The aggregate expense charged against earnings to allocate the cost of intangible assets (nonphysical assets not used in production) in a systematic and rational manner to the periods expected to benefit from such assets. As a noncash expense, this element is added back to net income when calculating cash provided by or used in operations using the indirect method.

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Goodwill and Other Intangible Assets - Additional Information (Detail) - USD ($)	12 Months Ended
	May 31, 2020	May 31, 2019	May 31, 2018
Other non-amortizable intangible assets	$ 15,217,000	$ 15,510,000
Amortization expense for intangible assets	6,489,000	$ 6,309,000	$ 6,743,000
Estimated amortization expense for period, 2021	6,573,000
Estimated amortization expense for period, 2022	6,445,000
Estimated amortization expense for period, 2023	6,006,000
Estimated amortization expense for period, 2024	5,700,000
Estimated amortization expense for period, 2025	$ 5,370,000
Finite lived intangible assets, useful life	9 years	10 years
Maximum
Finite lived intangible assets, useful life	25 years
Minimum
Finite lived intangible assets, useful life	5 years
Licenses
Other non-amortizable intangible assets	$ 569,000	$ 569,000
Licenses \| Maximum
Finite lived intangible assets, useful life	20 years
Licenses \| Minimum
Finite lived intangible assets, useful life	2 years
Trademarks
Other non-amortizable intangible assets	$ 13,424,000	13,717,000
Other Intangible Assets
Other non-amortizable intangible assets	$ 1,224,000	$ 1,224,000
Noncompete Agreements \| Maximum
Finite lived intangible assets, useful life	13 years
Noncompete Agreements \| Minimum
Finite lived intangible assets, useful life	3 years
Patents \| Maximum
Finite lived intangible assets, useful life	25 years
Patents \| Minimum
Finite lived intangible assets, useful life	5 years
Customer-based intangibles \| Maximum
Finite lived intangible assets, useful life	20 years
Customer-based intangibles \| Minimum
Finite lived intangible assets, useful life	5 years
Other products and service-related intangibles \| Maximum
Finite lived intangible assets, useful life	20 years
Other products and service-related intangibles \| Minimum
Finite lived intangible assets, useful life	5 years