Debt - Settlement of debt (Details) - USD ($) $ in Millions	1 Months Ended			3 Months Ended					9 Months Ended
	Dec. 31, 2021	Aug. 31, 2021	Jun. 30, 2021	Dec. 31, 2021	Sep. 30, 2021	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Dec. 31, 2021	Dec. 31, 2020
Debt Instrument [Line Items]
Cash Paid									$ 1,000.0	$ 0.0
Value of Shares Issued				$ 196.9	$ 399.2	$ 1,160.1	$ 768.7	$ 651.5
Net Loss on Inducements and Settlements				$ 16.1		$ 142.1			$ 101.6	$ 214.0
Line of Credit | Revolving Credit Facility
Debt Instrument [Line Items]
Net Loss on Inducements and Settlements	$ 0.6
3.922% 2021 Notes | Senior Indebtedness
Debt Instrument [Line Items]
Principal Amount Settled			$ 1,000.0
Cash Paid			1,000.0
Total			1,000.0
Net Loss on Inducements and Settlements			$ 0.3
2015 Senior Convertible Debt | Senior Convertible Debt
Debt Instrument [Line Items]
Principal Amount Settled	36.6	$ 70.4
Cash Paid	36.6	70.4
Value of Shares Issued	103.9	159.9
Total	140.5	230.3
Fair Value Settled	36.2	71.0
Equity Component	104.2	158.9
Net Loss on Inducements and Settlements	4.1	10.6
2017 Senior Convertible Debt | Senior Convertible Debt
Debt Instrument [Line Items]
Principal Amount Settled	39.7	100.7
Cash Paid	39.7	100.7
Value of Shares Issued	61.4	123.5
Total	101.1	224.2
Fair Value Settled	37.4	100.0
Equity Component	63.0	113.0
Net Loss on Inducements and Settlements	6.3	31.5
2017 Junior Convertible Debt | Junior Convertible Debt
Debt Instrument [Line Items]
Principal Amount Settled	19.9	92.5
Cash Paid	19.9	92.5
Value of Shares Issued	31.6	115.8
Total	51.5	208.3
Fair Value Settled	15.7	87.7
Equity Component	35.9	116.6
Net Loss on Inducements and Settlements	$ 5.1	$ 43.1
0.983% 2024 Notes | Senior Indebtedness
Debt Instrument [Line Items]
Debt instrument, redemption price (percent)									101.00%