Unusual Items - Summary of Loss Incurred on Repurchase of Debt Instruments (Parenthetical) (Detail) (Convertible Subordinated Debentures, Bearing Interest at 4.0625% Maturing in December 2034 [Member])	May 31, 2014
Convertible Subordinated Debentures, Bearing Interest at 4.0625% Maturing in December 2034 [Member]
Unusual or Infrequent Item [Line Items]
Debt instrument interest rate stated percentage	4.0625%