Revenues - Impact of Adoption (Details) - USD ($) $ / shares in Units, $ in Millions		3 Months Ended						9 Months Ended
		Feb. 28, 2019	Nov. 30, 2018	Aug. 31, 2018	Feb. 28, 2018	Nov. 30, 2017	Aug. 31, 2017	Feb. 28, 2019		Feb. 28, 2018	May 31, 2018
Statement of Financial Position [Abstract]
Accounts receivable, net		$ 317.3			$ 186.0			$ 317.3		$ 186.0	$ 204.9
Inventories, net		356.8			356.9			356.8		356.9	294.9
Prepaid expenses and other current assets		84.8			100.1			84.8		100.1	66.6
Noncurrent deferred income taxes		43.6			17.8			43.6		17.8	25.2
Deferred revenue		154.7			56.5			154.7		56.5	24.7
Other accrued expenses		236.2			162.6			236.2		162.6	177.9
Retained earnings		1,000.5			1,019.6			1,000.5		1,019.6	1,065.2
Book fair incentive credits		10.2			35.8			10.2		35.8	35.8
Returns liability		97.3			0.0			97.3		0.0	0.0
Income Statement [Abstract]
Revenues		360.1			344.7			1,183.2		1,132.2
Cost of goods sold		176.9			166.4			564.6		535.6
Selling, general and administrative expenses		190.9			186.7			584.3		573.9
Provision for losses on accounts receivable		1.6			1.7			5.7		7.9
Depreciation and amortization		13.7			11.0			41.3		30.0
Operating income (loss)		(21.4)			(23.7)			(7.0)		(18.3)
Interest income (expense), net		1.0			0.2			2.3		0.5
Other components of net periodic benefit (cost)		(0.4)			(39.8)			(1.1)		(55.4)
Provision (benefit) for income taxes		(8.2)			(14.1)			(3.5)		(17.4)
Net Income (loss)		$ (12.6)	$ 71.6	$ (61.3)	$ (49.2)	$ 57.1	$ (63.7)	$ (2.3)		$ (55.8)
Basic earnings (loss) (in Dollars per share)		$ (0.36)			$ (1.41)			$ (0.07)		$ (1.59)
Diluted earnings (loss) (in Dollars per share)		$ (0.36)			$ (1.41)			$ (0.07)		$ (1.59)
ASU 2014-09
Income Statement [Abstract]
Provision (benefit) for income taxes				$ 16.0
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],[3]										(4.3)
Noncurrent deferred income taxes	[4]										16.0
Deferred revenue	[5]										86.3
Other accrued expenses	[6]										1.1
Retained earnings											(46.5)
Book fair incentive credits											27.2
Returns liability											28.3
Income Statement [Abstract]
Revenues		$ (9.4)						$ (11.1)
Cost of goods sold		(2.0)						(3.5)
Selling, general and administrative expenses	[7]	0.1						(0.5)
Depreciation and amortization		0.0						0.0
Operating income (loss)		(7.5)						(7.1)
Interest income (expense), net		0.0						0.0
Other components of net periodic benefit (cost)		0.0						0.0
Provision (benefit) for income taxes		(2.0)						(1.9)	[8]
Net Income (loss)		$ (5.5)						$ (5.2)
Basic earnings (loss) (in Dollars per share)		$ (0.16)						$ (0.15)
Diluted earnings (loss) (in Dollars per share)		$ (0.16)						$ (0.15)
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		$ 350.7						$ 1,172.1
Cost of goods sold		174.9						561.1
Selling, general and administrative expenses		191.0						583.8
Depreciation and amortization		13.7						41.3
Operating income (loss)		(28.9)						(14.1)
Interest income (expense), net		1.0						2.3
Other components of net periodic benefit (cost)		(0.4)						(1.1)
Provision (benefit) for income taxes		(10.2)						(5.4)
Net Income (loss)		$ (18.1)						$ (7.5)
Basic earnings (loss) (in Dollars per share)		$ (0.52)						$ (0.22)
Diluted earnings (loss) (in Dollars per share)		$ (0.52)						$ (0.22)

[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 reclassification of a return asset from Inventory to Prepaid expenses and other current assets.

[3] Primarily represents the adjustment for previously capitalized direct response advertising costs.

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

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

[6] 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.

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

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