconsolidation of subsidiary			(372)
Net cash provided by financing activities	8,386	3,075	1,113
Effect of foreign exchange rates on cash	9	(25)	52
Net increase (decrease) in cash and cash equivalents	26,327	(11,940)	(6,810)
Cash and cash equivalents at beginning of year	44,230	56,170	62,980
Cash and cash equivalents at end of year	70,557	44,230	56,170
Change in current assets and liabilities, excluding effects of deconsolidation of subsidiary:
Accounts receivable	(8,834)	(9,210)	780
Inventories, net	(10,827)	(9,309)	(3,677)
Other current assets	176	(357)	(158)
Accounts payable and accrued liabilities	7,450	3,186	339
Accrued severance and other charges	234		(195)
Income taxes payable	410	208	61
Deferred revenue	3,139	2,388	1,415
Change in current assets and liabilities, net	(8,252)	(13,094)	(1,435)
Supplemental disclosures:
Cash paid during the year for income taxes, net of refunds	$ 743	$ 373	$ 230

Consolidated Statements of Equi

Consolidated Statements of Equity - USD ($) $ in Thousands	Total	Common Stock [Member]	Additional Paid-In Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Treasury Stock [Member]	Total Vicor Corporation Stockholders' Equity [Member]	Noncontrolling Interest [Member]	Class B Common Stock [Member]
Beginning Balance at Dec. 31, 2015	$ 136,085	$ 395	$ 174,337	$ 99,685	$ (577)	$ (138,927)	$ 135,031	$ 1,054	$ 118
Sales of Common Stock	1,589	2	1,587				1,589
Acquisition of noncontrolling interest	(918)		(81)				(81)	(837)
Stock-based compensation expense	506		506				506
Net settlement stock option exercises	(5)		(5)				(5)
Components of comprehensive income, net of tax
Net (loss)	(6,261)			(6,247)			(6,247)	(14)
Other comprehensive income	21				16		16	5
Total comprehensive (loss)	(6,240)						(6,231)	(9)
Ending Balance at Dec. 31, 2016	131,017	397	176,344	93,438	(561)	(138,927)	130,809	208	118
Sales of Common Stock	3,300	4	3,296				3,300
Stock-based compensation expense	1,735		1,735				1,735
Other	20		20				20
Components of comprehensive income, net of tax
Net (loss)	258			167			167	91
Other comprehensive income	89				83		83	6
Total comprehensive (loss)	347						250	97
Ending Balance at Dec. 31, 2017	136,419	401	181,395	93,605	(478)	(138,927)	136,114	305	118
Sales of Common Stock	6,782	6	6,776				6,782
Stock-based compensation expense	3,396		3,396				3,396
Issuances of stock through employee stock purchase plan	1,874	1	1,873				1,874
Cumulative effect of adoption of new accounting principle (Topic 606)	3,670			3,670			3,670
Other	11	(6)	17				11
Components of comprehensive income, net of tax
Net (loss)	31,846			31,725			31,725	121
Other comprehensive income	92				84		84	8
Total comprehensive (loss)	31,938						31,809	129
Ending Balance at Dec. 31, 2018	$ 184,090	$ 402	$ 193,457	$ 129,000	$ (394)	$ (138,927)	$ 183,656	$ 434	$ 118

Description of Business

Description of Business	12 Months Ended
	Dec. 31, 2018
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Description of Business	1. DESCRIPTION OF BUSINESS Vicor Corporation (the “Company” or “Vicor”) designs, develops, manufactures, and markets modular power components and power systems for converting electrical power. The Company also licenses certain rights to its technology in return for recurring royalties. The principal markets for the Company’s power converters and systems are large original equipment manufacturers (“OEMs”) and their contract manufacturers, and smaller, lower volume users, which are broadly distributed across several major market areas.

Significant Accounting Policies

Significant Accounting Policies	12 Months Ended
	Dec. 31, 2018
Accounting Policies [Abstract]
Significant Accounting Policies	2. SIGNIFICANT ACCOUNTING POLICIES Principles of consolidation The Consolidated Financial Statements include the accounts of the Company and its subsidiaries. All intercompany transactions and balances have been eliminated upon consolidation. One of the Company’s subsidiaries was not majority owned by the Company prior to 2016, and a second was not majority owned prior to March 31, 2016. Prior to the transactions described in Note 8, these entities were consolidated by the Company as management believed that the Company had the ability to exercise control over their activities and operations. Use of estimates The preparation of financial statements in conformity with accounting principles generally accepted in the United States requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingencies at the date of the financial statements and the reported amounts of revenue and expenses during the reporting period. Such estimates and assumptions relate to the useful lives of fixed assets and identified intangible assets, recoverability of long-lived assets, fair value of long-term investments, allowances for doubtful accounts, the net realizable value of inventory, potential reserves relating to litigation matters, accrued liabilities, accrued taxes, deferred tax valuation allowances, assumptions pertaining to share-based payments, and other reserves. Actual results could differ from those based on these estimates and assumptions, and such differences may be material to the financial statements. Recently Adopted Accounting Standards Revenue Recognition In May 2014, the Financial Accounting Standards Board (“FASB”) issued new guidance for revenue recognition (“Topic 606”), which requires an entity to recognize the amount of revenue to which it expects to be entitled for the transfer of promised goods or services to customers. The new guidance, which includes several amendments, replaces most of the prior revenue recognition guidance under U.S. The Company adopted the new guidance as of January 1, 2018 using the modified retrospective method, as applied to all contracts. As a result, the Company has changed its accounting policy for revenue recognition, as detailed below. The most significant impact of the adoption was on the timing of recognition of sales to the Company’s stocking distributors and including the additional required disclosures under the new standard. Through December 31, 2017, the Company deferred revenue and the related cost of sales on shipments to stocking distributors until the distributors resold the products to their customers. Upon adoption, the Company is no longer permitted to defer revenue until sale by the stocking distributor to the end customer, but rather, is required to estimate the effects of returns and allowances provided to stocking distributors and record revenue at the time of sale to the stocking distributor. In addition, the Company modified the accounting for a contractual arrangement due to a reassessment of the number of performance obligations in the arrangement, and adjusted for the timing of certain royalty revenue. The cumulative effect of adopting this guidance, recorded as an increase to the balance of retained earnings as of January 1, 2018, was approximately $3,670,000. The comparative information for the years ended December 31, 2017 including disclosures, has not been restated and continues to be reported under the accounting standards in effect for periods . The following tables summarize the impacts of adopting the new revenue recognition guidance on certain components of the Company’s consolidated financial statements (in thousands): a) Consolidated Balance Sheet Items As of December 31, 2018 As reported Adjustments Balances without adoption of Topic 606 Accounts receivable, net $ 43,673 $ (72 ) $ 43,601 Inventories, net 47,370 (110 ) 47,260 Total assets 221,068 (182 ) 220,886 Income taxes payable 710 (59 ) 651 Deferred revenue 5,069 5,768 10,837 Sales allowances 548 (483 ) 65 Total liabilities 36,978 5,226 42,204 Retained earnings 129,000 (5,408 ) 123,592 Total equity 184,090 (5,408 ) 178,682 Total liabilities and equity 221,068 (182 ) 220,886 b) Consolidated Statement of Operations Items Year Ended December 31, 2018 As reported Adjustments Balances without adoption of Topic 606 Net revenues $ 291,220 $ (3,946 ) $ 287,274 Cost of revenues 152,249 (2,149 ) 150,100 Gross margin 138,971 (1,797 ) 137,174 Income before income taxes 32,933 (1,797 ) 31,136 Provision for income taxes 1,087 (59 ) 1,028 Consolidated net income 31,846 (1,738 ) 30,108 Net income attributable to Vicor Corporation 31,725 (1,738 ) 29,987 The impact of the adoption of the new revenue recognition standard on the consolidated statements of comprehensive income (loss) and cash flows for the year ended December 31, 2018 was not material. Prior to January 1 , 2018 Product revenue was recognized in the period when persuasive evidence of an arrangement with a customer existed, the products were shipped and title was transferred to the customer, the price was fixed or determinable, and collection was considered probable. The Company deferred revenue and the related cost of sales on shipments to stocking distributors until the distributors resold the products to their customers. The agreements with these stocking distributors allowed them to receive price adjustment credits or to return qualifying products for credit, as determined by the Company, in order to reduce the amounts of slow-moving, discontinued, or obsolete product from their inventory. These stocking distributors were also granted price adjustment credits in the event of a price decrease subsequent to the date the product was shipped and invoiced to the stocking distributor. Given the uncertainties associated with the levels of price adjustment credits to be granted to stocking distributors, the sales price to the stocking distributor was not fixed or determinable until the stocking distributor resold the products to its customers. Therefore, the Company deferred revenue and the related cost of sales on shipments to stocking distributors until the stocking distributors resold the products to their customers. Accordingly, the Company’s revenue fully reflected end-customer purchases and was not impacted by stocking distributor inventory levels. Agreements with stocking distributors limited returns of qualifying product to the Company to a certain percentage of the value of the Company’s shipments to that stocking distributor during the prior quarter. In addition, stocking distributors were allowed to return unsold products if the Company terminated the relationship with the stocking distributor. Title to the inventory transferred to the stocking distributor at the time of shipment or delivery to the stocking distributor. Payments from the stocking distributors were due in accordance with the Company’s standard payment terms. These payment terms were not contingent upon the stocking distributors’ sale of the products to their end-customers. Upon title transfer to stocking distributors, the Company reduced inventory for the cost of goods shipped, the margin (i.e., revenues less cost of revenues) was recorded as deferred revenue, and an account receivable was recorded. As of December 31, 2017, the Company had gross deferred revenue of approximately $4,659,000 and gross deferred cost of revenues of approximately $2,135,000 under agreements with stocking distributors. The Company evaluated revenue arrangements with potential multi-element deliverables to determine if there were more than one unit of accounting. A deliverable constituted a separate unit of accounting when it had standalone value and there were no customer-negotiated refund or return rights for the undelivered elements. The Company entered into arrangements containing multiple elements that could include a combination of non-recurring engineering services (“NRE”), prototype units, and production units. The Company determined NRE and prototype units represented one unit of accounting and production units represented a separate unit of accounting, based on an assessment of the respective standalone value. The Company deferred revenue recognition for NRE and prototype units until completion of the final milestone under the NRE arrangement, which was generally the delivery of the prototype. Recognition generally took place within six to twelve months of the initiation of the arrangement. Revenue for the production units was recognized upon shipment, consistent with other product revenue summarized above. License fees were recognized as earned. The Company recognized revenue on such arrangements only when the contract was signed, the license term had begun, all obligations had been delivered to the customer, and collection was probable. Subsequent to January 1, 2018 Revenue is recognized when control of the promised goods or services is transferred to a customer, in an amount that reflects the consideration the Company expects to be entitled to in exchange for those goods or services. Sales, value add, and other taxes collected concurrent with revenue-producing activities are excluded from revenue. The expected costs associated with product warranties continue to be recognized at the time product revenue is recognized. Shipping and handling costs associated with outbound freight after control over a product has transferred to a customer are accounted for as a fulfillment cost and are included in cost of revenues. The Company’s primary source of net revenue comes from the sale of products, which are modular power components and power systems for converting, regulating and controlling electric current. The principal customers for the Company’s power converters and systems are large original equipment manufacturers and the original design manufacturers and contract manufacturers serving them, and smaller, lower volume users, which are broadly distributed across several major market areas. The Company recognizes revenue for product sales at a point in time following the transfer of control of such products to the customer, which typically occurs upon shipment or delivery, depending on the terms of the underlying contract. As noted above, the Company previously deferred revenue and the related cost of revenues on shipments to stocking distributors until the distributors resold the products to their customers. The Company now records revenue for such transactions at the time of sale to the stocking distributor. The Company establishes sales allowances for estimated future product returns including distributor returns and price adjustment credits, primarily based upon historical and anticipated rates of product returns and allowances. Certain contracts with customers contain multiple performance obligations, which typically may include a combination of NRE, prototype units, and production units. For these contracts, the individual performance obligations are accounted for separately if they are distinct. Generally, the Company has determined the NRE and prototype units represent one distinct performance obligation and the production units represent a separate distinct performance obligation. For such arrangements, revenue is allocated to each performance obligation based on its relative standalone selling price, based on prices charged to customers or using the expected cost plus a margin approach. The Company defers revenue recognition for NRE and prototype units until the point in time at which the final milestone under the NRE arrangement is completed and control is transferred to the customer, which is generally the shipment or delivery of the prototype. Revenue for production units is recognized upon shipment or delivery, consistent with product revenue summarized above. The Company licenses its intellectual property under right to use licenses, in which royalties due to the Company are based upon a percentage of the licensee’s sales. The Company utilizes the exception under the revenue recognition guidance for the recognition of sales- or usage-based royalties, in which the royalties are not recognized until the later of when 1) the customer’s subsequent sales or usages occur, or 2) the performance obligation to which some or all of the sales- or usage-based royalty has been allocated is satisfied or partially satisfied. Accounts receivable includes amounts billed and currently due from customers. The amounts due are stated at their estimated realizable value. The Company’s payment terms vary by the type and location of its customers and the products or services offered, although terms generally include a requirement of payment within 30 to 60 days. The Company maintains allowances for doubtful accounts for estimated losses resulting from the inability of its customers to make required payments, based on assessments of customers’ credit-risk profiles and payment histories. If the financial condition of the Company’s customers were to deteriorate, resulting in an impairment of their ability to make payments, additional allowances may be required. The Company does not require collateral from its customers, although there have been circumstances when the Company has required cash in advance (i.e., a partial down-payment) to facilitate orders in excess of a customer’s established credit limit. To date, such amounts have not been material. The Company records deferred revenue, which represents a contract liability, when cash payments are received or due in advance of performance under a contract with a customer. During the year ended December 31, 2018, under Topic 606, the Company recognized revenue of approximately $991,000 that was included in deferred revenue at the beginning of the respective period. The Company applies the practical expedient allowed under the new guidance for the incremental costs of obtaining a contract for sales commissions, which are expensed when incurred because the amortization period is generally less than one year. These costs are included in selling, general and administrative expenses. The Company also applies another practical expedient allowed under the new guidance and does not disclose the value of unsatisfied performance obligations for contracts with an original expected length of one year or less. The following table presents the Company’s net revenues disaggregated by geography based on the location of the customer, by reportable segment, (in thousands): Year Ended December 31, 2018 BBU VI Chip Picor Total United States $ 77,995 $ 30,118 $ 2,666 $ 110,779 Europe 23,484 3,883 322 27,689 Asia Pacific 80,097 47,174 19,807 147,078 All other 5,128 499 47 5,674 $ 186,704 $ 81,674 $ 22,842 $ 291,220 The following table presents the Company’s net revenues disaggregated by the category of revenue, by reportable segment, (in thousands): Year Ended December 31, 2018 BBU VI Chip Picor Total Direct customers, contract manufacturers and non-stocking distributors $ 163,206 $ 70,919 $ 20,660 $ 254,785 Stocking distributors, net of sales allowances 22,362 7,653 1,717 31,732 Non-recurring engineering 1,066 2,996 360 4,422 Royalties 70 70 70 210 Other — 36 35 71 $ 186,704 $ 81,674 $ 22,842 $ 291,220 The following table presents the changes in certain contract assets and (liabilities) (in thousands): December 31, 2018 December 31, 2017 Increase (decrease) Accounts receivable $ 43,673 $ 34,487 $ 9,186 Deferred revenue (3,820 ) (5,015 ) 1,195 Deferred expenses 501 859 (358 ) Customer prepayments (1,250 ) (776 ) (474 ) Sales allowances (548 ) — (548 ) The increase in accounts receivable was primarily due to an increase in net revenues of approximately $14,949 in the fourth quarter of 2018 compared to the fourth quarter of 2017. The decrease in deferred revenue was primarily due to the adoption of the new revenue recognition guidance, as the balances related to stocking distributors were reversed as part of the transition adjustment recorded as of January 1, 2018 (see Recently Adopted Accounting Standards , above). The increase in sales allowances was due to the establishment of new allowances, in connection with the new revenue recognition guidance, for potential returns and price adjustment credits on sales to stocking distributors. Deferred expenses are included in Other current assets, and customer prepayments are included in Deferred revenue, in the accompanying Consolidated Balance Sheets, respectively. Other Recently Adopted Accounting Standards In June 2018, the FASB issued new guidance, Improvements to Nonemployee Share-Based Payment Accounting, which more closely aligns the accounting for share-based payments to non-employees with the accounting for share-based payments to employees. This new guidance is effective for public business entities for annual and interim periods in fiscal years beginning after December 15, 2018, with early adoption permitted. The Company early-adopted the new standard on July 1, 2018. The adoption of this new guidance did not have a material impact on its consolidated financial statements and related disclosures. In May 2017, the FASB issued guidance about which changes to the terms or conditions of a share-based payment award require an entity to apply modification accounting in Topic 718, Compensation — Stock Compensation. The new guidance is effective for annual and interim periods beginning after December 15, 2017, with early adoption permitted. The Company adopted the new standard on January 1, 2018. The adoption of this new guidance did not have a material impact on its consolidated financial statements and related disclosures. In August 2016, the FASB issued guidance to clarify how certain cash receipts and cash payments should be presented in the statement of cash flows. These include debt prepayment, settlement of zero-coupon debt instruments, contingent consideration payments made after a business combination, proceeds from the settlement of insurance claims, proceeds from the settlement of corporate-owned life insurance policies, distributions received from equity method investees and beneficial interests in securitization transactions. The new guidance is effective for interim and annual reporting periods beginning after December 15, 2017, with early adoption permitted. The Company adopted the new standard on January 1, 2018. The adoption of this new guidance did not have a material impact on its consolidated financial statements and related disclosures. Foreign currency translation The financial statements of Vicor Japan Company, Ltd. (“VJCL”), a majority-owned subsidiary, for which the functional currency is the Japanese Yen, have been translated into U.S. Dollars using the exchange rate in effect at the balance sheet date for balance sheet amounts and the average exchange rates in effect during the year for income statement amounts. The gains and losses resulting from the changes in exchange rates from year to year have been reported in other comprehensive income. Transaction gains and losses resulting from the remeasurement of foreign currency denominated assets and liabilities of the Company’s foreign subsidiaries where the functional currency is the U.S. Dollar are included in other income (expense), net. Foreign currency gains (losses) included in other income (expense), net, were approximately $(260,000), $323,000, and $(268,000) in 2018, 2017, and 2016, respectively. Cash and cash equivalents Cash and cash equivalents include funds held in disbursement (i.e., checking) and money market accounts, certificates of deposit, and debt securities with maturities of less than three months at the time of purchase. Cash and cash equivalents are valued at cost, approximating market value. The Company’s money market securities, which are classified as cash equivalents on the balance sheet, are purchased and redeemed at par value. Their estimated fair value is equal to their cost, and, due to the nature of the securities and their classification as cash equivalents, there are no unrealized gains or losses recorded at the balance sheet dates. Long-term investment The Company’s principal sources of liquidity are its existing balances of cash and cash equivalents, as well as cash generated from operations. Consistent with the guidelines of the Company’s investment policy, the Company can invest, and has historically invested, its cash balances in demand deposit accounts, money market funds, and auction rate securities meeting certain quality criteria. The Company’s long-term investment is subject to credit, liquidity, market, and interest rate risk. The Company’s long-term investment, which is a debt security, is classified as an available-for-sale security. The available-for-sale security is recorded at fair value, with unrealized gains and losses, net of tax, attributable to credit loss recorded through the Consolidated Statement of Operations and unrealized gains and losses, net of tax, attributable to other non-credit factors recorded in “Accumulated other comprehensive loss,” a component of Total Equity. In determining the amount of credit loss, the Company compares the present value of cash flows expected to be collected to the amortized cost basis of the security, considering credit default risk probabilities and changes in credit ratings, among other factors. The amortized cost of the debt security is adjusted for amortization of premiums and accretion of discounts to maturity, the net amount of which, along with interest and realized gains and losses, is included in “Other income (expense), net” in the Consolidated Statements of Operations. The Company periodically evaluates the investment to determine if impairment is required, whether an impairment is other than temporary, and the measurement of an impairment loss. The Company considers a variety of impairment indicators such as, but not limited to, a significant deterioration in the earnings performance, credit rating, or asset quality of the investment. Fair value measurements The Company accounts for certain financial assets at fair value, defined as the price that would be received to sell an asset or paid to transfer a liability (i.e., an exit price) in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants on the measurement date. As such, fair value is a market-based measurement that should be determined based on assumptions that market participants would use in pricing an asset or liability. A three-level hierarchy is used to show the extent and level of judgment used to estimate fair value measurements: Level 1 Inputs used to measure fair value are unadjusted quoted prices available in active markets for the identical assets or liabilities as of the reporting date. Level 2 Inputs used to measure fair value, other than quoted prices included in Level 1, are either directly or indirectly observable as of the reporting date through correlation with market data, including quoted prices for similar assets and liabilities in active markets and quoted prices in inactive markets. Level 2 also includes assets and liabilities valued using models or other pricing methodologies that do not require significant judgment since the input assumptions used in the models, such as interest rates and volatility factors, are corroborated by readily observable data from actively quoted markets for substantially the full term of the financial instrument. Level 3 Inputs used to measure fair value are unobservable inputs supported by little or no market activity and reflect the use of significant management judgment. These values are generally determined using pricing models for which the assumptions utilize management’s estimates of market participant assumptions. The carrying amounts of cash and cash equivalents, accounts receivable and accounts payable approximate fair value because of the short maturity of these financial instruments. Inventories Inventories are valued at the lower of cost (determined using the first-in, first-out method) or net realizable value. Fixed production overhead is allocated to the inventory cost per unit based on the normal capacity of the production facilities. Abnormal production costs, including fixed cost variances from normal production capacity, if any, are charged to cost of revenues in the period incurred. All shipping and handling costs incurred in connection with the sale of products are included in cost of revenues. The Company provides reserves for inventories estimated to be excess, obsolete, or unmarketable. The Company’s estimation process for assessing net realizable value is based upon its known backlog, projected future demand, historical consumption and expected market conditions. If the Company’s estimated demand and/or market expectations were to change or if product sales were to decline, the Company’s estimation process may cause larger inventory reserves to be recorded, resulting in larger charges to cost of revenues. Concentrations of risk Financial instruments potentially subjecting the Company to significant concentrations of credit risk consist principally of cash and cash equivalents, of which a significant portion is held by one financial institution, its long-term investment, and trade accounts receivable. The Company maintains cash and cash equivalents and certain other financial instruments with various large financial institutions. Generally, amounts invested with these financial institutions are in excess of federal deposit insurance limits. The Company has not experienced any losses in such accounts, and management believes the Company is not exposed to significant credit risk. The Company’s long-term investment as of December 31, 2018 consists of a single auction rate security with a par value of $3,000,000, which is collateralized by student loans. It is a highly rated (Aaa/AA+) municipal and corporate debt security. Through December 31, 2018, auctions held for the Company’s auction rate security have failed. The funds associated with an auction rate security that has failed auction may not be accessible until a successful auction occurs, a buyer is found outside of the auction process, the security is called, or the underlying securities have matured. If the credit rating of the issuer of the auction rate security held deteriorates, the Company may be required to adjust the carrying value of the investment for an other-than-temporary decline in value through an impairment charge. The Company’s investment policy, approved by the Board of Directors, limits the amount the Company may invest in any issuer, thereby reducing credit risk concentrations. The Company’s products are sold worldwide to customers ranging from smaller, independent manufacturers of highly specialized electronic devices, to larger OEMs and their contract manufacturers. The Company’s Brick Business Unit (“BBU”) segment has customers concentrated in aerospace and defense electronics, industrial automation, industrial equipment, instrumentation and test equipment, and transportation (e.g., rail). The Company’s other segments, the VI Chip subsidiary and Picor (see Note 17) have customers concentrated in computing (voltage distribution in server racks and across datacenter infrastructure), although they also target applications in aerospace and aviation, defense electronics, industrial automation, instrumentation, test equipment, solid state lighting, telecommunications and networking infrastructure and vehicles (e.g., in autonomous driving applications, electric vehicles, and hybrid electric vehicles). While, overall, the Company has a broad customer base and sells into a variety of industries, VI Chip and Picor have derived a substantial portion of their revenue from a limited number of customers. This concentration of revenue is a reflection of the relatively early stage of adoption of the technologies, architectures and products offered by these subsidiaries, and their targeting of market leading innovators as initial customers. Concentrations of credit risk with respect to trade accounts receivable are limited due to the number of entities comprising the Company’s customer base. As of December 31, 2018 and 2017, one customer accounted for approximately 14.3% and 17.5%, respectively, of trade account receivables. Components and materials used in the Company’s products are purchased from a variety of vendors. While most of the components are available from multiple sources, some key components for certain VI Chip and Picor products, in particular, are supplied by single vendors. In instances of single source items, the Company maintains levels of inventories management considers appropriate to enable meeting the delivery requirements of customers. If suppliers or subcontractors cannot provide their products or services on time or to the required specifications, the Company may not be able to meet the demand for its products and its delivery times may be negatively affected. Long-lived assets The Company reviews property, plant and equipment and finite-lived intangible assets for impairment whenever events or changes in circumstances indicate the carrying value of such assets may not be recoverable. Management determines whether the carrying value of an asset or asset group is recoverable based on comparison to the undiscounted expected future cash flows the assets are expected to generate over their remaining economic lives. If an asset value is not recoverable, the impairment loss is equal to the amount by which the carrying value of the asset exceeds its fair value, which is determined by either a quoted market price, if any, or a value determined by utilizing a discounted cash flow technique. Evaluation of impairment of long-lived assets requires estimates of future operating results that are used in the preparation of the expected future undiscounted cash flows. Actual future operating results and the remaining economic lives of our long-lived assets could differ from the estimates used in assessing the recoverability of these assets. These differences could result in impairment charges, which could be material. Intangible assets Values assigned to patents are amortized using the straight-line method over periods ranging from three to 20 years. Patents and other intangible assets are included in “Other assets” in the accompanying Consolidated Balance Sheets. Advertising expense The cost of advertising is expensed as incurred. The Company incurred approximately $2,610,000, $2,150,000, and $1,818,000 in advertising costs during 2018, 2017 and 2016, respectively. Product warranties The Company generally offers a two-year warranty for all of its products, though it has extended the warranty period to three years for certain military grade products sold after January 1, 2017. The Company is party to a limited number of supply agreements with certain customers contractually committing the Company to warranty and indemnification requirements exceeding those to which the Company has been exposed in the past. The Company provides for the estimated cost of product warranties at the time product revenue is recognized. Factors influencing the Company’s warranty reserves include the number of units sold, historical and anticipated rates of warranty returns, and the cost per return. The Company periodically assesses the adequacy of warranty reserves and adjusts the amounts as necessary. Warranty obligations are included in “Accrued expenses” in the accompanying Consolidated Balance Sheets. Legal Costs Legal costs in connection with litigation are expensed as incurred. Net income (loss) per common share The Company computes basic net income (loss) per share using the weighted average number of common shares outstanding and diluted net income (loss) per share using the weighted average number of common shares outstanding plus the effect of The following table sets forth the computation of basic and diluted net income (loss) per share for the years ended December 31 (in thousands, except per share amounts): 2018 2017 2016 Numerator: Net income (loss) attributable to Vicor Corporation $ 31,725 $ 167 $ (6,247 ) Denominator: Denominator for basic net income (loss) per share-weighted average shares (1) 39,872 39,228 38,842 Effect of dilutive securities: Employee stock options (2) 857 705 — Denominator for diluted net income (loss) per share-adjusted weighted-average shares and assumed conversions (3) 40,729 39,933 38,842 Basic net income (loss) per share $ 0.80 $ 0.00 $ (0.16 ) Diluted net income (loss) per share $ 0.78 $ 0.00 $ (0.16 ) (1) Denomin

Stock-Based Compensation and Em

Stock-Based Compensation and Employee Benefit Plans	12 Months Ended
	Dec. 31, 2018
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Stock-Based Compensation and Employee Benefit Plans	3. STOCK-BASED COMPENSATION AND EMPLOYEE BENEFIT PLANS Vicor currently grants options for the purchase of Common Stock (i.e., “stock options”) under the following equity compensation plan that is stockholder-approved: Amended and Restated 2000 Stock Option and Incentive Plan, as amended and restated (the “2000 Plan”) — Under the 2000 Plan, the Board of Directors or the Compensation Committee of the Board of Directors may grant stock incentive awards based on the Company’s Common Stock, including stock options, stock appreciation rights, restricted stock, performance shares, unrestricted stock, deferred stock, and dividend equivalent rights. Awards may be granted to employees and other key persons, including non-employee directors. Incentive stock options may be granted to employees at a price at least equal to the fair market value per share of the Common Stock on the date of grant, and non-qualified options may be granted to non-employee directors at a price at least equal to 85% of the fair market value of the Common Stock on the date of grant. A total of 10,000,000 shares of Common Stock have been reserved for issuance under the 2000 Plan. The period of time during which an option may be exercised and the vesting periods are determined by the Compensation Committee. The term of each option may not exceed 10 years from the date of grant. Picor Corporation (“Picor”) was a privately held, majority-owned subsidiary of Vicor until May 30, 2018, at which date it was merged with and into Vicor, and its separate corporate existence ceased (see Note 16). Until that time, Picor could grant stock options under the Picor Corporation Amended and Restated 2001 Stock Option and Incentive Plan VI Chip Corporation (“VI Chip”), a privately held, majority-owned subsidiary of Vicor, currently grants stock options under the following equity compensation plan that has been approved by its Board of Directors: VI Chip Corporation Amended and Restated 2007 Stock Option and Incentive Plan (the “2007 VI Chip Plan”) All time-based (i.e., non-performance-based) options for the purchase of Vicor common stock are granted at an exercise price equal to or greater than the market price for Vicor Common Stock at the date of the grant. All time-based (i.e., non-performance-based) options for the purchase of VI Chip, and, prior to the merger and assumption of the 2001 Picor Plan, Picor Common Stock have been granted at an exercise price equal to or greater than the estimated fair market value of the respective share price, based on valuation methodologies consistent with U.S. GAAP and the requirements of Section 409A of the Internal Revenue Code, as amended (“the Code”). On December 31, 2010, the Company granted 2,984,250 non-qualified stock options under the 2007 VI Chip Plan with performance-based vesting provisions tied to achievement of certain margin targets by VI Chip. As of December 31, 2010, the Company determined it was probable the margin targets would be achieved and, accordingly, began recording stock-based compensation expense relating to these options beginning January 1, 2011. During the third quarter of 2016, the Company determined the margin targets would not be met prior to the expiration date of the corresponding options, as VI Chip’s revenue growth had been below levels necessary to achieve the targets. As a result, the Company reversed approximately $768,000 of previously recorded stock-based compensation expense in the third quarter of 2016, representing all expense taken for these performance-based options through June 30, 2016. This resulted in decreases in cost of revenues of $86,000, selling, general and administrative expense of $516,000, and research and development expense of $166,000 in the third quarter of 2016. On April 30, 2018, all such options were cancelled. On April 26, 2017, the Company’s Board of Directors approved the Vicor Corporation 2017 Employee Stock Purchase Plan (the “Plan” or the “ESPP”). The ESPP became effective on June 16, 2017, the date the Company’s stockholders approved the Plan at the 2017 Annual Meeting of Stockholders. The Company has reserved 2,000,000 shares of Common Stock under the Plan for issuance to eligible employees who elect to participate. The ESPP is intended to qualify as an “employee stock purchase plan” under Section 423 of the Internal Revenue Code. The ESPP operates in successive periods of approximately six months, each referred to as an “offering period.” Generally, offering periods commence on or around September 1 and March 1 and end on or around the following February 28 or August 31, respectively. Under the ESPP, an option is granted to participating employees on the first day of an offering period to purchase shares of the Company’s Common Stock at the end of that offering period at a purchase price equal to 85% of the lesser of the fair market value of a share of Common Stock on either the first day or the last day of that offering period. The purchase of shares is funded by means of periodic payroll deductions, which may not exceed 15.0% of the employee’s eligible compensation, as defined in the Plan. Among other provisions, the Plan limits the number of shares that can be purchased by a participant during any offering period and cumulatively for any calendar year. Stock-based compensation expense for the years ended December 31 was as follows (in thousands): 2018 2017 2016 Cost of revenues $ 237 $ 187 $ 95 Selling, general and administrative 2,517 1,125 412 Research and development 642 423 (1 ) Total stock-based compensation $ 3,396 $ 1,735 $ 506 The increase in stock-based compensation in 2018 compared to 2017 was due to an increase in stock options granted between July 1, 2017 and December 31, 2018 and ESPP expense, which was recorded for only part of 2017. The increase in stock-based compensation expense in 2017 compared to 2016 was primarily due to the reversal of previously recorded stock-based compensation for VI Chip performance-based options in 2016, as described above. Compensation expense by type of award for the years ended December 31 was as follows (in thousands): 2018 2017 2016 Stock options $ 2,649 $ 1,546 $ 506 ESPP 747 189 — Total stock-based compensation $ 3,396 $ 1,735 $ 506 The fair value for non performance-based stock options awarded for the years shown below was estimated at the date of grant using the Black-Scholes option pricing model with the following weighted-average assumptions: Vicor: 2018 2017 2016 Risk-free interest rate 2.9 % 2.1 % 1.5 % Expected dividend yield — — — Expected volatility 44 % 43 % 45 % Expected lives (years) 6.4 7.1 7.2 VI Chip: 2018 2017 2016 Risk-free interest rate N/A 1.9 % 1.7 % Expected dividend yield — — — Expected volatility N/A 32 % 34 % Expected lives (years) N/A 6.5 6.5 No stock options were granted in 2018 under the 2007 VI Chip Plan. Risk-free interest rate: Vicor — The Company uses the yield on zero-coupon U.S. Treasury “Strip” securities for a period that is commensurate with the expected term assumption for each vesting period. VI Chip — VI Chip uses the yield to maturity of a seven-year U.S. Treasury bond, as it most closely aligns to the expected exercise period. Expected dividend yield: Vicor — The Company determines the expected dividend yield by annualizing the most recent prior cash dividends declared by the Company’s Board of Directors, if any, and dividing that result by the closing stock price on the date of that dividend declaration. Dividends are not paid on options. VI Chip — VI Chip has not and does not expect to declare and pay dividends in the foreseeable future. Therefore, the expected dividend yield is not applicable. Expected volatility: Vicor — Vicor uses historical volatility to estimate the grant-date fair value of the options, using the expected term for the period over which to calculate the volatility (see below). The Company does not expect its future volatility to differ from its historical volatility. The computation of the Company’s volatility is based on a simple average calculation of monthly volatilities over the expected term. VI Chip — As VI Chip is a nonpublic entity, historical volatility information is not available. An industry sector index of 11 publicly traded fabless semiconductor firms was developed for calculating historical volatility for VI Chip. Historical prices for each of the companies in the index based on the market price of the shares on each day of trading over the expected term were used to determine the historical volatility. Expected term: Vicor — The Company uses historical employee exercise and option expiration data to estimate the expected term assumption for the Black-Scholes grant-date valuation. The Company believes this historical data is currently the best estimate of the expected term of options, and all groups of the Company’s employees exhibit similar exercise behavior. VI Chip — Due to the lack of historical information, the “simplified” method as prescribed by the Securities and Exchange Commission is used to determine the expected term. Forfeiture rate: The amount of stock-based compensation recognized during a period is based on the value of the portion of the awards that are ultimately expected to vest. Forfeitures are estimated at the time of grant and revised, if necessary, in subsequent periods if actual forfeitures differ from those estimates. The term “forfeitures” is distinct from “cancellations” or “expirations” and represents only the unvested portion of the surrendered option. The forfeiture analysis is re-evaluated annually and the forfeiture rate is adjusted as necessary. Ultimately, the actual expense recognized over the vesting period will only be for those shares that vest. Vicor — The Company currently expects, for Vicor options, based on an analysis of historical forfeitures, approximately 85% of its options will actually vest. An annual forfeiture rate of 5.25% has been applied to all unvested options as of December 31, 2018. For 2017 and 2016, the Company expected 85% and 86%, respectively, of its options would actually vest and applied an annual forfeiture rate of 5.25% and 5.00%, respectively. VI Chip — The Company currently expects, for VI Chip options, based on an analysis of historical forfeitures, approximately 89% of its options will actually vest. An annual forfeiture rate of 4.25% has been applied to all unvested options as of December 31, 2018. For 2017 and 2016, the Company expected 76% of its options would actually vest and applied an annual forfeiture rate of 9.00% for both years. Vicor Stock Options A summary of the activity under the 2000 Plan as of December 31, 2018 and changes during the year then ended, is presented below (in thousands except for share and weighted-average data): Options Outstanding Weighted- Average Exercise Price Weighted- Average Remaining Contractual Life in Aggregate Intrinsic Value Outstanding on December 31, 2017 1,365,917 $ 9.63 Granted 684,077 $ 18.40 Forfeited and expired (25,923 ) $ 16.08 Exercised (641,090 ) $ 10.58 Outstanding on December 31, 2018 1,382,981 $ 13.41 5.40 $ 34,329 Exercisable on December 31, 2018 888,257 $ 8.93 4.46 $ 25,635 Vested or expected to vest as of December 31, 2018 (1) 1,345,938 $ 13.07 5.34 $ 33,820 (1) In addition to the vested options, the Company expects a portion of the unvested options to vest at some point in the future. The number of options expected to vest is calculated by applying an estimated forfeiture rate to the unvested options. As of December 31, 2017 and 2016 the Company had options exercisable for 707,244 and 730,388 shares respectively, for which the weighted average exercise prices were $8.01 and $7.74, respectively. During the years ended December 31, 2018, 2017, and 2016 under all plans, the total intrinsic value of Vicor options exercised (i.e., the difference between the market price at exercise and the price paid by the employee to exercise the options) was $22,938,000, $4,395,000, and $1,392,000, respectively. The total amount of cash received by the Company from options exercised in 2018, 2017, and 2016, was $6,782,000, $3,295,000, and $1,572,000, respectively. The total grant-date fair value of stock options that vested during the years ended December 31, 2018, 2017, and 2016 was approximately $2,921,000, $774,000, and $365,000, respectively. As of December 31, 2018, there was $2,487,000 of total unrecognized compensation cost related to unvested non-performance based awards for Vicor. That cost is expected to be recognized over a weighted-average period of 1.9 years for those awards. The expense will be recognized as follows: $1,183,000 in 2019, $689,000 in 2020, $395,000 in 2021, $180,000 in 2022, and $40,000 in 2023. The weighted-average fair value of Vicor options granted was $17.46, $8.71, and $4.94, in 2018, 2017, and 2016, respectively. Picor Stock Options A summary of the activity under the 2001 Picor Plan as of May 30, 2018, the date of the merger with and into Vicor, and changes during the period then ended, is presented below: Options Outstanding Weighted- Average Exercise Price Outstanding on December 31, 2017 10,065,987 $ 0.62 Granted — Forfeited and expired — Exercised — Options transferred in merger with Vicor (10,065,987 ) $ 1.91 Outstanding on May 30, 2018 — VI Chip Stock Options A summary of the activity under the 2007 VI Chip Plan as of December 31, 2018 and changes during the year then ended, is presented below (in thousands except for share and weighted-average data): Options Outstanding Weighted- Average Exercise Price Weighted- Average Remaining Contractual Life in Years Aggregate Intrinsic Value Outstanding on December 31, 2017 13,092,250 $ 0.97 Granted — $ — Forfeited and expired (2,678,250 ) $ 1.00 Exercised — $ — Outstanding on December 31, 2018 (1) 10,414,000 $ 0.96 5.39 $ — Exercisable on December 31, 2018 2,743,400 $ 0.97 5.04 $ — Vested or expected to vest as of December 31, 2018 (2) 9,853,685 $ 0.96 5.38 $ — (1) Of the total VI Chip options outstanding on December 31, 2018, 5,500,000 options had been granted to Dr. Vinciarelli, the Company’s Chief Executive Officer. (2) In addition to the vested options, the Company expects a portion of the unvested options to vest at some point in the future. Options expected to vest is calculated by applying an estimated forfeiture rate to the unvested options. As of December 31, 2017 and 2016, VI Chip had options exercisable for 810,700 and 7,074,650 shares, respectively, for which the weighted average exercise price was $1.00. There were no VI Chip options exercised in 2018, 2017 and 2016. The total grant-date fair value of stock options that vested during the years ended December 31, 2018, 2017, and 2016 was approximately $0, $2,900,000, and $0, respectively. As of December 31, 2018, there was $1,792,000 of total unrecognized compensation cost related to unvested share-based awards for VI Chip. That cost is expected to be recognized over a weighted-average period of 3.40 years for all VI Chip awards. The expense will be recognized as follows: $544,000 in 2019, $503,000 in 2020, $483,000 in 2021, and $262,000 in 2022. There were no VI Chip options granted in 2018. The weighted-average fair value of VI Chip options granted in 2017 and 2016 was $0.29, and $0.01, respectively. 401(k) Plan The Company sponsors a savings plan available to all domestic employees, which qualifies under Section 401(k) of the Internal Revenue Code. Employees may contribute to the plan in amounts representing from 1% to 80% of their pre-tax salary, subject to statutory limitations. The Company matches employee contributions to the plan at a rate of 50%, up to the first 3% of an employee’s compensation. The Company’s matching contributions currently vest at a rate of 20% per year, based upon years of service. The Company’s contributions to the plan were approximately $976,000, $937,000, and $882,000 in 2018, 2017, and 2016, respectively. Stock Bonus Plan Under the Company’s 1985 Stock Bonus Plan, as amended, shares of Common Stock may be awarded to employees from time to time as determined by the Board of Directors. On December 31, 2018, 109,964 shares were available for further award. All shares awarded to employees under this plan have vested. No further awards are contemplated under this plan at the present time.

Long-Term Investments

Long-Term Investments	12 Months Ended
	Dec. 31, 2018
Investments, Debt and Equity Securities [Abstract]
Long-Term Investments	4. LONG-TERM INVESTMENT As of December 31, 2018 and 2017, the Company held one auction rate security with a par value of $3,000,000, purchased through and held in custody by a broker-dealer affiliate of Bank of America, N.A., that has experienced failed auctions (the “Failed Auction Security”) since February 2008. The Failed Auction Security held by the Company is Aaa/AA+ rated by major credit rating agencies, is collateralized by student loans, and is guaranteed by the U.S. Department of Education under the Federal Family Education Loan Program. Management is not aware of any reason to believe the issuer of the Failed Auction Security is presently at risk of default. Through December 31, 2018, the Company has continued to receive interest payments on the Failed Auction Security in accordance with the terms of its indenture. Management believes the Company ultimately should be able to liquidate the Failed Auction Security without significant loss primarily due to the overall quality of the issue held and the collateral securing the substantial majority of the underlying obligation. However, current conditions in the auction rate securities market have led management to conclude the recovery period for the Failed Auction Security exceeds 12 months. As a result, the Company continued to classify the Failed Auction Security as long-term as of December 31, 2018. The following is a summary of the available-for-sale security (in thousands): December 31, 2018 Cost Gross Unrealized Gains Gross Unrealized Losses Estimated Fair Value Failed Auction Security $ 3,000 $ — $ 474 $ 2,526 December 31, 2017 Failed Auction Security $ 3,000 $ — $ 475 $ 2,525 As of December 31, 2018 and 2017, the Failed Auction Security had been in an unrealized loss position for greater than 12 months. The amortized cost and estimated fair value of the available-for-sale security on December 31, 2018, by contractual maturities, are shown below (in thousands): Cost Estimated Fair Value Due in twenty to forty years $ 3,000 $ 2,526 Based on the fair value measurements described in Note 5, the fair value of the Failed Auction Security on December 31, 2018, with a par value of $3,000,000, was estimated by the Company to be approximately $2,526,000. The gross unrealized loss of $474,000 on the Failed Auction Security consists of two types of estimated loss: an aggregate credit loss of $41,000 and an aggregate temporary impairment of $433,000. In determining the amount of credit loss, the Company compared the present value of cash flows expected to be collected to the amortized cost basis of the security, considering credit default risk probabilities and changes in credit ratings as significant inputs, among other factors (see Note 5). The following table represents a rollforward of the activity related to the credit loss recognized in earnings on the available-for-sale auction rate security held by the Company for the years ended December 31 (in thousands): 2018 2017 2016 Balance at the beginning of the period $ 48 $ 59 $ 72 Reductions in the amount related to credit gain for which other-than-temporary impairment was not previously recognized (7 ) (11 ) (13 ) Balance at the end of the period $ 41 $ 48 $ 59 At this time, the Company has no intent to sell the Failed Auction Security and does not believe it is more likely than not the Company will be required to sell the security. If current market conditions deteriorate further, the Company may be required to record additional unrealized losses. If the credit rating of the security deteriorates, the Company may be required to adjust the carrying value of the investment through impairment charges recorded in the Consolidated Statement of Operations, and any such impairment adjustments may be material. Based on the Company’s ability to access cash and cash equivalents and its expected operating cash flows, management does not anticipate the current lack of liquidity associated with the Failed Auction Security held will affect the Company’s ability to execute its current operating plan.

Fair Value Measurements

Fair Value Measurements	12 Months Ended
	Dec. 31, 2018
Fair Value Disclosures [Abstract]
Fair Value Measurements	5. FAIR VALUE MEASUREMENTS The Company accounts for certain financial assets at fair value, defined as the price that would be received to sell an asset or paid to transfer a liability (i.e., an exit price) in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants on the measurement date. As such, fair value is a market-based measurement that should be determined based on assumptions market participants would use in pricing an asset or liability. A three-level hierarchy is used to show the extent and level of judgment used to estimate fair value measurements. Assets and liabilities measured at fair value on a recurring basis included the following as of December 31, 2018 (in thousands): Using Quoted Prices in Active Markets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Total Fair Value as of December 31, 2018 Cash equivalents: Money market funds $ 9,433 $ — $ — $ 9,433 Long-term investments: Failed Auction Security — — 2,526 2,526 Liabilities: Contingent consideration obligations — — (408 ) (408 ) Assets measured at fair value on a recurring basis included the following as of December 31, 2017 (in thousands): Using Quoted Prices in Active Markets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Total Fair Value as of December 31, 2017 Cash equivalents: Money market funds $ 9,279 $ — $ — $ 9,279 Long-term investments: Failed Auction Security — — 2,525 2,525 Liabilities: Contingent consideration obligation — — (678 ) (678 ) As of December 31, 2018, there was insufficient observable auction rate security market information available to determine the fair value of the Failed Auction Security using Level 1 or Level 2 inputs. As such, the Company’s investment in the Failed Auction Security was deemed to require valuation using Level 3 inputs. Management, after consulting with advisors, valued the Failed Auction Security using analyses and pricing models similar to those used by market participants (i.e., buyers, sellers, and the broker-dealers responsible for execution of the Dutch auction pricing mechanism by which each issue’s interest rate was set). Management utilized a probability weighted discounted cash flow (“DCF”) model to determine the estimated fair value of this security as of December 31, 2018. The major assumptions used in preparing the DCF model included: estimates for the amount and timing of future interest and principal payments based on default probability assumptions used to measure the credit loss of 1.0%; the rate of return required by investors to own this type of security in the current environment, which we estimate to be 5.0% above the risk free rate of return; and an estimated time frame of three to five years for successful auctions for this type of security to occur. In making these assumptions, management considered relevant factors including: the formula applicable to each security defining the interest rate paid to investors in the event of a failed auction (the “Penalty Rate”); forward projections of the interest rate benchmarks specified in such formulas; the likely timing of principal repayments; the probability of full repayment considering the guarantees by the U.S. Department of Education of the underlying student loans, guarantees by other third parties, and additional credit enhancements provided through other means; and publicly available pricing data for recently issued student loan asset-backed securities not subject to auctions. In developing its estimate of the rate of return required by investors to own these securities, management compared the Penalty Rate of the Failed Auction Security with yields of actively traded long-term bonds with similar characteristics and, reflecting the limited liquidity for auction rate securities and the discounts to par value seen in recent tender offers by issuers and arm’s length market transactions between informed buyers and sellers, estimated the implied yield (i.e., the discount to par value) necessary to complete a sale of the Failed Auction Security. Management has calculated an increase or decrease in the liquidity risk premium of 5.0% referenced above of 1.0% (i.e., 100 basis points) as used in the model, would decrease or increase, respectively, the fair value of the Failed Auction Security by approximately $100,000. The significant unobservable inputs used in the fair value measurement of the Company’s Failed Auction Security are the cumulative probability of earning the maximum rate until maturity, the cumulative probability of principal return prior to maturity, the cumulative probability of default, the liquidity risk premium, and the recovery rate in default. Significant increases (decreases) in any of those inputs in isolation would result in changes in fair value measurement. Significant increases (decreases) in the cumulative probability of earning the maximum rate until maturity, the cumulative probability of principal return prior to maturity, and the recovery rate in default would result in a higher (lower) fair value measurement, while increases (decreases) in the cumulative probability of default and the liquidity risk premium would result in a (lower) higher fair value measurement. Generally, the interrelationships are such that a change in the assumption used for the cumulative probability of principal return prior to maturity is accompanied by a directionally similar change in the assumption used for the cumulative probability of earning the maximum rate until maturity and a directionally opposite change in the assumptions used for the cumulative probability of default and the liquidity risk premium. The recovery rate in default is somewhat independent and based upon the securities’ specific underlying assets and published recovery rate indices. Quantitative information about Level 3 fair value measurements as of December 31, 2018 are as follows (dollars in thousands): Fair Value Valuation Technique Unobservable Input Weighted Average Failed Auction Security $ 2,526 Discounted cash flow Cumulative probability of earning the maximum rate until maturity 0.08 % Cumulative probability of principal return prior to maturity 93.69 % Cumulative probability of default 6.24 % Liquidity risk premium 5.00 % Recovery rate in default 40.00 % The change in the estimated fair value calculated for the investment valued on a recurring basis utilizing Level 3 inputs (i.e., the Failed Auction Security) for the year ended December 31, 2018 was as follows (in thousands): Balance at the beginning of the period $ 2,525 Credit gain on available-for-sale security included in Other income (expense), net 7 Gain included in Other comprehensive income (loss) (6 ) Balance at the end of the period $ 2,526 The Company has classified its contingent consideration obligations as Level 3 because the fair value for this liability was determined using unobservable inputs. The liability was based on estimated sales of legacy products over the period of royalty payments at the royalty rate (see Note 8), discounted using the Company’s estimated cost of capital. The change in the estimated fair value calculated for the liabilities valued on a recurring basis utilizing Level 3 inputs (i.e., the Contingent consideration obligations) for the year ended December 31, 2018 was as follows (in thousands): Balance at the beginning of the period $ 678 Payments (270 ) Balance at the end of the period $ 408 There were no transfers between Level 1 and Level 2 of the fair value hierarchy during the year ended December 31, 2018.

Inventories

Inventories	12 Months Ended
	Dec. 31, 2018
Inventory Disclosure [Abstract]
Inventories	6. INVENTORIES Inventories as of December 31 were as follows (in thousands): 2018 2017 Raw materials $ 37,696 $ 27,400 Work-in-process 4,740 3,596 Finished goods 4,934 5,503 Net balance $ 47,370 $ 36,499

Property, Plant and Equipment

Property, Plant and Equipment	12 Months Ended
	Dec. 31, 2018
Property, Plant and Equipment [Abstract]
Property, Plant and Equipment	7. PROPERTY, PLANT AND EQUIPMENT Property, plant and equipment are stated at cost and are depreciated and amortized over a period of three to 39 years generally under the straight-line method for financial reporting purposes and accelerated methods for income tax purposes. Property, plant and equipment as of December 31 were as follows (in thousands): 2018 2017 Land $ 2,089 $ 2,089 Buildings and improvements 45,170 45,147 Machinery and equipment 208,135 243,392 Furniture and fixtures 7,239 6,320 Construction in-progress and deposits 9,251 4,120 271,884 301,068 Accumulated depreciation and amortization (221,452 ) (259,712 ) Net balance $ 50,432 $ 41,356 Depreciation expense for the years ended December 31, 2018, 2017 and 2016 was approximately $9,135,000, $8,763,000, and $8,304,000 respectively. As of December 31, 2018, the Company had approximately $8,862,000 of capital expenditure commitments.

Noncontrolling Interest Transac

Noncontrolling Interest Transactions	12 Months Ended
	Dec. 31, 2018
Noncontrolling Interest [Abstract]
Noncontrolling Interest Transactions	8. NONCONTROLLING INTEREST TRANSACTIONS On March 30, 2016, the Company acquired 100% ownership of certain operating assets and cash of its consolidated Vicor Custom Power subsidiary, Converpower Corporation (“Converpower”), in which it held a 49% ownership interest. The operating assets and cash were acquired in exchange for the Company’s common shares representing that 49% interest and the aggregate dollar amount of royalty payments to be made by the Company to Converpower. The transaction was executed through a newly-formed, wholly-owned subsidiary, Granite Power Technologies, Inc. (“GPT”), the business operations of which had formerly existed as a division of the Company. The shares of Converpower common stock held by the Company were contributed to GPT prior to the transaction. At the same time that it entered into the Asset Purchase Agreement associated with this transaction, the Company and Converpower entered into a license agreement providing the Company the right to continue manufacturing certain Converpower products in exchange for payment of royalties, quarterly through June 30, 2021, equal to a percentage of the revenue generated by the manufacture and sale of these products by GPT. The estimated present value of total future royalties, included in “Contingent consideration obligations” in the accompanying Consolidated Balance Sheet as of December 31, 2018, is $282,000 (initially $208,000, as of March 31, 2016). The Company increased the liability by approximately $448,000 in 2017 based on a reassessment of the total obligation through the end of license agreement. The amount was included in selling, general, and administrative expenses. GPT was merged into Vicor Development Corporation, a wholly-owned subsidiary of Vicor, effective December 31, 2018, at which time the separate corporate existence of GPT ceased. The manufacture of those certain Converpower products going forward will be performed by the two remaining Vicor Custom Power subsidiaries and the payment of royalties will continue as under the license agreement. On December 28, 2015, the Company acquired the noncontrolling interest holder’s 18% ownership interest in Mission Power Solutions, Inc. (“MPS”) for approximately $216,000, which equaled the noncontrolling interest holder’s share of the net equity of MPS. This transaction was achieved through a statutory merger of MPS with and into an existing Vicor Custom Power wholly-owned subsidiary, Northwest Power, Inc. (“NPI”). In addition to the payment noted above, the selling principal will be eligible to receive quarterly royalty payments through June 30, 2021 equal to a percentage of the revenue generated by the sale of certain MPS legacy products to be manufactured by NPI going forward. The estimated obligation for total future royalties, recorded as Contingent consideration obligation in the accompanying Consolidated Balance Sheets as of December 31, 2018 is $126,000 (initially $144,000 as of December 31, 2015). The Company increased the liability by approximately $202,000 in 2017, based on a reassessment of the total obligation under the royalty arrangement. The amount was included in selling, general, and administrative expenses. The respective noncontrolling interest holders of Converpower and MPS served as key employees of each company prior to the transactions described above.

Intangible Assets

Intangible Assets	12 Months Ended
	Dec. 31, 2018
Goodwill and Intangible Assets Disclosure [Abstract]
Intangible Assets	9. INTANGIBLE ASSETS Patent costs, which are included in other assets in the accompanying Consolidated Balance Sheets, as of December 31 were as follows (in thousands): 2018 2017 Patent costs $ 1,979 $ 2,093 Accumulated amortization (1,380 ) (1,386 ) $ 599 $ 707 Definite lived intangible assets, such as patent rights, are amortized and tested for impairment if a triggering event occurs. Amortization expense was approximately $ , $ and $ in 2018, 2017 and 2016, respectively. The estimated future amortization expense from patent assets held as of December 31, 2018, is projected to be $ , $ , $ , $ and $ , in fiscal years 2019, 2020, 2021, 2022, and 2023, respectively.

Severance and Other Charges

Severance and Other Charges	12 Months Ended
	Dec. 31, 2018
Restructuring and Related Activities [Abstract]
Restructuring and Related Activities Disclosure [Text Block]	10. SEVERANCE AND OTHER CHARGES In May 2018, the Company’s management authorized the closure of its GPT subsidiary, which was part of the BBU segment, by the end of 2018. The closure was completed in December 2018. GPT, located in Manchester, N.H., was one of three Vicor Custom Power (“VCP”) entities. Certain of GPT’s products will continue to be manufactured and sold by the two remaining VCP entities. As a result, the Company recorded a pre-tax charge of $350,000 in the second quarter of 2018, for the cost of severance and other employee-related costs involving cash payments based on each employee’s respective length of service. This was recorded as “Severance and other charges” in the Consolidated Statement of Operations. The related liability is presented as “Accrued severance and other charges” in the Consolidated Balance Sheets. Adjustments to reduce the liability were due to certain GPT employees accepting positions with Vicor, and for severance payments made to employees who have left GPT after the authorization of the closure. Adjustments to increase the liability, and the expense, were due to an early termination fee under GPT’s lease and for freight costs to transport GPT inventory and fixed assets to the two remaining VCP entities. The adjustments were recorded in the third and fourth quarters of 2018 for a total expense of $402,000 in 2018, as reported in the Consolidated Statement of Operations.

Product Warranties

Product Warranties	12 Months Ended
	Dec. 31, 2018
Guarantees and Product Warranties [Abstract]
Product Warranties	11. PRODUCT WARRANTIES Product warranty activity for the years ended December 31 was as follows (in thousands): 2018 2017 2016 Balance at the beginning of the period $ 290 $ 214 $ 585 Accruals for warranties for products sold in the period 173 346 358 Fulfillment of warranty obligations (117 ) (194 ) (527 ) Revisions of estimated obligations (78 ) (76 ) (202 ) Balance at the end of the period $ 268 $ 290 $ 214

Stockholders' Equity

Stockholders' Equity	12 Months Ended
	Dec. 31, 2018
Equity [Abstract]
Stockholders' Equity	12. STOCKHOLDERS’ EQUITY Each share of Common Stock entitles the holder thereof to one vote on all matters submitted to the stockholders. Each share of Class B Common Stock entitles the holder thereof to ten votes on all such matters. Shares of Class B Common Stock are not transferable by a stockholder except to or among the stockholder’s spouse, certain of the stockholder’s relatives, and certain other defined transferees. Class B Common Stock is not listed or traded on any exchange or in any market. Class B Common Stock is convertible at the option of the holder thereof at any time and without cost to the stockholder into shares of Common Stock on a one-for-one basis. In November 2000, the Board of Directors of the Company authorized the repurchase of up to $30,000,000 of the Company’s Common Stock (the “November 2000 Plan”). The plan authorizes the Company to make repurchases from time to time in the open market or through privately negotiated transactions. The timing of this program and the amount of the stock that may be repurchased is at the discretion of management based on its view of economic and financial market conditions. There were no repurchases under the November 2000 Plan in 2018, 2017, and 2016. On December 31, 2018, the Company had approximately $8,541,000 available for share repurchases under the November 2000 Plan. Dividends are declared at the discretion of the Company’s Board of Directors and depend on actual cash from operations, the Company’s financial condition and capital requirements and any other factors the Company’s Board of Directors may consider relevant at the time. Common Stock and Class B Common Stock participate in dividends and earnings equally. During the year ended December 31, 2018 and December 31, 2016, one subsidiary paid a total of $632,000 and $750,000, respectively, in cash dividends, all of which was paid to the Company. On December 31, 2018, 2017, and 2016, there were 21,233,659, 21,976,340, and 14,377,880, respectively, shares of Vicor Common Stock reserved for issuance upon exercise of Vicor stock options, upon conversion of Class B Common Stock and under the ESPP.

Other Income (Expense), Net

Other Income (Expense), Net	12 Months Ended
	Dec. 31, 2018
Other Income and Expenses [Abstract]
Other Income (Expense), Net	13. OTHER INCOME (EXPENSE), NET The major changes in the components of Other income (expense), net for the years ended December 31 were as follows (in thousands): 2018 2017 2016 Rental income $ 792 $ 792 $ 462 Foreign currency (losses) gains, net (260 ) 323 (268 ) Interest income 257 124 68 Gain (loss) on disposal of equipment 57 14 (4 ) Credit gains on available-for-sale securities 7 11 13 Other 21 (2 ) 13 $ 874 $ 1,262 $ 284 During the second quarter of 2016, the Company began recognizing rental income under a leasing agreement with a third party for its facility in Sunnyvale, California.

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2018
Income Tax Disclosure [Abstract]
Income Taxes	14. INCOME TAXES The tax provision includes estimated federal, state and foreign income taxes on the Company’s pre-tax income. The tax provisions also may include discrete items, principally related to increases or decreases in tax reserves, tax provision vs. tax return differences and accrued interest for potential liabilities. On December 22, 2017, H.R.1., known as the Tax Cuts and Jobs Act (the “Tax Act”), was signed into law. The Tax Act did not have a significant impact on the Company’s consolidated financial statements for the year ended December 31, 2017. However, the reduction of the U.S. federal corporate tax rate from 35% to 21% r Also, on December 22, 2017, the Securities and Exchange Commission staff issued Staff Accounting Bulletin No. 118 to address the application of U.S. GAAP in situations when a registrant does not have the necessary information available, prepared, or analyzed (including computations) in reasonable detail to complete the accounting for certain income tax effects of the Tax Act. The Company recognized the provisional tax impacts related to deemed repatriated earnings and the revaluation of deferred tax assets and liabilities and included these amounts in its consolidated financial statements for the year ended December 31, 2017. The Company did not record any adjustments in the year ended December 31, 2018 to these provisional amounts that were material to its financial statements. As of December 31, 2018, the Company’s accounting treatment with regards to the Tax Act is complete. The reconciliation of the federal statutory rate on the income (loss) before income taxes to the effective income tax rate for the years ended December is as follows: 2018 2017 2016 Statutory federal tax rate 21.0 % (34.0 )% (34.0 )% State income taxes, net of federal income tax benefit 3.6 97.2 1.9 Increase (decrease) in valuation allowance (9.1 ) (936.1 ) 46.5 Permanent items (5.9 ) (861.2 ) 0.9 Tax credits (5.5 ) (1,222.3 ) (13.6 ) Provision vs. tax return differences (1.7 ) — — Foreign rate differential and deferred items 0.7 (91.8 ) (0.8 ) Decrease in tax reserves 0.1 (5.1 ) — Rate change due to tax reform — 3,441.1 — Refundable income taxes — AMT credit — (751.0 ) — Capital gain on sale to noncontrolling interest — — 3.9 Decrease in unremitted Vicor Custom Power earnings — — (0.9 ) Book income attributable to noncontrolling interest — — 0.1 Other 0.1 (0.1 ) (0.2 ) 3.3 % (363.3 )% 3.8 % In 2018, the Company utilized net operating loss carryforwards to offset federal income tax expense. In 2017 and 2016, the Company did not recognize a tax benefit for the majority of its losses as it maintained a full valuation allowance against all net domestic deferred tax assets due to the inability to project net future taxable income, as described below. In 2017, the benefit for income taxes was primarily due to the Company’s AMT credit carryforwards of approximately $736,000 becoming fully refundable in future years, due to the repeal of the corporate AMT under the Tax Act. In 2016, in connection with the Company’s acquisition of 100% ownership of certain operating assets and cash of Converpower, the related deferred tax liability for unremitted earnings of $55,000 was reversed and recorded as a discrete benefit in the first quarter of 2016 (see Note 8). For financial reporting purposes, income (loss) before income taxes for the years ended December include the following components (in thousands): 2018 2017 2016 Domestic $ 31,455 $ (1,591 ) $ (6,034 ) Foreign 1,478 1,493 4 $ 32,933 $ (98 ) $ (6,030 ) Significant components of the provision (benefit) for income taxes for the years ended December 31 are as follows (in thousands): 2018 2017 2016 Current: Federal $ — $ (736 ) $ — State 231 156 172 Foreign 911 396 137 1,142 (184 ) 309 Deferred: Federal — — (55 ) Foreign (55 ) (172 ) (23 ) (55 ) (172 ) (78 ) $ 1,087 $ (356 ) $ 231 The Tax Act eliminates the deferral of U.S. income tax on accumulated foreign earnings by imposing a one-time As noted above, the change in the U.S. federal corporate tax rate, which was effective January 1, 2018, is reflected in the Company’s deferred tax table below. Significant components of the Company’s deferred tax assets and liabilities as of December 31 were as follows (in thousands): 2018 2017 Deferred tax assets: Research and development tax credit carryforwards $ 23,244 $ 20,019 Stock-based compensation 3,133 2,793 Inventory reserves 2,109 2,059 Investment tax credit carryforwards 1,976 2,181 Vacation accrual 1,218 1,255 Net operating loss carryforwards 1,091 4,918 UNICAP 275 3 International deferred tax assets 265 210 Unrealized loss on investments 132 135 Sales allowances 128 25 Contingent consideration liabilities 88 148 Deferred revenue 66 79 Bad debt reserves 52 36 Warranty reserves 35 45 Other 233 35 Total deferred tax assets 34,045 33,941 Less: Valuation allowance for deferred tax assets (30,031 ) (33,024 ) Net deferred tax assets 4,014 917 Deferred tax liabilities: Depreciation (3,144 ) (76 ) Prepaid expenses (473 ) (470 ) Patent amortization (107 ) (161 ) Other (25 ) — Total deferred tax liabilities (3,749 ) (707 ) Net deferred tax assets (liabilities) $ 265 $ 210 As of December 31, 2018, the Company has a valuation allowance of approximately $30,031,000 against The state and federal research and development tax credit carryforwards of approximately $12,139,000 and $14,920,000, respectively, expire beginning in 2019 for state purposes and in 2025 for federal purposes. The Company has federal net operating loss carryforwards of approximately $2,584,000, which expire beginning in 2033, as well as net operating loss carryforwards in certain states of approximately $8,249,000, which expire beginning in 2019 through 2037. A reconciliation of the beginning and ending amount of unrecognized tax benefits is as follows (in thousands): 2018 2017 2016 Balance on January 1 $ 1,104 $ 946 $ 830 Additions based on tax positions related to the current year 245 138 125 Additions for tax positions of prior years 120 29 — Settlements — (1 ) — Lapse of statute (7 ) (8 ) (9 ) Balance on December 31 $ 1,462 $ 1,104 $ 946 The Company has reviewed the tax positions taken, or to be taken, in its tax returns for all tax years currently open to examination by a taxing authority. The total amount of unrecognized tax benefits, that is the aggregate tax effect of differences between tax return positions and the benefits recognized in the Company’s financial statements, as of December 31, 2018, 2017, and 2016 of $1,462,000, $1,104,000, and $946,000, respectively, if recognized, may decrease the Company’s income tax provision and effective tax rate. None of the unrecognized tax benefits as of December 31, 2018, are expected to significantly change during the next twelve months. The Company recognizes accrued interest and penalties, if any, related to unrecognized tax benefits as a component of income tax expense. During the years ended December 31, 2018, 2017, and 2016, the Company recognized approximately $7,000, $6,000, and $6,000, respectively, in net interest expense. As of December 31, 2018 and 2017, the Company had accrued approximately $35,000 and $29,000, respectively, for the potential payment of interest. The Company files income tax returns in the United States and various foreign tax jurisdictions. These tax returns are generally open to examination by the relevant tax authorities from three to seven years from the date they are filed. The tax filings relating to the Company’s federal and state taxes are currently open to examination for tax years 2016 and 2017 and 2009 through 2017, respectively. In addition, 2012 and 2014 tax years resulted in losses and the Company generated federal research and development credits in tax years 2005 through 2015. These years may also be subject to examination when the losses or credits are carried forward and utilized in future years. The Company’s subsidiary in Italy, Vicor Italy S.r.l. (“Vicor Italy”), underwent a tax inspection during 2014 for tax years 2009 through 2013, covering corporation, regional and value added taxes. Vicor Italy received a preliminary tax audit report dated June 30, 2014. The Company filed a response to the preliminary tax audit report in the third quarter of 2014. The statute of limitations for the tax authorities in Italy to file an assessment, if any, expired on December 31, 2015 for tax year 2009, on December 31, 2016 for tax year 2010 on December 31, 2017 for tax year 2011, and on December 31, 2018 for tax year 2012. Due to the non-response by Italian authorities after nearly five years, and the lapse of the first four out of the five years under examination, the Company does not believe the ultimate impact will be material to the Company’s financial statements. In May 2017, the Company received notice from the Internal Revenue Service that its federal corporate tax return for tax year 2015 had been selected for examination. The examination was completed in May 2018 resulting in no tax liability to the Company. In January 2018, the Company received notice from the New York State Department of Taxation and Finance that its New York State tax returns for tax years 2014 through 2016 were selected for audit. The audit was completed in the third quarter of 2018, resulting in an immaterial assessment. There are no other income tax examinations or audits currently in process.

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2018
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	15. COMMITMENTS AND CONTINGENCIES The Company leases certain of its offices, manufacturing space, and several automobiles. The future minimum rental commitments under non- cancelable Year 2019 $ 1,962 2020 1,502 2021 688 2022 447 2023 and thereafter 830 Rent expense for the Company’s leases was approximately $2,102,000, $1,889,000 and $1,866,000 in 2018, 2017 and 2016, respectively. The Company also pays tenant-related executory costs such as taxes, maintenance, and insurance. The Company is the defendant in a patent infringement lawsuit originally filed on January 28, 2011 by SynQor, Inc. (“SynQor”) in the U.S. District Court for the Eastern District of Texas (the “Texas Action”). The complaint, as amended in September 2011, alleges that the Company’s products, including but not limited to, unregulated bus converters used in intermediate bus architecture power supply systems, infringe SynQor’s U.S. patent numbers 7,072,190, 7,272,021, 7,564,702, and 8,023,290 (“the ‘190 patent”, “the ‘021 patent”, “the ‘702 patent”, and “the ‘290 patent”, respectively). SynQor’s complaint sought an injunction against further infringement and an award of unspecified compensatory and enhanced damages, interest, costs and attorney fees. The Company has denied that its products infringe any of the SynQor patents, asserted that the SynQor patents are invalid, and asserted that the ‘290 patent is unenforceable due to inequitable conduct by SynQor or its agents during the examination of the ‘290 patent at the United States Patent and Trademark Office (“USPTO”). The Company also asserted counterclaims seeking damages against SynQor for deceptive trade practices and tortious interference with prospective economic advantage arising from SynQor’s attempted enforcement of its patents against the Company. On May 23, 2016, after extensive discovery, the Texas Action was stayed by the court pending completion of certain inter partes reexamination proceedings at the USPTO (including any appeals from such proceedings to the Federal Circuit (as defined below)) concerning the SynQor patents, which are described below. On November 2, 2018, SynQor filed a motion to lift the stay of the Texas Action. On January 3, 2019, the Court denied the motion and reaffirmed its original decision that the stay should remain at least until the conclusion of all pending inter partes reexaminations and related appeals. In 2011, in response to the filing of the Texas Action, the Company initiated inter partes reexamination proceedings at the USPTO challenging the validity of certain claims of the SynQor patents asserted in the Texas Action, including all claims that were asserted against the Company by SynQor. The current status of these proceedings is as follows. Regarding the ‘190 patent, the United States Court of Appeals for the Federal Circuit (the “Federal Circuit”) issued a decision on March 13, 2015, determining that certain claims were invalid, remanding the matter to the Patent Trial and Appeal Board (“PTAB”) of the USPTO for further proceedings. On May 2, 2016, the PTAB issued a decision affirming the examiner’s original rejection of all but one of the remaining claims of the ‘190 patent, and identifying a new basis for rejecting the remaining claim (“claim 34”), which had been added by SynQor during the reexamination. SynQor then requested further examination of claim 34 by the examiner, pursuant to 37 C.F.R. § 41.77(b)(1). On June 22, 2017, the examiner issued a determination under 37 C.F.R. § 41.77(d), finding claim 34 was unpatentable. That decision is expected to be further reviewed by the PTAB pursuant to 37 C.F.R. § 41.77(f). After the PTAB reviews the examiner’s decision with respect to claim 34, it is expected that the PTAB’s decisions with respect to all of the challenged and still pending claims of the ‘190 patent will be subject to further review by the Federal Circuit. On May 2, 2016, the PTAB also issued decisions finding all challenged claims of SynQor’s ‘021 patent invalid and upholding the validity of all challenged claims of SynQor’s ‘702 and ‘290 patents. On August 30, 2017, the Federal Circuit issued rulings with regard to those decisions. With respect to the ‘021 patent, the Federal Circuit affirmed the PTAB’s determination that all of the challenged claims of the ‘021 patent were invalid. The Federal Circuit remanded the case to the PTAB for further consideration of the patentability of certain claims that had been added by amendment during the reexamination. With respect to the ‘702 patent, the Federal Circuit affirmed the PTAB’s determination that all of the challenged claims of the ‘702 patent were patentable. With respect to the ‘290 patent, the Federal Circuit vacated the PTAB’s decision upholding the patentability of the ‘290 patent claims, and remanded the case to the PTAB for further consideration. The PTAB has not issued any rulings with respect to the ‘290 patent after remand. On October 31, 2017, the Company filed a request with the USPTO for ex parte inter partes ex parte ex parte ex parte On August 6, 2018, the Company filed a request with the USPTO for ex parte reexamination of the asserted claims of the ‘190 patent, based on different prior art references than had been at issue in the previous inter partes reexamination of the ‘190 patent. On September 11, 2018, SynQor filed a petition asking the USPTO to reject the Company’s request on the ground that it presented substantially the same prior art or arguments presented to the USPTO in the prior inter partes reexamination of the ‘190 patent. On December 3, 2018, the USPTO denied SynQor’s petition to reject the Company’s ex parte reexamination request. On December 4, 2018, the USPTO instituted ex parte reexamination of the ‘190 patent after finding that the Company’s request had raised a substantial new question affecting the patentability of the challenged claims. On January 23, 2018, the 20-year terms of the ‘190 patent, the ‘021 patent and the ‘702 patent expired. The 20-year term of the ‘290 patent expired on July 16, 2018. As a consequence of these expirations, the Company cannot be liable under any of the SynQor patents for allegedly infringing activities occurring after the patents’ respective expiration dates. The Company continues to believe none of its products, including its unregulated bus converters, infringe any valid claim of the asserted SynQor patents, either alone or when used in an intermediate bus architecture implementation. The Company believes SynQor’s claims lack merit and, therefore, it continues to vigorously defend itself against SynQor’s patent infringement allegations. The Company does not believe a loss is probable for this matter. If a loss were to be incurred, however, the Company cannot estimate the amount of possible loss or range of possible loss at this time. In addition to the SynQor matter, the Company is involved in certain other litigation and claims incidental to the conduct of its business. While the outcome of lawsuits and claims against the Company cannot be predicted with certainty, management does not expect any current litigation or claims will have a material adverse impact on the Company’s financial position or results of operations.

Picor Merger

Picor Merger	12 Months Ended
	Dec. 31, 2018
Business Combinations [Abstract]
Business Combination Disclosure [Text Block]	16. PICOR MERGER On May 25, 2018, the Company’s Board of Directors unanimously approved the merger of Picor Corporation (“Picor”), a subsidiary of Vicor, fully consolidated for financial reporting purposes, with and into the Company. The merger was completed as of May 30, 2018, at which time the separate corporate existence of Picor ceased. To effect the merger, holders of Picor Common Stock and Picor stock options received an equivalent value of Vicor Common Stock and Vicor stock options, respectively, pursuant to the assumption of the Picor Corporation Amended and Restated 2001 Stock Option and Incentive Plan, and options outstanding thereunder, by the Company. While Picor’s subsidiary status and corporate form ceased to exist upon the closing of the merger, the operations previously conducted by Picor, which are now conducted by Vicor, continue to be managed and remain categorized as an operating segment for financial reporting purposes. There was no net impact on the Company’s consolidated financial statements nor any impact on the Company’s segment reporting for the year ended December 31, 2018 as a result of the merger.

Segment Information

Segment Information	12 Months Ended
	Dec. 31, 2018
Segment Reporting [Abstract]
Segment Information	17. SEGMENT INFORMATION The Company has organized its operating business segments according to its key product lines. The BBU segment designs, develops, manufactures, and markets the Company’s modular DC-DC The Company’s Chief Executive Officer (i.e., identified as the “chief operating decision maker,”) (“CODM”), pursuant to U.S. GAAP, evaluates performance and allocates resources based on segment revenues and segment operating income (loss). The operating income (loss) for each segment includes selling, general, and administrative and research and development expenses directly attributable to the segment. Certain of the Company’s indirect overhead costs, which include corporate selling, general, and administrative expenses, are allocated among the segments based upon an estimate of costs associated with each segment. Assets allocated to each segment are based upon specific identification of such assets, which include accounts receivable, inventories, fixed assets, and certain other assets. The Corporate segment consists of those operations and assets shared by all operating segments. The costs of certain centralized executive and administrative functions are recorded in this segment, as are certain shared assets, most notably cash and cash equivalents, deferred tax assets, long-term investments, the Company’s facilities in Massachusetts, real estate, and other assets. The Company’s accounting policies and method of presentation for segments are consistent with that used throughout the Consolidated Financial Statements. The following table provides significant segment financial data as of and for the years ended December 31 (in thousands): BBU VI Chip Picor Corporate Eliminations Total (1) 2018: Net revenues $ 186,715 $ 84,728 $ 34,552 $ — $ (14,775 ) $ 291,220 Income (loss) from operations 22,544 3,612 7,517 (1,614 ) — 32,059 Total assets 279,671 56,619 14,869 85,851 (215,942 ) 221,068 Depreciation and amortization 3,621 3,504 792 1,337 — 9,254 Capital expenditures 2,954 13,386 621 1,250 — 18,211 2017: Net revenues $ 151,789 $ 61,330 $ 26,297 $ — $ (11,586 ) $ 227,830 Income (loss) from operations 5,615 (11,495 ) 5,400 (880 ) — (1,360 ) Total assets 232,255 34,809 13,509 59,550 (174,399 ) 165,724 Depreciation and amortization 3,907 2,782 747 1,457 — 8,893 Capital expenditures 3,188 7,505 1,249 603 — 12,545 2016: Net revenues $ 151,428 $ 39,947 $ 16,684 $ — $ (7,779 ) $ 200,280 Income (loss) from operations 11,750 (16,494 ) (637 ) (933 ) — (6,314 ) Total assets 196,987 21,389 8,583 73,253 (146,145 ) 154,067 Depreciation and amortization 4,258 2,235 545 1,400 — 8,438 Capital expenditures 2,325 4,041 1,178 884 — 8,428 (1) The elimination for net revenues is principally related to inter-segment revenues of Picor to BBU and VI Chip and for inter-segment revenues of VI Chip to BBU. The elimination for total assets is principally related to inter-segment accounts receivable due to BBU for the funding of VI Chip and Picor operations. Substantially all long-lived assets are located in the United States. During 2018, 2017, and 2016, one customer accounted for approximately 13.4%, 13.0%, and 16.4% of net Net revenues from unaffiliated customers by country, based on the location of the customer, for the years ended December 31 were as follows (in thousands): 2018 2017 2016 United States $ 110,779 $ 83,871 $ 80,603 Europe 27,689 24,078 22,495 Asia Pacific 147,078 114,365 91,848 All other 5,674 5,516 5,334 $ 291,220 $ 227,830 $ 200,280 Net revenues from customers in China (including Hong Kong), our largest international market, accounted for approximately 37.4% of total net revenues in 2018, 35.8% in 2017 and 32.1% in 2016, respectively.

Quarterly Results of Operations

Quarterly Results of Operations (Unaudited)	12 Months Ended
	Dec. 31, 2018
Quarterly Financial Information Disclosure [Abstract]
Quarterly Results of Operations (Unaudited)	18. QUARTERLY RESULTS OF OPERATIONS (Unaudited) The following table sets forth certain unaudited quarterly financial data for the years ended December 31 (in thousands, except per share amounts): First Second Third Fourth Total 2018: Net revenues $ 65,269 $ 74,196 $ 78,035 $ 73,720 $ 291,220 Gross margin 30,211 35,883 39,004 33,873 138,971 Consolidated net income 3,982 7,909 13,048 6,907 31,846 Net income (loss) attributable to noncontrolling interest 39 49 36 (3 ) 121 Net income attributable to Vicor Corporation 3,943 7,860 13,012 6,910 31,725 Net income per share attributable to Vicor Corporation: Basic 0.10 0.20 0.32 0.17 0.80 Diluted 0.10 0.19 0.32 0.17 0.78 First Second Third Fourth Total 2017: Net revenues $ 54,462 $ 57,709 $ 56,888 $ 58,771 $ 227,830 Gross margin 23,652 25,930 25,143 26,931 101,656 Consolidated net income (loss) (954 ) (445 ) 38 1,619 258 Net income attributable to noncontrolling interest 20 14 49 8 91 Net income (loss) attributable to Vicor Corporation (974 ) (459 ) (11 ) 1,611 167 Net income (loss) per share attributable to Vicor Corporation: Basic and diluted (0.02 ) (0.01 ) (0.00 ) 0.04 0.00

Valuation and Qualifying Accoun

Valuation and Qualifying Accounts	12 Months Ended
	Dec. 31, 2018
Valuation and Qualifying Accounts [Abstract]
Valuation and Qualifying Accounts	VICOR CORPORATION SCHEDULE II VALUATION AND QUALIFYING ACCOUNTS Years ended December 31, 2018, 2017 and 2016 Description Balance at Beginning of Period Charge (Recovery) to Costs and Expenses Other Charges, Deductions (1) Balance at End of Period Allowance for doubtful accounts: Year ended: December 31, 2018 $ 159,000 $ 65,000 $ — $ 224,000 December 31, 2017 153,000 6,000 — 159,000 December 31, 2016 171,000 (22,000 ) 4,000 153,000 (1) Reflects uncollectible accounts written off, net of recoveries.

Significant Accounting Polici_2

Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2018
Accounting Policies [Abstract]
Principles of consolidation	Principles of consolidation The Consolidated Financial Statements include the accounts of the Company and its subsidiaries. All intercompany transactions and balances have been eliminated upon consolidation. One of the Company’s subsidiaries was not majority owned by the Company prior to 2016, and a second was not majority owned prior to March 31, 2016. Prior to the transactions described in Note 10, these entities were consolidated by the Company as management believed that the Company had the ability to exercise control over their activities and operations.
Use of estimates	Use of estimates The preparation of financial statements in conformity with accounting principles generally accepted in the United States requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingencies at the date of the financial statements and the reported amounts of revenue and expenses during the reporting period. Such estimates and assumptions relate to the useful lives of fixed assets and identified intangible assets, recoverability of long-lived assets, fair value of long-term investments, allowances for doubtful accounts, the net realizable value of inventory, potential reserves relating to litigation matters, accrued liabilities, accrued taxes, deferred tax valuation allowances, assumptions pertaining to share-based payments, and other reserves. Actual results could differ from those based on these estimates and assumptions, and such differences may be material to the financial statements.
Recently Adopted Accounting Standards	Recently Adopted Accounting Standards Revenue Recognition In May 2014, the Financial Accounting Standards Board (“FASB”) issued new guidance for revenue recognition (“Topic 606”), which requires an entity to recognize the amount of revenue to which it expects to be entitled for the transfer of promised goods or services to customers. The new guidance, which includes several amendments, replaces most of the prior revenue recognition guidance under U.S. The Company adopted the new guidance as of January 1, 2018 using the modified retrospective method, as applied to all contracts. As a result, the Company has changed its accounting policy for revenue recognition, as detailed below. The most significant impact of the adoption was on the timing of recognition of sales to the Company’s stocking distributors and including the additional required disclosures under the new standard. Through December 31, 2017, the Company deferred revenue and the related cost of sales on shipments to stocking distributors until the distributors resold the products to their customers. Upon adoption, the Company is no longer permitted to defer revenue until sale by the stocking distributor to the end customer, but rather, is required to estimate the effects of returns and allowances provided to stocking distributors and record revenue at the time of sale to the stocking distributor. In addition, the Company modified the accounting for a contractual arrangement due to a reassessment of the number of performance obligations in the arrangement, and adjusted for the timing of certain royalty revenue. The cumulative effect of adopting this guidance, recorded as an increase to the balance of retained earnings as of January 1, 2018, was approximately $3,670,000. The comparative information for the years ended December 31, 2017 including disclosures, has not been restated and continues to be reported under the accounting standards in effect for periods . The following tables summarize the impacts of adopting the new revenue recognition guidance on certain components of the Company’s consolidated financial statements (in thousands): a) Consolidated Balance Sheet Items As of December 31, 2018 As reported Adjustments Balances without adoption of Topic 606 Accounts receivable, net $ 43,673 $ (72 ) $ 43,601 Inventories, net 47,370 (110 ) 47,260 Total assets 221,068 (182 ) 220,886 Income taxes payable 710 (59 ) 651 Deferred revenue 5,069 5,768 10,837 Sales allowances 548 (483 ) 65 Total liabilities 36,978 5,226 42,204 Retained earnings 129,000 (5,408 ) 123,592 Total equity 184,090 (5,408 ) 178,682 Total liabilities and equity 221,068 (182 ) 220,886 b) Consolidated Statement of Operations Items Year Ended December 31, 2018 As reported Adjustments Balances without adoption of Topic 606 Net revenues $ 291,220 $ (3,946 ) $ 287,274 Cost of revenues 152,249 (2,149 ) 150,100 Gross margin 138,971 (1,797 ) 137,174 Income before income taxes 32,933 (1,797 ) 31,136 Provision for income taxes 1,087 (59 ) 1,028 Consolidated net income 31,846 (1,738 ) 30,108 Net income attributable to Vicor Corporation 31,725 (1,738 ) 29,987 The impact of the adoption of the new revenue recognition standard on the consolidated statements of comprehensive income (loss) and cash flows for the year ended December 31, 2018 was not material. Prior to January 1 , 2018 Product revenue was recognized in the period when persuasive evidence of an arrangement with a customer existed, the products were shipped and title was transferred to the customer, the price was fixed or determinable, and collection was considered probable. The Company deferred revenue and the related cost of sales on shipments to stocking distributors until the distributors resold the products to their customers. The agreements with these stocking distributors allowed them to receive price adjustment credits or to return qualifying products for credit, as determined by the Company, in order to reduce the amounts of slow-moving, discontinued, or obsolete product from their inventory. These stocking distributors were also granted price adjustment credits in the event of a price decrease subsequent to the date the product was shipped and invoiced to the stocking distributor. Given the uncertainties associated with the levels of price adjustment credits to be granted to stocking distributors, the sales price to the stocking distributor was not fixed or determinable until the stocking distributor resold the products to its customers. Therefore, the Company deferred revenue and the related cost of sales on shipments to stocking distributors until the stocking distributors resold the products to their customers. Accordingly, the Company’s revenue fully reflected end-customer purchases and was not impacted by stocking distributor inventory levels. Agreements with stocking distributors limited returns of qualifying product to the Company to a certain percentage of the value of the Company’s shipments to that stocking distributor during the prior quarter. In addition, stocking distributors were allowed to return unsold products if the Company terminated the relationship with the stocking distributor. Title to the inventory transferred to the stocking distributor at the time of shipment or delivery to the stocking distributor. Payments from the stocking distributors were due in accordance with the Company’s standard payment terms. These payment terms were not contingent upon the stocking distributors’ sale of the products to their end-customers. Upon title transfer to stocking distributors, the Company reduced inventory for the cost of goods shipped, the margin (i.e., revenues less cost of revenues) was recorded as deferred revenue, and an account receivable was recorded. As of December 31, 2017, the Company had gross deferred revenue of approximately $4,659,000 and gross deferred cost of revenues of approximately $2,135,000 under agreements with stocking distributors. The Company evaluated revenue arrangements with potential multi-element deliverables to determine if there were more than one unit of accounting. A deliverable constituted a separate unit of accounting when it had standalone value and there were no customer-negotiated refund or return rights for the undelivered elements. The Company entered into arrangements containing multiple elements that could include a combination of non-recurring engineering services (“NRE”), prototype units, and production units. The Company determined NRE and prototype units represented one unit of accounting and production units represented a separate unit of accounting, based on an assessment of the respective standalone value. The Company deferred revenue recognition for NRE and prototype units until completion of the final milestone under the NRE arrangement, which was generally the delivery of the prototype. Recognition generally took place within six to twelve months of the initiation of the arrangement. Revenue for the production units was recognized upon shipment, consistent with other product revenue summarized above. License fees were recognized as earned. The Company recognized revenue on such arrangements only when the contract was signed, the license term had begun, all obligations had been delivered to the customer, and collection was probable. Subsequent to January 1, 2018 Revenue is recognized when control of the promised goods or services is transferred to a customer, in an amount that reflects the consideration the Company expects to be entitled to in exchange for those goods or services. Sales, value add, and other taxes collected concurrent with revenue-producing activities are excluded from revenue. The expected costs associated with product warranties continue to be recognized at the time product revenue is recognized. Shipping and handling costs associated with outbound freight after control over a product has transferred to a customer are accounted for as a fulfillment cost and are included in cost of revenues. The Company’s primary source of net revenue comes from the sale of products, which are modular power components and power systems for converting, regulating and controlling electric current. The principal customers for the Company’s power converters and systems are large original equipment manufacturers and the original design manufacturers and contract manufacturers serving them, and smaller, lower volume users, which are broadly distributed across several major market areas. The Company recognizes revenue for product sales at a point in time following the transfer of control of such products to the customer, which typically occurs upon shipment or delivery, depending on the terms of the underlying contract. As noted above, the Company previously deferred revenue and the related cost of revenues on shipments to stocking distributors until the distributors resold the products to their customers. The Company now records revenue for such transactions at the time of sale to the stocking distributor. The Company establishes sales allowances for estimated future product returns including distributor returns and price adjustment credits, primarily based upon historical and anticipated rates of product returns and allowances. Certain contracts with customers contain multiple performance obligations, which typically may include a combination of NRE, prototype units, and production units. For these contracts, the individual performance obligations are accounted for separately if they are distinct. Generally, the Company has determined the NRE and prototype units represent one distinct performance obligation and the production units represent a separate distinct performance obligation. For such arrangements, revenue is allocated to each performance obligation based on its relative standalone selling price, based on prices charged to customers or using the expected cost plus a margin approach. The Company defers revenue recognition for NRE and prototype units until the point in time at which the final milestone under the NRE arrangement is completed and control is transferred to the customer, which is generally the shipment or delivery of the prototype. Revenue for production units is recognized upon shipment or delivery, consistent with product revenue summarized above. The Company licenses its intellectual property under right to use licenses, in which royalties due to the Company are based upon a percentage of the licensee’s sales. The Company utilizes the exception under the revenue recognition guidance for the recognition of sales- or usage-based royalties, in which the royalties are not recognized until the later of when 1) the customer’s subsequent sales or usages occur, or 2) the performance obligation to which some or all of the sales- or usage-based royalty has been allocated is satisfied or partially satisfied. Accounts receivable includes amounts billed and currently due from customers. The amounts due are stated at their estimated realizable value. The Company’s payment terms vary by the type and location of its customers and the products or services offered, although terms generally include a requirement of payment within 30 to 60 days. The Company maintains allowances for doubtful accounts for estimated losses resulting from the inability of its customers to make required payments, based on assessments of customers’ credit-risk profiles and payment histories. If the financial condition of the Company’s customers were to deteriorate, resulting in an impairment of their ability to make payments, additional allowances may be required. The Company does not require collateral from its customers, although there have been circumstances when the Company has required cash in advance (i.e., a partial down-payment) to facilitate orders in excess of a customer’s established credit limit. To date, such amounts have not been material. The Company records deferred revenue, which represents a contract liability, when cash payments are received or due in advance of performance under a contract with a customer. During the year ended December 31, 2018, under Topic 606, the Company recognized revenue of approximately $991,000 that was included in deferred revenue at the beginning of the respective period. The Company applies the practical expedient allowed under the new guidance for the incremental costs of obtaining a contract for sales commissions, which are expensed when incurred because the amortization period is generally less than one year. These costs are included in selling, general and administrative expenses. The Company also applies another practical expedient allowed under the new guidance and does not disclose the value of unsatisfied performance obligations for contracts with an original expected length of one year or less. The following table presents the Company’s net revenues disaggregated by geography based on the location of the customer, by reportable segment, (in thousands): Year Ended December 31, 2018 BBU VI Chip Picor Total United States $ 77,995 $ 30,118 $ 2,666 $ 110,779 Europe 23,484 3,883 322 27,689 Asia Pacific 80,097 47,174 19,807 147,078 All other 5,128 499 47 5,674 $ 186,704 $ 81,674 $ 22,842 $ 291,220 The following table presents the Company’s net revenues disaggregated by the category of revenue, by reportable segment, (in thousands): Year Ended December 31, 2018 BBU VI Chip Picor Total Direct customers, contract manufacturers and non-stocking distributors $ 163,206 $ 70,919 $ 20,660 $ 254,785 Stocking distributors, net of sales allowances 22,362 7,653 1,717 31,732 Non-recurring engineering 1,066 2,996 360 4,422 Royalties 70 70 70 210 Other — 36 35 71 $ 186,704 $ 81,674 $ 22,842 $ 291,220 The following table presents the changes in certain contract assets and (liabilities) (in thousands): December 31, 2018 December 31, 2017 Increase (decrease) Accounts receivable $ 43,673 $ 34,487 $ 9,186 Deferred revenue (3,820 ) (5,015 ) 1,195 Deferred expenses 501 859 (358 ) Customer prepayments (1,250 ) (776 ) (474 ) Sales allowances (548 ) — (548 ) The increase in accounts receivable was primarily due to an increase in net revenues of approximately $14,949 in the fourth quarter of 2018 compared to the fourth quarter of 2017. The decrease in deferred revenue was primarily due to the adoption of the new revenue recognition guidance, as the balances related to stocking distributors were reversed as part of the transition adjustment recorded as of January 1, 2018 (see Recently Adopted Accounting Standards , above). The increase in sales allowances was due to the establishment of new allowances, in connection with the new revenue recognition guidance, for potential returns and price adjustment credits on sales to stocking distributors. Deferred expenses are included in Other current assets, and customer prepayments are included in Deferred revenue, in the accompanying Consolidated Balance Sheets, respectively. Other Recently Adopted Accounting Standards In June 2018, the FASB issued new guidance, Improvements to Nonemployee Share-Based Payment Accounting, which more closely aligns the accounting for share-based payments to non-employees with the accounting for share-based payments to employees. This new guidance is effective for public business entities for annual and interim periods in fiscal years beginning after December 15, 2018, with early adoption permitted. The Company early-adopted the new standard on July 1, 2018. The adoption of this new guidance did not have a material impact on its consolidated financial statements and related disclosures. In May 2017, the FASB issued guidance about which changes to the terms or conditions of a share-based payment award require an entity to apply modification accounting in Topic 718, Compensation — Stock Compensation. The new guidance is effective for annual and interim periods beginning after December 15, 2017, with early adoption permitted. The Company adopted the new standard on January 1, 2018. The adoption of this new guidance did not have a material impact on its consolidated financial statements and related disclosures. In August 2016, the FASB issued guidance to clarify how certain cash receipts and cash payments should be presented in the statement of cash flows. These include debt prepayment, settlement of zero-coupon debt instruments, contingent consideration payments made after a business combination, proceeds from the settlement of insurance claims, proceeds from the settlement of corporate-owned life insurance policies, distributions received from equity method investees and beneficial interests in securitization transactions. The new guidance is effective for interim and annual reporting periods beginning after December 15, 2017, with early adoption permitted. The Company adopted the new standard on January 1, 2018. The adoption of this new guidance did not have a material impact on its consolidated financial statements and related disclosures.
Foreign currency translation	Foreign currency translation The financial statements of Vicor Japan Company, Ltd. (“VJCL”), a majority-owned subsidiary, for which the functional currency is the Japanese Yen, have been translated into U.S. Dollars using the exchange rate in effect at the balance sheet date for balance sheet amounts and the average exchange rates in effect during the year for income statement amounts. The gains and losses resulting from the changes in exchange rates from year to year have been reported in other comprehensive income. Transaction gains and losses resulting from the remeasurement of foreign currency denominated assets and liabilities of the Company’s foreign subsidiaries where the functional currency is the U.S. Dollar are included in other income (expense), net. Foreign currency gains (losses) included in other income (expense), net, were approximately $(260,000), $323,000, and $(268,000) in 2018, 2017, and 2016, respectively.
Cash and cash equivalents	Cash and cash equivalents Cash and cash equivalents include funds held in disbursement (i.e., checking) and money market accounts, certificates of deposit, and debt securities with maturities of less than three months at the time of purchase. Cash and cash equivalents are valued at cost, approximating market value. The Company’s money market securities, which are classified as cash equivalents on the balance sheet, are purchased and redeemed at par value. Their estimated fair value is equal to their cost, and, due to the nature of the securities and their classification as cash equivalents, there are no unrealized gains or losses recorded at the balance sheet dates.
Long-term investments	Long-term investment The Company’s principal sources of liquidity are its existing balances of cash and cash equivalents, as well as cash generated from operations. Consistent with the guidelines of the Company’s investment policy, the Company can invest, and has historically invested, its cash balances in demand deposit accounts, money market funds, and auction rate securities meeting certain quality criteria. The Company’s long-term investment is subject to credit, liquidity, market, and interest rate risk. The Company’s long-term investment, which is a debt security, is classified as an available-for-sale security. The available-for-sale security is recorded at fair value, with unrealized gains and losses, net of tax, attributable to credit loss recorded through the Consolidated Statement of Operations and unrealized gains and losses, net of tax, attributable to other non-credit factors recorded in “Accumulated other comprehensive loss,” a component of Total Equity. In determining the amount of credit loss, the Company compares the present value of cash flows expected to be collected to the amortized cost basis of the security, considering credit default risk probabilities and changes in credit ratings, among other factors. The amortized cost of the debt security is adjusted for amortization of premiums and accretion of discounts to maturity, the net amount of which, along with interest and realized gains and losses, is included in “Other income (expense), net” in the Consolidated Statements of Operations. The Company periodically evaluates the investment to determine if impairment is required, whether an impairment is other than temporary, and the measurement of an impairment loss. The Company considers a variety of impairment indicators such as, but not limited to, a significant deterioration in the earnings performance, credit rating, or asset quality of the investment.
Fair value measurements	Fair value measurements The Company accounts for certain financial assets at fair value, defined as the price that would be received to sell an asset or paid to transfer a liability (i.e., an exit price) in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants on the measurement date. As such, fair value is a market-based measurement that should be determined based on assumptions that market participants would use in pricing an asset or liability. A three-level hierarchy is used to show the extent and level of judgment used to estimate fair value measurements: Level 1 Inputs used to measure fair value are unadjusted quoted prices available in active markets for the identical assets or liabilities as of the reporting date. Level 2 Inputs used to measure fair value, other than quoted prices included in Level 1, are either directly or indirectly observable as of the reporting date through correlation with market data, including quoted prices for similar assets and liabilities in active markets and quoted prices in inactive markets. Level 2 also includes assets and liabilities valued using models or other pricing methodologies that do not require significant judgment since the input assumptions used in the models, such as interest rates and volatility factors, are corroborated by readily observable data from actively quoted markets for substantially the full term of the financial instrument. Level 3 Inputs used to measure fair value are unobservable inputs supported by little or no market activity and reflect the use of significant management judgment. These values are generally determined using pricing models for which the assumptions utilize management’s estimates of market participant assumptions. The carrying amounts of cash and cash equivalents, accounts receivable and accounts payable approximate fair value because of the short maturity of these financial instruments.
Inventories	Inventories Inventories are valued at the lower of cost (determined using the first-in, first-out method) or net realizable value. Fixed production overhead is allocated to the inventory cost per unit based on the normal capacity of the production facilities. Abnormal production costs, including fixed cost variances from normal production capacity, if any, are charged to cost of revenues in the period incurred. All shipping and handling costs incurred in connection with the sale of products are included in cost of revenues. The Company provides reserves for inventories estimated to be excess, obsolete, or unmarketable. The Company’s estimation process for assessing net realizable value is based upon its known backlog, projected future demand, historical consumption and expected market conditions. If the Company’s estimated demand and/or market expectations were to change or if product sales were to decline, the Company’s estimation process may cause larger inventory reserves to be recorded, resulting in larger charges to cost of revenues.
Concentrations of risk	Concentrations of risk Financial instruments potentially subjecting the Company to significant concentrations of credit risk consist principally of cash and cash equivalents, of which a significant portion is held by one financial institution, its long-term investment, and trade accounts receivable. The Company maintains cash and cash equivalents and certain other financial instruments with various large financial institutions. Generally, amounts invested with these financial institutions are in excess of federal deposit insurance limits. The Company has not experienced any losses in such accounts, and management believes the Company is not exposed to significant credit risk. The Company’s long-term investment as of December 31, 2018 consists of a single auction rate security with a par value of $3,000,000, which is collateralized by student loans. It is a highly rated (Aaa/AA+) municipal and corporate debt security. Through December 31, 2018, auctions held for the Company’s auction rate security have failed. The funds associated with an auction rate security that has failed auction may not be accessible until a successful auction occurs, a buyer is found outside of the auction process, the security is called, or the underlying securities have matured. If the credit rating of the issuer of the auction rate security held deteriorates, the Company may be required to adjust the carrying value of the investment for an other-than-temporary decline in value through an impairment charge. The Company’s investment policy, approved by the Board of Directors, limits the amount the Company may invest in any issuer, thereby reducing credit risk concentrations. The Company’s products are sold worldwide to customers ranging from smaller, independent manufacturers of highly specialized electronic devices, to larger OEMs and their contract manufacturers. The Company’s Brick Business Unit (“BBU”) segment has customers concentrated in aerospace and defense electronics, industrial automation, industrial equipment, instrumentation and test equipment, and transportation (e.g., rail). The Company’s other segments, the VI Chip subsidiary and Picor (see Note 17) have customers concentrated in computing (voltage distribution in server racks and across datacenter infrastructure), although they also target applications in aerospace and aviation, defense electronics, industrial automation, instrumentation, test equipment, solid state lighting, telecommunications and networking infrastructure and vehicles (e.g., in autonomous driving applications, electric vehicles, and hybrid electric vehicles). While, overall, the Company has a broad customer base and sells into a variety of industries, VI Chip and Picor have derived a substantial portion of their revenue from a limited number of customers. This concentration of revenue is a reflection of the relatively early stage of adoption of the technologies, architectures and products offered by these subsidiaries, and their targeting of market leading innovators as initial customers. Concentrations of credit risk with respect to trade accounts receivable are limited due to the number of entities comprising the Company’s customer base. As of December 31, 2018 and 2017, one customer accounted for approximately 14.3% and 17.5%, respectively, of trade account receivables. Components and materials used in the Company’s products are purchased from a variety of vendors. While most of the components are available from multiple sources, some key components for certain VI Chip and Picor products, in particular, are supplied by single vendors. In instances of single source items, the Company maintains levels of inventories management considers appropriate to enable meeting the delivery requirements of customers. If suppliers or subcontractors cannot provide their products or services on time or to the required specifications, the Company may not be able to meet the demand for its products and its delivery times may be negatively affected.
Long-lived assets	Long-lived assets The Company reviews property, plant and equipment and finite-lived intangible assets for impairment whenever events or changes in circumstances indicate the carrying value of such assets may not be recoverable. Management determines whether the carrying value of an asset or asset group is recoverable based on comparison to the undiscounted expected future cash flows the assets are expected to generate over their remaining economic lives. If an asset value is not recoverable, the impairment loss is equal to the amount by which the carrying value of the asset exceeds its fair value, which is determined by either a quoted market price, if any, or a value determined by utilizing a discounted cash flow technique. Evaluation of impairment of long-lived assets requires estimates of future operating results that are used in the preparation of the expected future undiscounted cash flows. Actual future operating results and the remaining economic lives of our long-lived assets could differ from the estimates used in assessing the recoverability of these assets. These differences could result in impairment charges, which could be material.
Intangible assets	Intangible assets Values assigned to patents are amortized using the straight-line method over periods ranging from three to 20 years. Patents and other intangible assets are included in “Other assets” in the accompanying Consolidated Balance Sheets.
Advertising expense	Advertising expense The cost of advertising is expensed as incurred. The Company incurred approximately $2,610,000, $2,150,000, and $1,818,000 in advertising costs during 2018, 2017 and 2016, respectively.
Product warranties	Product warranties The Company generally offers a two-year warranty for all of its products, though it has extended the warranty period to three years for certain military grade products sold after January 1, 2017. The Company is party to a limited number of supply agreements with certain customers contractually committing the Company to warranty and indemnification requirements exceeding those to which the Company has been exposed in the past. The Company provides for the estimated cost of product warranties at the time product revenue is recognized. Factors influencing the Company’s warranty reserves include the number of units sold, historical and anticipated rates of warranty returns, and the cost per return. The Company periodically assesses the adequacy of warranty reserves and adjusts the amounts as necessary. Warranty obligations are included in “Accrued expenses” in the accompanying Consolidated Balance Sheets.
Legal Costs	Legal Costs Legal costs in connection with litigation are expensed as incurred.
Net income (loss) per common share	Net income (loss) per common share The Company computes basic net income (loss) per share using the weighted average number of common shares outstanding and diluted net income (loss) per share using the weighted average number of common shares outstanding plus the effect of The following table sets forth the computation of basic and diluted net income (loss) per share for the years ended December 31 (in thousands, except per share amounts): 2018 2017 2016 Numerator: Net income (loss) attributable to Vicor Corporation $ 31,725 $ 167 $ (6,247 ) Denominator: Denominator for basic net income (loss) per share-weighted average shares (1) 39,872 39,228 38,842 Effect of dilutive securities: Employee stock options (2) 857 705 — Denominator for diluted net income (loss) per share-adjusted weighted-average shares and assumed conversions (3) 40,729 39,933 38,842 Basic net income (loss) per share $ 0.80 $ 0.00 $ (0.16 ) Diluted net income (loss) per share $ 0.78 $ 0.00 $ (0.16 ) (1) Denominator represents weighted average number of Common Shares and Class B Common Shares outstanding. (2) Options to purchase 67,247, 53,913 and 1,696,222 shares of Common Stock in 2018, 2017, and 2016, respectively, were not included in the calculation of net income (loss) per share as the effect would have been antidilutive. (3) Denominator represents weighted average number of Common Shares and Class B Common Shares outstanding for the year, adjusted to include the dilutive effect, if any, of outstanding options.
Income taxes	Income taxes Deferred tax assets and liabilities are determined based on the differences between financial reporting and tax bases of assets and liabilities and are measured using the enacted income tax rates and laws expected to be in effect when the temporary differences are expected to reverse. Deferred tax assets are reduced by a valuation allowance if management determines it is more likely than not that some portion or all of the deferred tax assets will not be realized. All deferred tax assets and liabilities are classified as noncurrent. The Company follows a two-step process to determine the amount of tax benefit to recognize. The first step is to evaluate the tax position to determine the likelihood it would be sustained upon examination by a tax authority. If the tax position is deemed “more-likely-than-not” to be sustained, the second step is to assess the tax position to determine the amount of tax benefit to be recognized in the financial statements. The amount of the benefit that may be recognized is the largest amount that possesses greater than 50 percent likelihood of being realized upon ultimate settlement. If the tax position does not meet the “more-likely-than-not” threshold, then it is not recognized in the financial statements. Additionally, the Company accrues interest and penalties, if any, related to unrecognized tax benefits as a component of income tax expense. The unrecognized tax benefits, including accrued interest and penalties, if any, are included in “Long-term income taxes payable” in the accompanying Consolidated Balance Sheets.
Stock-based compensation	Stock-based compensation The Company uses the Black-Scholes option-pricing model to calculate the fair value of stock option awards, whether they possess time-based vesting provisions or performance-based vesting provisions, and awards granted under the Vicor Corporation 2017 Employee Stock Purchase Plan (“ESPP”), as of their grant date. For stock options with time-based vesting provisions, the calculated compensation expense, net of expected forfeitures, is recognized on a straight-line basis over the service period of the award, which is generally five years for stock options. For stock options with performance-based vesting provisions, recognition of compensation expense, net of expected forfeitures, commences if and when the achievement of the performance criteria is deemed probable. For stock options with performance-based vesting provisions, compensation expense, net of expected forfeitures, when recognized, is recognized over the relevant performance period.
Comprehensive income (loss)	Comprehensive income (loss) The components of comprehensive income (loss) include, in addition to net income (loss), unrealized gains and losses on investments, net of tax and foreign currency translation adjustments related to VJCL, net of tax.
Impact of recently issued accounting standards	Impact of recently issued accounting standards In August 2018, the Financial Accounting Standards Board (“FASB”) issued guidance which modifies the disclosure requirements on fair value measurements under Topic 820, Fair Value Measurements (“Topic 820”). Certain disclosure requirements under Topic 820 were removed, others modified, and certain disclosures have been added. The changes that will impact the Company primarily pertain to those affecting Level 3 fair value measurements. The new guidance is effective for all entities for annual and interim periods in fiscal years beginning after December 15, 2019, with early adoption permitted. It is required to be applied on a retrospective approach with certain elements being adopted prospectively for only the most recent interim or annual period presented in the initial fiscal year of adoption. The Company has not yet determined the impact this new guidance will have on its consolidated financial statements and related disclosures. In June 2016, the FASB issued new guidance which will require measurement and recognition of expected credit losses on certain types of financial instruments. It also modifies the impairment model for available -for-sale debt securities and provides for a simplified accounting model for purchased financial assets with credit deterioration since their origination. The new guidance is effective for interim and annual reporting periods beginning after December 15, 2019, with early adoption permitted. It is required to be applied on a modified-retrospective approach with certain elements being adopted prospectively. The Company does not expect the adoption of the new guidance will have a material impact on its consolidated financial statements and related disclosures. Lease Accounting In February 2016, the FASB issued new guidance for lease accounting, which will require lessees to recognize leases on the balance sheet and disclose key information about leasing arrangements. The new guidance establishes a right-of-use model (“ROU”) that will require a lessee to recognize a ROU asset and a lease liability on the balance sheet for all leases with a term longer than twelve months. Leases will be classified as finance or operating, with classification affecting the pattern and classification of expense recognition in the income statement. For lessors, the guidance modifies the classification criteria and accounting for sales-type and direct financing leases. The majority of the Company’s leases are for certain of its office and manufacturing space, along with several automobiles. The Company is a party to one arrangement as the lessor, for its former Westcor facility located in Sunnyvale, California. The new standard is effective for the Company of January 1, 2019, with early adoption permitted. The Company plans to adopt the new guidance on its effective date. The new standard must be adopted using a modified retrospective transition approach, applying the guidance to all leases existing at the date of initial application. An entity may choose to use either (1) its effective date or (2) the beginning of the earliest comparative period presented in the financial statements as its date of application. The Company plans to adopt the new standard on January 1, 2019 and use the effective date as our date of initial application. As a result, financial information will not be updated and the disclosures required under the new standard will not be provided for dates and periods before January 1, 2019. The new standard provides a number of optional practical expedients. The Company expects to elect the ‘package of practical expedients’, which permits companies to not reassess under the new standard lease identification, lease classification and initial direct costs. The Company does not plan to elect the use-of-hindsight or the practical expedient pertaining to land easements, the latter not being applicable. The Company estimates the adoption of the standard will result in recognition of ROU assets and lease liabilities of approximately $4,500,000, as of January 1, 2019. The implementation team’s remaining tasks are to complete documentation for the systems and controls to support the lease recognition and disclosure requirements under the new standard, and to complete the required disclosures in preparation for filing the Company’s Form 10-Q for the quarter ending March 31, 2019. Other new pronouncements issued but not effective until after December 31, 2018 are not expected to have a material impact on the Company’s consolidated financial statements.

Significant Accounting Polici_3

Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2018
Revenue, Major Customer [Line Items]
Summary of Cumulative Effect of Adoption on Consolidated Statement of Operations	The following tables summarize the impacts of adopting the new revenue recognition guidance on certain components of the Company’s consolidated financial statements (in thousands): a) Consolidated Balance Sheet Items As of December 31, 2018 As reported Adjustments Balances without adoption of Topic 606 Accounts receivable, net $ 43,673 $ (72 ) $ 43,601 Inventories, net 47,370 (110 ) 47,260 Total assets 221,068 (182 ) 220,886 Income taxes payable 710 (59 ) 651 Deferred revenue 5,069 5,768 10,837 Sales allowances 548 (483 ) 65 Total liabilities 36,978 5,226 42,204 Retained earnings 129,000 (5,408 ) 123,592 Total equity 184,090 (5,408 ) 178,682 Total liabilities and equity 221,068 (182 ) 220,886 b) Consolidated Statement of Operations Items Year Ended December 31, 2018 As reported Adjustments Balances without adoption of Topic 606 Net revenues $ 291,220 $ (3,946 ) $ 287,274 Cost of revenues 152,249 (2,149 ) 150,100 Gross margin 138,971 (1,797 ) 137,174 Income before income taxes 32,933 (1,797 ) 31,136 Provision for income taxes 1,087 (59 ) 1,028 Consolidated net income 31,846 (1,738 ) 30,108 Net income attributable to Vicor Corporation 31,725 (1,738 ) 29,987
Summary of Net Revenues Disaggregated by Geography	The following table presents the Company’s net revenues disaggregated by geography based on the location of the customer, by reportable segment, (in thousands): Year Ended December 31, 2018 BBU VI Chip Picor Total United States $ 77,995 $ 30,118 $ 2,666 $ 110,779 Europe 23,484 3,883 322 27,689 Asia Pacific 80,097 47,174 19,807 147,078 All other 5,128 499 47 5,674 $ 186,704 $ 81,674 $ 22,842 $ 291,220 The following table presents the Company’s net revenues disaggregated by the category of revenue, by reportable segment, (in thousands): Year Ended December 31, 2018 BBU VI Chip Picor Total Direct customers, contract manufacturers and non-stocking distributors $ 163,206 $ 70,919 $ 20,660 $ 254,785 Stocking distributors, net of sales allowances 22,362 7,653 1,717 31,732 Non-recurring engineering 1,066 2,996 360 4,422 Royalties 70 70 70 210 Other — 36 35 71 $ 186,704 $ 81,674 $ 22,842 $ 291,220
Computation Of Basic And Diluted Net Income (Loss) Per Share	The following table sets forth the computation of basic and diluted net income (loss) per share for the years ended December 31 (in thousands, except per share amounts): 2018 2017 2016 Numerator: Net income (loss) attributable to Vicor Corporation $ 31,725 $ 167 $ (6,247 ) Denominator: Denominator for basic net income (loss) per share-weighted average shares (1) 39,872 39,228 38,842 Effect of dilutive securities: Employee stock options (2) 857 705 — Denominator for diluted net income (loss) per share-adjusted weighted-average shares and assumed conversions (3) 40,729 39,933 38,842 Basic net income (loss) per share $ 0.80 $ 0.00 $ (0.16 ) Diluted net income (loss) per share $ 0.78 $ 0.00 $ (0.16 ) (1) Denominator represents weighted average number of Common Shares and Class B Common Shares outstanding. (2) Options to purchase 67,247, 53,913 and 1,696,222 shares of Common Stock in 2018, 2017, and 2016, respectively, were not included in the calculation of net income (loss) per share as the effect would have been antidilutive. (3) Denominator represents weighted average number of Common Shares and Class B Common Shares outstanding for the year, adjusted to include the dilutive effect, if any, of outstanding options.
Accounting Standards Update 2014-09 [Member]
Revenue, Major Customer [Line Items]
Summary of Changes in Certain Contract Assets and Liabilities	The following table presents the changes in certain contract assets and (liabilities) (in thousands): December 31, 2018 December 31, 2017 Increase (decrease) Accounts receivable $ 43,673 $ 34,487 $ 9,186 Deferred revenue (3,820 ) (5,015 ) 1,195 Deferred expenses 501 859 (358 ) Customer prepayments (1,250 ) (776 ) (474 ) Sales allowances (548 ) — (548 )

Stock-Based Compensation and _2

Stock-Based Compensation and Employee Benefit Plans (Tables)	12 Months Ended
	Dec. 31, 2018
Stock-Based Compensation Expense	Stock-based compensation expense for the years ended December 31 was as follows (in thousands): 2018 2017 2016 Cost of revenues $ 237 $ 187 $ 95 Selling, general and administrative 2,517 1,125 412 Research and development 642 423 (1 ) Total stock-based compensation $ 3,396 $ 1,735 $ 506
Summary of Compensation Expense by Type of Award	Compensation expense by type of award for the years ended December 31 was as follows (in thousands): 2018 2017 2016 Stock options $ 2,649 $ 1,546 $ 506 ESPP 747 189 — Total stock-based compensation $ 3,396 $ 1,735 $ 506
Weighted-Average Assumptions for Non Performance-Based Fair Value for Stock Options	The fair value for non performance-based stock options awarded for the years shown below was estimated at the date of grant using the Black-Scholes option pricing model with the following weighted-average assumptions: Vicor: 2018 2017 2016 Risk-free interest rate 2.9 % 2.1 % 1.5 % Expected dividend yield — — — Expected volatility 44 % 43 % 45 % Expected lives (years) 6.4 7.1 7.2 VI Chip: 2018 2017 2016 Risk-free interest rate N/A 1.9 % 1.7 % Expected dividend yield — — — Expected volatility N/A 32 % 34 % Expected lives (years) N/A 6.5 6.5
2000 Plan, Vicor [Member]
Stock-Based Compensation Expense	A summary of the activity under the 2000 Plan as of December 31, 2018 and changes during the year then ended, is presented below (in thousands except for share and weighted-average data): Options Outstanding Weighted- Average Exercise Price Weighted- Average Remaining Contractual Life in Aggregate Intrinsic Value Outstanding on December 31, 2017 1,365,917 $ 9.63 Granted 684,077 $ 18.40 Forfeited and expired (25,923 ) $ 16.08 Exercised (641,090 ) $ 10.58 Outstanding on December 31, 2018 1,382,981 $ 13.41 5.40 $ 34,329 Exercisable on December 31, 2018 888,257 $ 8.93 4.46 $ 25,635 Vested or expected to vest as of December 31, 2018 (1) 1,345,938 $ 13.07 5.34 $ 33,820 (1) In addition to the vested options, the Company expects a portion of the unvested options to vest at some point in the future. The number of options expected to vest is calculated by applying an estimated forfeiture rate to the unvested options.
Picor Plan [Member]
Stock-Based Compensation Expense	A summary of the activity under the 2001 Picor Plan as of May 30, 2018, the date of the merger with and into Vicor, and changes during the period then ended, is presented below: Options Outstanding Weighted- Average Exercise Price Outstanding on December 31, 2017 10,065,987 $ 0.62 Granted — Forfeited and expired — Exercised — Options transferred in merger with Vicor (10,065,987 ) $ 1.91 Outstanding on May 30, 2018 —
Vi Chip Plan [Member]
Stock-Based Compensation Expense	A summary of the activity under the 2007 VI Chip Plan as of December 31, 2018 and changes during the year then ended, is presented below (in thousands except for share and weighted-average data): Options Outstanding Weighted- Average Exercise Price Weighted- Average Remaining Contractual Life in Years Aggregate Intrinsic Value Outstanding on December 31, 2017 13,092,250 $ 0.97 Granted — $ — Forfeited and expired (2,678,250 ) $ 1.00 Exercised — $ — Outstanding on December 31, 2018 (1) 10,414,000 $ 0.96 5.39 $ — Exercisable on December 31, 2018 2,743,400 $ 0.97 5.04 $ — Vested or expected to vest as of December 31, 2018 (2) 9,853,685 $ 0.96 5.38 $ — (1) Of the total VI Chip options outstanding on December 31, 2018, 5,500,000 options had been granted to Dr. Vinciarelli, the Company’s Chief Executive Officer. (2) In addition to the vested options, the Company expects a portion of the unvested options to vest at some point in the future. Options expected to vest is calculated by applying an estimated forfeiture rate to the unvested options.

Long-Term Investments (Tables)

Long-Term Investments (Tables)	12 Months Ended
	Dec. 31, 2018
Investments, Debt and Equity Securities [Abstract]
Summary of Available-for-Sale Securities	The following is a summary of the available-for-sale security (in thousands): December 31, 2018 Cost Gross Unrealized Gains Gross Unrealized Losses Estimated Fair Value Failed Auction Security $ 3,000 $ — $ 474 $ 2,526 December 31, 2017 Failed Auction Security $ 3,000 $ — $ 475 $ 2,525
Cost and Estimated Fair Value of Failed Auction Security by Contractual Maturities	The amortized cost and estimated fair value of the available-for-sale security on December 31, 2018, by contractual maturities, are shown below (in thousands): Cost Estimated Fair Value Due in twenty to forty years $ 3,000 $ 2,526
Rollforward of Credit (Gain) Loss Recognized in Earnings on Failed Auction Security	The following table represents a rollforward of the activity related to the credit loss recognized in earnings on the available-for-sale auction rate security held by the Company for the years ended December 31 (in thousands): 2018 2017 2016 Balance at the beginning of the period $ 48 $ 59 $ 72 Reductions in the amount related to credit gain for which other-than-temporary impairment was not previously recognized (7 ) (11 ) (13 ) Balance at the end of the period $ 41 $ 48 $ 59

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	12 Months Ended
	Dec. 31, 2018
Fair Value Disclosures [Abstract]
Assets and Liabilities Measured at Fair Value on Recurring Basis	Assets and liabilities measured at fair value on a recurring basis included the following as of December 31, 2018 (in thousands): Using Quoted Prices in Active Markets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Total Fair Value as of December 31, 2018 Cash equivalents: Money market funds $ 9,433 $ — $ — $ 9,433 Long-term investments: Failed Auction Security — — 2,526 2,526 Liabilities: Contingent consideration obligations — — (408 ) (408 ) Assets measured at fair value on a recurring basis included the following as of December 31, 2017 (in thousands): Using Quoted Prices in Active Markets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Total Fair Value as of December 31, 2017 Cash equivalents: Money market funds $ 9,279 $ — $ — $ 9,279 Long-term investments: Failed Auction Security — — 2,525 2,525 Liabilities: Contingent consideration obligation — — (678 ) (678 )
Quantitative Information about Level 3 Fair Value Measurements	Fair Value Valuation Technique Unobservable Input Weighted Average Failed Auction Security $ 2,526 Discounted cash flow Cumulative probability of earning the maximum rate until maturity 0.08 % Cumulative probability of principal return prior to maturity 93.69 % Cumulative probability of default 6.24 % Liquidity risk premium 5.00 % Recovery rate in default 40.00 %
Change in Estimated Fair Values Calculated for Investment Valued on Recurring Basis Utilizing Level 3 Inputs	The change in the estimated fair value calculated for the investment valued on a recurring basis utilizing Level 3 inputs (i.e., the Failed Auction Security) for the year ended December 31, 2018 was as follows (in thousands): Balance at the beginning of the period $ 2,525 Credit gain on available-for-sale security included in Other income (expense), net 7 Gain included in Other comprehensive income (loss) (6 ) Balance at the end of the period $ 2,526
Change in Estimated Fair Value Calculated for Liabilities Valued on Recurring Basis Utilizing Level 3 Inputs	The change in the estimated fair value calculated for the liabilities valued on a recurring basis utilizing Level 3 inputs (i.e., the Contingent consideration obligations) for the year ended December 31, 2018 was as follows (in thousands): Balance at the beginning of the period $ 678 Payments (270 ) Balance at the end of the period $ 408

Inventories (Tables)

Inventories (Tables)	12 Months Ended
	Dec. 31, 2018
Inventory Disclosure [Abstract]
Summary of Inventories	Inventories as of December 31 were as follows (in thousands): 2018 2017 Raw materials $ 37,696 $ 27,400 Work-in-process 4,740 3,596 Finished goods 4,934 5,503 Net balance $ 47,370 $ 36,499

Property, Plant and Equipment (

Property, Plant and Equipment (Tables)	12 Months Ended
	Dec. 31, 2018
Property, Plant and Equipment [Abstract]
Property, Plant and Equipment	Property, plant and equipment as of December 31 were as follows (in thousands): 2018 2017 Land $ 2,089 $ 2,089 Buildings and improvements 45,170 45,147 Machinery and equipment 208,135 243,392 Furniture and fixtures 7,239 6,320 Construction in-progress and deposits 9,251 4,120 271,884 301,068 Accumulated depreciation and amortization (221,452 ) (259,712 ) Net balance $ 50,432 $ 41,356

Intangible Assets (Tables)

Intangible Assets (Tables)	12 Months Ended
	Dec. 31, 2018
Patents [Member]
Schedule of Patent Cost and Other Asset	Patent costs, which are included in other assets in the accompanying Consolidated Balance Sheets, as of December 31 were as follows (in thousands): 2018 2017 Patent costs $ 1,979 $ 2,093 Accumulated amortization (1,380 ) (1,386 ) $ 599 $ 707

Product Warranties (Tables)

Product Warranties (Tables)	12 Months Ended
	Dec. 31, 2018
Guarantees and Product Warranties [Abstract]
Product Warranty Activity	Product warranty activity for the years ended December 31 was as follows (in thousands): 2018 2017 2016 Balance at the beginning of the period $ 290 $ 214 $ 585 Accruals for warranties for products sold in the period 173 346 358 Fulfillment of warranty obligations (117 ) (194 ) (527 ) Revisions of estimated obligations (78 ) (76 ) (202 ) Balance at the end of the period $ 268 $ 290 $ 214

Other Income (Expense), Net (Ta

Other Income (Expense), Net (Tables)	12 Months Ended
	Dec. 31, 2018
Other Income and Expenses [Abstract]
Components of Other Income	The major changes in the components of Other income (expense), net for the years ended December 31 were as follows (in thousands): 2018 2017 2016 Rental income $ 792 $ 792 $ 462 Foreign currency (losses) gains, net (260 ) 323 (268 ) Interest income 257 124 68 Gain (loss) on disposal of equipment 57 14 (4 ) Credit gains on available-for-sale securities 7 11 13 Other 21 (2 ) 13 $ 874 $ 1,262 $ 284

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2018
Income Tax Disclosure [Abstract]
Schedule of Reconciliation of Federal Statutory Rate on Loss before Income Taxes and before Gain from Sale of Equity Method Investment Rate to Effective Income Tax Rate	The reconciliation of the federal statutory rate on the income (loss) before income taxes to the effective income tax rate for the years ended December is as follows: 2018 2017 2016 Statutory federal tax rate 21.0 % (34.0 )% (34.0 )% State income taxes, net of federal income tax benefit 3.6 97.2 1.9 Increase (decrease) in valuation allowance (9.1 ) (936.1 ) 46.5 Permanent items (5.9 ) (861.2 ) 0.9 Tax credits (5.5 ) (1,222.3 ) (13.6 ) Provision vs. tax return differences (1.7 ) — — Foreign rate differential and deferred items 0.7 (91.8 ) (0.8 ) Decrease in tax reserves 0.1 (5.1 ) — Rate change due to tax reform — 3,441.1 — Refundable income taxes — AMT credit — (751.0 ) — Capital gain on sale to noncontrolling interest — — 3.9 Decrease in unremitted Vicor Custom Power earnings — — (0.9 ) Book income attributable to noncontrolling interest — — 0.1 Other 0.1 (0.1 ) (0.2 ) 3.3 % (363.3 )% 3.8 %
Schedule of Domestic and Foreign Components of Income (Loss) Before Income Taxes and before the Gain from Sale of Equity Method Investment	For financial reporting purposes, income (loss) before income taxes for the years ended December include the following components (in thousands): 2018 2017 2016 Domestic $ 31,455 $ (1,591 ) $ (6,034 ) Foreign 1,478 1,493 4 $ 32,933 $ (98 ) $ (6,030 )
Schedule of Components of Provision (Benefit) for Income Taxes	Significant components of the provision (benefit) for income taxes for the years ended December 31 are as follows (in thousands): 2018 2017 2016 Current: Federal $ — $ (736 ) $ — State 231 156 172 Foreign 911 396 137 1,142 (184 ) 309 Deferred: Federal — — (55 ) Foreign (55 ) (172 ) (23 ) (55 ) (172 ) (78 ) $ 1,087 $ (356 ) $ 231
Schedule of Significant Components of Deferred Tax Assets and Liabilities	Significant components of the Company’s deferred tax assets and liabilities as of December 31 were as follows (in thousands): 2018 2017 Deferred tax assets: Research and development tax credit carryforwards $ 23,244 $ 20,019 Stock-based compensation 3,133 2,793 Inventory reserves 2,109 2,059 Investment tax credit carryforwards 1,976 2,181 Vacation accrual 1,218 1,255 Net operating loss carryforwards 1,091 4,918 UNICAP 275 3 International deferred tax assets 265 210 Unrealized loss on investments 132 135 Sales allowances 128 25 Contingent consideration liabilities 88 148 Deferred revenue 66 79 Bad debt reserves 52 36 Warranty reserves 35 45 Other 233 35 Total deferred tax assets 34,045 33,941 Less: Valuation allowance for deferred tax assets (30,031 ) (33,024 ) Net deferred tax assets 4,014 917 Deferred tax liabilities: Depreciation (3,144 ) (76 ) Prepaid expenses (473 ) (470 ) Patent amortization (107 ) (161 ) Other (25 ) — Total deferred tax liabilities (3,749 ) (707 ) Net deferred tax assets (liabilities) $ 265 $ 210
Schedule of Reconciliation of Beginning and Ending Amount of Unrecognized Tax Benefits	A reconciliation of the beginning and ending amount of unrecognized tax benefits is as follows (in thousands): 2018 2017 2016 Balance on January 1 $ 1,104 $ 946 $ 830 Additions based on tax positions related to the current year 245 138 125 Additions for tax positions of prior years 120 29 — Settlements — (1 ) — Lapse of statute (7 ) (8 ) (9 ) Balance on December 31 $ 1,462 $ 1,104 $ 946

Commitments and Contingencies (

Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2018
Commitments and Contingencies Disclosure [Abstract]
Summary of Future Minimum Rental Commitments under Non-Cancelable Operating Leases	The Company leases certain of its offices, manufacturing space, and several automobiles. The future minimum rental commitments under non- cancelable Year 2019 $ 1,962 2020 1,502 2021 688 2022 447 2023 and thereafter 830

Segment Information (Tables)

Segment Information (Tables)	12 Months Ended
	Dec. 31, 2018
Segment Reporting [Abstract]
Significant Segment Financial Data	The following table provides significant segment financial data as of and for the years ended December 31 (in thousands): BBU VI Chip Picor Corporate Eliminations Total (1) 2018: Net revenues $ 186,715 $ 84,728 $ 34,552 $ — $ (14,775 ) $ 291,220 Income (loss) from operations 22,544 3,612 7,517 (1,614 ) — 32,059 Total assets 279,671 56,619 14,869 85,851 (215,942 ) 221,068 Depreciation and amortization 3,621 3,504 792 1,337 — 9,254 Capital expenditures 2,954 13,386 621 1,250 — 18,211 2017: Net revenues $ 151,789 $ 61,330 $ 26,297 $ — $ (11,586 ) $ 227,830 Income (loss) from operations 5,615 (11,495 ) 5,400 (880 ) — (1,360 ) Total assets 232,255 34,809 13,509 59,550 (174,399 ) 165,724 Depreciation and amortization 3,907 2,782 747 1,457 — 8,893 Capital expenditures 3,188 7,505 1,249 603 — 12,545 2016: Net revenues $ 151,428 $ 39,947 $ 16,684 $ — $ (7,779 ) $ 200,280 Income (loss) from operations 11,750 (16,494 ) (637 ) (933 ) — (6,314 ) Total assets 196,987 21,389 8,583 73,253 (146,145 ) 154,067 Depreciation and amortization 4,258 2,235 545 1,400 — 8,438 Capital expenditures 2,325 4,041 1,178 884 — 8,428 (1) The elimination for net revenues is principally related to inter-segment revenues of Picor to BBU and VI Chip and for inter-segment revenues of VI Chip to BBU. The elimination for total assets is principally related to inter-segment accounts receivable due to BBU for the funding of VI Chip and Picor operations.
Schedule of Net Revenues from Unaffiliated Customers by Country Based on the Location of the Customer	Net revenues from unaffiliated customers by country, based on the location of the customer, for the years ended December 31 were as follows (in thousands): 2018 2017 2016 United States $ 110,779 $ 83,871 $ 80,603 Europe 27,689 24,078 22,495 Asia Pacific 147,078 114,365 91,848 All other 5,674 5,516 5,334 $ 291,220 $ 227,830 $ 200,280

Quarterly Results of Operatio_2

Quarterly Results of Operations (Unaudited) (Tables)	12 Months Ended
	Dec. 31, 2018
Quarterly Financial Information Disclosure [Abstract]
Summary of Unaudited Quarterly Financial Data	The following table sets forth certain unaudited quarterly financial data for the years ended December 31 (in thousands, except per share amounts): First Second Third Fourth Total 2018: Net revenues $ 65,269 $ 74,196 $ 78,035 $ 73,720 $ 291,220 Gross margin 30,211 35,883 39,004 33,873 138,971 Consolidated net income 3,982 7,909 13,048 6,907 31,846 Net income (loss) attributable to noncontrolling interest 39 49 36 (3 ) 121 Net income attributable to Vicor Corporation 3,943 7,860 13,012 6,910 31,725 Net income per share attributable to Vicor Corporation: Basic 0.10 0.20 0.32 0.17 0.80 Diluted 0.10 0.19 0.32 0.17 0.78 First Second Third Fourth Total 2017: Net revenues $ 54,462 $ 57,709 $ 56,888 $ 58,771 $ 227,830 Gross margin 23,652 25,930 25,143 26,931 101,656 Consolidated net income (loss) (954 ) (445 ) 38 1,619 258 Net income attributable to noncontrolling interest 20 14 49 8 91 Net income (loss) attributable to Vicor Corporation (974 ) (459 ) (11 ) 1,611 167 Net income (loss) per share attributable to Vicor Corporation: Basic and diluted (0.02 ) (0.01 ) (0.00 ) 0.04 0.00

Significant Accounting Polici_4

Significant Accounting Policies - Additional Information (Detail)	3 Months Ended		12 Months Ended
	Dec. 31, 2018USD ($)Customer	Dec. 31, 2017USD ($)	Dec. 31, 2018USD ($)Customer	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)	Jan. 01, 2019USD ($)	Jan. 01, 2018USD ($)
Revenue, Major Customer [Line Items]
Gross deferred revenue	$ 3,820,000	$ 5,015,000	$ 3,820,000	$ 5,015,000
Gross deferred cost of revenue		2,135,000		2,135,000
Foreign currency gains (losses)			$ (260,000)	323,000	$ (268,000)
Maturity period of cash and cash equivalents			Less than three months
Available-for-sale securities, failed auction, value	$ 3,000,000		$ 3,000,000
Number of customers accounted for trade account receivable | Customer	1		1
Cost of advertising			$ 2,610,000	2,150,000	$ 1,818,000
Percentage likelihood of tax benefit settlement			50.00%
Retained Earnings (Accumulated Deficit)	$ 129,000,000	93,605,000	$ 129,000,000	$ 93,605,000
Finance Lease, Liability						$ 4,500,000
Accounting Standards Update 2014-09 [Member]
Revenue, Major Customer [Line Items]
Gross deferred revenue	(1,195,000)		(1,195,000)
Deferred revenue current			991,000
Accounting Standards Update 2014-09 [Member] | Adjustments [Member]
Revenue, Major Customer [Line Items]
Retained Earnings (Accumulated Deficit)	(5,408,000)		$ (5,408,000)				$ 3,670,000
Increase in revenue	$ 14,949	$ 14,949
Customer One [Member]
Revenue, Major Customer [Line Items]
Percentage of trade account receivable			14.30%	17.50%
Maximum [Member]
Revenue, Major Customer [Line Items]
Estimated useful life of intangible assets			20 years
Customer Payments Period			60 days
Minimum [Member]
Revenue, Major Customer [Line Items]
Customer Payments Period			30 days

Significant Accounting Polici_5

Significant Accounting Policies - Summary of Cumulative Effect of Adoption on Consolidated Balance Sheets (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Jan. 01, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Accounts receivable, net	$ 43,673
Inventories, net	47,370		$ 36,499
Total assets	221,068		165,724	$ 154,067
Income taxes payable	710		300
Deferred revenue	5,069		5,791
Sales allowances	548
Total liabilities	36,978		29,305
Retained earnings	129,000		93,605
Total equity	184,090		136,419	$ 131,017	$ 136,085
Total liabilities and equity	221,068		$ 165,724
Accounting Standards Update 2014-09 [Member]
Sales allowances	(548)
Accounting Standards Update 2014-09 [Member] | Adjustments [Member]
Accounts receivable, net	(72)
Inventories, net	(110)
Total assets	(182)
Income taxes payable	(59)
Deferred revenue	5,768
Sales allowances	(483)
Total liabilities	5,226
Retained earnings	(5,408)	$ 3,670
Total equity	(5,408)
Total liabilities and equity	(182)
Accounting Standards Update 2014-09 [Member] | Balances without adoption of Topic 606 [Member]
Accounts receivable, net	43,601
Inventories, net	47,260
Total assets	220,886
Income taxes payable	651
Deferred revenue	10,837
Sales allowances	65
Total liabilities	42,204
Retained earnings	123,592
Total equity	178,682
Total liabilities and equity	$ 220,886

Significant Accounting Polici_6

Significant Accounting Policies -Summary of Cumulative Effect of Adoption on Consolidated Statement of Operations (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Net revenues	$ 73,720	$ 78,035	$ 74,196	$ 65,269	$ 58,771	$ 56,888	$ 57,709	$ 54,462	$ 291,220	$ 227,830	$ 200,280
Cost of revenues									152,249	126,174	109,071
Gross margin	33,873	39,004	35,883	30,211	26,931	25,143	25,930	23,652	138,971	101,656	91,209
Income before income taxes									32,933	(98)	(6,030)
Provision for income taxes									1,087	(356)	231
Consolidated net income	6,907	13,048	7,909	3,982	1,619	38	(445)	(954)	31,846	258	(6,261)
Net income attributable to Vicor Corporation	$ 6,910	$ 13,012	$ 7,860	$ 3,943	$ 1,611	$ (11)	$ (459)	$ (974)	31,725	$ 167	$ (6,247)
Accounting Standards Update 2014-09 [Member] | Adjustments [Member]
Net revenues									(3,946)
Cost of revenues									(2,149)
Gross margin									(1,797)
Income before income taxes									(1,797)
Provision for income taxes									(59)
Consolidated net income									(1,738)
Net income attributable to Vicor Corporation									(1,738)
Accounting Standards Update 2014-09 [Member] | Balances without adoption of Topic 606 [Member]
Net revenues									287,274
Cost of revenues									150,100
Gross margin									137,174
Income before income taxes									31,136
Provision for income taxes									1,028
Consolidated net income									30,108
Net income attributable to Vicor Corporation									$ 29,987

Significant Accounting Polici_7

Significant Accounting Policies -Summary of Net Revenues Disaggregated by Geography (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Revenue	$ 73,720	$ 78,035	$ 74,196	$ 65,269	$ 58,771	$ 56,888	$ 57,709	$ 54,462	$ 291,220	$ 227,830	$ 200,280
BBU [Member]
Revenue									186,704
Vi Chip [Member]
Revenue									81,674
Picor [Member]
Revenue									22,842
United States [Member]
Revenue									110,779	83,871	80,603
United States [Member] | BBU [Member]
Revenue									77,995
United States [Member] | Vi Chip [Member]
Revenue									30,118
United States [Member] | Picor [Member]
Revenue									2,666
Europe [Member]
Revenue									27,689	24,078	22,495
Europe [Member] | BBU [Member]
Revenue									23,484
Europe [Member] | Vi Chip [Member]
Revenue									3,883
Europe [Member] | Picor [Member]
Revenue									322
Asia Pacific [Member]
Revenue									147,078	114,365	91,848
Asia Pacific [Member] | BBU [Member]
Revenue									80,097
Asia Pacific [Member] | Vi Chip [Member]
Revenue									47,174
Asia Pacific [Member] | Picor [Member]
Revenue									19,807
All Other [Member]
Revenue									5,674	$ 5,516	$ 5,334
All Other [Member] | BBU [Member]
Revenue									5,128
All Other [Member] | Vi Chip [Member]
Revenue									499
All Other [Member] | Picor [Member]
Revenue									$ 47

Significant Accounting Polici_8

Significant Accounting Policies -Summary of Net Revenues Disaggregated by Category (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Revenue	$ 73,720	$ 78,035	$ 74,196	$ 65,269	$ 58,771	$ 56,888	$ 57,709	$ 54,462	$ 291,220	$ 227,830	$ 200,280
BBU [Member]
Revenue									186,704
Vi Chip [Member]
Revenue									81,674
Picor [Member]
Revenue									22,842
Direct Customers Contract Manufacturers And Non stocking Distributors [Member]
Revenue									254,785
Direct Customers Contract Manufacturers And Non stocking Distributors [Member] | BBU [Member]
Revenue									163,206
Direct Customers Contract Manufacturers And Non stocking Distributors [Member] | Vi Chip [Member]
Revenue									70,919
Direct Customers Contract Manufacturers And Non stocking Distributors [Member] | Picor [Member]
Revenue									20,660
Stocking Distributors Net Of Sales Allowances [Member]
Revenue									31,732
Stocking Distributors Net Of Sales Allowances [Member] | BBU [Member]
Revenue									22,362
Stocking Distributors Net Of Sales Allowances [Member] | Vi Chip [Member]
Revenue									7,653
Stocking Distributors Net Of Sales Allowances [Member] | Picor [Member]
Revenue									1,717
Non recurring Engineering [Member]
Revenue									4,422
Non recurring Engineering [Member] | BBU [Member]
Revenue									1,066
Non recurring Engineering [Member] | Vi Chip [Member]
Revenue									2,996
Non recurring Engineering [Member] | Picor [Member]
Revenue									360
Royalties [Member]
Revenue									210
Royalties [Member] | BBU [Member]
Revenue									70
Royalties [Member] | Vi Chip [Member]
Revenue									70
Royalties [Member] | Picor [Member]
Revenue									70
Other [Member]
Revenue									71
Other [Member] | BBU [Member]
Revenue									0
Other [Member] | Vi Chip [Member]
Revenue									36
Other [Member] | Picor [Member]
Revenue									$ 35

Significant Accounting Polici_9

Significant Accounting Policies -Summary of Changes in Certain Contract Assets and Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Accounts receivable	$ 43,673	$ 34,487
Deferred Revenue	(3,820)	(5,015)
Deferred expenses	501	859
Customer prepayments	(1,250)	$ (776)
Sales Allowances Current	548
Accounting Standards Update 2014-09 [Member]
Accounts receivable	9,186
Deferred Revenue	1,195
Deferred expenses	(358)
Customer prepayments	(474)
Sales Allowances Current	$ (548)

Significant Accounting Polic_10

Significant Accounting Policies - Computation Of Basic And Diluted Net Income (Loss) Per Share (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Numerator:
Net income (loss) attributable to Vicor Corporation	$ 6,910	$ 13,012	$ 7,860	$ 3,943	$ 1,611	$ (11)	$ (459)	$ (974)	$ 31,725	$ 167	$ (6,247)
Denominator:
Denominator for basic net income (loss) per share-weighted average shares									39,872	39,228	38,842
Effect of dilutive securities:
Employee stock options									857	705
Denominator for diluted net income (loss) per share - adjusted weighted-average shares and assumed conversions									40,729	39,933	38,842
Basic net income (loss) per share	$ 0.17	$ 0.32	$ 0.20	$ 0.10					$ 0.80	$ 0	$ (0.16)
Diluted net income (loss) per share	$ 0.17	$ 0.32	$ 0.19	$ 0.10					$ 0.78	$ 0	$ (0.16)

Significant Accounting Polic_11

Significant Accounting Policies - Computation Of Basic And Diluted Net Income (Loss) Per Share (Parenthetical) (Detail) - shares	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Earnings Per Share [Abstract]
Options to purchase shares of Common Stock not included in the computation of diluted income (loss) per share	67,247	53,913	1,696,222

Stock-Based Compensation and _3

Stock-Based Compensation and Employee Benefit Plans - Additional Information (Detail) - USD ($)	Nov. 11, 2011	Sep. 30, 2016	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2010
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Term of Option			10 years
Employee's compensation plan			The Company matches employee contributions to the plan at a rate of 50%, up to the first 3% of an employee’s compensation.
Employee contributions			20.00%
Company contribution to the plan			$ 976,000	$ 937,000	$ 882,000
Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Employees pre-tax salary			1.00%
Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Employees pre-tax salary			80.00%
Vi Chip Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Non-qualified stock options			10,414,000	13,092,250
Stock options, grants in period			0
Maturity period of US Treasury Bond			7 years
Chip options actually vest forfeiture			89.00%	76.00%	76.00%
Annual forfeiture rate			4.25%	9.00%	9.00%
Share exercisable			2,743,400	810,700	7,074,650
Weighted average exercise prices			$ 0.97	$ 1	$ 1
Options Exercised			$ 0	$ 0	$ 0
Fair value of stock options that vested			0	$ 2,900,000	$ 0
Total unrecognized compensation cost			$ 1,792,000
Compensation cost recognized over a weighted-average period			3 years 4 months 24 days
Expected recognized expenses, Year One			$ 544,000
Expected recognized expenses, Year Two			503,000
Expected recognized expenses, Year Three			483,000
Expected recognized expenses, Year Four			$ 262,000
Weighted-average fair value				$ 0.29	$ 0.01
2000 Plan, Vicor [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common Stock reserved for issuance			10,000,000
Non-qualified stock options granted to non-employees			85.00%
Non-qualified stock options			1,382,981	1,365,917
Stock options, grants in period			684,077
Chip options actually vest forfeiture			85.00%	85.00%	86.00%
Annual forfeiture rate			5.25%	5.25%	5.00%
Share exercisable			888,257	707,244	730,388
Weighted average exercise prices			$ 8.93	$ 8.01	$ 7.74
Total Intrinsic value			$ 22,938,000	$ 4,395,000	$ 1,392,000
Options Exercised			6,782,000	3,295,000	1,572,000
Fair value of stock options that vested			2,921,000	$ 774,000	$ 365,000
Total unrecognized compensation cost			$ 2,487,000
Compensation cost recognized over a weighted-average period			1 year 10 months 24 days
Expected recognized expenses, Year One			$ 1,183,000
Expected recognized expenses, Year Two			689,000
Expected recognized expenses, Year Three			395,000
Expected recognized expenses, Year Four			180,000
Expected recognized expenses, Year Five			$ 40,000
Weighted-average fair value			$ 17.46	$ 8.71	$ 4.94
Stock Bonus Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock purchase by non-employees			109,964
2007 VI Chip Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common Stock reserved for issuance			14,000,000
Non-qualified stock options			0			2,984,250
Stock options, grants in period	0
Stock-based compensation expense reversed		$ 768,000
2007 VI Chip Plan [Member] | Cost of Revenues [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Decrease in costs and expenses due to reversal of share-based compensation expense		86,000
2007 VI Chip Plan [Member] | Selling, General and Administrative [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Decrease in costs and expenses due to reversal of share-based compensation expense		516,000
2007 VI Chip Plan [Member] | Research and Development [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Decrease in costs and expenses due to reversal of share-based compensation expense		$ 166,000
2017 Employee Stock Purchase Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Non-qualified stock options granted to non-employees			85.00%
Maximum number of shares authorized for issuances			2,000,000
Maximum percentage of payroll deductions on employee's compensation			15.00%
Offering period of employee stock purchase plan			6 months

Stock-Based Compensation - Stoc

Stock-Based Compensation - Stock-Based Compensation Expense (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation	$ 3,396	$ 1,735	$ 506
Cost of Revenues [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation	237	187	95
Selling, General and Administrative [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation	2,517	1,125	412
Research and Development [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation	$ 642	$ 423	$ (1)

Stock-Based Compensation - Summ

Stock-Based Compensation - Summary of Compensation Expense by Type of Award (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation	$ 3,396	$ 1,735	$ 506
Stock Options [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation	2,649	1,546	$ 506
ESPP [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation	$ 747	$ 189

Stock-Based Compensation and _4

Stock-Based Compensation and Employee Benefit Plans - Weighted-Average Assumptions for Non Performance-Based Fair Value for Stock Options (Detail) - Non Performance-Based Stock Options [Member]	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Risk-free interest rate	0.00%
Expected volatility	0.00%
Expected lives (years)	0 years
Vicor [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Risk-free interest rate	2.90%	2.10%	1.50%
Expected dividend yield	0.00%	0.00%	0.00%
Expected volatility	44.00%	43.00%	45.00%
Expected lives (years)	6 years 4 months 24 days	7 years 1 month 6 days	7 years 2 months 12 days
VI Chip [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Risk-free interest rate		1.90%	1.70%
Expected dividend yield	0.00%	0.00%	0.00%
Expected volatility		32.00%	34.00%
Expected lives (years)		6 years 6 months	6 years 6 months

Stock-Based Compensation and _5

Stock-Based Compensation and Employee Benefit Plans - Summary of the Activity under the 2000 Plan (Detail) - 2000 Plan, Vicor [Member] - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Options Outstanding, Beginning balance	1,365,917
Options Outstanding, Granted	684,077
Options Outstanding, Forfeited and expired	(25,923)
Options Outstanding, Exercised	(641,090)
Options Outstanding, Ending balance	1,382,981	1,365,917
Options Outstanding, Exercisable	888,257	707,244	730,388
Options Outstanding, Vested or expected to vest	1,345,938
Weighted Average Exercise Price, Beginning balance	$ 9.63
Weighted Average Exercise Price, Granted	18.40
Weighted Average Exercise Price, Forfeited and expired	16.08
Weighted Average Exercise Price, Exercised	10.58
Weighted Average Exercise Price, Ending balance	13.41	$ 9.63
Weighted Average Exercise Price, Exercisable	8.93	$ 8.01	$ 7.74
Weighted Average Exercise Price, Vested or expected to vest	$ 13.07
Weighted-Average Remaining Contractual Life in Years, Outstanding	5 years 4 months 24 days
Weighted-Average Remaining Contractual Life in Years, Exercisable	4 years 5 months 16 days
Weighted-Average Remaining Contractual Life in Years, Vested or expected to vest	5 years 4 months 2 days
Aggregate Intrinsic Value, Outstanding	$ 34,329
Aggregate Intrinsic Value, Exercisable	25,635
Aggregate Intrinsic Value, Vested or expected to vest	$ 33,820

Stock-Based Compensation and _6

Stock-Based Compensation and Employee Benefit Plans - Summary of the Activity under the Picor Stock Option Plans (Detail) - Picor Plan [Member]	12 Months Ended
	Dec. 31, 2018$ / sharesshares
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Options Outstanding, Beginning balance	10,065,987
Options Outstanding, Granted	0
Options Outstanding, Forfeited and expired	0
Options Outstanding, Exercised	0
Options transferred in merger with Vicor	(10,065,987)
Options Outstanding, Ending balance	0
Weighted Average Exercise Price, Beginning balance | $ / shares	$ 0.62
Options transferred in merger with Vicor Weighted Average Exercise Price | $ / shares	$ 1.91

Stock-Based Compensation and _7

Stock-Based Compensation and Employee Benefit Plans - Summary of the Activity under the VI Chip Stock Option Plans (Detail) - Vi Chip Plan [Member] - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Options Outstanding, Beginning balance	13,092,250
Options Outstanding, Granted	0
Options Outstanding, Forfeited and expired	(2,678,250)
Options Outstanding, Exercised	0
Options Outstanding, Ending balance	10,414,000	13,092,250
Options Outstanding, Exercisable	2,743,400	810,700	7,074,650
Options Outstanding, Vested or expected to vest	9,853,685
Weighted Average Exercise Price, Beginning balance	$ 0.97
Weighted Average Exercise Price, Granted	0
Weighted Average Exercise Price, Forfeited and expired	1
Weighted Average Exercise Price, Exercised	0
Weighted Average Exercise Price, Ending balance	0.96	$ 0.97
Weighted Average Exercise Price, Exercisable	0.97	$ 1	$ 1
Weighted Average Exercise Price, Vested or expected to vest	$ 0.96
Weighted-Average Remaining Contractual Life in Years, Outstanding	5 years 4 months 20 days
Weighted-Average Remaining Contractual Life in Years, Exercisable	5 years 14 days
Weighted-Average Remaining Contractual Life in Years, Vested or expected to vest		5 years 4 months 17 days
Aggregate Intrinsic Value, Outstanding	$ 0
Aggregate Intrinsic Value, Exercisable	0
Aggregate Intrinsic Value, Vested or expected to vest	$ 0

Stock-Based Compensation and _8

Stock-Based Compensation and Employee Benefit Plans - Summary of the Activity under the VI Chip Stock Option Plans (Parenthetical) (Detail) - Vi Chip Plan [Member]	12 Months Ended
	Dec. 31, 2018shares
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Granted, shares	0
Chief Executive Officer [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Granted, shares	5,500,000

Long-Term Investments - Additio

Long-Term Investments - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Unrealized Losses On Short Term And Long Term Investments [Line Items]
Minimum period for which failed auction securities been in unrealized loss position	12 months
Failed Auction Security [Member]
Unrealized Losses On Short Term And Long Term Investments [Line Items]
Amortized cost of securities	$ 3,000,000	$ 3,000,000
Period for which failed auction securities been in unrealized loss position	exceeds 12 months
Estimated Fair Value	$ 2,526,000	2,525,000
Gross Unrealized Losses	474,000	475,000
Aggregate credit loss	41,000	$ 48,000	$ 59,000	$ 72,000
Aggregate temporary impairment loss	$ 433,000

Long-Term Investments - Summary

Long-Term Investments - Summary of Available-for-Sale Securities (Detail) - Failed Auction Security [Member] - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Debt Securities, Available-for-sale [Line Items]
Cost	$ 3,000	$ 3,000
Gross Unrealized Gains	0	0
Gross Unrealized Losses	474	475
Estimated Fair Value	$ 2,526	$ 2,525

Long-Term Investments - Amortiz

Long-Term Investments - Amortized Cost and Estimated Fair Value of Available-for-Sale Securities by Contractual Maturities (Detail) $ in Thousands	Dec. 31, 2018USD ($)
Available-for-sale Securities, Debt Maturities [Abstract]
Due in twenty to forty years, Cost	$ 3,000
Due in twenty to forty years, Estimated Fair Value	$ 2,526

Long-Term Investments - Rollfor

Long-Term Investments - Rollforward of Credit (Gain) Loss Recognized in Earnings on Available-for-Sale Auction Rate Securities (Detail) - Failed Auction Security [Member] - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Line Items]
Balance at the beginning of the period	$ 48	$ 59	$ 72
Reductions in the amount related to credit gain for which other-than-temporary impairment was not previously recognized	(7)	(11)	(13)
Balance at the end of the period	$ 41	$ 48	$ 59

Fair Value Measurements - Asset

Fair Value Measurements - Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Contingent Consideration Obligations [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Liabilities, fair value on recurring basis	$ (408)	$ (678)
Failed Auction Security [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Estimated Fair Value	2,526	2,525
Money Market Funds [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Cash equivalents	9,433	9,279
Recurring [Member] | Quoted Prices in Active Markets (Level 1) [Member] | Money Market Funds [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Cash equivalents	9,433	9,279
Recurring [Member] | Significant Unobservable Inputs (Level 3) [Member] | Contingent Consideration Obligations [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Liabilities, fair value on recurring basis	(408)	(678)
Recurring [Member] | Significant Unobservable Inputs (Level 3) [Member] | Failed Auction Security [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Estimated Fair Value	$ 2,526	$ 2,525

Fair Value Measurements - Quant

Fair Value Measurements - Quantitative Information about Level 3 Fair Value Measurements (Detail) - Failed Auction Security [Member] - Significant Unobservable Inputs (Level 3) [Member] $ in Thousands	12 Months Ended
	Dec. 31, 2018USD ($)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Estimated Fair Value	$ 2,526
Cumulative Probability of Earning Maximum Rate Until Maturity [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Valuation Technique	Discounted cash flow
Unobservable Input	Cumulative probability of earning the maximum rate until maturity
Weighted Average Interest Rate	0.08%
Cumulative Probability of Principal Return Prior to Maturity [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Unobservable Input	Cumulative probability of principal return prior to maturity
Weighted Average Interest Rate	93.69%
Cumulative Probability of Default [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Unobservable Input	Cumulative probability of default
Weighted Average Interest Rate	6.24%
Liquidity Risk Premium [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Unobservable Input	Liquidity risk premium
Weighted Average Interest Rate	5.00%
Recovery Rate in Default [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Unobservable Input	Recovery rate in default
Weighted Average Interest Rate	40.00%

Fair Value Measurements - Chang

Fair Value Measurements - Change in Estimated Fair Values Calculated for Investment Valued on Recurring Basis Utilizing Level 3 Inputs (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2018USD ($)
Fair Value Disclosures [Abstract]
Balance at the beginning of the period	$ 2,525
Credit gain on available-for-sale security included in Other income (expense), net	7
Gain included in Other comprehensive income (loss)	(6)
Balance at the end of the period	$ 2,526

Fair Value Measurements - Cha_2

Fair Value Measurements - Change in Estimated Fair Value Calculated for Liabilities Valued on Recurring Basis Utilizing Level 3 Inputs (Detail) - Significant Unobservable Inputs (Level 3) [Member] - Contingent Consideration Obligations [Member] $ in Thousands	12 Months Ended
	Dec. 31, 2018USD ($)
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Balance at the beginning of the period	$ 678
Payments	(270)
Balance at the end of the period	$ 408

Fair Value Measurements - Addit

Fair Value Measurements - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2018USD ($)
Fair Value Disclosures [Abstract]
Percent of credit loss	1.00%
Rate of return required	5.00%
Estimated timeframe for auctions of securities minimum	3 years
Estimated timeframe for auctions of securities maximum	5 years
Percentage of liquidity risk premium	5.00%
Increase or decrease in the liquidity risk premium	1.00%
Increase or decrease, respectively, the fair value of the Failed Auction Securities	$ 100,000
Fair Value, Assets, Level 1 to Level 2 Transfers, Amount	$ 0

Inventories - Summary of Invent

Inventories - Summary of Inventories (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Inventory Disclosure [Abstract]
Raw materials	$ 37,696	$ 27,400
Work-in-process	4,740	3,596
Finished goods	4,934	5,503
Net balance	$ 47,370	$ 36,499

Property, Plant and Equipment -

Property, Plant and Equipment - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Property, Plant and Equipment [Line Items]
Depreciation expense	$ 9,135,000	$ 8,763,000	$ 8,304,000
Capital expenditure commitments	$ 8,862,000
Maximum [Member]
Property, Plant and Equipment [Line Items]
Depreciation and amortization period	39 years
Minimum [Member]
Property, Plant and Equipment [Line Items]
Depreciation and amortization period	3 years

Property, Plant and Equipment_2

Property, Plant and Equipment - Property, Plant and Equipment (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Property, Plant and Equipment [Abstract]
Land	$ 2,089	$ 2,089
Buildings and improvements	45,170	45,147
Machinery and equipment	208,135	243,392
Furniture and fixtures	7,239	6,320
Construction in-progress and deposits	9,251	4,120
Property, plant and equipment, gross, total	271,884	301,068
Accumulated depreciation and amortization	(221,452)	(259,712)
Net balance	$ 50,432	$ 41,356

Noncontrolling Interest Trans_2

Noncontrolling Interest Transactions - Additional Information (Detail) - USD ($)	Mar. 30, 2016	Dec. 28, 2015	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2018	Dec. 31, 2015
Noncontrolling Interest [Line Items]
Contingent consideration				$ 678,000	$ 408,000
Converpower Corporation [Member]
Noncontrolling Interest [Line Items]
Ownership percentage by parent in certain operating assets and cash	100.00%
Minority interest percentage by non controlling interest	49.00%
Percentage of common shares exchanged	49.00%
Contingent consideration			$ 208,000		282,000
Increased in liability reassessment obligation			$ 448,000
Mission Power Solutions Inc [Member]
Noncontrolling Interest [Line Items]
Minority interest percentage by non controlling interest		18.00%
Contingent consideration					$ 126,000	$ 144,000
Noncontrolling interest		$ 216,000
Mission Power Solutions Inc [Member]
Noncontrolling Interest [Line Items]
Increased in liability reassessment obligation				$ 202,000

Intangible Assets - Schedule of

Intangible Assets - Schedule of Patent Cost and Other Asset (Detail) - Patents [Member] - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Finite-Lived Intangible Assets [Line Items]
Patent costs	$ 1,979	$ 2,093
Accumulated amortization	(1,380)	(1,386)
Finite-lived intangible assets, net	$ 599	$ 707

Intangible Assets - Additional

Intangible Assets - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Finite-Lived Intangible Assets [Line Items]
Amortization expense	$ 119,000	$ 130,000	$ 134,000
Patents [Member]
Finite-Lived Intangible Assets [Line Items]
Future amortization expense from patent assets held for 2019	108,000
Future amortization expense from patent assets held for 2020	103,000
Future amortization expense from patent assets held for 2021	93,000
Future amortization expense from patent assets held for 2022	62,000
Future amortization expense from patent assets held for 2023	$ 51,000

Severance and Other Charges - A

Severance and Other Charges - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Jun. 30, 2018	Dec. 31, 2018
Schedule Of Sale Of Subsidiary [Abstract]
Severance charges	$ 350
Severance And Other Charges Credits		$ 402

Product Warranties - Product Wa

Product Warranties - Product Warranty Activity (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Guarantees [Abstract]
Balance at the beginning of the period	$ 290	$ 214	$ 585
Accruals for warranties for products sold in the period	173	346	358
Fulfillment of warranty obligations	(117)	(194)	(527)
Revisions of estimated obligations	(78)	(76)	(202)
Balance at the end of the period	$ 268	$ 290	$ 214

Stockholders' Equity - Addition

Stockholders' Equity - Additional information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Nov. 30, 2000
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common Stock repurchased as per November plan				$ 30,000,000
Stock repurchase program amount available	$ 8,541,000
Stock repurchase	0	0	0
Cash dividends paid to the Company	$ 632,000		$ 750,000
Subsidiaries [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Cash dividends on subsidiary common stock	$ 632,000		$ 750,000
2000 Plan, Vicor [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common Stock reserved for issuance	21,233,659	21,976,340	14,377,880

Other Income (Expense), Net - C

Other Income (Expense), Net - Components of Other Income (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Other Income and Expenses [Abstract]
Rental income	$ 792	$ 792	$ 462
Foreign currency gains (losses), net	(260)	323	(268)
Interest income	257	124	68
Gain (loss) on disposal of equipment	57	14	(4)
Credit gains on available-for-sale securities	7	11	13
Other	21	(2)	13
Total other income (expense), net	$ 874	$ 1,262	$ 284

Income Taxes - Additional Infor

Income Taxes - Additional Information (Detail) - USD ($)	3 Months Ended	12 Months Ended
	Mar. 31, 2016	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Mar. 30, 2016	Dec. 31, 2015
Income Tax Disclosure [Line Items]
Effective income tax rate		21.00%	34.00%	34.00%
Tax benefit recognized			$ 0	$ 0
AMT credit carryforwards		$ 736,000
Provisional tax benefit due to new Tax Act		122,000
Untaxed accumulated unremitted foreign earnings		813,000
Valuation allowance, deferred tax assets		30,031,000	33,024,000
Research and development tax credit carryforwards		23,244,000	20,019,000
Accrued interest		1,462,000	1,104,000	946,000		$ 830,000
Net interest expense		7,000	6,000	$ 6,000
Potential payment of interest		$ 35,000	$ 29,000
Converpower Corporation [Member]
Income Tax Disclosure [Line Items]
Ownership percentage by parent in certain operating assets and cash					100.00%
Unremitted earnings reversed	$ 55,000
Maximum [Member]
Income Tax Disclosure [Line Items]
Effective income tax rate			35.00%
Domestic Tax Authority [Member]
Income Tax Disclosure [Line Items]
Federal net operating loss carryforwards expiry, beginning year		2,033
Research and development tax credit carryforwards		$ 12,139,000
Net operating loss carryforwards		$ 2,584,000
Certain States [Member]
Income Tax Disclosure [Line Items]
Federal net operating loss carryforwards expiry, beginning year		2,019
Federal net operating loss carryforwards expiry, ending year		2,037
Research and development tax credit carryforwards		$ 14,920,000
Net operating loss carryforwards		$ 8,249,000

Income Taxes - Schedule of Reco

Income Taxes - Schedule of Reconciliation of Federal Statutory Rate on Loss before Income Taxes and before Gain from Sale of Equity Method Investment Rate to Effective Income Tax Rate (Detail)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Tax Disclosure [Abstract]
Statutory federal tax rate	(21.00%)	(34.00%)	(34.00%)
State income taxes, net of federal income tax benefit	3.60%	97.20%	1.90%
Increase (decrease) in valuation allowance	(9.10%)	(936.10%)	46.50%
Permanent items	(5.90%)	(861.20%)	0.90%
Tax credits	(5.50%)	(1222.30%)	(13.60%)
Provision vs. tax return differences	(1.70%)
Foreign rate differential and deferred items	0.70%	(91.80%)	(0.80%)
Decrease in tax reserves	0.10%	(5.10%)
Rate change due to tax reform		3441.10%
Refundable income taxes - AMT credit		(751.00%)
Capital gain on sale to noncontrolling interest			3.90%
Decrease in unremitted Vicor Custom Power earnings			(0.90%)
Book income attributable to noncontrolling interest			0.10%
Other	0.10%	(0.10%)	(0.20%)
Effective income tax rate	3.30%	(363.30%)	3.80%

Income Taxes - Schedule of Dome

Income Taxes - Schedule of Domestic and Foreign Components of Income (Loss) Before Income Taxes and before the Gain from Sale of Equity Method Investment (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Tax Disclosure [Abstract]
Domestic	$ 31,455	$ (1,591)	$ (6,034)
Foreign	1,478	1,493	4
Income (loss) before income taxes	$ 32,933	$ (98)	$ (6,030)

Income Taxes - Schedule of Comp

Income Taxes - Schedule of Components of Provision (Benefit) for Income Taxes (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Current:
Federal		$ (736)
State	$ 231	156	$ 172
Foreign	911	396	137
Current, Total	1,142	(184)	309
Deferred:
Federal			(55)
Foreign	(55)	(172)	(23)
Deferred Income Tax Expense (Benefit)	(55)	(172)	(78)
Provision (benefit) for income taxes	$ 1,087	$ (356)	$ 231

Income Taxes - Schedule of Sign

Income Taxes - Schedule of Significant Components of Deferred Tax Assets and Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Deferred tax assets:
Research and development tax credit carryforwards	$ 23,244	$ 20,019
Stock-based compensation	3,133	2,793
Inventory reserves	2,109	2,059
Investment tax credit carryforwards	1,976	2,181
Vacation accrual	1,218	1,255
Net operating loss carryforwards	1,091	4,918
UNICAP	275	3
International deferred tax assets	265	210
Unrealized loss on investments	132	135
Sales allowances	128	25
Contingent consideration liabilities	88	148
Deferred revenue	66	79
Bad debt reserves	52	36
Warranty reserves	35	45
Other	233	35
Total deferred tax assets	34,045	33,941
Less: Valuation allowance for deferred tax assets	(30,031)	(33,024)
Net deferred tax assets	4,014	917
Deferred tax liabilities:
Depreciation	(3,144)	(76)
Prepaid expenses	(473)	(470)
Patent amortization	(107)	(161)
Other	(25)
Total deferred tax liabilities	(3,749)	(707)
Net deferred tax assets (liabilities)	$ 265	$ 210

Income Taxes - Schedule of Re_2

Income Taxes - Schedule of Reconciliation of Beginning and Ending Amount of Unrecognized Tax Benefits (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Tax Disclosure [Abstract]
Unrecognized tax benefits, Beginning Balance	$ 1,104	$ 946	$ 830
Additions based on tax positions related to the current year	245	138	125
Additions for tax positions of prior years	120	29
Settlements		(1)
Lapse of statute	(7)	(8)	(9)
Unrecognized tax benefits, Ending Balance	$ 1,462	$ 1,104	$ 946

Commitments and Contingencies -

Commitments and Contingencies - Summary of Future Minimum Rental Commitments under Non-Cancelable Operating Leases (Detail) $ in Thousands	Dec. 31, 2018USD ($)
Commitments and Contingencies Disclosure [Abstract]
2,019	$ 1,962
2,020	1,502
2,021	688
2,022	447
2023 and thereafter	$ 830

Commitments and Contingencies_2

Commitments and Contingencies - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Commitments and Contingencies Disclosure [Abstract]
Rent expense	$ 2,102,000	$ 1,889,000	$ 1,866,000

Segment Information - Significa

Segment Information - Significant Segment Financial Data (Detail) - USD ($) $ in Thousands		3 Months Ended								12 Months Ended
		Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Segment Reporting Information [Line Items]
Net revenues		$ 73,720	$ 78,035	$ 74,196	$ 65,269	$ 58,771	$ 56,888	$ 57,709	$ 54,462	$ 291,220	$ 227,830	$ 200,280
Income (loss) from operations										32,059	(1,360)	(6,314)
Total assets		221,068				165,724				221,068	165,724	154,067
Depreciation and amortization										9,254	8,893	8,438
Capital expenditures										18,211	12,545	8,428
BBU [Member]
Segment Reporting Information [Line Items]
Net revenues										186,704
VI Chip [Member]
Segment Reporting Information [Line Items]
Net revenues										81,674
Picor [Member]
Segment Reporting Information [Line Items]
Net revenues										22,842
Operating Segments [Member] | BBU [Member]
Segment Reporting Information [Line Items]
Net revenues										186,715	151,789	151,428
Income (loss) from operations										22,544	5,615	11,750
Total assets		279,671				232,255				279,671	232,255	196,987
Depreciation and amortization										3,621	3,907	4,258
Capital expenditures										2,954	3,188	2,325
Operating Segments [Member] | VI Chip [Member]
Segment Reporting Information [Line Items]
Net revenues										84,728	61,330	39,947
Income (loss) from operations										3,612	(11,495)	(16,494)
Total assets		56,619				34,809				56,619	34,809	21,389
Depreciation and amortization										3,504	2,782	2,235
Capital expenditures										13,386	7,505	4,041
Operating Segments [Member] | Picor [Member]
Segment Reporting Information [Line Items]
Net revenues										34,552	26,297	16,684
Income (loss) from operations										7,517	5,400	(637)
Total assets		14,869				13,509				14,869	13,509	8,583
Depreciation and amortization										792	747	545
Capital expenditures										621	1,249	1,178
Operating Segments [Member] | Corporate [Member]
Segment Reporting Information [Line Items]
Income (loss) from operations										(1,614)	(880)	(933)
Total assets		85,851				59,550				85,851	59,550	73,253
Depreciation and amortization										1,337	1,457	1,400
Capital expenditures										1,250	603	884
Eliminations [Member]
Segment Reporting Information [Line Items]
Net revenues	[1]									(14,775)	(11,586)	(7,779)
Total assets	[1]	$ (215,942)				$ (174,399)				$ (215,942)	$ (174,399)	$ (146,145)
[1]	The elimination for net revenues is principally related to inter-segment revenues of Picor to BBU and VI Chip and for inter-segment revenues of VI Chip to BBU. The elimination for total assets is principally related to inter-segment accounts receivable due to BBU for the funding of VI Chip and Picor operations.

Segment Information - Additiona

Segment Information - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Segment Reporting Information [Line Items]
Number of customers	1	1	1
Sales Revenue, Net [Member] | Customer Concentration Risk [Member]
Segment Reporting Information [Line Items]
Percentage of total net revenues	13.40%	13.00%	16.40%
Sales Revenue, Net [Member] | Customer Concentration Risk [Member] | China [Member]
Segment Reporting Information [Line Items]
Percentage of total net revenues	37.40%	35.80%	32.10%

Segment Information - Schedule

Segment Information - Schedule of Net Revenues from Unaffiliated Customers by Country Based on the Location of the Customer (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenue	$ 73,720	$ 78,035	$ 74,196	$ 65,269	$ 58,771	$ 56,888	$ 57,709	$ 54,462	$ 291,220	$ 227,830	$ 200,280
United States [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenue									110,779	83,871	80,603
Europe [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenue									27,689	24,078	22,495
Asia Pacific [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenue									147,078	114,365	91,848
All Other Countries [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenue									$ 5,674	$ 5,516	$ 5,334

Quarterly Results of Operatio_3

Quarterly Results of Operations (Unaudited) - Summary of Unaudited Quarterly Financial Data (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Quarterly Financial Information Disclosure [Abstract]
Net revenues	$ 73,720	$ 78,035	$ 74,196	$ 65,269	$ 58,771	$ 56,888	$ 57,709	$ 54,462	$ 291,220	$ 227,830	$ 200,280
Gross margin	33,873	39,004	35,883	30,211	26,931	25,143	25,930	23,652	138,971	101,656	91,209
Consolidated net income (loss)	6,907	13,048	7,909	3,982	1,619	38	(445)	(954)	31,846	258	(6,261)
Net income (loss) attributable to noncontrolling interest	(3)	36	49	39	8	49	14	20	121	91	(14)
Net income (loss) attributable to Vicor Corporation	$ 6,910	$ 13,012	$ 7,860	$ 3,943	$ 1,611	$ (11)	$ (459)	$ (974)	$ 31,725	$ 167	$ (6,247)
Net income (loss) per share attributable to Vicor Corporation:
Basic	$ 0.17	$ 0.32	$ 0.20	$ 0.10					$ 0.80	$ 0	$ (0.16)
Diluted	$ 0.17	$ 0.32	$ 0.19	$ 0.10					$ 0.78	0	$ (0.16)
Basic and diluted					$ 0.04	$ 0	$ (0.01)	$ (0.02)		$ 0

Schedule II - Valuation and Qua

Schedule II - Valuation and Qualifying Accounts (Detail) - Allowance for Doubtful Accounts [Member] - USD ($)		12 Months Ended
		Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at Beginning of Period		$ 159,000	$ 153,000	$ 171,000
Charge (Recovery) to Costs and Expenses		65,000	6,000	(22,000)
Other Charges, Deductions	[1]			4,000
Balance at End of Period		$ 224,000	$ 159,000	$ 153,000
[1]	Reflects uncollectible accounts written off, net of recoveries.