Revenues - Deferred Revenue (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Nov. 30, 2025	Nov. 30, 2024	Nov. 30, 2025	Nov. 30, 2024	May 31, 2025
Deferred Revenue Arrangement [Line Items]
Deferred revenue	$ 230.5	$ 230.9	$ 230.5	$ 230.9	$ 183.0
Contract with customer, liability, revenue recognized	43.3	41.9	80.3	71.1
Book fairs incentive credits
Deferred Revenue Arrangement [Line Items]
Deferred revenue	124.2	120.8	124.2	120.8	122.1
Magazines+ subscriptions
Deferred Revenue Arrangement [Line Items]
Deferred revenue	43.2	48.3	43.2	48.3	3.9
U.S. digital subscriptions
Deferred Revenue Arrangement [Line Items]
Deferred revenue	10.5	17.9	10.5	17.9	11.1
U.S. Education-related
Deferred Revenue Arrangement [Line Items]
Deferred revenue	6.6	9.5	6.6	9.5	7.5
Entertainment-related (2)
Deferred Revenue Arrangement [Line Items]
Deferred revenue	12.4	7.7	12.4	7.7	8.2
Stored value programs
Deferred Revenue Arrangement [Line Items]
Deferred revenue	27.1	21.0	27.1	21.0	22.4
Other
Deferred Revenue Arrangement [Line Items]
Deferred revenue	$ 6.5	$ 5.7	$ 6.5	$ 5.7	$ 7.8