Debt (Debt Table) (Details) - USD ($)	Jun. 30, 2020	Dec. 31, 2019	Sep. 15, 2016
Debt Instrument [Line Items]
Outstanding borrowings	$ 350,000,000	$ 350,000,000
Unamortized debt issuance costs related to senior secured notes	(3,550,000)	(3,968,000)
Total debt	346,450,000	346,032,000
Less: Current portion of long-term debt	0	0
Long-term debt	346,450,000	346,032,000
Senior secured notes, due 2024 [Member]
Debt Instrument [Line Items]
Outstanding borrowings	350,000,000	350,000,000	$ 350,000,000.0
Revolving credit agreement [Member]
Debt Instrument [Line Items]
Outstanding borrowings	$ 0	$ 0

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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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. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

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Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt, classified as current. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

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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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