CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2023	Dec. 31, 2022
Statement of Comprehensive Income [Abstract]
Net income	$ 419.2	$ 580.3	$ 1,752.2	$ 1,633.7
Components of other comprehensive (loss) income:
Actuarial (losses) gains related to defined benefit pension plans, net of tax effect	(2.0)	(5.9)	(0.7)	3.2
Change in net foreign currency translation adjustment	0.0	0.0	0.0	(0.1)
Other comprehensive (loss) income, net of tax effect	(2.0)	(5.9)	(0.7)	3.1
Comprehensive income	$ 417.2	$ 574.4	$ 1,751.5	$ 1,636.8