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.

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Including the current and noncurrent portions, carrying amount of debt identified as being convertible into another form of financial instrument (typically the entity's common stock) as of the balance sheet date, which originally required full repayment more than twelve months after issuance or greater than the normal operating cycle of the company.

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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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Face (par) amount of debt instrument at time of issuance.

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Amount, after accumulated amortization, of debt discount.

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Amount of unamortized debt discount (premium) and debt issuance costs.

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The remaining balance of debt issuance expenses that were capitalized and are being amortized against income over the lives of the respective bond issues. This does not include the amounts capitalized as part of the cost of the utility plant or asset.

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Debt - Components of the Convertible Notes (Details) - USD ($)	3 Months Ended
	Apr. 28, 2018	Apr. 29, 2017	Jan. 27, 2018	Sep. 15, 2015
Debt Instrument [Line Items]
Equity component of 0.75% senior convertible notes due 2021, net	$ 112,600,000
Amortization of debt discount	4,672,000	$ 4,425,000
Estimate of Fair Value Measurement
Debt Instrument [Line Items]
Debt instrument, face amount	614,059,000		$ 659,649,000
Less: Debt discount and debt issuance costs	(77,639,000)		(82,751,000)
Net carrying amount of Notes	536,420,000		576,898,000
0.75% Convertible Senior Notes Due 2021
Debt Instrument [Line Items]
Debt instrument, face amount	485,000,000		485,000,000	$ 485,000,000.0
Debt Instrument, Unamortized Discount	(70,227,000)		(74,899,000)
Debt issuance cost	(7,412,000)		(7,852,000)
Net carrying amount of Notes	407,361,000		$ 402,249,000
Amortization of debt discount	$ 4,700,000	$ 4,400,000