Revenues - Impact of Adoption (Details) - USD ($) $ / shares in Units, $ in Millions		3 Months Ended
		Aug. 31, 2018	Aug. 31, 2017	May 31, 2018
Statement of Financial Position [Abstract]
Accounts receivable, net		$ 223.7	$ 145.4	$ 204.9
Inventories, net		402.3	386.5	294.9
Prepaid expenses and other current assets		107.6	113.0	66.6
Noncurrent deferred income taxes		40.9	53.8	25.2
Deferred revenue		130.4	44.7	24.7
Other accrued expenses		185.9	153.3	177.9
Retained earnings		952.1	1,022.2	1,065.2
Book fair incentive credits		9.7	31.9	35.8
Returns liability		45.4	0.0	0.0
Income Statement [Abstract]
Revenues		218.4	189.2
Cost of goods sold		125.3	115.6
Selling, general and administrative expenses		163.7	159.5
Provision for losses on accounts receivable		1.4	1.9
Depreciation and amortization		13.2	9.2
Operating income (loss)		(83.8)	(101.8)
Interest income (expense), net		0.8	0.3
Other components of net periodic benefit (cost)		(0.4)	(0.1)
Provision (benefit) for income taxes		(22.1)	(37.9)
Net income (loss)		$ (61.3)	$ (63.7)
Basic earnings (loss) (in Dollars per share)		$ (1.75)	$ (1.81)
Diluted earnings (loss) (in Dollars per share)		$ (1.75)	$ (1.81)
ASU 2014-09 | Adjustments due to adoption
Statement of Financial Position [Abstract]
Accounts receivable, net	[1]			31.1
Inventories, net	[2]			(1.9)
Prepaid expenses and other current assets	[2]			(4.3)
Noncurrent deferred income taxes	[3]			16.0
Deferred revenue	[4]			86.3
Other accrued expenses	[5]			1.1
Retained earnings				(46.5)
Direct response advertising costs				5.5
Book fair incentive credits				27.2
Returns liability				28.3
Income Statement [Abstract]
Revenues	[6]	$ (12.5)
Cost of goods sold	[6]	(4.1)
Selling, general and administrative expenses	[7]	(3.2)
Depreciation and amortization		0.0
Operating income (loss)		(5.2)
Interest income (expense), net		0.0
Other components of net periodic benefit (cost)		0.0
Provision (benefit) for income taxes	[8]	0.0
Net income (loss)		$ (3.8)
Basic earnings (loss) (in Dollars per share)		$ (0.11)
Diluted earnings (loss) (in Dollars per share)		$ (0.11)
ASU 2014-09 | Adjusted balance
Statement of Financial Position [Abstract]
Accounts receivable, net				236.0
Inventories, net				293.0
Prepaid expenses and other current assets				62.3
Noncurrent deferred income taxes				41.2
Deferred revenue				111.0
Other accrued expenses				179.0
Retained earnings				$ 1,018.7
Income Statement [Abstract]
Revenues		$ 205.9
Cost of goods sold		121.2
Selling, general and administrative expenses		160.5
Depreciation and amortization		13.2
Operating income (loss)		(89.0)
Interest income (expense), net		0.8
Other components of net periodic benefit (cost)		(0.4)
Provision (benefit) for income taxes		(23.5)
Net income (loss)		$ (65.1)
Basic earnings (loss) (in Dollars per share)		$ (1.86)
Diluted earnings (loss) (in Dollars per share)		$ (1.86)

[1] Primarily represents the reclassification of the Company’s accounting for estimated returns from a reduction to Accounts receivable, net, to a current liability within Other accrued expenses.

[2] represents the adjustment for previously capitalized direct response advertising costs of $5.5 and the reclassification of a return asset from Inventory to Prepaid expenses and other current assets.

[3] Represents the income tax impact of Topic 606 adjustments.

[4] Represents the deferred revenue related to outstanding book fairs incentive credits as of June 1, 2018.

[5] Represents a reduction to Other accrued expenses of $27.2 for outstanding book fair incentive credits as of June 1, 2018. This decrease was offset by a $28.3 increase for estimated returns recorded to Other accrued expenses.

[6] Represents incremental revenue and cost of goods sold related to the redemption of book fairs incentive program credits, partially offset by additional deferred revenue on incentive credits awarded during the period.

[7] Represents direct response advertising costs being expensed as incurred.

[8] Represents the income tax impact of Topic 606 adjustments.