Long-Term Debt - Maturities Of Long-Term Debt (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Debt Instrument [Line Items]
Less than one year	$ 36,621
One to two years	43,133
Two to three years	38,539
Three to four years	8,965
Four to five years	209,412
Over five years	9,881
Gross debt	346,551	$ 404,732
Unamortized debt issuance costs	(10,513)
Total debt	336,038
Less: current maturities	(36,478)	(90,651)
Long-term debt	299,560	258,912
Term Loan Maturing December 2021
Debt Instrument [Line Items]
Less than one year	28,875
Gross debt	28,875	29,750
Unamortized debt issuance costs	(143)
Total debt	28,732
Less: current maturities	(28,732)
Convertible Senior Notes Maturing May 2022
Debt Instrument [Line Items]
One to two years	35,000
Gross debt	35,000	35,000
Unamortized debt issuance costs	(206)
Total debt	34,794
Long-term debt	34,794
Convertible Senior Notes Maturing September 2023
Debt Instrument [Line Items]
Two to three years	30,000
Gross debt	30,000	30,000
Unamortized debt issuance costs	(445)
Total debt	29,555
Long-term debt	29,555
Convertible Senior Notes Maturing February 2026
Debt Instrument [Line Items]
Four to five years	200,000
Gross debt	200,000	200,000
Unamortized debt issuance costs	(6,792)
Total debt	193,208
Long-term debt	193,208
MARAD Debt Maturing February 2027
Debt Instrument [Line Items]
Less than one year	7,746
One to two years	8,133
Two to three years	8,539
Three to four years	8,965
Four to five years	9,412
Over five years	9,881
Gross debt	52,676	$ 56,410
Unamortized debt issuance costs	(2,927)
Total debt	49,749
Less: current maturities	(7,746)
Long-term debt	$ 42,003

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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