Revenues - Disaggregation of Revenue (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Nov. 30, 2020	Nov. 30, 2019	Nov. 30, 2020	Nov. 30, 2019
Disaggregation of Revenue [Line Items]
Revenues	$ 406.2	$ 597.2	$ 621.4	$ 829.8
Children's Book Publishing and Distribution | U.S. Book Clubs
Disaggregation of Revenue [Line Items]
Revenues	66.9	85.9	72.7	93.9
Children's Book Publishing and Distribution | U.S. Book Fairs
Disaggregation of Revenue [Line Items]
Revenues	47.7	224.1	60.9	251.6
Children's Book Publishing and Distribution | U.S. Trade
Disaggregation of Revenue [Line Items]
Revenues	116.4	93.5	182.2	161.2
Education
Disaggregation of Revenue [Line Items]
Revenues	67.3	69.8	120.8	118.2
International | Major Markets
Disaggregation of Revenue [Line Items]
Revenues	83.1	94.6	139.7	150.9
International | Other Markets
Disaggregation of Revenue [Line Items]
Revenues	$ 24.8	$ 29.3	$ 45.1	$ 54.0