Debt (Schedule of Long-term Debt) (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Debt Instrument [Line Items]
Long-term Debt, Gross	$ 475,000	$ 475,000
Less unamortized debt discount (based on imputed interest rate of 10.46%)	(2,668)	(3,387)
Less unamortized debt issuance costs	(7,780)	(9,948)
Long-term Debt, Excluding Current Maturities	464,552	461,665
Senior Notes [Member] \| Senior Notes [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross	$ 300,000	$ 300,000

Amount, before unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but is not limited to, notes payable, bonds payable, commercial loans, mortgage loans, convertible debt, subordinated debt and other types of debt.

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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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Amount, after accumulated amortization, of debt discount.

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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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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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