Indebtedness - Carrying Value of Convertible Notes (Detail) - USD ($) $ in Thousands |
Apr. 30, 2016 |
Jan. 31, 2016 |
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|---|---|---|---|---|
| Schedule Of Convertible Notes [Line Items] | ||||
| Net carrying amount | $ 159,783 | $ 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 | (1,407) | (1,523) | ||
| Unamortized debt discount | [1] | (5,695) | (6,211) | |
| Net carrying amount | 62,398 | 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 | (2,513) | (2,693) | ||
| Net carrying amount | $ 97,385 | $ 97,205 | ||
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