Long-Term Debt - Narrative (Detail) - 12 months ended May 31, 2017	USD ($)	JPY (¥)
2.6% and 2.0% Japanese Yen note, maturing August 20, 2001 through November 20, 2020
Debt Instrument [Line Items]
Long-term debt, original principal | ¥		¥ 13,000,000,000
Corporate Bond Payables
Debt Instrument [Line Items]
Percent of aggregate principal amount of the notes to be redeemed	100.00%
Corporate Bond Payables | 2.25% Corporate bond, payable May 1, 2023
Debt Instrument [Line Items]
Long-term debt, original principal	$ 500,000,000
Corporate Bond Payables | 3.63% Corporate bond, payable May 1, 2043
Debt Instrument [Line Items]
Long-term debt, original principal	500,000,000
Corporate Bond Payables | 3.88% Corporate bond, payable November 1, 2045
Debt Instrument [Line Items]
Long-term debt, original principal	1,000,000,000
Notes Payable | 6.20% Promissory note, payable April 1, 2017
Debt Instrument [Line Items]
Long-term debt, original principal	$ 40,000,000
Notes Payable | 2.60% Japanese Yen note, maturing August 20, 2001 through November 20, 2020
Debt Instrument [Line Items]
Long-term debt, original principal | ¥		9,000,000,000
Notes Payable | 2.00% Japanese Yen note, maturing August 20, 2001 through November 20, 2020
Debt Instrument [Line Items]
Long-term debt, original principal | ¥		¥ 4,000,000,000