Debt - Interest Expense (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2020	Dec. 31, 2019
Debt Instrument [Line Items]
Debt issuance amortization			$ 13.2	$ 12.8
Debt discount amortization			57.5	90.9
Other interest expense	$ 0.9	$ 1.3	3.0	2.6
Total interest expense	86.5	119.7	278.9	381.9
Senior Secured Indebtedness
Debt Instrument [Line Items]
Debt issuance amortization	3.7	3.3	11.5	9.9
Debt discount amortization	1.6	0.7	4.7	2.1
Interest expense	59.2	64.1	171.3	217.7
Total interest expense	64.5	68.1	187.5	229.7
Convertible Debt
Debt Instrument [Line Items]
Debt issuance amortization	0.5	1.0	1.7	2.9
Debt discount amortization	12.8	30.0	52.8	88.8
Interest expense	7.8	19.3	33.9	57.9
Total interest expense	$ 21.1	$ 50.3	$ 88.4	$ 149.6