Long-Term Debt - Maturities Of Long-Term Debt (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Aug. 14, 2020	Dec. 31, 2019
Debt Instrument [Line Items]
Less than one year	$ 90,882
One to two years	42,937
Two to three years	38,333
Three to four years	8,749
Four to five years	9,186
Over five years	214,645
Gross debt	404,732
Unamortized debt discounts	(45,692)		$ (22,540)
Unamortized debt issuance costs	(9,477)		(7,753)
Total debt	349,563		405,853
Less current maturities	(90,651)		(99,731)
Long-term debt	258,912		306,122
Term Loan Maturing December 2021
Debt Instrument [Line Items]
Less than one year	29,750
One to two years	0
Two to three years	0
Three to four years	0
Four to five years	0
Over five years	0
Gross debt	29,750		33,250
Unamortized debt discounts	0
Unamortized debt issuance costs	(191)
Total debt	29,559
Less current maturities	(29,559)
Long-term debt	0
Convertible Senior Notes Maturing May 2022
Debt Instrument [Line Items]
Less than one year	0
One to two years	35,000
Two to three years	0
Three to four years	0
Four to five years	0
Over five years	0
Gross debt	35,000		125,000
Unamortized debt discounts	(1,325)		(8,000)
Unamortized debt issuance costs	(198)
Total debt	33,477
Less current maturities	0
Long-term debt	33,477
Convertible Senior Notes Maturing September 2023
Debt Instrument [Line Items]
Less than one year	0
One to two years	0
Two to three years	30,000
Three to four years	0
Four to five years	0
Over five years	0
Gross debt	30,000		125,000
Unamortized debt discounts	(2,651)		(14,500)
Unamortized debt issuance costs	(427)
Total debt	26,922
Less current maturities	0
Long-term debt	26,922
Convertible Senior Notes Maturing February 2026
Debt Instrument [Line Items]
Less than one year	0
One to two years	0
Two to three years	0
Three to four years	0
Four to five years	0
Over five years	200,000
Gross debt	200,000	$ 200,000	0
Unamortized debt discounts	(41,716)
Unamortized debt issuance costs	(5,572)
Total debt	152,712
Less current maturities	0
Long-term debt	152,712
MARAD Debt Maturing February 2027
Debt Instrument [Line Items]
Less than one year	7,560
One to two years	7,937
Two to three years	8,333
Three to four years	8,749
Four to five years	9,186
Over five years	14,645
Gross debt	56,410		63,610
Unamortized debt discounts	0
Unamortized debt issuance costs	(3,049)
Total debt	53,361
Less current maturities	(7,560)
Long-term debt	45,801
Nordea Q5000 Loan Maturing January 2021
Debt Instrument [Line Items]
Less than one year	53,572
One to two years	0
Two to three years	0
Three to four years	0
Four to five years	0
Over five years	0
Gross debt	53,572		$ 89,286
Unamortized debt discounts	0
Unamortized debt issuance costs	(40)
Total debt	53,532
Less current maturities	(53,532)
Long-term debt	$ 0