Income Taxes	9 Months Ended
Income Taxes	Jan. 31, 2021
Income Tax Disclosure [Abstract]
Income Taxes	. Income TaxesIncome tax benefits of $813,000 and $350,000 were recorded for the three months ended January 31, 2021 and 2020, respectively. An income tax benefit of $989,000 and an income tax expense of $1,822,000 were recorded for the nine months ended January 31, 2021 and 2020, respectively. The effective tax rates were 113.2% and 15.5% for the three months ended January 31, 2021 and 2020, respectively. The effective tax rates were 59.3% and 104.5% for the nine months ended January 31, 2021 and 2020, respectively. The change in the effective tax rate for the three and nine-month periods is primarily due to the revocation of the Company's indefinite reinvestment of foreign unremitted earnings position (discussed below) and the impact of foreign operations which are taxed at different rates than the U.S. tax rate of 21%. In addition, the change in the effective tax rates for the three and nine months ended January 31, 2021 was impacted by the recording of a Domestic income tax benefit as a result of the Company's current Domestic net loss position. This loss is permitted to be carried back and used to offset Domestic taxable income incurred in previous tax filing periods as allowed by the Coronavirus Aid, Relief and Economic Security Act ("CARES Act"). The Company recorded income tax receivables of $4,205,000 and $2,717,000 as of January 31, 2021 and April 30, 2020, respectively, which includes Domestic income tax benefits attributable to the carryback claims for the applied Research and Development tax credit for the year ended April 30, 2018, the taxable losses generated during the year ended April 30, 2020 and the nine months ended January 31, 2021. In August 2019, the Company revoked its indefinite reinvestment of foreign unremitted earnings position in compliance with ASC 740 "Income Taxes" and terminated its indefinite reinvestment of unremitted earnings assertion for the Singapore, China, and Kewaunee Labway India Pvt. Ltd. international subsidiaries. The Company recognized a tax withholding expense, for the dividends paid to the US and Singapore shareholders, imposed by the India Income Tax Department in accordance with international tax treaties between India and the U.S. and Singapore governments, at a rate of 10.0% and 15.0%, respectively. The Company recognized a withholding tax expense of $18,000 and $99,000 for the three and nine months ended January 31, 2021, respectively, related to the unremitted earnings of the subsidiaries listed above. The Company recognized a withholding tax expense of $50,000 and $2,214,000 for the three and nine months ended January 31, 2020 related to the unremitted earnings position of the subsidiaries listed above. The Company has a deferred tax liability of $647,000 and $785,000 for the withholding tax related to Kewaunee Labway India Pvt. Ltd. as of January 31, 2021 and April 30, 2020, respectively. The Company recorded all deferred tax assets and liabilities related to its outside basis differences in its foreign subsidiaries consistent with ASC 740. In July 2020, the U.S. Department of the Treasury issued final tax regulations (proposed regulations were originally published in 2019) with respect to global intangible low-taxed income (''GILTI''.) Among other changes, these regulations now permit an election to exclude, from the GILTI calculation, items of income which are subject to a high effective foreign tax rate. The Company excluded certain items, as permitted by these final regulations, in the current fiscal year and reflected the benefit in the estimated annual effective tax rate.