Notes Payable - Redemption Prices Expressed as a Percentage of Principal, Plus any Accrued and Unpaid Interest (Detail) (4.00% Debentures due 2031, Convertible Subordinated Debt)	9 Months Ended
	Oct. 31, 2013
Redemption period beginning on April 5, 2016 and ending on March 31, 2017
Debt Instrument [Line Items]
Debentures redemption price	101.143%
Redemption period beginning on April 1, 2017 and ending on March 31, 2018
Debt Instrument [Line Items]
Debentures redemption price	100.571%
Redemption period On April 1, 2018 and thereafter
Debt Instrument [Line Items]
Debentures redemption price	100.00%