Fair Value and Carrying Value of Financial Instruments and Long-Term Debt (Detail) - USD ($) $ in Thousands	Feb. 28, 2019	May 31, 2018
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Marketable equity securities	$ 89,200	$ 144,555
Marketable debt securities	23,784	23,516
Carrying Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	195,169	244,422
Marketable equity securities	89,234	144,555
Marketable debt securities	23,784	23,516
Long-term debt, including current portion	2,524,218	2,174,144
Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	195,169	244,422
Marketable equity securities	89,234	144,555
Marketable debt securities	23,784	23,516
Long-term debt, including current portion	$ 2,464,343	$ 2,215,458