Description of Business, Basis of Presentation, and Significant Accounting Policies (Narrative) (Details) $ in Millions		3 Months Ended			6 Months Ended			12 Months Ended
	Jun. 01, 2019 USD ($)	Nov. 30, 2019 USD ($)	Nov. 30, 2018 USD ($)		Nov. 30, 2019 USD ($) segment	Nov. 30, 2018 USD ($)		May 31, 2020 USD ($)	May 31, 2019 USD ($)	May 31, 2018 USD ($)
Accounting Policies [Line Items]
Number of reportable segments | segment					1
Net cash provided by investing activities					$ 565.2	$ 53.7	[1]
Cash, cash equivalents, restricted cash and restricted cash equivalents		$ 1,420.0	$ 1,467.8	[1]	1,420.0	1,467.8	[1]		$ 935.2	$ 2,300.5	[1]
Allowance for doubtful accounts		10.8			10.8				7.5
Advance collections		3.6			3.6				4.2
Maximum individual health insurance claims liability									0.3
Operating lease, impairment loss					0.0
Stock-based compensation costs recognized		13.3	11.9		23.8	22.8
Operating lease, right-of-use asset		119.2			119.2
Operating lease, liability		138.2			138.2
Forecast [Member]
Accounting Policies [Line Items]
Maximum individual workers' compensation claims liability								$ 1.0
Maximum individual health insurance claims liability								$ 0.3
ASU 2016-18 [Member]
Accounting Policies [Line Items]
Net cash provided by investing activities						(985.1)
Cash, cash equivalents, restricted cash and restricted cash equivalents			$ 1,000.0			$ 1,000.0				$ 1,900.0
ASU 2016-02 [Member]
Accounting Policies [Line Items]
Increase in lease-related assets and liabilities	$ 116.4
Operating lease, right-of-use asset	116.4
Operating lease, liability	135.3
Unamortized landlord allowances and lease incentives	$ 18.9
Trade Receivables [Member]
Accounting Policies [Line Items]
Receivables		90.1			90.1				94.5
Purchased Receivables [Member]
Accounting Policies [Line Items]
Receivables		$ 385.6			$ 385.6				333.5
Minimum [Member]
Accounting Policies [Line Items]
Maximum individual workers' compensation claims liability									0.5
Maximum [Member]
Accounting Policies [Line Items]
Maximum individual workers' compensation claims liability									$ 1.0
Europe [Member] | Revenue [Member] | Geographic Concentration Risk [Member]
Accounting Policies [Line Items]
Total percentage		1.00%	1.00%		1.00%	1.00%
Europe [Member] | Long Lived Assets [Member] | Geographic Concentration Risk [Member]
Accounting Policies [Line Items]
Total percentage					5.00%				5.00%

[1] Amounts have been adjusted to reflect adoption of Accounting Standards Update (“ASU”) No. 2016-18, “Statement of Cash Flows (Topic 230): Restricted Cash (a consensus of the FASB Emerging Issues Task Force).”