Revenues - Disaggregation of Revenue (Details) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
		Feb. 28, 2019	Feb. 28, 2018	Feb. 28, 2019	Feb. 28, 2018
Disaggregation of Revenue [Line Items]
Revenues		$ 360.1	$ 344.7	$ 1,183.2	$ 1,132.2
Children's Book Publishing and Distribution
Disaggregation of Revenue [Line Items]
Revenues		218.0	201.6	731.6	684.2
Children's Book Publishing and Distribution | Book Clubs
Disaggregation of Revenue [Line Items]
Revenues		55.0	57.7	165.4	165.6
Children's Book Publishing and Distribution | Book Fairs
Disaggregation of Revenue [Line Items]
Revenues		97.4	91.5	343.3	334.6
Children's Book Publishing and Distribution | Trade
Disaggregation of Revenue [Line Items]
Revenues		65.6	52.4	222.9	184.0
Education
Disaggregation of Revenue [Line Items]
Revenues		60.3	59.5	179.7	171.4
International
Disaggregation of Revenue [Line Items]
Revenues		81.8	83.6	271.9	276.6
International | Major Markets
Disaggregation of Revenue [Line Items]
Revenues	[1]	54.5	55.3	192.7	195.6
International | Other Markets
Disaggregation of Revenue [Line Items]
Revenues	[2]	$ 27.3	$ 28.3	$ 79.2	$ 81.0

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

[2] Primarily includes markets in Asia.