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Long-Term Debt - Schedule Of Long-Term Debt (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Jun. 30, 2017	Dec. 31, 2016	Nov. 01, 2016	Mar. 31, 2012
Debt Instrument [Line Items]
Carrying value	$ 520,329
Unamortized debt discounts	(14,406)		$ (19,094)
Unamortized debt issuance costs	(10,296)		(11,963)
Total debt	495,627		625,967
Less current maturities	(109,861)		(67,571)
Long-term debt	385,766		558,396
Former Term Loan Maturing June 2018 [Member]
Debt Instrument [Line Items]
Carrying value	0		192,258
Term Loan Maturing June 2020 [Member]
Debt Instrument [Line Items]
Carrying value	97,500	$ 100,000	0
Unamortized debt discounts	0
Unamortized debt issuance costs	(1,658)
Less current maturities	(7,500)
Long-term debt	88,342
Convertible Senior Notes Maturing May 2022 [Member]
Debt Instrument [Line Items]
Carrying value	125,000		125,000	$ 125,000
Unamortized debt discounts	(13,876)		(16,500)	$ (16,900)
Unamortized debt issuance costs	(2,295)
Less current maturities	0
Long-term debt	108,829
Convertible Senior Notes Maturing March 2032 [Member]
Debt Instrument [Line Items]
Carrying value	60,115		60,115		$ 200,000
Unamortized debt discounts	(530)		(2,600)		$ (35,400)
Unamortized debt issuance costs	(46)
Less current maturities	(60,115)
Long-term debt	(576)
MARAD Debt Maturing February 2027 [Member]
Debt Instrument [Line Items]
Carrying value	77,000		83,222
Unamortized debt discounts	0
Unamortized debt issuance costs	(4,513)
Less current maturities	(6,532)
Long-term debt	65,955
Nordea Q5000 Loan Maturing April 2020 [Member]
Debt Instrument [Line Items]
Carrying value	160,714		$ 196,429
Unamortized debt discounts	0
Unamortized debt issuance costs	(1,784)
Less current maturities	(35,714)
Long-term debt	$ 123,216