Fair Value Measurements - Fair Value of Derivative Liabilities (Details) - Interest rate swap agreements - USD ($) $ in Thousands	Jul. 31, 2021	Apr. 30, 2021
Fair Value Measurements
Derivative liabilities	$ 11,900
Level 2 \| Fair Value, Measurements, Recurring
Fair Value Measurements
Derivative liabilities	$ 18,405	$ 21,004

Fair value, after the effects of master netting arrangements, of a financial liability or contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes liabilities not subject to a master netting arrangement and not elected to be offset.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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