Revenues - Disaggregation of Revenue (Details) - USD ($) $ in Millions		3 Months Ended
		Aug. 31, 2018	Aug. 31, 2017
Disaggregation of Revenue [Line Items]
Revenues		$ 218.4	$ 189.2
Children's Book Publishing and Distribution
Disaggregation of Revenue [Line Items]
Revenues		93.3	66.8
Children's Book Publishing and Distribution | Book Clubs
Disaggregation of Revenue [Line Items]
Revenues		9.1	8.0
Children's Book Publishing and Distribution | Book Fairs
Disaggregation of Revenue [Line Items]
Revenues		25.2	12.1
Children's Book Publishing and Distribution | Trade
Disaggregation of Revenue [Line Items]
Revenues		59.0	46.7
Education
Disaggregation of Revenue [Line Items]
Revenues		50.3	45.0
International
Disaggregation of Revenue [Line Items]
Revenues		74.8	77.4
International | Major Markets
Disaggregation of Revenue [Line Items]
Revenues	[1]	50.3	51.7
International | Other Markets
Disaggregation of Revenue [Line Items]
Revenues	[2]	$ 24.5	$ 25.7

[1] Includes Canada, UK, Australia and New Zealand

[2] .