Fair Value of Financial Instruments - Estimated Fair Value and Carrying Value of 2019 and 2020 Notes (Detail) - USD ($) $ in Thousands	Aug. 01, 2015	Jan. 31, 2015
Convertible Senior Notes Due 2019 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Convertible senior notes, Carrying Value	$ 294,024	$ 287,487
Convertible Senior Notes Due 2020 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Convertible senior notes, Carrying Value	217,747
Level 2 [Member] | Convertible Senior Notes Due 2019 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Convertible senior notes, Fair Value	272,460	$ 260,444
Level 2 [Member] | Convertible Senior Notes Due 2020 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Convertible senior notes, Fair Value	$ 214,793