Debt - Interest Expense (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Debt Instrument [Line Items]
Debt issuance cost amortization			$ 6.4	$ 9.0
Debt discount amortization			24.2	43.1
Other interest expense	$ 1.2	$ 1.1	1.9	2.1
Total interest expense	64.8	93.3	137.1	192.4
Senior Secured Indebtedness
Debt Instrument [Line Items]
Debt issuance cost amortization	2.3	3.7	5.2	7.8
Debt discount amortization	1.7	1.6	3.6	3.1
Interest expense	46.9	59.4	99.6	112.1
Total interest expense	50.9	64.7	108.4	123.0
Convertible Debt
Debt Instrument [Line Items]
Debt issuance cost amortization	0.6	0.5	1.2	1.2
Debt discount amortization	9.9	16.2	20.6	40.0
Interest expense	2.2	10.8	5.0	26.1
Total interest expense	$ 12.7	$ 27.5	$ 26.8	$ 67.3