Revenues - Disaggregation of Revenue (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Nov. 30, 2019	Nov. 30, 2018	Nov. 30, 2019	Nov. 30, 2018
Disaggregation of Revenue [Line Items]
Revenues	$ 597.2	$ 604.7	$ 829.8	$ 823.1
Children's Book Publishing and Distribution | U.S. Book Clubs
Disaggregation of Revenue [Line Items]
Revenues	85.9	101.3	93.9	110.4
Children's Book Publishing and Distribution | U.S. Book Fairs
Disaggregation of Revenue [Line Items]
Revenues	224.1	220.7	251.6	245.9
Children's Book Publishing and Distribution | U.S. Trade
Disaggregation of Revenue [Line Items]
Revenues	93.5	95.9	161.2	157.3
Education
Disaggregation of Revenue [Line Items]
Revenues	69.8	71.4	118.2	119.3
International | Major Markets
Disaggregation of Revenue [Line Items]
Revenues	94.6	88.0	150.9	138.3
International | Other Markets
Disaggregation of Revenue [Line Items]
Revenues	$ 29.3	$ 27.4	$ 54.0	$ 51.9