Convertible Senior Notes, Net - Schedule of Senior Notes (Detail) - USD ($) |
3 Months Ended | |||||
|---|---|---|---|---|---|---|
Apr. 30, 2017 |
Jan. 31, 2017 |
Jun. 30, 2013 |
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| Convertible Debt [Abstract] | ||||||
| Net carrying amount | $ 541,393,000 | $ 534,423,000 | [1] | |||
| 2018 Notes | ||||||
| Convertible Debt [Abstract] | ||||||
| Principal | 350,000,000 | 350,000,000 | $ 350,000,000 | |||
| Unamortized debt discount | (20,336,000) | (24,380,000) | ||||
| Net carrying amount before unamortized debt issuance costs | 329,664,000 | 325,620,000 | ||||
| Unamortized debt issuance costs | (1,698,000) | (2,050,000) | ||||
| Net carrying amount | 327,966,000 | 323,570,000 | ||||
| Carrying amount of the equity component | 74,892,000 | 74,892,000 | ||||
| Equity issuance costs | 2,000,000 | |||||
| 2020 Notes | ||||||
| Convertible Debt [Abstract] | ||||||
| Principal | 250,000,000 | 250,000,000 | $ 250,000,000 | |||
| Unamortized debt discount | (34,414,000) | (36,820,000) | ||||
| Net carrying amount before unamortized debt issuance costs | 215,586,000 | 213,180,000 | ||||
| Unamortized debt issuance costs | (2,159,000) | (2,327,000) | ||||
| Net carrying amount | 213,427,000 | 210,853,000 | ||||
| Carrying amount of the equity component | 66,007,000 | $ 66,007,000 | ||||
| Equity issuance costs | $ 2,000,000 | |||||
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