Fair Value Measurements (Carrying Amount and Estimated Fair Value of Financial Instruments) (Details) - USD ($) $ in Thousands	12 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Carrying [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	$ 113,101	$ 410,405
Investment in business purchase option		146,500
Fair Value [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	113,101	410,405
Investment in business purchase option		146,500
Senior Notes due March 1, 2025 [Member] | Significant Other Observable Inputs (Level 2) | Carrying [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt	1,318,079	997,772
Senior Notes due March 1, 2025 [Member] | Significant Other Observable Inputs (Level 2) | Fair Value [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt	1,351,500	950,000
Senior Amortizing Notes due June 30, 2022 [Member] | Significant Other Observable Inputs (Level 2) | Carrying [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt component of tangible equity units	20,345	35,431
Senior Amortizing Notes due June 30, 2022 [Member] | Significant Other Observable Inputs (Level 2) | Fair Value [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt component of tangible equity units	21,435	34,806
Senior Credit Facilities [Member] | Significant Other Observable Inputs (Level 2) | Carrying [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt	3,405,552	3,682,457
Senior Credit Facilities [Member] | Significant Other Observable Inputs (Level 2) | Fair Value [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt	$ 3,488,883	$ 3,452,687