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Long-Term Debt - Schedule Of Long-Term Debt (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Jun. 28, 2019	Dec. 31, 2018	Mar. 20, 2018	Nov. 01, 2016
Debt Instrument [Line Items]
Principal amount	$ 436,146
Unamortized debt discounts	(22,540)		$ (28,802)
Unamortized debt issuance costs	(7,753)		(10,044)
Total debt	405,853		440,315
Less current maturities	(99,731)		(47,252)
Long-term debt	306,122		393,063
Term Loan Maturing June 2020
Debt Instrument [Line Items]
Principal amount	0		33,693
Term Loan Maturing December 2021
Debt Instrument [Line Items]
Principal amount	33,250	$ 35,000	0
Unamortized debt discounts	0
Unamortized debt issuance costs	(381)
Total debt	32,869
Less current maturities	(3,500)
Long-term debt	29,369
Convertible Senior Notes Maturing May 2022
Debt Instrument [Line Items]
Principal amount	125,000		125,000		$ 125,000
Unamortized debt discounts	(7,999)		(11,000)		$ (16,900)
Unamortized debt issuance costs	(1,236)
Total debt	115,765
Less current maturities	0
Long-term debt	115,765
Convertible Senior Notes Maturing September 2023
Debt Instrument [Line Items]
Principal amount	125,000		125,000	$ 125,000
Unamortized debt discounts	(14,541)		(17,800)	$ (20,100)
Unamortized debt issuance costs	(2,344)
Total debt	108,115
Less current maturities	0
Long-term debt	108,115
MARAD Debt Maturing February 2027
Debt Instrument [Line Items]
Principal amount	63,610		70,468
Unamortized debt discounts	0
Unamortized debt issuance costs	(3,537)
Total debt	60,073
Less current maturities	(7,200)
Long-term debt	52,873
Nordea Q5000 Loan Maturing April 2020
Debt Instrument [Line Items]
Principal amount	89,286		$ 125,000
Unamortized debt discounts	0
Unamortized debt issuance costs	(255)
Total debt	89,031
Less current maturities	(89,031)
Long-term debt	$ 0