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Debt - Convertible Senior Notes Due 2021 (Details) |  | 3 Months Ended | 6 Months Ended |
--- | --- | --- | --- | ---
Sep. 15, 2015 USD ($) $ / shares | Jul. 28, 2018 USD ($) | Jul. 29, 2017 USD ($) | Oct. 24, 2015 trading_day | Jul. 28, 2018 USD ($) | Jul. 29, 2017 USD ($) | Jan. 27, 2018 USD ($)
Debt Instrument [Line Items] |  |  |  |  |  |  |
Amortization of debt discount |  |  |  |  | $ 9,422,000 | $ 8,924,000 |
0.75% Convertible Senior Notes Due 2021 |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |
Debt, interest rate (in percent) |  | 0.75% |  |  | 0.75% |  |
Debt intrument, conversion installments amount | $ 1,000 |  |  |  |  |  |
Debt instrument,conversion ratio | 10.3211 |  |  |  |  |  |
Debt instrument, face amount | $ 485,000,000.0 | $ 485,000,000 |  |  | $ 485,000,000 |  | $ 485,000,000
Debt instrument, convertible, conversion price (per share) | $ / shares | $ 96.89 |  |  |  |  |  |
Convertible debt, trading day threshold | trading_day |  |  |  | 20 |  |  |
Convertible debt, consecutive trading day threshold | trading_day |  |  |  | 30 |  |  |
Convertible debt, percentage of stock trigger price threshold |  |  |  | 130.00% |  |  |
Debt instrument conversion trigger price | $ / shares | $ 125.96 |  |  |  |  |  |
Convertible debt, measurement period for percentage of product sale price of common stock and applicable conversion threshold |  |  |  | 98.00% |  |  |
Convertible debt, comparable yield |  | 5.50% |  |  |  |  |
Amortization of debt discount |  | $ 4,800,000 | $ 4,500,000 |  | 9,400,000 | $ 8,900,000 |
Convertible Debt |  | 412,568,000 |  |  | 412,568,000 |  | 402,249,000
Unamortized discount |  | 65,477,000 |  |  | 65,477,000 |  | 74,899,000
Debt issuance cost |  | 6,955,000 |  |  | 6,955,000 |  | 7,852,000
Standby Letters of Credit |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |
Line of credit |  | $ 0 |  |  | $ 0 |  | $ 0

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- Definition Debt Instrument, Convertible, Measurement Period, Threshold Percentage of Product of Sale Price of Common Stock and Applicable Conversion Rate + References No definition available. + Details
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- Definition Amount of noncash expense included in interest expense to amortize debt discount and premium associated with the related debt instruments. Excludes amortization of financing costs. Alternate captions include noncash interest expense. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 835 -SubTopic 30 -Section 45 -Paragraph 1A -URI http://asc.fasb.org/extlink&oid=114775744&loc=d3e28541-108399 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=109223946&loc=d3e3602-108585 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section S99 -Paragraph 2 -Subparagraph (SX 210.5-03.8) -URI http://asc.fasb.org/extlink&oid=115205541&loc=SL114868664-224227 + Details
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- Definition The value of the financial instrument(s) that the original debt is being converted into in a noncash (or part noncash) transaction. "Part noncash" refers to that portion of the transaction not resulting in cash receipts or cash payments in the period. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 50 -Paragraph 3 -URI http://asc.fasb.org/extlink&oid=98513485&loc=d3e4304-108586 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 50 -Paragraph 5 -URI http://asc.fasb.org/extlink&oid=98513485&loc=d3e4332-108586 + Details
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- Definition Ratio applied to the conversion of debt instrument into equity with equity shares divided by debt principal amount. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 505 -SubTopic 10 -Section 50 -Paragraph 7 -URI http://asc.fasb.org/extlink&oid=109259400&loc=d3e21521-112644 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 505 -SubTopic 10 -Section 50 -Paragraph 6 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=109259400&loc=d3e21506-112644 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.22(a)(5)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 505 -SubTopic 10 -Section 50 -Paragraph 3 -URI http://asc.fasb.org/extlink&oid=109259400&loc=d3e21475-112644 + Details
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- Definition Threshold period of specified consecutive trading days within which common stock price to conversion price of convertible debt instrument must exceed threshold percentage for specified number of trading days to trigger conversion feature. + References No definition available. + Details
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- Definition The carrying value as of the balance sheet date of the current and noncurrent portions of long-term obligations drawn from a line of credit, which is a bank's commitment to make loans up to a specific amount. Examples of items that might be included in the application of this element may consist of letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to a maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. Includes short-term obligations that would normally be classified as current liabilities but for which (a) postbalance sheet date issuance of a long term obligation to refinance the short term obligation on a long term basis, or (b) the enterprise has entered into a financing agreement that clearly permits the enterprise to refinance the short-term obligation on a long term basis and the following conditions are met (1) the agreement does not expire within 1 year and is not cancelable by the lender except for violation of an objectively determinable provision, (2) no violation exists at the BS date, and (3) the lender has entered into the financing agreement is expected to be financially capable of honoring the agreement. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02(22)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-03(16)) -URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-03(16)) -URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910 + Details
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