Common Stock (Narrative) (Details) - USD ($)	3 Months Ended
	Jul. 31, 2019	Jul. 31, 2018	Mar. 27, 2018
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Net of Forfeitures	0	7,500
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Weighted Average Grant Date Fair Value		$ 2.47
Shares issued pursuant to cashless exercises of stock options		6,958
Stock options exercised	0	35,500
Adjustments Related to Tax Withholding for Share-based Compensation		$ 2,386
Employee Stock Ownership Plan (ESOP), Plan Description	Under the terms of the Employee Stock Purchase Plan (the "ESPP") all regular salaried (non-probationary) employees can purchase up to 6% of their base salary in shares of the Company's common stock at market price. The Company matches 50% of the shares purchased by issuing or purchasing in the market up to 3% of the respective employee's base salary in shares
Employee Stock Ownership Plan (ESOP), Shares Contributed to ESOP	5,263	7,890
Employee Stock Ownership Plan (ESOP), Shares in ESOP	220,000
Employee Stock Ownership Plan (ESOP), Number of Suspense Shares	145,550
Deferred Share Units Granted During Period	0	136,981
Deferred Share Units Available for Issuance	42,495
Stock Repurchase Program, Number of Shares Authorized to be Repurchased			284,278
Shares purchased on the open market [Member]
Employee Stock Ownership Plan (ESOP), Shares Contributed to ESOP	6,624	5,960
Shares issued from treasury under the ESPP [Member]
Employee Stock Ownership Plan (ESOP), Shares Contributed to ESOP	3,134	2,172