Short Term Borrowings and Credit Lines - Additional Information (Detail) (USD $)	1 Months Ended	12 Months Ended
	Nov. 01, 2011	May 31, 2014	May 31, 2013
Debt Instrument [Line Items]
Notes payable (Note 7)		$ 167,000,000	$ 98,000,000
Amounts outstanding under commercial paper program		0	0
Revolving credit facility, borrowing capacity	1,000,000,000
Revolving credit facility, optional maximum borrowing capacity	1,500,000,000.0
Revolving credit facility, optional extension period (in years)	1 year
Revolving credit facility, fee		0.055%
Line of credit facility, amount outstanding		$ 0	$ 0
Sojitz America Accounts Payable
Debt Instrument [Line Items]
Accounts payable, due date period (in days)		60 days
60-day London Interbank Offered Rate (LIBOR)
Debt Instrument [Line Items]
Basis spread on variable rate, above LIBOR		0.445%
60-day London Interbank Offered Rate (LIBOR) | Sojitz America Accounts Payable
Debt Instrument [Line Items]
Basis spread on variable rate, above LIBOR		0.75%