Long-Term Debt - Maturities Of Long-Term Debt (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019	Jun. 28, 2019	Mar. 20, 2018	Nov. 01, 2016
Debt Instrument [Line Items]
Less than one year	$ 91,235
One to two years	36,621
Two to three years	133,133
Three to four years	133,538
Four to five years	8,965
Over five years	19,294
Gross debt	422,786
Unamortized debt discounts	(20,907)
Unamortized debt issuance costs	(7,458)
Total debt	394,421
Less: current maturities	(90,837)	$ (99,731)
Long-term debt	303,584	306,122
Term Loan Maturing December 2021
Debt Instrument [Line Items]
Less than one year	3,500
One to two years	28,875
Two to three years	0
Three to four years	0
Four to five years	0
Over five years	0
Gross debt	32,375	33,250	$ 35,000
Unamortized debt discounts	0
Unamortized debt issuance costs	(334)
Total debt	32,041
Less: current maturities	(3,500)
Long-term debt	28,541
Convertible Senior Notes Maturing May 2022
Debt Instrument [Line Items]
Less than one year	0
One to two years	0
Two to three years	125,000
Three to four years	0
Four to five years	0
Over five years	0
Gross debt	125,000	125,000			$ 125,000
Unamortized debt discounts	(7,207)	(8,000)			$ (16,900)
Unamortized debt issuance costs	(1,103)
Total debt	116,690
Less: current maturities	0
Long-term debt	116,690
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		$ 125,000
Unamortized debt discounts	(13,700)	(14,500)		$ (20,100)
Unamortized debt issuance costs	(2,208)
Total debt	109,092
Less: current maturities	0
Long-term debt	109,092
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	(3,415)
Total debt	56,639
Less: current maturities	(7,378)
Long-term debt	49,261
Nordea Q5000 Loan Maturing January 2021
Debt Instrument [Line Items]
Less than one year	80,357
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	80,357	$ 89,286
Unamortized debt discounts	0
Unamortized debt issuance costs	(398)
Total debt	79,959
Less: current maturities	(79,959)
Long-term debt	$ 0