LONG-TERM DEBT - 1.50% CONVERTIBLE SENIOR NOTES (Details)
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3 Months Ended |
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Jun. 18, 2014
USD ($)
shares
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Apr. 30, 2018
USD ($)
$ / shares
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Jan. 31, 2018
USD ($)
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| Debt Instrument |
|
|
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| Common Stock Issued (in shares) | shares |
5,750,000
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| 1.50% Convertible Senior Notes |
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| Debt Instrument |
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| Principal Amount - 1.50% Convertible Senior Notes |
$ 400,000,000
|
$ 400,000,000
|
$ 400,000,000
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| Coupon Interest Rate |
1.50%
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|
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| Proceeds from issuance of convertible notes, net of underwriting discounts |
$ 391,900,000
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| 1.50% Convertible Notes - Conversion Ratio |
|
15.5129
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| 1.50% Convertible Notes - Base Principal Amount For Conversion Rate |
|
$ 1,000
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| 1.50% Convertible Notes - Conversion Price (in dollars per share) | $ / shares |
|
$ 64.46
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| 1.50% Convertible Notes - Number of Common Shares (in shares) |
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6,205,000
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| 1.50% Convertible Notes - Carrying Value of Debt Component |
319,900,000
|
$ 357,200,000
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| 1.50% Convertible Notes - Carrying Value of Equity Component |
$ 80,100,000
|
78,200,000
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| Assumed Nonconvertible Debt Interest Rate |
5.00%
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| Unamortized Debt Discount |
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39,100,000
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| Unamortized Debt Issuance Expense |
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$ 3,700,000
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| Effective interest rate (as a percent) |
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5.29%
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| Debt Component of Convertible Note Issuance Costs |
$ 7,600,000
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| Adjustment To Additional Paid In Capital Debt Issuance Cost |
$ 1,900,000
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