Alpha and Omega Semiconductor Limited (AOSL) 10-Q 5 Nov 18 2019 Q1 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	3 Months Ended
	Sep. 30, 2018	Oct. 25, 2018
Document and Entity Information [Abstract]
Entity Registrant Name	ALPHA & OMEGA SEMICONDUCTOR Ltd
Entity Central Index Key	1,387,467
Current Fiscal Year End Date	--06-30
Entity Filer Category	Accelerated Filer
Document Type	10-Q
Document Period End Date	Sep. 30, 2018
Document Fiscal Year Focus	2,019
Document Fiscal Period Focus	Q1
Amendment Flag	false
Entity Common Stock, Shares Outstanding		23,787,936

CONDENSED CONSOLIDATED BALANCE

CONDENSED CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Sep. 30, 2018	Jun. 30, 2018
Current assets:
Cash and cash equivalents	$ 113,173	$ 131,535
Restricted cash	181	189
Accounts receivable, net	37,108	33,755
Inventories	98,049	90,182
Other current assets	32,755	29,551
Total current assets	281,266	285,212
Property, plant and equipment, net	368,549	331,656
Intangible assets, net	16,567	16,591
Deferred income tax assets	4,918	4,892
Other long-term assets	13,697	28,698
Total assets	684,997	667,049
Current liabilities:
Accounts payable	96,296	92,661
Accrued liabilities	56,054	49,841
Income taxes payable	2,218	2,211
Short term debt	8,251	3,811
Deferred margin	0	1,665
Capital leases	5,893	4,491
Total current liabilities	168,712	154,680
Long-term debt	38,795	26,786
Income taxes payable - long-term	936	924
Deferred income tax liabilities	1,063	713
Capital leases - long-term	52,925	56,791
Other long-term liabilities	894	993
Total liabilities	263,325	240,887
Commitments and contingencies (Note 11)
Preferred shares, par value $0.002 per share:
Authorized: 10,000 shares, issued and outstanding: none at September 30, 2018 and June 30, 2018	0	0
Common shares, par value $0.002 per share:
Authorized: 100,000 shares, issued and outstanding: 30,437 shares and 23,786 shares, respectively at September 30, 2018 and 30,400 shares and 23,860 shares, respectively at June 30, 2018	61	61
Treasury shares at cost, 6,651 shares at September 30, 2018 and 6,540 shares at June 30, 2018	(66,283)	(64,790)
Additional paid-in capital	223,369	220,244
Accumulated other comprehensive income (loss)	(2,808)	440
Retained earnings	126,083	122,639
Total Alpha and Omega Semiconductor Limited shareholder's equity	280,422	278,594
Noncontrolling interest	141,250	147,568
Total equity	421,672	426,162
Total liabilities and equity	$ 684,997	$ 667,049

CONSOLIDATED BALANCE SHEETS (Pa

CONSOLIDATED BALANCE SHEETS (Parenthetical) - $ / shares	Sep. 30, 2018	Jun. 30, 2018
Common shares, par value (in dollars per share)	$ 0.002	$ 0.002
Common shares, authorized (in shares)	100,000,000	100,000,000
Common stock, shares issued (in shares)	30,437,000	30,400,000
Common stock, shares outstanding (in shares)	23,786,000	23,860,000
Preferred stock, par value (in dollars per share)	$ 0.002	$ 0.002
Preferred stock, shares authorized (in shares)	10,000,000	10,000,000
Preferred stock, shares issued (in shares)	0	0
Preferred stock, shares outstanding (in shares)	0	0
Treasury shares (in shares)	6,651,000	6,540,000

CONDENSED CONSOLIDATED STATEMEN

CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Revenue	$ 115,072	$ 104,858
Cost of goods sold	82,461	77,328
Gross profit	32,611	27,530
Operating expenses
Research and development	11,384	8,325
Selling, general and administrative	20,352	14,615
Total operating expenses	31,736	22,940
Operating income	875	4,590
Interest income and other income (loss), net	262	40
Interest expense	(1,490)	(17)
Net income (loss) before income taxes	(353)	4,613
Income tax expense	560	1,274
Net income (loss) including noncontrolling interest	(913)	3,339
Net loss attributable to noncontrolling interest	(3,329)	(1,461)
Net income attributable to Alpha and Omega Semiconductor Limited	$ 2,416	$ 4,800
Net income per common share attributable to Alpha and Omega Semiconductor Limited
Basic (in dollars per share)	$ 0.10	$ 0.20
Diluted (in dollars per share)	$ 0.10	$ 0.19
Weighted average number of common shares attributable to Alpha and Omega Semiconductor Limited used to compute net income per share
Basic (in shares)	23,844	24,021
Diluted (in shares)	24,594	24,960

CONDENSED CONSOLIDATED STATEM_2

CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	3 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Net income (loss) including noncontrolling interest	$ (913)	$ 3,339
Other comprehensive income, net of tax
Foreign currency translation adjustment	(6,237)	701
Comprehensive income (loss)	(7,150)	4,040
Noncontrolling interest	(6,318)	(1,127)
Comprehensive income (loss) attributable to Alpha and Omega Semiconductor Limited	$ (832)	$ 5,167

CONDENSED CONSOLIDATED STATEM_3

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	3 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Cash flows from operating activities
Net income (loss) including noncontrolling interest	$ (913)	$ 3,339
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Depreciation and amortization	7,870	6,978
Share-based compensation expense	3,129	2,008
Deferred income taxes, net	49	103
Loss on disposal of property and equipment	0	11
Changes in assets and liabilities:
Accounts receivable, net	(3,575)	3,004
Inventories	(7,867)	(2,932)
Other current and long-term assets	344	(3,202)
Accounts payable	9,653	(70)
Income taxes payable	20	655
Accrued and other liabilities	9,277	2,356
Net cash provided by operating activities	17,987	12,250
Cash flows from investing activities
Purchases of property and equipment excluding JV Company	(15,216)	(7,118)
Purchases of property and equipment in JV Company	(34,272)	(21,171)
Purchase of intangible assets	(5)	(5,720)
Net cash used in investing activities	(49,493)	(34,009)
Cash flows from financing activities
Proceeds from investment by noncontrolling interest	0	86,994
Withholding tax on restricted stock units	(109)	(129)
Proceeds from exercise of stock options	105	179
Payment for repurchases of common shares	(1,501)	0
Proceeds from borrowings	16,650	0
Repayments of borrowings	(223)	0
Principal payments on capital leases	(207)	(198)
Net cash provided by financing activities	14,715	86,846
Effect of exchange rate changes on cash, cash equivalents and restricted cash	(1,579)	182
Net increase (decrease) in cash, cash equivalents and restricted cash	(18,370)	65,269
Cash, cash equivalents and restricted cash at beginning of period	131,724	115,929
Cash, cash equivalents and restricted cash at end of period	113,354	181,198
Supplemental disclosures of non-cash investing and financing information:
Property and equipment purchased but not yet paid	57,202	23,894
Re-issuance of treasury stock	$ 8	$ (9)

The Company and Significant Acc

The Company and Significant Accounting Policies	3 Months Ended
	Sep. 30, 2018
Organization, Consolidation and Presentation of Financial Statements [Abstract]
The Company and Significant Accounting Policies	The Company and Significant Accounting Policies The Company Alpha and Omega Semiconductor Limited and its subsidiaries (the “Company”, "AOS", "we" or "us") design, develop and supply a broad range of power semiconductors. The Company's portfolio of products targets high-volume applications, including personal computers, flat panel TVs, LED lighting, smart phones, battery packs, quick chargers, home appliances, consumer and industrial motor controls and power supplies for TVs, computers, servers and telecommunications equipment. The Company conducts its operations primarily in the United States of America (“USA”), Hong Kong, China, and Taiwan. Basis of Preparation The accompanying unaudited condensed consolidated financial statements have been prepared in accordance with accounting principles generally accepted in the United States (“U.S. GAAP”) for interim financial information and with the instructions to Article 10 of Securities and Exchange Commission Regulation S-X, as amended. They do not include all information and footnotes necessary for a fair presentation of financial position, results of operations and cash flows in conformity with U.S. GAAP for complete financial statements. These condensed consolidated financial statements should be read in conjunction with the consolidated financial statements and related notes contained in the Company’s Annual Report on Form 10-K for the fiscal year ended June 30, 2018 . All significant intercompany balances and transactions have been eliminated in consolidation. In the opinion of management, all adjustments (consisting of normal recurring adjustments and accruals) considered necessary for a fair presentation of the results of operations for the periods presented have been included in the interim periods. Operating results for the three months ended September 30, 2018 are not necessarily indicative of the results that may be expected for the fiscal year ending June 30, 2019 . The condensed consolidated balance sheet at June 30, 2018 is derived from the audited financial statements included in the Company’s Annual Report on Form 10-K for the fiscal year ended June 30, 2018 . Joint Venture In March 2016, the Company executed an agreement with two strategic investment funds owned by the Municipality of Chongqing, China (the "Chongqing Funds") to form a joint venture, (the "JV Company"), for a new state-of-the-art power semiconductor packaging, testing and wafer fabrication facility in Liangjiang New Area of Chongqing (the "Joint Venture"). The initial capitalization of the Joint Venture under the agreement was $330.0 million , which includes cash contributions from the Chongqing Funds and contributions of cash, equipment and intangible assets from the Company. In August 2018, the Company invested an additional $25.0 million of cash contribution to the JV Company, which resulted in the Company owning 54.4% , and the Chongqing Funds owning 45.6% , of the equity interest in the JV Company. The Joint Venture is accounted for under the provisions of the consolidation guidance since the Company has a controlling financial interest. Use of Estimates The preparation of the condensed consolidated financial statements in conformity with U.S. GAAP requires the Company to make estimates, judgments and assumptions that affect the reported amounts of assets, liabilities, revenue and expenses. To the extent there are material differences between these estimates and actual results, the Company's condensed consolidated financial statements will be affected. On an ongoing basis, the Company evaluates the estimates, judgments and assumptions including those related to stock rotation returns, price adjustments, allowance for doubtful accounts, inventory reserves, warranty accrual, income taxes, share-based compensation, and useful lives for property, plant and equipment and intangible assets. Share-based Compensation Expense The Company recognizes expense related to share-based compensation awards that are ultimately expected to vest based on estimated fair values on the date of grant. The fair value of restricted share units is based on the market value of the Company's common share on the date of grant. For restricted stock awards subject to market conditions, the fair value of each restricted stock award is estimated at the date of grant using the Monte-Carlo pricing model. The fair value of stock options is estimated on the date of grant using the Black-Scholes option valuation model. Share-based compensation expense is recognized on the accelerated attribution basis, net of estimated forfeitures, over the requisite service period of the award, which generally equals the vesting period. Fair Value of Financial Instruments The fair value of cash equivalents are based on observable market prices and have been categorized in Level 1 in the fair value hierarchy. Cash equivalents consist primarily of short term bank deposits. The carrying values of financial instruments such as cash and cash equivalents, accounts receivable and accounts payable approximate their carrying values due to their short-term maturities. The carrying value of the company's debt is considered a reasonable estimate of fair value which is estimated by considering the current rates available to the Company for debt of the same remaining maturities, structure and terms of the debts. Comprehensive Income (Loss) Comprehensive income (loss) is defined as the change in equity of a business enterprise during a period from transactions and other events and circumstances from non-owner sources. The Company's accumulated other comprehensive income (loss) consists of cumulative foreign currency translation adjustments. Total comprehensive income (loss) is presented in the condensed consolidated statements of comprehensive income (loss). Recent Accounting Pronouncements Recently Issued Accounting Standards not yet adopted In August 2018, the SEC adopted the final rule under SEC Release No. 33-10532, Disclosure Update and Simplification, amending certain disclosure requirements that were redundant, duplicative, overlapping, outdated or superseded. In addition, the amendments expanded the disclosure requirements on the analysis of stockholders' equity for interim financial statements. Under the amendments, an analysis of changes in each caption of stockholders' equity presented in the balance sheet must be provided in a note or separate statement. The analysis should present a reconciliation of the beginning balance to the ending balance of each period for which a statement of comprehensive income is required to be filed with the SEC. The Company anticipates its first presentation of changes in stockholders' equity will be included in its Form 10-Q for the quarter ending March 31, 2019. In August 2018, the Financial Accounting Standards Board (FASB) issued Accounting Standards Update (ASU) No. 2018-15 “Intangibles - Goodwill and Other - Internal-Use Software (Subtopic 350-40): Customer’s Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That Is a Service Contract ("ASU 2018-15”). These amendments align the requirements for capitalizing implementation costs incurred in a hosting arrangement that is a service contact with the requirements for capitalizing implementation costs incurred to develop or obtain internal-use software (and hosting arrangements that include an internal-use software license). The accounting for the service element of a hosting arrangement that is a service contract is not affected by these amendments. ASU 2018-15 is effective for annual periods, including interim periods within those annual periods, beginning after December 15, 2019. Early adoption is permitted. The Company is currently assessing the impact that adoption of this guidance will have on its consolidated financial statements. In August 2018, the FASB issued Accounting Standard Updates ("ASU") ASU No. 2018-13, “Fair Value Measurement (Topic 820): Disclosure Framework-Changes to the Disclosure Requirements for Fair Value Measurement ("ASU 2018-13”). ASU 2018-13 amends existing fair value measurement disclosure requirements by adding, changing, or removing certain disclosures. The amendments on changes in unrealized gains and losses, the range and weighted average of significant unobservable inputs used to develop Level 3 fair value measurements, and the narrative description of measurement uncertainty should be applied prospectively for only the most recent interim or annual period presented in the initial fiscal year of adoption. All other amendments should be applied retrospectively to all periods presented upon their effective date. ASU No. 2018-13 is effective for fiscal years and interim periods within those fiscal years, beginning after December 15, 2019. The Company does not expect the adoption of this guidance will have a material impact on its consolidated financial position, results of operations or cash flows. In June 2018, the FASB issued ASU 2018-07, "Compensation -Stock Compensation: Improvement to Nonemployees Share-Based Payment Accounting ("ASU 2018-07"), which expands the scope of Topic 718 to include all share-based payment transactions for acquiring goods and services from nonemployees. ASU 2018-07 specifies that Topic 718 applies to all share-based payment transactions in which the grantor acquires goods and services to be used or consumed in its own operations by issuing share-based payment awards. ASU 2018-07 also clarifies that Topic 718 does not apply to share-based payments used to effectively provide (1) financing to the issuer or (2) awards granted in conjunction with selling goods or services to customers as part of a contract accounted for under ASC 606. ASU 2018-07 is effective fiscal years beginning after December 15, 2018, including interim periods within that fiscal year, with early adoption permitted, but no earlier than our adoption of ASC 606. The Company does not expect the adoption of this guidance will have a material impact on its consolidated financial position, results of operations or cash flows. In February 2016, the FASB issued ASU 2016-02, Leases. This guidance requires a dual approach for lessee accounting under which a lessee will account for leases as finance leases or operating leases. Both finance and operating leases will result in the lessee recognizing a right-of-use asset and a corresponding liability on its balance sheet, with differing methodology for income statement recognition. This guidance is effective for public business entities for fiscal years, and interim periods within those years, beginning after December 15, 2018, and early adoption is permitted. A modified retrospective approach is required for all leases existing or entered into after the beginning of the earliest comparative period in the consolidated financial statements. In July 2018, the FASB issued ASU 2018-11, “Leases (Topic 842): Targeted Improvements.”, which permits an entity to elect an additional transition method to the existing modified retrospective transition requirements. Under the new transition method, an entity could adopt the provisions of ASU No. 2016-02 by recognizing a cumulative-effect adjustment to the opening balance of retained earnings in the period of adoption without adjustment to the financial statements for periods prior to adoption. Consequently, an entity’s reporting for the comparative periods presented in the financial statements in which it adopts the new leases standard will continue to be in accordance with the previous lease guidance in ASC Topic 840. ASU 2018-11 also allows a practical expedient that permits lessors to not separate non-lease components from the associated lease component if certain conditions are present. The recognition, measurement, and presentation of expenses and cash flows arising from a lease by a lessee have not significantly changed from previous Generally Accepted Accounting Principles. Although the Company is currently evaluating the impact the pronouncement will have on its consolidated financial statements and related disclosures, the Company expects that most of its operating lease commitments will be subject to the new standard and recognized as operating lease liabilities and right-of-use assets upon adoption. Recently Adopted Accounting Standards In May 2017, the FASB issued ASU 2017-09, "Compensation -Stock Compensation: Scope of Modification Accounting ("ASU 2017-09"). ASU 2017-09 is an update to the existing guidance to clarify when modification accounting would be applied for a change to the terms or conditions of a share-based award. Under this new guidance, modification accounting is required only if the fair value, a vesting condition, or the classification of the award changes as a result of the change in terms or conditions. This ASU is effective for annual periods, and interim periods within those annual periods, beginning after December 15, 2017 with early adoption permitted. The Company does not regularly modify the terms and conditions of its share-based awards and the adoption of this guidance has no impact on its financial statements. In November 2016, the FASB issued ASU 2016-18, "Statement of Cash Flows: Restricted Cash ("ASU 2016-18"). ASU 2016-18 requires amounts generally described as restricted cash and restricted cash equivalents be included with cash and cash equivalents when reconciling the total beginning and ending amounts for the periods shown on the statement of cash flows. This ASU is effective for fiscal years beginning after December 15, 2017, and interim periods within those fiscal years, with early adoption permitted and requires retrospective adoption. The Company adopted this standard effective July 1, 2018. The reclassified restricted cash balances from investing activities to changes in cash, cash equivalents and restricted cash on the condensed consolidated statements of cash flows were not material for all periods presented. In August 2016, the FASB issued ASU No. 2016-15, "Statement of Cash Flows (Topic 230): Classification of Certain Cash Receipts and Cash Payments ("ASU 2016-15"). ASU 2016-15 identifies how certain cash receipts and cash payments are presented and classified in the Statement of Cash Flows under Topic 230. ASU 2016-15 is effective for fiscal years beginning after December 15, 2017, and interim periods within those fiscal years, with early adoption permitted. Upon adoption, entities must apply the guidance retrospectively to all periods presented. There was no impact on the Company's consolidated financial statements upon the adoption of this standard. In May 2014, the FASB issued ASU No. 2014-09, Revenue from Contracts with Customers (ASC 606). The standard provides companies with a single model for use in accounting for revenue arising from contracts with customers and supersedes current revenue recognition guidance, including industry-specific revenue guidance. The core principle of the model is to recognize revenue when control of the goods or services transfers to the customer, as opposed to recognizing revenue when the risks and rewards transfer to the customer under the existing revenue guidance. The change for the Company under ASC 606 relates to the timing of revenue recognition with two U.S.-based distributors. Sales to these distributors are governed under the terms of agreements providing extended price protection and other return rights, and were historically deferred under the previous accounting guidance until the related product was sold to the end customer. Under ASC 606, the transaction price takes into consideration the effect of variable consideration such as price adjustments and returns rights, which are estimated and recorded at the time the goods are delivered. Accordingly, the Company recognizes revenue under ASC 606 at the time of shipment or delivery to these two distributors, adjusted for estimates of the price adjustments and product returns based on historical data and other available information. Revenue from other non-U.S. distributors and direct customers, which consists of majority of the Company's total revenue, is recognized at the time of shipment or delivery to the distributors and direct customers. Accordingly, revenue recognition with these distributors and direct customers remains unchanged upon adoption of ASC 606. See "Note 2 - Revenue" for additional information on the impact of the adoption of the new standard on the Company’s consolidated financial statements.

Revenue (Notes)

Revenue (Notes)	3 Months Ended
	Sep. 30, 2018
Revenue from Contract with Customer [Abstract]
Revenue	Revenue Impact from the Adoption of the New Revenue Standard On July 1, 2018, the Company adopted ASC 606 using the modified retrospective method applied to all contracts. Results for reporting periods beginning after July 1, 2018 are presented under ASC 606, while prior period amounts are not adjusted and continue to be reported in accordance with our historic accounting under ASC 605. The change for the Company under ASC 606 relates to the timing of revenue recognition with two U.S.-based distributors. Sales to these distributors are governed under the terms of agreements providing extended price protection and other return rights. The Company recorded a net increase to opening retained earnings of $1.0 million as of July 1, 2018 due to the cumulative impact of adopting ASC 606, with a corresponding $1.6 million decrease in deferred margin, a $0.2 million decrease in accounts receivables, a $0.1 million increase in current accrued liabilities, and a $0.3 million increase in deferred tax liabilities. Effective July 1, 2018, the Company recognized revenue at the time of shipment or delivery to these two distributors, adjusted for estimates of the price adjustments and return rights based on historical data and other available information. Based on the Company's assessment, only minimal changes were required to the Company's existing policies, processes, and controls to support the standard's measurement and disclosure requirements. The following tables compare the amounts reported in the condensed consolidated statements of income and condensed consolidated balance sheet to the amounts had the previous revenue recognition guidance been in effect: As of September 30, 2018 As Reported Adjustment Balances Without Adoption (in thousands) Accounts receivable, net $ 37,108 $ 224 $ 37,332 Accrued liabilities $ 56,054 $ (120 ) $ 55,934 Deferred margin $ — $ 1,691 $ 1,691 Deferred income tax liabilities $ 1,063 $ (285 ) $ 778 Retained earnings $ 126,083 $ (1,062 ) $ 125,021 Three Months Ended September 30, 2018 As Reported Adjustment Balances Without Adoption (in thousands) Revenue $ 115,072 $ 41 $ 115,113 Cost of goods sold $ 82,461 $ 20 $ 82,481 Gross profit $ 32,611 $ 21 $ 32,632 Income tax expense $ 560 $ (8 ) $ 552 Net income (loss) including noncontrolling interest $ (913 ) $ 29 $ (884 ) New Revenue Recognition Policy Including Significant Judgments and Estimates As a result of the adoption of the new revenue standard on July 1, 2018, at the beginning of the first quarter of fiscal year 2019, the Company determines revenue recognition through the following steps: (1) identification of the contract with a customer; (2) identification of the performance obligations in the contract; (3) determination of the transaction price; (4) allocation of the transaction price to the performance obligations in the contract; and (5) recognition of revenue when, or as, a performance obligation is satisfied. The Company has written contracts with combination of agreements and purchase orders with all customers including certain general terms and conditions. Often purchase orders entail merchandises, quantities and prices, which define the performance obligations of each party and are approved or accepted by the Company. The Company’s contracts with customers do not typically include extended payment terms. Payment terms vary by contract type and type of customer and generally range from 30 to 60 days. The Company’s performance obligations are to deliver the requested goods or services to customers according to the agreed shipping terms. As such, there is no material difference in regards to performance obligations vs. “deliverables” under ASC 606 vs. the legacy revenue guidance. The Company recognizes revenue when the performance obligation is satisfied. The majority of the Company’s total revenue is from non-U.S. distributors and direct customers, which is recognized at the time of shipment or delivery to the distributors and direct customers. Accordingly, revenue recognition with these distributors and direct customers remains unchanged upon adoption of ASC 606. As noted above, the change for the Company under ASC 606 relates to the timing of revenue recognition with two U.S.-based distributors. Sales to these distributors are governed under the terms of agreements providing extended price protection and other return rights, and were historically deferred under the previous accounting guidance until the related product was sold to end customers. Under ASC 606, the transaction price takes into consideration the effect of variable consideration such as price adjustments and return rights, which are estimated and recorded at the time the goods are delivered. Because all of the Company’s performance obligations relate to contracts with a duration of less than one year, the Company elected to apply the optional exemption practical expedient provided in ASC 606 and, therefore, is not required to disclose the aggregate amount of the transaction price allocated to performance obligations that are unsatisfied or partially unsatisfied at the end of the reporting period. The Company adjusts the transaction price for variable consideration. Variable consideration is not typically significant and primarily results from stock rotation rights and price adjustments provided to our distributors. As a practical expedient, the Company recognizes the incremental costs of obtaining a contract, specifically commission expenses that have a period of benefit of less than twelve months, as an expense when incurred. Additionally, the Company has adopted an accounting policy to recognize shipping costs that occur after control transfers to the customer as a fulfillment activity. The Company warrants its products to be free of defects generally for a period of one year. The Company estimates its warranty costs based on historical warranty claim experience and includes such costs in cost of goods sold. Warranty expenses and the accrued warranty liability were not material as of September 30, 2018. The following table presents the Company's revenue information by geographical location based on the country or region to which the products were shipped. The Company sells its products primarily to distributors in the Asia Pacific region, who in turn sell these products to end customers. Because the Company's distributors sell their products to end customers which may have a global presence, revenue by geographical location is not necessarily representative of the geographical distribution of sales to end user markets. Three Months Ended September 30, 2018 2017 (in thousands) Hong Kong $ 91,591 $ 85,230 China 20,397 17,120 South Korea 169 287 United States 1,973 1,378 Other countries 942 843 $ 115,072 $ 104,858 The following is a summary of revenue by product type: Three Months Ended September 30, 2018 2017 (in thousands) Power discrete $ 92,255 $ 83,678 Power IC 19,415 18,097 Packaging and testing services 3,402 3,083 $ 115,072 $ 104,858

Net Income (Loss) Per Share

Net Income (Loss) Per Share	3 Months Ended
	Sep. 30, 2018
Earnings Per Share [Abstract]
Net Income (Loss) Per Share	Net Income Per Common Share Attributable to Alpha and Omega Semiconductor Limited The following table presents the calculation of basic and diluted net income per share attributable to common shareholders: Three Months Ended September 30, 2018 2017 (in thousands, except per share data) Numerator: Net income attributable to Alpha and Omega Semiconductor Limited $ 2,416 $ 4,800 Denominator: Basic: Weighted average number of common shares used to compute basic net income per share 23,844 24,021 Diluted: Weighted average number of common shares used to compute basic net income per share 23,844 24,021 Effect of potentially dilutive securities: Stock options, RSUs and ESPP shares 750 939 Weighted average number of common shares used to compute diluted net income per share 24,594 24,960 Net income per share attributable to Alpha and Omega Semiconductor Limited: Basic $ 0.10 $ 0.20 Diluted $ 0.10 $ 0.19 The following potential dilutive securities were excluded from the computation of diluted net income per share as their effect would have been anti-dilutive: Three Months Ended September 30, 2018 2017 (in thousands) Employee stock options and RSUs 405 172 ESPP 216 90 Total potential dilutive securities 621 262

Concentration of Credit Risk an

Concentration of Credit Risk and Significant Customers	3 Months Ended
	Sep. 30, 2018
Risks and Uncertainties [Abstract]
Concentration of Credit Risk and Significant Customers	Concentration of Credit Risk and Significant Customers The Company manages its credit risk associated with exposure to distributors and direct customers on outstanding accounts receivable through the application and review of credit approvals, credit ratings and other monitoring procedures. In some instances, the Company also obtains letters of credit from certain customers. Credit sales, which are mainly on credit terms of 30 to 60 days , are only made to customers who meet the Company's credit requirements, while sales to new customers or customers with low credit ratings are usually made on an advance payment basis. The Company considers its trade accounts receivable to be of good credit quality because its key distributors and direct customers have long-standing business relationships with the Company and the Company has not experienced any significant write-offs of accounts receivable in the past. The Company closely monitors the aging of accounts receivable from its distributors and direct customers, and regularly reviews their financial positions, when available. Summarized below are individual customers whose revenue or accounts receivable balances were more than 10% of the respective total consolidated amounts: Three Months Ended September 30, Percentage of revenue 2018 2017 Customer A 27.7 % 27.5 % Customer B 38.0 % 33.9 % September 30, June 30, Percentage of accounts receivable Customer A 18.5 % 17.1 % Customer B 37.9 % 35.5 % Customer C 10.2 % 10.6 %

Balance Sheet Components

Balance Sheet Components	3 Months Ended
	Sep. 30, 2018
Balance Sheet Related Disclosures [Abstract]
Balance Sheet Components	Balance Sheet Components Accounts receivable, net: September 30, June 30, (in thousands) Accounts receivable $ 55,290 $ 52,687 Less: Allowance for price adjustments (18,152 ) (18,902 ) Less: Allowance for doubtful accounts (30 ) (30 ) Accounts receivable, net $ 37,108 $ 33,755 Inventories: September 30, June 30, (in thousands) Raw materials $ 51,854 $ 47,097 Work in-process 39,296 35,243 Finished goods 6,899 7,842 $ 98,049 $ 90,182 Other current assets: September 30, June 30, (in thousands) VAT receivable $ 25,722 $ 17,601 Other prepaid expenses 2,417 2,121 Prepaid insurance 1,109 906 Prepaid maintenance 685 556 Prepayment to supplier 735 227 Prepaid income tax 761 761 Custom deposit 26 5,749 Lease financing cost 910 960 Other receivable 390 670 $ 32,755 $ 29,551 Property, plant and equipment, net: September 30, June 30, (in thousands) Land $ 4,877 $ 4,877 Building 33,836 4,325 Manufacturing machinery and equipment 274,818 265,192 Equipment and tooling 17,891 16,605 Computer equipment and software 26,751 25,686 Office furniture and equipment 2,318 2,314 Leasehold improvements 30,499 29,900 Land use rights 8,750 9,089 399,740 357,988 Less: accumulated depreciation (229,627 ) (225,184 ) 170,113 132,804 Equipment and construction in progress 198,436 198,852 Property, plant and equipment, net $ 368,549 $ 331,656 Intangible assets, net: September 30, June 30, (in thousands) Patents and technology rights $ 17,637 $ 17,633 Trade name 268 268 Customer relationships 1,150 1,150 19,055 19,051 Less: accumulated amortization (2,757 ) (2,729 ) 16,298 16,322 Goodwill 269 269 Intangible assets, net $ 16,567 $ 16,591 Intangible assets of patents and technology rights are primarily related to a license agreement that the Company entered into with STMicroelectronics International N.V. (“STMicro”) on September 5, 2017, pursuant to which STMicro granted the Company a world-wide, royalty-free and fully-paid license to use its technologies to develop, market and distribute certain digital multi-phase controller products, which have been offered by STMicro. This agreement allows the Company to develop and market products in a new market for digital power products, primarily in the computer server segment. As of September 30, 2018 , the Company recorded $15.8 million of intangible assets related to STMicro. The Company begins amortizing such license fees when the technology has met the Company's qualification and is ready for its intended use in production. Other long-term assets: September 30, June 30, (in thousands) Prepayments for property and equipment $ 5,844 $ 17,599 Investment in a privately held company 700 700 Lease financing costs 1,630 1,922 VAT long-term receivable 478 3,396 Custom deposit 1,766 1,589 Other long-term deposits 1,983 2,252 Office leases deposits 981 853 Other 315 387 $ 13,697 $ 28,698 Accrued liabilities: September 30, June 30, (in thousands) Accrued compensation and benefits $ 23,674 $ 18,484 Warranty accrual 632 535 Stock rotation accrual 1,775 1,750 Accrued professional fees 1,860 1,922 Accrued inventory 640 667 Accrued facilities related expenses 3,446 2,163 Accrued financing lease costs 1,454 1,510 Accrued property, plant and equipment 15,038 18,145 Other accrued expenses 7,535 4,665 $ 56,054 $ 49,841 The activities in the warranty accrual, included in accrued liabilities, are as follows: Three Months Ended September 30, 2018 2017 (in thousands) Beginning balance $ 535 $ 1,866 Additions (reductions) 136 (237 ) Utilization (39 ) (7 ) Ending balance $ 632 $ 1,622 The activities in the stock rotation accrual, included in accrued liabilities, are as follows: Three Months Ended September 30, 2018 2017 (in thousands) Beginning balance $ 1,750 $ 1,871 Additions 748 791 Utilization (723 ) (668 ) Ending balance $ 1,775 $ 1,994

Bank Borrowing Bank Borrowing

Bank Borrowing Bank Borrowing	3 Months Ended
	Sep. 30, 2018
Debt Disclosure [Abstract]
Bank Borrowing	Bank Borrowings On May 9, 2018 (the “Effective Date”), the JV Company entered into a lease finance agreement and a security agreement (the “Agreements”) with YinHai Leasing Company and China Import/Export Bank (the “Lenders”). Pursuant to the Agreements, the Lenders agree to provide an aggregate of Chinese Renminbi (RMB) 400.0 million , or $62.8 million based on the currency exchange rate between RMB and U.S. Dollars on the Effective Date, of financing to the JV Company (the “Lease Financing”). In exchange for the Lease Financing, the JV Company agrees to transfer title of its assembly and testing equipment to the Lenders, and the Lenders lease such equipment to the JV Company under a five -year lease arrangement, pursuant to which the JV Company makes quarterly lease payments to the Lenders consisting of principal and interest based on a repayment schedule mutually agreed by the parties. The interest under the Lease Financing is accrued based on the China Base Rate multiplied by 1.15 , or 5.4625% on the Effective Date. Under the Agreements, at the end of the five-year lease term, the Lenders agree to sell such equipment back to the JV Company for a nominal amount (RMB 1 ). The JV Company’s obligations under the Lease Financing are secured by the land and building owned by the JV Company (the “Collateral”). The proceeds from the Lease Financing will be used primarily for the acquisition and installation of the 12-inch fabrication equipment and other expenses of the JV Company relating to the completion of the fabrication facility located in Chongqing. The Agreements contain customary representation, warranties and covenants, including restrictions on the transfer of the Collateral. The Agreements also contain customary events of default, including but are not limited to, failure to make payments and breach of material terms under the Agreements. The Agreements include certain customary closing conditions, including the payment of deposit by the JV Company. As of September 30, 2018 , the outstanding balance under the Agreement was 400 million RMB (equivalent of $58.2 million based on the currency exchange rate as of September 30, 2018 ), which was recorded under short-term and long-term capital lease liabilities. Capital lease liabilities include financing lease, computer software and exclusive technology rights. Future minimum lease payments are as follows (in thousands): Year ending June 30, 2019 (Remaining) $ 6,549 2020 14,201 2021 17,777 2022 16,907 2023 12,255 Thereafter — Total minimum lease payments 67,689 Less amount representing interest (8,871 ) Total capital lease liabilities $ 58,818 On May 1, 2018, Jireh Semiconductor Incorporated ("Jireh"), a wholly-owned subsidiary of the Company, entered into a loan agreement with a financial institution (the "Bank") that provided a term loan in an amount of $17.8 million . The obligation under the loan agreement is secured by certain real estate assets of Jireh and guaranteed by the Company. The loan has a five-year term and matures on June 1, 2023. Beginning June 1, 2018, Jireh shall make consecutive monthly payments of principal and interest to the Bank. The outstanding principal shall accrue interest at a fixed rate of 5.04% per annum on the basis of a 360-day year. The loan agreement contains customary restrictive covenants and includes certain financial covenants that require the Company to maintain, on a consolidated basis, specified financial ratios. As of September 30, 2018 , the outstanding balance of the term loan was $17.5 million . On August 15, 2017, Jireh entered into a credit agreement with the Bank that provided a term loan in an amount up to $30.0 million for the purpose of purchasing certain equipment for the Company's fabrication facility located in Oregon. The obligation under the credit agreement is secured by substantially all assets of Jireh and guaranteed by the Company. The credit agreement has a five -year term and matures on August 15, 2022. In January 2018 and July 2018, Jireh drew down the loan in the amount of $13.2 million and $16.7 million , respectively. Beginning in October 2018, Jireh is required to pay to the Bank on each payment date, the outstanding principal amount of the loan in monthly installments. The loan accrues interest based on an adjusted London Interbank Offered Rate ("LIBOR") as defined in the credit agreement, plus specified applicable margin in the range of 1.75% to 2.25% , based on the outstanding balance of the loan. The credit agreement contains customary restrictive covenants and includes certain financial covenants that require the Company to maintain, on a consolidated basis, specified financial ratios and fixed charge coverage ratio. As of September 30, 2018 , the outstanding balances of the term loan were $29.8 million . Maturities of Jireh debt were as follows (in thousands): Year ending June 30, 2019 (Remaining) $ 6,255 2020 8,340 2021 8,340 2022 8,340 2023 16,028 Total debt, excluding debt issuance costs 47,303 Less: debt issuance costs (257 ) Total debt, less debt issuance costs $ 47,046 In November 2018, the Company obtained a waiver from the Bank with respect to the term loans in Jireh which, among other things, waived the Company's violation of the minimum Adjusted Quick ratio covenant as required. Adjusted Quick ratio is the ratio of (a) current assets excluding inventory to (b) the sum of current liabilities plus the total amount of debt owing to the Bank and any other bank affiliate. Following the execution of such waiver, as of September 30, 2018, we were in compliance with all covenants under the term loans.

Joint Venture

Joint Venture	3 Months Ended
	Sep. 30, 2018
Equity Method Investments and Joint Ventures [Abstract]
Joint Venture	Joint Venture On March 29, 2016, the Company entered into a joint venture contract (the “JV Agreement”) with two investment funds owned by the Municipality of Chongqing (the “Chongqing Funds”), pursuant to which the Company and the Chongqing Funds formed a joint venture, (the “JV Company”), for the purpose of constructing and operating a power semiconductor packaging, testing and 12-inch wafer fabrication facility in the Liangjiang New Area of Chongqing, China (the “JV Transaction”). As of September 30, 2018, the Company owns 54.4% , and the Chongqing Funds own 45.6% , of the equity interest in the JV Company. In September 2018, the JV Company completed its assembly and testing facilities and commenced small mass production of assembly and testing. In addition, the JV Company substantially completed the 12-inch wafer fab facility and expects trial production of power semiconductors toward the end of calendar year 2018. As part of the JV Transaction, the JV Company entered into an Engineering, Procurement and Construction Contract (the “EPC Contract”) with The IT Electronics Eleventh Design & Research Institute Scientific and Technological Engineering Corporation Limited (the “Contractor”), effective as of January 10, 2017 (the "Effective Date"), pursuant which the Contractor was engaged to construct the manufacturing facility contemplated under the JV Agreement. The total price payable under the EPC Contract is Chinese Renminbi (RMB) 540.0 million, or approximately $78.0 million based on the currency exchange rate between RMB and U.S. Dollars on the Effective Date, which consists of $2.8 million (RMB 19.5 million) of design fees and $75.2 million (RMB 520.5 million) of construction and procurement fees (including compliance with safety and aesthetic requirements). As of September 30, 2018 , the JV Company paid approximately $68.3 million (RMB 469.5 million ), and expects to pay the remaining of $10.2 million (RMB 70.5 million ) in fiscal year 2019. The changes in total AOS stockholders' equity, noncontrolling interest and total equity were as follows (in thousands): Total AOS Stockholders' Equity Noncontrolling Interest Total Equity Balance, June 30, 2018 $ 278,594 $ 147,568 $ 426,162 Exercise of common stock options and release of RSUs 105 — 105 Withholding tax on restricted stock units (109 ) — (109 ) Repurchase of common shares under shares repurchase program (1,501 ) — (1,501 ) Stock-based compensation expense 3,129 — 3,129 Net income (loss) 2,416 (3,329 ) (913 ) Impact on retained earnings related to ASC 606 adoption 1,036 — 1,036 Cumulative translation adjustment (3,248 ) (2,989 ) (6,237 ) Balance, September 30, 2018 $ 280,422 $ 141,250 $ 421,672

Shareholders' Equity and Share-

Shareholders' Equity and Share-based Compensation	3 Months Ended
	Sep. 30, 2018
Share-based Compensation [Abstract]
Shareholders' Equity and Share-based Compensation	Stockholders' Equity and Share-based Compensation Share Repurchase In September 2017, the Board of Directors terminated the repurchase program that was previously approved in 2015 and approved a new repurchase program (the “Repurchase Program”), which allows the Company to repurchase its common shares from the open market pursuant to a pre-established Rule 10b5-1 trading plan or through privately negotiated transactions up to an aggregate of $30.0 million . The amount and timing of any repurchases under the Repurchase Program depend on a number of factors, including but not limited to, the trading price, volume, availability of the Company's common shares and the amount of available cash reserve. Shares repurchased under this program are accounted for as treasury shares and the total cost of shares repurchased is recorded as a reduction of shareholders' equity. During the three months ended September 30, 2018 , the Company repurchased an aggregate of 111,509 shares from the open market, for a total cost of $1.5 million , excluding fees and related expenses, at an average price of $13.43 per share. Since the inception of the prior repurchase program in 2010, the Company repurchased an aggregate of 6,784,648 shares from the open market including shares purchased in a dutch tender offer for a total cost of $67.3 million , at an average price of $9.92 per share, excluding fees and related expenses. No repurchased shares have been retired. Of the 6,784,648 repurchased shares, 133,728 shares with a weighted average repurchase price of $10.48 per share, were reissued at an average price of $5.77 per share pursuant to option exercises and vested restricted share units. As of September 30, 2018 , approximately $13.4 million remained available under the Repurchase Program. Time-based Restricted Stock Units ("TRSU") The following table summarizes the Company's TRSU activities for the three months ended September 30, 2018 : Number of Restricted Stock Units Weighted Average Grant Date Fair Value Per Share Weighted Average Remaining Recognition Period (Years) Aggregate Intrinsic Value Nonvested at June 30, 2018 919,023 $ 15.14 1.62 $ 13,086,888 Granted 39,676 $ 14.24 Vested (35,566 ) $ 14.64 Forfeited (5,375 ) $ 11.97 Nonvested at September 30, 2018 917,758 $ 15.14 1.46 $ 10,673,526 TRSUs vested and expected to vest 839,391 1.39 $ 9,762,119 Market-based Restricted Stock Units ("MSU") During the three months ended September 30, 2018, the Company granted 1.3 million market-based restricted stock units ("MSUs") to its certain personnel. The number of shares to be earned at the end of performance period is determined based on the Company’s achievement of specified stock prices and revenue thresholds during the performance period from January 1, 2019 to December 31, 2021as well as the recipients remaining in continuous service with the Company through such period. The MSU vests in four equal annual installments after the end of performance period. The Company estimated the grant date fair values of its MSU with derived service periods of 4.5 to 7.5 years using a Monte-Carlo simulation model with the following assumptions: Risk-free interest rate of 2.7% , expected term of 3.5 years, expected volatility of 38.8% and dividend yield of 0% . The Company recorded approximately $0.2 million of expenses for these MSUs during the three months ended September 30, 2018. The following table summarizes the Company's MSU activities for the three months ended September 30, 2018 : Number of Performance-based Restricted Stock Units Weighted Average Grant Date Fair Value Per Share Weighted Average Remaining Recognition Period (Years) Nonvested at June 30, 2018 — $ — — Granted 1,310,000 $ 5.17 Vested — $ — Forfeited — $ — Nonvested at September 30, 2018 1,310,000 $ 5.17 5.71 MSUs vested and expected to vest 920,140 5.63 Performance-based Restricted Stock Units ("PRSU") In March 2017 and 2018, the Company granted 170,000 and 298,000 performance-based RSUs (“PRSUs”) to certain personnel. The number shares to be earned under the PRSU are determined based on the level of attainment of predetermined financial goals. The PRSU vests in four equal annual installments from the first anniversary date after the grant date if certain predetermined financial goals were met. The Company recorded approximately $0.6 million and $0.2 million of expenses for these PRSUs during the three months ended September 30, 2018 , and 2017, respectively. The following table summarizes the Company's PRSU activities for the three months ended September 30, 2018 : Number of Performance-based Restricted Stock Units Weighted Average Grant Date Fair Value Per Share Weighted Average Remaining Recognition Period (Years) Aggregate Intrinsic Value Nonvested at June 30, 2018 422,300 $ 16.63 2.06 $ 6,013,552 Granted — — Vested — — Forfeited (500 ) $ 16.22 Nonvested at September 30, 2018 421,800 $ 16.63 1.80 $ 4,905,534 PRSUs vested and expected to vest 377,861 1.73 $ 4,394,528 Stock Options The Company did not grant any stock options during the three months ended September 30, 2018 . The number of options expected to vest is the result of applying the pre-vesting forfeiture rate assumption to total outstanding options. The following table summarizes the Company's stock option activities for the three months ended September 30, 2018 : Weighted Weighted Average Average Remaining Number of Exercise Price Contractual Aggregate Shares Per Share Term (in years) Intrinsic Value Outstanding at June 30, 2018 886,978 $ 10.97 4.03 $ 3,557,248 Exercised (10,000 ) $ 10.50 $ 43,115 Outstanding at September 30, 2018 876,978 $ 10.98 3.81 $ 1,947,927 Options vested and expected to vest 876,978 $ 10.98 3.81 $ 1,947,927 Exercisable at September 30, 2018 876,978 $ 10.98 3.81 $ 1,947,927 Share-based Compensation Expense T he total share-based compensation expense recognized in the condensed consolidated statements of operations for the periods presented was as follows: Three Months Ended September 30, 2018 2017 (in thousands) Cost of goods sold $ 497 $ 316 Research and development 632 362 Selling, general and administrative 2,000 1,330 $ 3,129 $ 2,008 As of September 30, 2018 , total unrecognized compensation cost under the Company's equity plans was $16.7 million , which is expected to be recognized over a weighted-average period of 3.0 years.

Income Taxes

Income Taxes	3 Months Ended
	Sep. 30, 2018
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes For the three months ended September 30, 2018 , the Company recognized income tax expense of approximately $0.6 million . For the three months ended September 30, 2017 , the Company recognized income tax expense of approximately $ 1.3 million , which included a discrete tax benefit of $0.4 million related principally to an intercompany asset transfer. Excluding the discrete income tax items, the estimated effective tax rate for the three months ended September 30, 2018 was (159.8)% compared to 19.1% for the three months ended September 30, 2017 . The changes in the effective tax rate and tax expense between the periods resulted primarily from changes in the mix of earnings in various geographic jurisdictions between the current year and the same period of last year somewhat offset by the reduction in the U.S. corporate tax rate following the enactment of the 2017 U.S. Tax Cut and Jobs Act. The Company files its income tax returns in the United States and in various foreign jurisdictions. The tax years 2001 to 2018 remain open to examination by U.S. federal and state tax authorities. The tax years 2011 to 2018 remain open to examination by foreign tax authorities. The Company's income tax returns are subject to examinations by the Internal Revenue Service and other tax authorities in various jurisdictions. In accordance with the guidance on the accounting for uncertainty in income taxes, the Company regularly assesses the likelihood of adverse outcomes resulting from these examinations to determine the adequacy of its provision for income taxes. These assessments can require considerable estimates and judgments. As of September 30, 2018 , the gross amount of unrecognized tax benefits was approximately $7.3 million , of which $4.5 million , if recognized, would reduce the effective income tax rate in future periods. If the Company's estimate of income tax liabilities proves to be less than the ultimate assessment, then a further charge to expense would be required. If events occur and the payment of these amounts ultimately proves to be unnecessary, the reversal of the liabilities would result in tax benefits being recognized in the period when the Company determines the liabilities are no longer necessary. The Company does not anticipate any material changes to its uncertain tax positions during the next twelve months. On July 27, 2015, in Altera Corp. v. Commissioner , the U.S. Tax Court issued an opinion related to the treatment of share-based compensation expense in an intercompany cost-sharing arrangement. A final decision has yet to be issued by the Tax Court due to other outstanding issues related to the case. At this time, the U.S. Department of the Treasury has not withdrawn the requirement to include share-based compensation from its regulations. Due to the uncertainty surrounding the status of the current regulations, questions related to the scope of potential benefits, and the risk of the Tax Court’s decision being overturned upon appeal, the Company has not recorded any benefit as of September 30, 2018. The Company will continue to monitor ongoing developments and potential impacts to its financial statements.

Segment and Geographic Informat

Segment and Geographic Information	3 Months Ended
	Sep. 30, 2018
Segment Reporting [Abstract]
Segment and Geographic Information	Segment and Geographic Information The Company is organized as, and operates in, one operating segment: the design, development and supply of power semiconductor products for computing, consumer electronics, communication and industrial applications. The chief operating decision-maker is the Chief Executive Officer. The financial information presented to the Company's Chief Executive Officer is on a consolidated basis, accompanied by information about revenue by customer and geographic region, for purposes of evaluating financial performance and allocating resources. The Company has one business segment, and there are no segment managers who are held accountable for operations, operating results and plans for products or components below the consolidated unit level. Accordingly, the Company reports as a single operating segment. Long-lived assets, net consisting of property, plant and equipment and land use rights, by geographical area are as follows: September 30, June 30, (in thousands) China $ 283,004 $ 248,003 United States 84,916 83,040 Other Countries 629 613 $ 368,549 $ 331,656 For our revenues by geography, please refer to Note 2.

Commitments and Contingencies

Commitments and Contingencies	3 Months Ended
	Sep. 30, 2018
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies Purchase Commitments As of September 30, 2018 and June 30, 2018 , the Company had approximately $49.2 million and $38.0 million , respectively, of outstanding purchase commitments primarily for purchases of semiconductor raw materials, wafers, spare parts and packaging and testing services, and approximately $32.5 million and $58.3 million , respectively, of capital commitments for the purchase of property and equipment and EPC construction. Other Commitments See Note 6 and Note 7 of the Notes to the Condensed Consolidated Financial Statements contained in this Quarterly Report on Form 10-Q for descriptions of commitments including bank borrowings and Joint Venture . Contingencies and Indemnities The Company is currently not a party to any pending material legal proceedings. The Company has in the past, and may from time to time in the future, become involved in legal proceedings arising from the normal course of business activities. The semiconductor industry is characterized by frequent claims and litigation, including claims regarding patent and other intellectual property rights as well as improper hiring practices. Irrespective of the validity of such claims, the Company could incur significant costs in the defense of such claims and suffer adverse effects on its operations. The Company is a party to a variety of agreements that it has contracted with various third parties. Pursuant to these agreements, the Company may be obligated to indemnify another party to such an agreement with respect to certain matters. Typically, these obligations arise in the context of contracts entered into by the Company, under which the Company customarily agrees to hold the other party harmless against losses arising from a breach of representations and covenants related to such matters as title to assets sold, certain intellectual property rights, specified environmental matters and certain income taxes. In these circumstances, payment by the Company is customarily conditioned on the other party making a claim pursuant to the procedures specified in the particular contract, which procedures typically allow the Company to challenge the other party's claim. Further, the Company's obligations under these agreements may be limited in time and/or amount, and in some instances, the Company may have recourse against third parties for certain payments made by it under these agreements. The Company has not historically paid or recorded any material indemnifications and no accrual has been made at September 30, 2018 and June 30, 2018 . The Company has agreed to indemnify its directors and certain employees as permitted by law and pursuant to its Bye-laws, and has entered into indemnification agreements with its directors and executive officers. The Company has not recorded a liability associated with these indemnification arrangements, as it historically has not incurred any material costs associated with such indemnification obligations. Costs associated with such indemnification obligations may be mitigated by insurance coverage that the Company maintains. However, such insurance may not cover any, or may cover only a portion of, the amounts the Company may be required to pay. In addition, the Company may not be able to maintain such insurance coverage in the future.

The Company and Significant A_2

The Company and Significant Accounting Policies (Policies)	3 Months Ended
	Sep. 30, 2018
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Basis of Preparation	Basis of Preparation The accompanying unaudited condensed consolidated financial statements have been prepared in accordance with accounting principles generally accepted in the United States (“U.S. GAAP”) for interim financial information and with the instructions to Article 10 of Securities and Exchange Commission Regulation S-X, as amended. They do not include all information and footnotes necessary for a fair presentation of financial position, results of operations and cash flows in conformity with U.S. GAAP for complete financial statements. These condensed consolidated financial statements should be read in conjunction with the consolidated financial statements and related notes contained in the Company’s Annual Report on Form 10-K for the fiscal year ended June 30, 2018 . All significant intercompany balances and transactions have been eliminated in consolidation. In the opinion of management, all adjustments (consisting of normal recurring adjustments and accruals) considered necessary for a fair presentation of the results of operations for the periods presented have been included in the interim periods. Operating results for the three months ended September 30, 2018 are not necessarily indicative of the results that may be expected for the fiscal year ending June 30, 2019 . The condensed consolidated balance sheet at June 30, 2018 is derived from the audited financial statements included in the Company’s Annual Report on Form 10-K for the fiscal year ended June 30, 2018 .
Use of Estimates	Use of Estimates The preparation of the condensed consolidated financial statements in conformity with U.S. GAAP requires the Company to make estimates, judgments and assumptions that affect the reported amounts of assets, liabilities, revenue and expenses. To the extent there are material differences between these estimates and actual results, the Company's condensed consolidated financial statements will be affected. On an ongoing basis, the Company evaluates the estimates, judgments and assumptions including those related to stock rotation returns, price adjustments, allowance for doubtful accounts, inventory reserves, warranty accrual, income taxes, share-based compensation, and useful lives for property, plant and equipment and intangible assets.
Fair Value of Financial Instruments	Fair Value of Financial Instruments The fair value of cash equivalents are based on observable market prices and have been categorized in Level 1 in the fair value hierarchy. Cash equivalents consist primarily of short term bank deposits. The carrying values of financial instruments such as cash and cash equivalents, accounts receivable and accounts payable approximate their carrying values due to their short-term maturities. The carrying value of the company's debt is considered a reasonable estimate of fair value which is estimated by considering the current rates available to the Company for debt of the same remaining maturities, structure and terms of the debts.
Comprehensive Income (Loss)	Comprehensive Income (Loss) Comprehensive income (loss) is defined as the change in equity of a business enterprise during a period from transactions and other events and circumstances from non-owner sources. The Company's accumulated other comprehensive income (loss) consists of cumulative foreign currency translation adjustments. Total comprehensive income (loss) is presented in the condensed consolidated statements of comprehensive income (loss).
Recent Accounting Pronouncements	Recent Accounting Pronouncements Recently Issued Accounting Standards not yet adopted In August 2018, the SEC adopted the final rule under SEC Release No. 33-10532, Disclosure Update and Simplification, amending certain disclosure requirements that were redundant, duplicative, overlapping, outdated or superseded. In addition, the amendments expanded the disclosure requirements on the analysis of stockholders' equity for interim financial statements. Under the amendments, an analysis of changes in each caption of stockholders' equity presented in the balance sheet must be provided in a note or separate statement. The analysis should present a reconciliation of the beginning balance to the ending balance of each period for which a statement of comprehensive income is required to be filed with the SEC. The Company anticipates its first presentation of changes in stockholders' equity will be included in its Form 10-Q for the quarter ending March 31, 2019. In August 2018, the Financial Accounting Standards Board (FASB) issued Accounting Standards Update (ASU) No. 2018-15 “Intangibles - Goodwill and Other - Internal-Use Software (Subtopic 350-40): Customer’s Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That Is a Service Contract ("ASU 2018-15”). These amendments align the requirements for capitalizing implementation costs incurred in a hosting arrangement that is a service contact with the requirements for capitalizing implementation costs incurred to develop or obtain internal-use software (and hosting arrangements that include an internal-use software license). The accounting for the service element of a hosting arrangement that is a service contract is not affected by these amendments. ASU 2018-15 is effective for annual periods, including interim periods within those annual periods, beginning after December 15, 2019. Early adoption is permitted. The Company is currently assessing the impact that adoption of this guidance will have on its consolidated financial statements. In August 2018, the FASB issued Accounting Standard Updates ("ASU") ASU No. 2018-13, “Fair Value Measurement (Topic 820): Disclosure Framework-Changes to the Disclosure Requirements for Fair Value Measurement ("ASU 2018-13”). ASU 2018-13 amends existing fair value measurement disclosure requirements by adding, changing, or removing certain disclosures. The amendments on changes in unrealized gains and losses, the range and weighted average of significant unobservable inputs used to develop Level 3 fair value measurements, and the narrative description of measurement uncertainty should be applied prospectively for only the most recent interim or annual period presented in the initial fiscal year of adoption. All other amendments should be applied retrospectively to all periods presented upon their effective date. ASU No. 2018-13 is effective for fiscal years and interim periods within those fiscal years, beginning after December 15, 2019. The Company does not expect the adoption of this guidance will have a material impact on its consolidated financial position, results of operations or cash flows. In June 2018, the FASB issued ASU 2018-07, "Compensation -Stock Compensation: Improvement to Nonemployees Share-Based Payment Accounting ("ASU 2018-07"), which expands the scope of Topic 718 to include all share-based payment transactions for acquiring goods and services from nonemployees. ASU 2018-07 specifies that Topic 718 applies to all share-based payment transactions in which the grantor acquires goods and services to be used or consumed in its own operations by issuing share-based payment awards. ASU 2018-07 also clarifies that Topic 718 does not apply to share-based payments used to effectively provide (1) financing to the issuer or (2) awards granted in conjunction with selling goods or services to customers as part of a contract accounted for under ASC 606. ASU 2018-07 is effective fiscal years beginning after December 15, 2018, including interim periods within that fiscal year, with early adoption permitted, but no earlier than our adoption of ASC 606. The Company does not expect the adoption of this guidance will have a material impact on its consolidated financial position, results of operations or cash flows. In February 2016, the FASB issued ASU 2016-02, Leases. This guidance requires a dual approach for lessee accounting under which a lessee will account for leases as finance leases or operating leases. Both finance and operating leases will result in the lessee recognizing a right-of-use asset and a corresponding liability on its balance sheet, with differing methodology for income statement recognition. This guidance is effective for public business entities for fiscal years, and interim periods within those years, beginning after December 15, 2018, and early adoption is permitted. A modified retrospective approach is required for all leases existing or entered into after the beginning of the earliest comparative period in the consolidated financial statements. In July 2018, the FASB issued ASU 2018-11, “Leases (Topic 842): Targeted Improvements.”, which permits an entity to elect an additional transition method to the existing modified retrospective transition requirements. Under the new transition method, an entity could adopt the provisions of ASU No. 2016-02 by recognizing a cumulative-effect adjustment to the opening balance of retained earnings in the period of adoption without adjustment to the financial statements for periods prior to adoption. Consequently, an entity’s reporting for the comparative periods presented in the financial statements in which it adopts the new leases standard will continue to be in accordance with the previous lease guidance in ASC Topic 840. ASU 2018-11 also allows a practical expedient that permits lessors to not separate non-lease components from the associated lease component if certain conditions are present. The recognition, measurement, and presentation of expenses and cash flows arising from a lease by a lessee have not significantly changed from previous Generally Accepted Accounting Principles. Although the Company is currently evaluating the impact the pronouncement will have on its consolidated financial statements and related disclosures, the Company expects that most of its operating lease commitments will be subject to the new standard and recognized as operating lease liabilities and right-of-use assets upon adoption. Recently Adopted Accounting Standards In May 2017, the FASB issued ASU 2017-09, "Compensation -Stock Compensation: Scope of Modification Accounting ("ASU 2017-09"). ASU 2017-09 is an update to the existing guidance to clarify when modification accounting would be applied for a change to the terms or conditions of a share-based award. Under this new guidance, modification accounting is required only if the fair value, a vesting condition, or the classification of the award changes as a result of the change in terms or conditions. This ASU is effective for annual periods, and interim periods within those annual periods, beginning after December 15, 2017 with early adoption permitted. The Company does not regularly modify the terms and conditions of its share-based awards and the adoption of this guidance has no impact on its financial statements. In November 2016, the FASB issued ASU 2016-18, "Statement of Cash Flows: Restricted Cash ("ASU 2016-18"). ASU 2016-18 requires amounts generally described as restricted cash and restricted cash equivalents be included with cash and cash equivalents when reconciling the total beginning and ending amounts for the periods shown on the statement of cash flows. This ASU is effective for fiscal years beginning after December 15, 2017, and interim periods within those fiscal years, with early adoption permitted and requires retrospective adoption. The Company adopted this standard effective July 1, 2018. The reclassified restricted cash balances from investing activities to changes in cash, cash equivalents and restricted cash on the condensed consolidated statements of cash flows were not material for all periods presented. In August 2016, the FASB issued ASU No. 2016-15, "Statement of Cash Flows (Topic 230): Classification of Certain Cash Receipts and Cash Payments ("ASU 2016-15"). ASU 2016-15 identifies how certain cash receipts and cash payments are presented and classified in the Statement of Cash Flows under Topic 230. ASU 2016-15 is effective for fiscal years beginning after December 15, 2017, and interim periods within those fiscal years, with early adoption permitted. Upon adoption, entities must apply the guidance retrospectively to all periods presented. There was no impact on the Company's consolidated financial statements upon the adoption of this standard. In May 2014, the FASB issued ASU No. 2014-09, Revenue from Contracts with Customers (ASC 606). The standard provides companies with a single model for use in accounting for revenue arising from contracts with customers and supersedes current revenue recognition guidance, including industry-specific revenue guidance. The core principle of the model is to recognize revenue when control of the goods or services transfers to the customer, as opposed to recognizing revenue when the risks and rewards transfer to the customer under the existing revenue guidance. The change for the Company under ASC 606 relates to the timing of revenue recognition with two U.S.-based distributors. Sales to these distributors are governed under the terms of agreements providing extended price protection and other return rights, and were historically deferred under the previous accounting guidance until the related product was sold to the end customer. Under ASC 606, the transaction price takes into consideration the effect of variable consideration such as price adjustments and returns rights, which are estimated and recorded at the time the goods are delivered. Accordingly, the Company recognizes revenue under ASC 606 at the time of shipment or delivery to these two distributors, adjusted for estimates of the price adjustments and product returns based on historical data and other available information. Revenue from other non-U.S. distributors and direct customers, which consists of majority of the Company's total revenue, is recognized at the time of shipment or delivery to the distributors and direct customers. Accordingly, revenue recognition with these distributors and direct customers remains unchanged upon adoption of ASC 606. See "Note 2 - Revenue" for additional information on the impact of the adoption of the new standard on the Company’s consolidated financial statements.
Concentration of Credit Risk	The Company manages its credit risk associated with exposure to distributors and direct customers on outstanding accounts receivable through the application and review of credit approvals, credit ratings and other monitoring procedures. In some instances, the Company also obtains letters of credit from certain customers. Credit sales, which are mainly on credit terms of 30 to 60 days , are only made to customers who meet the Company's credit requirements, while sales to new customers or customers with low credit ratings are usually made on an advance payment basis. The Company considers its trade accounts receivable to be of good credit quality because its key distributors and direct customers have long-standing business relationships with the Company and the Company has not experienced any significant write-offs of accounts receivable in the past. The Company closely monitors the aging of accounts receivable from its distributors and direct customers, and regularly reviews their financial positions, when available.

Revenue (Tables)

Revenue (Tables)	3 Months Ended
	Sep. 30, 2018
Revenue from Contract with Customer [Abstract]
Schedule of New Accounting Pronouncements and Changes in Accounting Principles	The following tables compare the amounts reported in the condensed consolidated statements of income and condensed consolidated balance sheet to the amounts had the previous revenue recognition guidance been in effect: As of September 30, 2018 As Reported Adjustment Balances Without Adoption (in thousands) Accounts receivable, net $ 37,108 $ 224 $ 37,332 Accrued liabilities $ 56,054 $ (120 ) $ 55,934 Deferred margin $ — $ 1,691 $ 1,691 Deferred income tax liabilities $ 1,063 $ (285 ) $ 778 Retained earnings $ 126,083 $ (1,062 ) $ 125,021 Three Months Ended September 30, 2018 As Reported Adjustment Balances Without Adoption (in thousands) Revenue $ 115,072 $ 41 $ 115,113 Cost of goods sold $ 82,461 $ 20 $ 82,481 Gross profit $ 32,611 $ 21 $ 32,632 Income tax expense $ 560 $ (8 ) $ 552 Net income (loss) including noncontrolling interest $ (913 ) $ 29 $ (884 )
Disaggregation of Revenue	The following table presents the Company's revenue information by geographical location based on the country or region to which the products were shipped. The Company sells its products primarily to distributors in the Asia Pacific region, who in turn sell these products to end customers. Because the Company's distributors sell their products to end customers which may have a global presence, revenue by geographical location is not necessarily representative of the geographical distribution of sales to end user markets. Three Months Ended September 30, 2018 2017 (in thousands) Hong Kong $ 91,591 $ 85,230 China 20,397 17,120 South Korea 169 287 United States 1,973 1,378 Other countries 942 843 $ 115,072 $ 104,858 The following is a summary of revenue by product type: Three Months Ended September 30, 2018 2017 (in thousands) Power discrete $ 92,255 $ 83,678 Power IC 19,415 18,097 Packaging and testing services 3,402 3,083 $ 115,072 $ 104,858

Net Income (Loss) Per Share (Ta

Net Income (Loss) Per Share (Tables)	3 Months Ended
	Sep. 30, 2018
Earnings Per Share [Abstract]
Schedule of Earnings Per Share, Basic and Diluted	The following table presents the calculation of basic and diluted net income per share attributable to common shareholders: Three Months Ended September 30, 2018 2017 (in thousands, except per share data) Numerator: Net income attributable to Alpha and Omega Semiconductor Limited $ 2,416 $ 4,800 Denominator: Basic: Weighted average number of common shares used to compute basic net income per share 23,844 24,021 Diluted: Weighted average number of common shares used to compute basic net income per share 23,844 24,021 Effect of potentially dilutive securities: Stock options, RSUs and ESPP shares 750 939 Weighted average number of common shares used to compute diluted net income per share 24,594 24,960 Net income per share attributable to Alpha and Omega Semiconductor Limited: Basic $ 0.10 $ 0.20 Diluted $ 0.10 $ 0.19
Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share	The following potential dilutive securities were excluded from the computation of diluted net income per share as their effect would have been anti-dilutive: Three Months Ended September 30, 2018 2017 (in thousands) Employee stock options and RSUs 405 172 ESPP 216 90 Total potential dilutive securities 621 262

Concentration of Credit Risk _2

Concentration of Credit Risk and Significant Customers (Tables)	3 Months Ended
	Sep. 30, 2018
Risks and Uncertainties [Abstract]
Schedules of Concentration of Risk, by Risk Factor	Summarized below are individual customers whose revenue or accounts receivable balances were more than 10% of the respective total consolidated amounts: Three Months Ended September 30, Percentage of revenue 2018 2017 Customer A 27.7 % 27.5 % Customer B 38.0 % 33.9 % September 30, June 30, Percentage of accounts receivable Customer A 18.5 % 17.1 % Customer B 37.9 % 35.5 % Customer C 10.2 % 10.6 %

Balance Sheet Components (Table

Balance Sheet Components (Tables)	3 Months Ended
	Sep. 30, 2018
Balance Sheet Related Disclosures [Abstract]
Schedule of Accounts, Notes, Loans and Financing Receivable	Accounts receivable, net: September 30, June 30, (in thousands) Accounts receivable $ 55,290 $ 52,687 Less: Allowance for price adjustments (18,152 ) (18,902 ) Less: Allowance for doubtful accounts (30 ) (30 ) Accounts receivable, net $ 37,108 $ 33,755
Schedule of Inventory, Current	Inventories: September 30, June 30, (in thousands) Raw materials $ 51,854 $ 47,097 Work in-process 39,296 35,243 Finished goods 6,899 7,842 $ 98,049 $ 90,182
Other Current Assets	Other current assets: September 30, June 30, (in thousands) VAT receivable $ 25,722 $ 17,601 Other prepaid expenses 2,417 2,121 Prepaid insurance 1,109 906 Prepaid maintenance 685 556 Prepayment to supplier 735 227 Prepaid income tax 761 761 Custom deposit 26 5,749 Lease financing cost 910 960 Other receivable 390 670 $ 32,755 $ 29,551
Property, Plant and Equipment	operty, plant and equipment, net: September 30, June 30, (in thousands) Land $ 4,877 $ 4,877 Building 33,836 4,325 Manufacturing machinery and equipment 274,818 265,192 Equipment and tooling 17,891 16,605 Computer equipment and software 26,751 25,686 Office furniture and equipment 2,318 2,314 Leasehold improvements 30,499 29,900 Land use rights 8,750 9,089 399,740 357,988 Less: accumulated depreciation (229,627 ) (225,184 ) 170,113 132,804 Equipment and construction in progress 198,436 198,852 Property, plant and equipment, net $ 368,549 $ 331,656
Intangible Assets Disclosure	Intangible assets, net: September 30, June 30, (in thousands) Patents and technology rights $ 17,637 $ 17,633 Trade name 268 268 Customer relationships 1,150 1,150 19,055 19,051 Less: accumulated amortization (2,757 ) (2,729 ) 16,298 16,322 Goodwill 269 269 Intangible assets, net $ 16,567 $ 16,591
Schedule of Other Assets, Noncurrent	Other long-term assets: September 30, June 30, (in thousands) Prepayments for property and equipment $ 5,844 $ 17,599 Investment in a privately held company 700 700 Lease financing costs 1,630 1,922 VAT long-term receivable 478 3,396 Custom deposit 1,766 1,589 Other long-term deposits 1,983 2,252 Office leases deposits 981 853 Other 315 387 $ 13,697 $ 28,698
Schedule of Accrued Liabilities	Accrued liabilities: September 30, June 30, (in thousands) Accrued compensation and benefits $ 23,674 $ 18,484 Warranty accrual 632 535 Stock rotation accrual 1,775 1,750 Accrued professional fees 1,860 1,922 Accrued inventory 640 667 Accrued facilities related expenses 3,446 2,163 Accrued financing lease costs 1,454 1,510 Accrued property, plant and equipment 15,038 18,145 Other accrued expenses 7,535 4,665 $ 56,054 $ 49,841
Schedule of Product Warranty Liability	The activities in the warranty accrual, included in accrued liabilities, are as follows: Three Months Ended September 30, 2018 2017 (in thousands) Beginning balance $ 535 $ 1,866 Additions (reductions) 136 (237 ) Utilization (39 ) (7 ) Ending balance $ 632 $ 1,622
Stock Rotation Accrual	The activities in the stock rotation accrual, included in accrued liabilities, are as follows: Three Months Ended September 30, 2018 2017 (in thousands) Beginning balance $ 1,750 $ 1,871 Additions 748 791 Utilization (723 ) (668 ) Ending balance $ 1,775 $ 1,994

Bank Borrowing (Tables)

Bank Borrowing (Tables)	3 Months Ended
	Sep. 30, 2018
Debt Disclosure [Abstract]
Schedule of Capital Lease Liabilities	Capital lease liabilities include financing lease, computer software and exclusive technology rights. Future minimum lease payments are as follows (in thousands): Year ending June 30, 2019 (Remaining) $ 6,549 2020 14,201 2021 17,777 2022 16,907 2023 12,255 Thereafter — Total minimum lease payments 67,689 Less amount representing interest (8,871 ) Total capital lease liabilities $ 58,818
Schedule of Maturities	Maturities of Jireh debt were as follows (in thousands): Year ending June 30, 2019 (Remaining) $ 6,255 2020 8,340 2021 8,340 2022 8,340 2023 16,028 Total debt, excluding debt issuance costs 47,303 Less: debt issuance costs (257 ) Total debt, less debt issuance costs $ 47,046

Joint Venture (Tables)

Joint Venture (Tables)	3 Months Ended
	Sep. 30, 2018
Equity Method Investments and Joint Ventures [Abstract]
Schedule of Stockholders Equity	The changes in total AOS stockholders' equity, noncontrolling interest and total equity were as follows (in thousands): Total AOS Stockholders' Equity Noncontrolling Interest Total Equity Balance, June 30, 2018 $ 278,594 $ 147,568 $ 426,162 Exercise of common stock options and release of RSUs 105 — 105 Withholding tax on restricted stock units (109 ) — (109 ) Repurchase of common shares under shares repurchase program (1,501 ) — (1,501 ) Stock-based compensation expense 3,129 — 3,129 Net income (loss) 2,416 (3,329 ) (913 ) Impact on retained earnings related to ASC 606 adoption 1,036 — 1,036 Cumulative translation adjustment (3,248 ) (2,989 ) (6,237 ) Balance, September 30, 2018 $ 280,422 $ 141,250 $ 421,672

Shareholders' Equity and Shar_2

Shareholders' Equity and Share-based Compensation (Tables)	3 Months Ended
	Sep. 30, 2018
Share-based Compensation [Abstract]
Restricted Stock Units Activity	The following table summarizes the Company's MSU activities for the three months ended September 30, 2018 : Number of Performance-based Restricted Stock Units Weighted Average Grant Date Fair Value Per Share Weighted Average Remaining Recognition Period (Years) Nonvested at June 30, 2018 — $ — — Granted 1,310,000 $ 5.17 Vested — $ — Forfeited — $ — Nonvested at September 30, 2018 1,310,000 $ 5.17 5.71 MSUs vested and expected to vest 920,140 5.63 The following table summarizes the Company's PRSU activities for the three months ended September 30, 2018 : Number of Performance-based Restricted Stock Units Weighted Average Grant Date Fair Value Per Share Weighted Average Remaining Recognition Period (Years) Aggregate Intrinsic Value Nonvested at June 30, 2018 422,300 $ 16.63 2.06 $ 6,013,552 Granted — — Vested — — Forfeited (500 ) $ 16.22 Nonvested at September 30, 2018 421,800 $ 16.63 1.80 $ 4,905,534 PRSUs vested and expected to vest 377,861 1.73 $ 4,394,528 Time-based Restricted Stock Units ("TRSU") The following table summarizes the Company's TRSU activities for the three months ended September 30, 2018 : Number of Restricted Stock Units Weighted Average Grant Date Fair Value Per Share Weighted Average Remaining Recognition Period (Years) Aggregate Intrinsic Value Nonvested at June 30, 2018 919,023 $ 15.14 1.62 $ 13,086,888 Granted 39,676 $ 14.24 Vested (35,566 ) $ 14.64 Forfeited (5,375 ) $ 11.97 Nonvested at September 30, 2018 917,758 $ 15.14 1.46 $ 10,673,526 TRSUs vested and expected to vest 839,391 1.39 $ 9,762,119
Summary of Stock Option Activities	The following table summarizes the Company's stock option activities for the three months ended September 30, 2018 : Weighted Weighted Average Average Remaining Number of Exercise Price Contractual Aggregate Shares Per Share Term (in years) Intrinsic Value Outstanding at June 30, 2018 886,978 $ 10.97 4.03 $ 3,557,248 Exercised (10,000 ) $ 10.50 $ 43,115 Outstanding at September 30, 2018 876,978 $ 10.98 3.81 $ 1,947,927 Options vested and expected to vest 876,978 $ 10.98 3.81 $ 1,947,927 Exercisable at September 30, 2018 876,978 $ 10.98 3.81 $ 1,947,927
Share-based Compensation, Allocation of Recognized Period Costs	Share-based Compensation Expense T he total share-based compensation expense recognized in the condensed consolidated statements of operations for the periods presented was as follows: Three Months Ended September 30, 2018 2017 (in thousands) Cost of goods sold $ 497 $ 316 Research and development 632 362 Selling, general and administrative 2,000 1,330 $ 3,129 $ 2,008

Segment and Geographic Inform_2

Segment and Geographic Information (Tables)	3 Months Ended
	Sep. 30, 2018
Segment Reporting [Abstract]
Schedule of Revenue from External Customers and Long-Lived Assets, by Geographical Areas	Long-lived assets, net consisting of property, plant and equipment and land use rights, by geographical area are as follows: September 30, June 30, (in thousands) China $ 283,004 $ 248,003 United States 84,916 83,040 Other Countries 629 613 $ 368,549 $ 331,656

The Company and Significant A_3

The Company and Significant Accounting Policies - Joint Venture (Details) - Facility in Liangjiang New Area of Chongqing (the 'Joint Venture') - USD ($) $ in Millions	Sep. 30, 2018	Aug. 31, 2018	Mar. 29, 2016
Consideration Transferred to Acquire Interest in Joint Venture		$ 25
Parent Company
Subsidiary or Equity Method Investee, Cumulative Percentage Ownership after All Transactions	54.40%	54.40%
Chongqing Funds
Subsidiary or Equity Method Investee, Cumulative Percentage Ownership after All Transactions	45.60%	45.60%
Corporate Joint Venture
Initial capitalization of joint venture			$ 330

Revenue - Narrative (Details)

Revenue - Narrative (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Jul. 01, 2018	Jun. 30, 2018
Disaggregation of Revenue [Line Items]
Change in deferred margin	$ 0		$ (1,665)
Change in accounts receivable	(37,108)		(33,755)
Change in current accrued liabilities	56,054		$ 49,841
Accounting Standards Update 2014-09
Disaggregation of Revenue [Line Items]
Net increase to opening retained earnings		$ 1,000
Accounting Standards Update 2014-09 | Difference between Revenue Guidance in Effect before and after Topic 606
Disaggregation of Revenue [Line Items]
Change in deferred margin	(1,691)	1,600
Change in accounts receivable	(224)	200
Change in current accrued liabilities	$ (120)	100
Change in deferred tax assets		$ 300

Revenue - Effect on Balance She

Revenue - Effect on Balance Sheet (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Jul. 01, 2018	Jun. 30, 2018
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Accounts receivable, net	$ 37,108		$ 33,755
Deferred income tax assets	4,918		4,892
Accrued liabilities	56,054		49,841
Income taxes payable	2,218		2,211
Deferred margin	0		1,665
Deferred income tax liabilities	1,063		713
Retained earnings	126,083		$ 122,639
Effect of Change | Accounting Standards Update 2014-09
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Accounts receivable, net	224	$ (200)
Accrued liabilities	(120)	100
Deferred margin	1,691	$ (1,600)
Deferred income tax liabilities	(285)
Retained earnings	(1,062)
Balances Without Adoption
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Accounts receivable, net	37,332
Accrued liabilities	55,934
Deferred margin	1,691
Deferred income tax liabilities	778
Retained earnings	$ 125,021

Revenue - Effect on Income Stat

Revenue - Effect on Income Statement (Details) - USD ($) $ in Thousands	3 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue	$ 115,072	$ 104,858
Cost of goods sold	82,461	77,328
Gross profit	32,611	27,530
Income tax expense	560	1,274
Net income (loss) including noncontrolling interest	(913)	$ 3,339
Effect of Change | Accounting Standards Update 2014-09
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue	41
Cost of goods sold	20
Gross profit	21
Income tax expense	(8)
Net income (loss) including noncontrolling interest	29
Balances Without Adoption
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue	115,113
Cost of goods sold	82,481
Gross profit	32,632
Income tax expense	552
Net income (loss) including noncontrolling interest	$ (884)

Revenue - Disaggregation of Rev

Revenue - Disaggregation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Disaggregation of Revenue [Line Items]
Revenue	$ 115,072	$ 104,858
Power discrete
Disaggregation of Revenue [Line Items]
Revenue	92,255	83,678
Power IC
Disaggregation of Revenue [Line Items]
Revenue	19,415	18,097
Packaging and testing services
Disaggregation of Revenue [Line Items]
Revenue	3,402	3,083
Hong Kong
Disaggregation of Revenue [Line Items]
Revenue	91,591	85,230
China
Disaggregation of Revenue [Line Items]
Revenue	20,397	17,120
South Korea
Disaggregation of Revenue [Line Items]
Revenue	169	287
United States
Disaggregation of Revenue [Line Items]
Revenue	1,973	1,378
Other Countries
Disaggregation of Revenue [Line Items]
Revenue	$ 942	$ 843

Net Income (Loss) Per Share - B

Net Income (Loss) Per Share - Basic and Diluted Income Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Numerator:
Net income attributable to Alpha and Omega Semiconductor Limited	$ 2,416	$ 4,800
Basic:
Weighted average number of common shares used to compute basic net income per share	23,844	24,021
Effect of potentially dilutive securities:
Stock options, RSUs and ESPP shares	750	939
Weighted average number of common shares used to compute diluted net income per share	24,594	24,960
Net income per share attributable to Alpha and Omega Semiconductor Limited:
Basic (in dollars per share)	$ 0.10	$ 0.20
Diluted (in dollars per share)	$ 0.10	$ 0.19

Net Income (Loss) Per Share - P

Net Income (Loss) Per Share - Potential Dilutive Shares (Details) - shares shares in Thousands	3 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potential dilutive securities (in shares)	621	262
Employee stock options and RSUs
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potential dilutive securities (in shares)	405	172
ESPP
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potential dilutive securities (in shares)	216	90

Concentration of Credit Risk _3

Concentration of Credit Risk and Significant Customers - (Details)	3 Months Ended
	Sep. 30, 2018	Jun. 30, 2018	Sep. 30, 2017
Minimum
Concentration Risk
Terms of credit sales, (in days)	30 days
Maximum
Concentration Risk
Terms of credit sales, (in days)	60 days
Customer A | Sales Revenue, Goods, Net | Customer Concentration Risk
Concentration Risk
Customers greater than 10% of total	27.70%		27.50%
Customer A | Accounts Receivable | Customer Concentration Risk
Concentration Risk
Customers greater than 10% of total	18.50%	17.10%
Customer B | Sales Revenue, Goods, Net | Customer Concentration Risk
Concentration Risk
Customers greater than 10% of total	38.00%		33.90%
Customer B | Accounts Receivable | Customer Concentration Risk
Concentration Risk
Customers greater than 10% of total	37.90%	35.50%
Customer C | Accounts Receivable | Customer Concentration Risk
Concentration Risk
Customers greater than 10% of total	10.20%	10.60%

Balance Sheet Components - Acco

Balance Sheet Components - Accounts receivable (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Jun. 30, 2018
Balance Sheet Related Disclosures [Abstract]
Accounts receivable	$ 55,290	$ 52,687
Less: Allowance for price adjustments	(18,152)	(18,902)
Less: Allowance for doubtful accounts	(30)	(30)
Accounts receivable, net	$ 37,108	$ 33,755

Balance Sheet Components - Inve

Balance Sheet Components - Inventories (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Jun. 30, 2018
Balance Sheet Related Disclosures [Abstract]
Raw materials	$ 51,854	$ 47,097
Work in-process	39,296	35,243
Finished goods	6,899	7,842
Inventory, net	$ 98,049	$ 90,182

Balance Sheet Components - Othe

Balance Sheet Components - Other current assets (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Jun. 30, 2018
Balance Sheet Related Disclosures [Abstract]
VAT receivable	$ 25,722	$ 17,601
Other prepaid expenses	2,417	2,121
Prepaid Insurance	1,109	906
Prepaid Maintenance, Current	685	556
Prepayment to supplier	735	227
Prepaid income tax	761	761
Customs deposit	26	5,749
Lease Financing Costs, Current	910	960
Other receivable	390	670
Other Assets, Current	$ 32,755	$ 29,551

Balance Sheet Components - Prop

Balance Sheet Components - Property, plant, and equipment (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Jun. 30, 2018
Property, Plant and Equipment [Line Items]
Property, plant, and equipment excluding equipment and construction In progress, gross	$ 399,740	$ 357,988
Land use rights	8,750	9,089
Less: accumulated depreciation	(229,627)	(225,184)
Property, plant and equipment excluding equipment and construction in progress, net	170,113	132,804
Equipment and construction in progress	198,436	198,852
Property, plant and equipment, net	368,549	331,656
Land
Property, Plant and Equipment [Line Items]
Property, plant, and equipment excluding equipment and construction In progress, gross	4,877	4,877
Building
Property, Plant and Equipment [Line Items]
Property, plant, and equipment excluding equipment and construction In progress, gross	33,836	4,325
Manufacturing machinery and equipment
Property, Plant and Equipment [Line Items]
Property, plant, and equipment excluding equipment and construction In progress, gross	274,818	265,192
Equipment and tooling
Property, Plant and Equipment [Line Items]
Property, plant, and equipment excluding equipment and construction In progress, gross	17,891	16,605
Computer equipment and software
Property, Plant and Equipment [Line Items]
Property, plant, and equipment excluding equipment and construction In progress, gross	26,751	25,686
Office furniture and equipment
Property, Plant and Equipment [Line Items]
Property, plant, and equipment excluding equipment and construction In progress, gross	2,318	2,314
Leasehold improvements
Property, Plant and Equipment [Line Items]
Property, plant, and equipment excluding equipment and construction In progress, gross	$ 30,499	$ 29,900

Balance Sheet Components - Inta

Balance Sheet Components - Intangible assets (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Jun. 30, 2018
Schedule of Finite-lived Intangible Assets and Goodwill [Line Items]
Finite-Lived Intangible Assets, Gross	$ 19,055	$ 19,051
Less: accumulated amortization	(2,757)	(2,729)
Intangible Assets, Net (Excluding Goodwill)	16,298	16,322
Goodwill	269	269
Intangible assets, net	16,567	16,591
Patents and technology rights
Schedule of Finite-lived Intangible Assets and Goodwill [Line Items]
Finite-Lived Intangible Assets, Gross	17,637	17,633
Trade name
Schedule of Finite-lived Intangible Assets and Goodwill [Line Items]
Finite-Lived Intangible Assets, Gross	268	268
Customer relationships
Schedule of Finite-lived Intangible Assets and Goodwill [Line Items]
Finite-Lived Intangible Assets, Gross	$ 1,150	$ 1,150

Balance Sheet Components - In_2

Balance Sheet Components - Intangible Assets, Additional Information (Details) - USD ($) $ in Thousands	3 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Finite-Lived Intangible Assets [Line Items]
Payments to Acquire Intangible Assets	$ 5	$ 5,720
STMicro | License fees
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Net	$ 15,800

Balance Sheet Components - Ot_2

Balance Sheet Components - Other long term assets (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Jun. 30, 2018
Balance Sheet Related Disclosures [Abstract]
Prepayments for property and equipment	$ 5,844	$ 17,599
Investment in a privately held company	700	700
Lease financing costs, noncurrent	1,630	1,922
VAT long-term receivable	478	3,396
Custom deposit, noncurrent	1,766	1,589
Other long-term deposits	1,983	2,252
Office lease deposit, noncurrent	981	853
Other	315	387
Other long-term assets	$ 13,697	$ 28,698

Balance Sheet Components - Accr

Balance Sheet Components - Accrued liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Jun. 30, 2018	Sep. 30, 2017	Jun. 30, 2017
Balance Sheet Related Disclosures [Abstract]
Accrued compensation and benefits	$ 23,674	$ 18,484
Warranty accrual	632	535	$ 1,622	$ 1,866
Stock rotation accrual	1,775	1,750	$ 1,994	$ 1,871
Accrued professional fees	1,860	1,922
Accrued inventory	640	667
Accrued facilities related expenses	3,446	2,163
Accrued financing lease costs	1,454	1,510
Accrued property, plant and equipment	15,038	18,145
Other accrued expenses	7,535	4,665
Accrued liabilities	$ 56,054	$ 49,841

Balance Sheet Components - Prod

Balance Sheet Components - Product Warranty Accrual (Details) - USD ($) $ in Thousands	3 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Movement in Standard and Extended Product Warranty Accrual, Increase (Decrease) [Roll Forward]
Beginning balance	$ 535	$ 1,866
Additions (reductions)	136	(237)
Utilization	(39)	(7)
Ending balance	$ 632	$ 1,622

Balance Sheet Components - Stoc

Balance Sheet Components - Stock Rotation Accrual (Details) - USD ($) $ in Thousands	3 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Stock Rotation Accrual Increae (Decrease) [Roll Forward]
Beginning balance	$ 1,750	$ 1,871
Additions	748	791
Utilization	(723)	(668)
Ending balance	$ 1,775	$ 1,994

Bank Borrowing (Details)

Bank Borrowing (Details) $ in Thousands	May 09, 2018CNY (¥)	Aug. 15, 2017USD ($)	Jul. 31, 2018USD ($)	Jan. 31, 2018USD ($)	Sep. 30, 2018CNY (¥)	Sep. 30, 2018USD ($)	May 09, 2018USD ($)	May 01, 2018USD ($)
Capital lease liability
2019 (Remaining)						$ 6,549
2,020						14,201
2,021						17,777
2,022						16,907
2,023						12,255
Thereafter						0
Total minimum lease payments						67,689
Less amount representing interest						(8,871)
Total capital lease liabilities						58,818
Maturities of debt
2019 (Remaining)						6,255
2,020						8,340
2,021						8,340
2,022						8,340
2,023						16,028
Total debt, excluding debt issuance costs						47,303
Less: debt issuance costs						(257)
Total debt, less debt issuance costs						47,046
Secured Debt
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity								$ 17,800
Amount outstanding						17,500
Stated percentage								5.04%
Term Loan | Secured Debt | Variable Interest Rate Term Loan Maturing August 2022
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity		$ 30,000
Debt instrument, term		5 years
Amount outstanding						29,800
Proceeds from lines of credit			$ 16,700	$ 13,200
Minimum | London Interbank Offered Rate (LIBOR) | Term Loan | Secured Debt | Variable Interest Rate Term Loan Maturing August 2022
Debt Instrument [Line Items]
Basis spread on variable rate		1.75%
Maximum | London Interbank Offered Rate (LIBOR) | Term Loan | Secured Debt | Variable Interest Rate Term Loan Maturing August 2022
Debt Instrument [Line Items]
Basis spread on variable rate		2.25%
YinHai Leasing Company and China Import/Export Bank [Member] | Lease Financing [Member]
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity	¥ 400,000,000						$ 62,800
Nominal sale amount at end of lease term | ¥	¥ 1
Amount outstanding					¥ 400,000,000	$ 58,200
China | YinHai Leasing Company and China Import/Export Bank [Member] | Base Rate [Member] | Lease Financing [Member]
Debt Instrument [Line Items]
Basis spread on variable rate, multiple	1.15						1.15
Basis spread on variable rate	5.4625%

Joint Venture - Narrative (Deta

Joint Venture - Narrative (Details) $ in Thousands	Sep. 30, 2018CNY (¥)	Aug. 31, 2018	Sep. 30, 2018USD ($)	Sep. 30, 2017USD ($)	Sep. 30, 2018CNY (¥)	Sep. 30, 2018USD ($)	Sep. 30, 2018USD ($)	Jan. 10, 2017CNY (¥)	Jan. 10, 2017USD ($)	Mar. 29, 2016USD ($)
Schedule of Equity Method Investments [Line Items]
Proceeds from investment by noncontrolling interest			$ 0	$ 86,994
Parent Company | Facility in Liangjiang New Area of Chongqing (the 'Joint Venture')
Schedule of Equity Method Investments [Line Items]
Percent ownership in joint venture	54.40%	54.40%
Chongqing Funds | Facility in Liangjiang New Area of Chongqing (the 'Joint Venture')
Schedule of Equity Method Investments [Line Items]
Percent ownership in joint venture	45.60%	45.60%
Corporate Joint Venture
Schedule of Equity Method Investments [Line Items]
Total price payable under EPC Contract								¥ 540,000,000	$ 78,000
Contractual obligation, payment					¥ 469,500,000	$ 68,300
Contract amount payable in fiscal year 2019	¥ 70,500,000				¥ 70,500,000		$ 10,200
Corporate Joint Venture | Facility in Liangjiang New Area of Chongqing (the 'Joint Venture')
Schedule of Equity Method Investments [Line Items]
Initial capitalization of joint venture										$ 330,000
Corporate Joint Venture | Design Fees
Schedule of Equity Method Investments [Line Items]
Total price payable under EPC Contract								19,500,000	2,800
Corporate Joint Venture | Construction and Procurement Fees
Schedule of Equity Method Investments [Line Items]
Total price payable under EPC Contract								¥ 520,500,000	$ 75,200

Joint Venture - Changes in Tota

Joint Venture - Changes in Total Stockholders' Equity (Details) - USD ($) $ in Thousands	3 Months Ended		95 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018
Schedule of Equity Method Investments [Line Items]
Balance, June 30, 2018	$ 426,162
Exercise of common stock options and release of RSUs	105
Withholding tax on restricted stock units	(109)
Repurchase of common shares under shares repurchase program	(1,501)		$ (67,300)
Stock-based compensation expense	3,129
Net income (loss)	(913)	$ 3,339
Net loss attributable to noncontrolling interest	(3,329)	$ (1,461)
Cumulative translation adjustment	(6,237)
Balance, September 30, 2018	421,672		421,672
Accounting Standards Update 2016-16
Schedule of Equity Method Investments [Line Items]
Impact on retained earnings related to ASC 606 adoption	1,036
Parent
Schedule of Equity Method Investments [Line Items]
Balance, June 30, 2018	278,594
Exercise of common stock options and release of RSUs	105
Withholding tax on restricted stock units	(109)
Repurchase of common shares under shares repurchase program	(1,501)
Stock-based compensation expense	3,129
Net income (loss)	2,416
Cumulative translation adjustment	(3,248)
Balance, September 30, 2018	280,422		280,422
Parent | Accounting Standards Update 2016-16
Schedule of Equity Method Investments [Line Items]
Impact on retained earnings related to ASC 606 adoption	1,036
Noncontrolling Interest
Schedule of Equity Method Investments [Line Items]
Balance, June 30, 2018	147,568
Exercise of common stock options and release of RSUs	0
Withholding tax on restricted stock units	0
Repurchase of common shares under shares repurchase program	0
Stock-based compensation expense	0
Net loss attributable to noncontrolling interest	(3,329)
Cumulative translation adjustment	(2,989)
Balance, September 30, 2018	141,250		$ 141,250
Noncontrolling Interest | Accounting Standards Update 2016-16
Schedule of Equity Method Investments [Line Items]
Impact on retained earnings related to ASC 606 adoption	$ 0

Shareholders' Equity and Shar_3

Shareholders' Equity and Share-based Compensation - Shares Repurchase (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		95 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018
Class of Stock [Line Items]
Share repurchase program, authorized amount (USD in Millions)	$ 30,000		$ 30,000
Shares Repurchase Program Remaining Balance	$ 13,400		$ 13,400
Repurchase of common shares under shares repurchase program	111,509		6,784,648
Treasury Stock, Value, Acquired, Cost Method Less Handling Fees	$ 1,500
Repurchase of common shares under shares repurchase program	$ (1,501)		$ (67,300)
Treasury stock acquired, average price per share (in dollars per share)	$ 13.43		$ 9.92
Treasury Stock, Shares, Retired	0
Allocated share-based compensation expense	$ 3,129	$ 2,008
Treasury Stock Reissued
Class of Stock [Line Items]
Treasury stock acquired, average price per share (in dollars per share)			$ 10.48
Stock Issued During Period, Shares, Share-based Compensation, Net of Forfeitures (in shares)			133,728
Treasury Stock Reissued, Average Price Per Share			$ 5.77
Performance Based Restricted Stock Units (PRSUs) Member [Member]
Class of Stock [Line Items]
Allocated share-based compensation expense	$ 600	$ 200

Shareholders' Equity and Shar_4

Shareholders' Equity and Share-based Compensation - Share-based Compensation (Details) - USD ($)	1 Months Ended		3 Months Ended		95 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Sep. 30, 2018	Jun. 30, 2018	Sep. 30, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Repurchase of common shares under shares repurchase program			111,509		6,784,648
Options, Weighted-Average Remaining Contractual Life (in years)			3 years 9 months 22 days	4 years 11 days
Options vested and expected to vest, Number Outstanding (in shares)			876,978		876,978
Options vested and expected to vest, Weighted Average Exercise Price (in dollars per share)			$ 10.98		$ 10.98
Options vested and expected to vest, Weighted Average Remaining Contractual Life (in years)			3 years 9 months 22 days
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Outstanding, Aggregate Intrinsic Value			$ 1,947,927		$ 1,947,927
Options, Number Exercisable (in shares)			876,978		876,978
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range, Exercisable Options, Weighted Average Exercise Price			$ 10.98		$ 10.98
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Weighted Average Remaining Contractual Term			3 years 9 months 22 days
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Intrinsic Value			$ 1,947,927		$ 1,947,927
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Outstanding at June 30, 2018			886,978
Exercised (in shares)			(10,000)
Outstanding at September 30, 2018			876,978	886,978	876,978
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Roll Forward]
Outstanding at June 30, 2018 (in dollars per share)			$ 10.97
Exercised (in dollars per share)			10.50
Outstanding at September 30, 2018 (in dollars per share)			$ 10.98	$ 10.97	$ 10.98
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Intrinsic Value			$ 1,947,927	$ 3,557,248	$ 1,947,927
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period, Intrinsic Value			$ 43,115
Performance Based Restricted Stock Units (PRSUs) Member [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted	298,000	170,000	0

Shareholders' Equity and Shar_5

Shareholders' Equity and Share-based Compensation - Stock Options Outstanding and Exercisable (Details) - USD ($)	3 Months Ended
	Sep. 30, 2018	Jun. 30, 2018
Share-based Compensation [Abstract]
Options, Number Outstanding (in shares)	876,978	886,978
Options, Weighted-Average Remaining Contractual Life (in years)	3 years 9 months 22 days	4 years 11 days
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Intrinsic Value	$ 1,947,927	$ 3,557,248
Options, Weighted-Average Exercise Price (in dollars per share)	$ 10.98	$ 10.97
Options, Number Exercisable (in shares)	876,978
Options, Weighted-Average Exercise Price (in dollars per share)	$ 10.98
Options vested and expected to vest, Number Outstanding (in shares)	876,978
Options vested and expected to vest, Weighted Average Remaining Contractual Life (in years)	3 years 9 months 22 days
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Outstanding, Aggregate Intrinsic Value	$ 1,947,927
Options vested and expected to vest, Weighted Average Exercise Price (in dollars per share)	$ 10.98
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period	10,000
Share-based Compensation Arrangements by Share-based Payment Award, Options, Exercises in Period, Weighted Average Exercise Price	$ 10.50
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period, Intrinsic Value	$ 43,115
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Weighted Average Remaining Contractual Term	3 years 9 months 22 days
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Intrinsic Value	$ 1,947,927

Shareholders' Equity and Shar_6

Shareholders' Equity and Share-based Compensation - Restricted Stock Activity (Details) - USD ($)	1 Months Ended		3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Sep. 30, 2018	Jun. 30, 2018	Sep. 30, 2017
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Roll Forward]
Weighted Average Remaining Recognition Period (Years)			3 years
Allocated share-based compensation expense			$ 3,129,000		$ 2,008,000
Restricted Stock
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Nonvested at June 30, 2018			919,023
Granted			39,676
Vested			(35,566)
Forfeited			(5,375)
Nonvested at September 30, 2018			917,758	919,023
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Roll Forward]
Nonvested at June 30, 2018			$ 15.14
Granted			14.24
Vested			14.64
Forfeited			11.97
Nonvested at September 30, 2018			$ 15.14	$ 15.14
Weighted Average Remaining Recognition Period (Years)			1 year 5 months 16 days	1 year 7 months 13 days
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Aggregate Intrinsic Value, Nonvested			$ 10,673,526	$ 13,086,888
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested and Expected to Vest, Outstanding, Number			839,391
Employee Service Share-based Compensation, Vested and Expected to Vest Awards, Total Compensation Cost Not Yet Recognized, Period for Recognition			1 year 4 months 21 days
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested and Expected to Vest, Intrinsic Value			$ 9,762,119
Market-based Restricted Stock Units (MSU)
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Nonvested at June 30, 2018			0
Granted			1,310,000
Vested			0
Forfeited			0
Nonvested at September 30, 2018			1,310,000	0
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Roll Forward]
Nonvested at June 30, 2018			$ 0
Granted			5.17
Vested			0
Forfeited			0
Nonvested at September 30, 2018			$ 5.17	$ 0
Weighted Average Remaining Recognition Period (Years)			5 years 8 months 16 days	0 years
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested and Expected to Vest, Outstanding, Number			920,140
Employee Service Share-based Compensation, Vested and Expected to Vest Awards, Total Compensation Cost Not Yet Recognized, Period for Recognition			5 years 7 months 17 days
Allocated share-based compensation expense			$ 200,000
Performance Based Restricted Stock Units (PRSUs) Member [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Nonvested at June 30, 2018			422,300
Granted	298,000	170,000	0
Vested			0
Forfeited			(500)
Nonvested at September 30, 2018			421,800	422,300
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Roll Forward]
Nonvested at June 30, 2018			$ 16.63
Granted			0
Vested			0
Forfeited			16.22
Nonvested at September 30, 2018			$ 16.63	$ 16.63
Weighted Average Remaining Recognition Period (Years)			1 year 9 months 18 days	2 years 22 days
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Aggregate Intrinsic Value, Nonvested			$ 4,905,534	$ 6,013,552
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested and Expected to Vest, Outstanding, Number			377,861
Employee Service Share-based Compensation, Vested and Expected to Vest Awards, Total Compensation Cost Not Yet Recognized, Period for Recognition			1 year 8 months 23 days
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested and Expected to Vest, Intrinsic Value			$ 4,394,528
Allocated share-based compensation expense			$ 600,000		$ 200,000

Shareholders' Equity and Shar_7

Shareholders' Equity and Share-based Compensation - Share-based Compensation Expenses (Details) - USD ($) $ in Thousands	3 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Allocated share-based compensation expense	$ 3,129	$ 2,008
Unrecognized compensation expense	$ 16,700
Recognition period of share-based compensation expense (in years)	3 years
Cost of goods sold
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Allocated share-based compensation expense	$ 497	316
Research and development
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Allocated share-based compensation expense	632	362
Selling, general and administrative
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Allocated share-based compensation expense	$ 2,000	$ 1,330

Shareholders' Equity and Shar_8

Shareholders' Equity and Share-based Compensation - Performance-based Restricted Stock Units (Details) - USD ($)	1 Months Ended		3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Sep. 30, 2018	Jun. 30, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted Average Remaining Recognition Period (Years)			3 years
Performance Based Restricted Stock Units (PRSUs) Member [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number			421,800	422,300
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value			$ 16.63	$ 16.63
Weighted Average Remaining Recognition Period (Years)			1 year 9 months 18 days	2 years 22 days
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Aggregate Intrinsic Value, Nonvested			$ 4,905,534	$ 6,013,552
Granted	298,000	170,000	0
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value			$ 0
Vested			0
Vested			$ 0
Forfeited			(500)
Forfeited			$ 16.22
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested and Expected to Vest, Outstanding, Number			377,861
Employee Service Share-based Compensation, Vested and Expected to Vest Awards, Total Compensation Cost Not Yet Recognized, Period for Recognition			1 year 8 months 23 days
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested and Expected to Vest, Intrinsic Value			$ 4,394,528

Shareholders' Equity and Shar_9

Shareholders' Equity and Share-based Compensation - Market-based Restricted Stock Units Narrative (Details) - USD ($) $ in Thousands	3 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Allocated share-based compensation expense	$ 3,129	$ 2,008
Market-based Restricted Stock Units (MSU)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted (in shares)	1,310,000
Risk-free interest rate	2.70%
Expected term	3 years 6 months
Expected volatility	38.80%
Dividend yield	0.00%
Allocated share-based compensation expense	$ 200
Market-based Restricted Stock Units (MSU) | Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award service period	4 years 6 months
Market-based Restricted Stock Units (MSU) | Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award service period	7 years 6 months

Income Taxes - Narrative (Deta

Income Taxes - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Operating Loss Carryforwards [Line Items]
Income tax expense	$ 560	$ 1,274
Discrete tax benefit related to prior year tax reserve releases	$ 400
Estimated effective income tax rate excluding discrete income tax expense	(159.80%)	19.10%
Unrecognized tax benefits	$ 7,300
Unrecognized tax benefit that would impact effective tax rate	$ 4,500

Segment and Geographic Inform_3

Segment and Geographic Information - Revenue by Location and Product Type (Details) - USD ($) $ in Thousands	3 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	$ 115,072	$ 104,858
Power discrete
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	92,255	83,678
Power IC
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	19,415	18,097
Packaging and testing services
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	3,402	3,083
Hong Kong
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	91,591	85,230
China
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	20,397	17,120
South Korea
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	169	287
United States
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	1,973	1,378
Other countries
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	$ 942	$ 843

Segment and Geographic Inform_4

Segment and Geographic Information - Long-lived Assets (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Jun. 30, 2018
Revenues from External Customers and Long-Lived Assets [Line Items]
Property, plant and equipment, net and land use rights, net	$ 368,549	$ 331,656
China
Revenues from External Customers and Long-Lived Assets [Line Items]
Property, plant and equipment, net and land use rights, net	283,004	248,003
United States
Revenues from External Customers and Long-Lived Assets [Line Items]
Property, plant and equipment, net and land use rights, net	84,916	83,040
Other Countries
Revenues from External Customers and Long-Lived Assets [Line Items]
Property, plant and equipment, net and land use rights, net	$ 629	$ 613

Segment and Geographic Inform_5

Segment and Geographic Information - Narratives (Details)	3 Months Ended
	Sep. 30, 2018Segment
Segment Reporting [Abstract]
Number of operating segments	1
Number of reportable segments	1

Commitments and Contingencies -

Commitments and Contingencies - Purchase Commitments (Details) - USD ($) $ in Millions	Sep. 30, 2018	Jun. 30, 2018
Raw materials, wafers, and packaging and testing services puchase commitments
Purchase Commitment, Excluding Long-term Committment [Line Items]
Purchase commitment, amount	$ 49.2	$ 38
Property and equipment purchase commitments
Purchase Commitment, Excluding Long-term Committment [Line Items]
Purchase commitment, amount	$ 32.5	$ 58.3

Commitments and Contingencies_2

Commitments and Contingencies - Contingencies and Indemnities (Details) - USD ($)	Sep. 30, 2018	Jun. 30, 2018
Indemnification Agreement
Loss Contingencies [Line Items]
Indemnifications accrual	$ 0	$ 0