Business Segment Information - Sales and Gross Profit (Details) $ in Millions	3 Months Ended
Aug. 31, 2021 USD ($) segment	Aug. 31, 2020 USD ($)
Disaggregation of revenue by major customer markets
Operating segments (in segments) \| segment	2
Sales	$ 455.1	$ 400.8
Gross profit	64.6	48.6
Aviation Services
Disaggregation of revenue by major customer markets
Sales	435.6	363.6
Gross profit	60.9	44.6
Expeditionary Services
Disaggregation of revenue by major customer markets
Sales	19.5	37.2
Gross profit	$ 3.7	$ 4.0

Aggregate revenue less cost of goods and services sold or operating expenses directly attributable to the revenue generation activity.

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- Definition

Amount, including tax collected from customer, of revenue from satisfaction of performance obligation by transferring promised good or service to customer. Tax collected from customer is tax assessed by governmental authority that is both imposed on and concurrent with specific revenue-producing transaction, including, but not limited to, sales, use, value-added and excise.

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