Accumulated Other Comprehensive Income (Tables)

12 Months Ended

May 31, 2016

Accumulated Other Comprehensive Income [Abstract]

Changes in Accumulated Other Comprehensive Income

	Year ended May 31,
In millions	2016		2015		2014
Beginning balance	$	7.5	$	21.5	$	22.0
Other comprehensive income/(loss):
Unrealized holding gains/(losses)		34.2		(21.5)		0.3
Income tax (expense)/benefit related to unrealized holding gains/(losses)		(12.4)		7.7		(0.4)
Reclassification adjustment for the net gain on sale of available-for-sale    securities realized in net income		(0.1)		(0.3)		(0.6)
Income tax expense on reclassification adjustment for the net gain on    sale of available-for-sale securities		—		0.1		0.2
Total other comprehensive income/(loss), net of tax		21.7		(14.0)		(0.5)
Ending balance	$	29.2	$	7.5	$	21.5
Total tax expense/(benefit) included in other comprehensive income/(loss)	$	12.4	$	(7.8)	$	0.2