CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Statement of Comprehensive Income [Abstract]
Net income	$ 242.0	$ 73.6	$ 494.8	$ 197.2
Defined benefit plans:
Actuarial gains (losses) related to defined benefit pension plans, net of tax effect	1.8	(2.6)	0.7	(3.4)
Reclassification of realized transactions, net of tax effect	0.6	0.3	1.2	0.6
Change in net foreign currency translation adjustment	(0.6)	2.5	(0.1)	3.5
Other comprehensive income, net of tax effect	1.8	0.2	1.8	0.7
Comprehensive income	$ 243.8	$ 73.8	$ 496.6	$ 197.9