Long-Term Debt - Maturities Of Long-Term Debt (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Debt Instrument [Line Items]
Less than one year	$ 70,746
One to two years	8,133
Two to three years	38,538
Three to four years	8,965
Four to five years	209,412
Over five years	9,882
Gross debt	345,676	$ 404,732
Unamortized debt issuance costs	(9,962)
Total debt	335,714
Less: current maturities	(70,492)	(90,651)
Long-term debt	265,222	258,912
Term Loan Maturing December 2021
Debt Instrument [Line Items]
Less than one year	28,000
Gross debt	28,000	29,750
Unamortized debt issuance costs	(95)
Total debt	27,905
Less: current maturities	(27,905)
Convertible Senior Notes Maturing May 2022
Debt Instrument [Line Items]
Less than one year	35,000
Gross debt	35,000	35,000
Unamortized debt issuance costs	(159)
Total debt	34,841
Less: current maturities	(34,841)
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	(402)
Total debt	29,598
Long-term debt	29,598
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	(6,501)
Total debt	193,499
Long-term debt	193,499
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	8,538
Three to four years	8,965
Four to five years	9,412
Over five years	9,882
Gross debt	52,676	$ 56,410
Unamortized debt issuance costs	(2,805)
Total debt	49,871
Less: current maturities	(7,746)
Long-term debt	$ 42,125

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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