Redemption Prices Expressed as a Percentage of Principal, Plus any Accrued and Unpaid Interest (Detail) (4.00% Debentures due 2031, Convertible Subordinated Debt)	Oct. 31, 2011
Redemption Period Beginning on April 5, 2016 and ending on March 31, 2017
Debt Instrument [Line Items]
Redemption Price	101.143%
Redemption Period Beginning on April 1, 2017 and ending on March 31, 2018
Debt Instrument [Line Items]
Redemption Price	100.571%
Redemption Period On April 1, 2018 and thereafter
Debt Instrument [Line Items]
Redemption Price	100.00%