Fair Value Measurements (Tables)

9 Months Ended

Feb. 28, 2021

Fair Value Measurements [Abstract]

Financial Assets and Liabilities Measured at Fair Value on Recurring Basis

	February 28, 2021
			Quoted		Significant
			prices in		other		Significant
	Carrying		active		observable		unobservable
	value		markets		inputs		inputs
In millions	(Fair value)		(Level 1)		(Level 2)		(Level 3)
Assets:
Restricted and unrestricted cash equivalents:
Money market securities	$	7.9	$	7.9	$	—	$	—
Total restricted and unrestricted cash equivalents	$	7.9	$	7.9	$	—	$	—
AFS securities:
Asset-backed securities	$	83.9	$	—	$	83.9	$	—
Corporate bonds		656.6		—		656.6		—
Municipal bonds		1,730.3		—		1,730.3		—
U.S. government agency and treasury securities		565.5		—		565.5		—
VRDNs		171.1		—		171.1		—
Total AFS securities	$	3,207.4	$	—	$	3,207.4	$	—
Other	$	32.6	$	32.6	$	—	$	—
Liabilities:
Other long-term liabilities	$	31.4	$	31.4	$	—	$	—

	May 31, 2020
			Quoted		Significant
			prices in		other		Significant
	Carrying		active		observable		unobservable
	value		markets		inputs		inputs
In millions	(Fair value)		(Level 1)		(Level 2)		(Level 3)
Assets:
Restricted and unrestricted cash equivalents:
Money market securities	$	43.5	$	43.5	$	—	$	—
Total restricted and unrestricted cash equivalents	$	43.5	$	43.5	$	—	$	—
AFS securities:
Asset-backed securities	$	69.7	$	—	$	69.7	$	—
Corporate bonds		683.6		—		683.6		—
Municipal bonds		1,409.6		—		1,409.6		—
U.S. government agency and treasury securities		594.3		—		594.3		—
Total AFS securities	$	2,757.2	$	—	$	2,757.2	$	—
Other	$	27.2	$	27.2	$	—	$	—
Liabilities:
Other long-term liabilities	$	26.8	$	26.8	$	—	$	—