Fair Value of Financial Instruments (Details) - USD ($) $ in Millions	Dec. 31, 2019	Mar. 31, 2019
Carrying Amount | Revolving Credit Facility
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value disclosure for subordinated convertible debentures	$ 2,610.9	$ 3,251.8
Carrying Amount | Term Loan Facility
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value disclosure for subordinated convertible debentures	1,708.2	1,892.1
Carrying Amount | 2023 Senior Secured Notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value disclosure for subordinated convertible debentures	988.0	985.4
Carrying Amount | 2021 Senior Secured Notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value disclosure for subordinated convertible debentures	991.6	987.4
Carrying Amount | 2017 Senior Convertible Debt
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value disclosure for subordinated convertible debentures	1,537.7	1,493.6
Carrying Amount | 2015 Senior Convertible Debt
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value disclosure for subordinated convertible debentures	1,400.8	1,360.8
Carrying Amount | 2017 Junior Convertible Debt
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value disclosure for subordinated convertible debentures	343.3	335.9
Fair Value | Revolving Credit Facility
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value disclosure for subordinated convertible debentures	2,624.5	3,266.5
Fair Value | Term Loan Facility
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value disclosure for subordinated convertible debentures	1,723.5	1,911.5
Fair Value | 2023 Senior Secured Notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value disclosure for subordinated convertible debentures	1,058.8	1,020.1
Fair Value | 2021 Senior Secured Notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value disclosure for subordinated convertible debentures	1,022.5	1,008.1
Fair Value | 2017 Senior Convertible Debt
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value disclosure for subordinated convertible debentures	2,968.1	2,285.4
Fair Value | 2015 Senior Convertible Debt
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value disclosure for subordinated convertible debentures	3,710.8	2,810.6
Fair Value | 2017 Junior Convertible Debt
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value disclosure for subordinated convertible debentures	$ 994.1	$ 740.8