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	6 Months Ended
	Jul. 31, 2016
Redemption period beginning on April 5, 2016 and ending on March 31, 2017
Debt Instrument
Debentures redemption price	101.143%
Redemption period beginning on April 1, 2017 and ending on March 31, 2018
Debt Instrument
Debentures redemption price	100.571%
Redemption period beginning on April 1, 2018 and thereafter
Debt Instrument
Debentures redemption price	100.00%