Short-Term and Long-Term Debt - Summary of Notes Due 2020 (Details) (USD $) In Thousands, unless otherwise specified	Jan. 31, 2015
Debt Instrument [Line Items]
Liability component, Unamortized discount	$ 1,110
Convertible Notes Payable \| 4.0% Convertible Senior Notes due December 15, 2020
Debt Instrument [Line Items]
Liability component, Principal balance	194,879
Liability component, Unamortized discount	14,536
Liability component, Net carrying amount	180,343
Equity component, Net carrying amount	$ 43,131

Amount of long-term debt before deduction of unamortized discount or premium. Includes, but is not limited to, notes payable, bonds payable, commercial loans, mortgage loans, convertible debt, subordinated debt and other types of debt, with initial maturities beyond one year or the normal operating cycle, if longer.

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The carrying amount of the equity component of convertible debt which may be settled in cash upon conversion.

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The amount of debt discount that was originally recognized at the issuance of the instrument that has yet to be amortized.

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Carrying amount of long-term debt, net of unamortized discount or premium, including current and noncurrent amounts. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

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