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

Reference 1: http://www.xbrl.org/2003/role/presentationRef
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- Definition

Contractual interest rate for funds borrowed, under the debt agreement.

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-Name Accounting Standards Codification
-Topic 210
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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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- Definition

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

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Amount, after accumulated amortization, of debt issuance costs. Includes, but is not limited to, legal, accounting, underwriting, printing, and registration costs.

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The effective interest rate at the end of the reporting period.

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Amount after unamortized (discount) premium and debt issuance costs of long-term debt classified as noncurrent and excluding amounts to be repaid within one year or the normal operating cycle, if longer. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

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Long-Term Debt - Components Table (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017	Apr. 04, 2017	Jul. 28, 2014	Nov. 19, 2013
Long-Term Debt
Long-term debt	$ 915,586	$ 917,721
Revolving Credit Facility
Long-Term Debt
Long-term debt	$ 117,168	$ 122,461
Weighted average interest rate, as a percent	3.40%	3.20%
Convertible Senior Notes 1.00 percent due 2020
Long-Term Debt
Long-term debt	$ 254,797	$ 251,973
Interest rate, as a percentage	1.00%	1.00%
Aggregate principle amount	$ 287,500				$ 287,500
Unamortized discount and capitalized debt issuance costs	32,703	$ 35,527
Senior Notes 5.125 Percent Due 2022
Long-Term Debt
Long-term debt	$ 248,210	$ 248,038
Interest rate, as a percentage	5.125%	5.125%
Aggregate principle amount	$ 250,000			$ 250,000
Capitalized debt issuance costs	1,800	$ 2,000
Senior Notes 5.50 Percent Due 2025
Long-Term Debt
Long-term debt	295,411	295,249
Interest rate, as a percentage			5.50%
Aggregate principle amount	300,000		$ 300,000
Capitalized debt issuance costs	$ 4,600	$ 4,800