Fair Value Measurements - Carrying Values and Estimated Fair Values of Long-Term Debt (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014	Mar. 31, 2012
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying Value	$ 776,291
Unamortized debt discount	14,963
Term Loan Maturing June 2018 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying Value	255,000	$ 277,500
Fair Value	248,467	270,563
Unamortized debt discount	0
Nordea Q5000 Loan 2020 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying Value	232,143	0
Fair Value	221,553	0
Unamortized debt discount	0
MARAD Debt 2027 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying Value	89,148	94,792
Fair Value	104,897	104,830
Unamortized debt discount	0
Convertible Senior Notes 2032 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying Value	200,000	200,000	$ 200,000
Fair Value	150,250	222,900
Unamortized debt discount	14,963	20,920	$ 35,400
Loan Notes [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying Value	776,291	572,292
Fair Value	$ 725,167	$ 598,293