Indebtedness - Carrying Value of Convertible Notes (Detail) - USD ($) $ in Thousands		Jul. 31, 2016	Jan. 31, 2016
Schedule Of Convertible Notes [Line Items]
Net carrying amount		$ 160,618	$ 158,971
Convertible Senior Notes [Member] | 4.25% Convertible Notes [Member]
Schedule Of Convertible Notes [Line Items]
Carrying amount of the equity conversion component		3,106	3,106
Principal amount		69,500	69,500
Unamortized deferred financing fees		(1,286)	(1,523)
Unamortized debt discount	[1]	(5,166)	(6,211)
Net carrying amount		63,048	61,766
Convertible Senior Notes [Member] | 8.0% Convertible Notes [Member]
Schedule Of Convertible Notes [Line Items]
Principal amount		99,898	99,898
Unamortized deferred financing fees		(2,328)	(2,693)
Net carrying amount		$ 97,570	$ 97,205

[1] As of July 31, 2016, the remaining period over which the unamortized debt discount will be amortized is 27 months using an effective interest rate of 9.0%.