Segment Information - Schedule of segment reporting information (Details) $ in Millions	3 Months Ended		6 Months Ended
	Nov. 30, 2024 USD ($)	Nov. 30, 2023 USD ($)	Nov. 30, 2024 USD ($) segment	Nov. 30, 2023 USD ($)
Segment Reporting Information [Line Items]
Number of reportable segments | segment			4
Revenues	$ 544.6	$ 562.6	$ 781.8	$ 791.1
Segment operating income (loss)	74.7	101.3	$ (13.8)	2.2
Total Children's Book Publishing and Distribution
Segment Reporting Information [Line Items]
Number of operating segments | segment			2
Total Education Solutions
Segment Reporting Information [Line Items]
Number of operating segments | segment			1
Total Entertainment
Segment Reporting Information [Line Items]
Number of operating segments | segment			1
Total International
Segment Reporting Information [Line Items]
Number of operating segments | segment			3
Operating Segments | Total Children's Book Publishing and Distribution
Segment Reporting Information [Line Items]
Revenues	367.0	392.4	$ 472.4	494.8
Segment operating income (loss)	102.1	111.6	65.5	70.6
Operating Segments | Total Education Solutions
Segment Reporting Information [Line Items]
Revenues	71.2	81.0	126.9	147.0
Segment operating income (loss)	(0.5)	5.8	(17.5)	(12.9)
Operating Segments | Total Entertainment
Segment Reporting Information [Line Items]
Revenues	16.8	0.4	33.4	0.8
Segment operating income (loss)	(4.7)	(0.8)	(5.2)	(1.3)
Operating Segments | Total International
Segment Reporting Information [Line Items]
Revenues	86.7	86.5	143.5	143.7
Segment operating income (loss)	5.7	8.0	(2.6)	(0.2)
Corporate, Non-Segment
Segment Reporting Information [Line Items]
Revenues	2.9	2.3	5.6	4.8
Corporate, Non-Segment | Overhead
Segment Reporting Information [Line Items]
Revenues	2.9	2.3	5.6	4.8
Segment operating income (loss)	$ (27.9)	$ (23.3)	$ (54.0)	$ (54.0)