Long-Term Debt - Maturities Of Long-Term Debt (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019	Jun. 28, 2019
Debt Instrument [Line Items]
Less than one year	$ 82,306
One to two years	160,746
Two to three years	8,133
Three to four years	133,538
Four to five years	8,965
Over five years	19,294
Gross debt	412,982
Unamortized debt discounts	(19,224)
Unamortized debt issuance costs	(6,896)
Total debt	386,862
Less: current maturities	(82,028)	$ (99,731)
Long-term debt	304,834	306,122
Term Loan Maturing December 2021
Debt Instrument [Line Items]
Less than one year	3,500
One to two years	28,000
Two to three years	0
Three to four years	0
Four to five years	0
Over five years	0
Gross debt	31,500	33,250	$ 35,000
Unamortized debt discounts	0
Unamortized debt issuance costs	(286)
Total debt	31,214
Less: current maturities	(3,500)
Long-term debt	27,714
Convertible Senior Notes Maturing May 2022
Debt Instrument [Line Items]
Less than one year	0
One to two years	125,000
Two to three years	0
Three to four years	0
Four to five years	0
Over five years	0
Gross debt	125,000	125,000
Unamortized debt discounts	(6,395)	(8,000)
Unamortized debt issuance costs	(971)
Total debt	117,634
Less: current maturities	0
Long-term debt	117,634
Convertible Senior Notes Maturing September 2023
Debt Instrument [Line Items]
Less than one year	0
One to two years	0
Two to three years	0
Three to four years	125,000
Four to five years	0
Over five years	0
Gross debt	125,000	125,000
Unamortized debt discounts	(12,829)	(14,500)
Unamortized debt issuance costs	(2,068)
Total debt	110,103
Less: current maturities	0
Long-term debt	110,103
MARAD Debt Maturing February 2027
Debt Instrument [Line Items]
Less than one year	7,378
One to two years	7,746
Two to three years	8,133
Three to four years	8,538
Four to five years	8,965
Over five years	19,294
Gross debt	60,054	63,610
Unamortized debt discounts	0
Unamortized debt issuance costs	(3,293)
Total debt	56,761
Less: current maturities	(7,378)
Long-term debt	49,383
Nordea Q5000 Loan Maturing January 2021
Debt Instrument [Line Items]
Less than one year	71,428
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	71,428	$ 89,286
Unamortized debt discounts	0
Unamortized debt issuance costs	(278)
Total debt	71,150
Less: current maturities	(71,150)
Long-term debt	$ 0