Fair Value of Financial Instruments (Details) - USD ($) $ in Thousands	Mar. 31, 2016	Mar. 31, 2015
Fair Value | Senior Subordinated Convertible Debentures Due 2025 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value disclosure for Subordinated Convertible Debentures	$ 1,762,088	$ 1,787,531
Fair Value | Junior Subordinated Convertible Debentures Due2037 Member
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value disclosure for Subordinated Convertible Debentures	1,143,117	1,124,125
Carrying Amount | Senior Subordinated Convertible Debentures Due 2025 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value disclosure for Subordinated Convertible Debentures	1,234,733	1,174,036
Carrying Amount | Junior Subordinated Convertible Debentures Due2037 Member
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value disclosure for Subordinated Convertible Debentures	$ 196,304	$ 190,870