Long-Term Debt (Maturities Of Long-Term Debt) (Details) - USD ($)	1 Months Ended	9 Months Ended
	Aug. 31, 2002	Sep. 30, 2015	Dec. 31, 2014	Mar. 31, 2012
Debt Instrument [Line Items]
Less than one year		$ 71,640,000
One to two years		71,937,000
Two to three years		244,746,000
Three to four years		42,572,000
Four to five years		105,414,000
Over five years		256,410,000
Total debt		792,719,000
Current maturities		(71,640,000)	$ (28,144,000)
Long-term Debt, Excluding Current Maturities, Gross		721,079,000
Long-term debt, less current maturities		704,568,000	523,228,000
Unamortized debt discount		(16,511,000)	(20,900,000)
Term Loan Maturing June 2018 [Member]
Debt Instrument [Line Items]
Less than one year		30,000,000
One to two years		30,000,000
Two to three years		202,500,000
Three to four years		0
Total debt		262,500,000	277,500,000
Current maturities		(30,000,000)
Long-term Debt, Excluding Current Maturities, Gross		232,500,000
Long-term debt, less current maturities		232,500,000
Nordea Q5000 Loan [Member]
Debt Instrument [Line Items]
Less than one year		35,714,000
One to two years		35,715,000
Two to three years		35,714,000
Three to four years		35,714,000
Four to five years		98,214,000
Total debt		241,071,000	0
Current maturities		(35,714,000)
Long-term Debt, Excluding Current Maturities, Gross		205,357,000
Long-term debt, less current maturities		205,357,000
MARAD Debt [Member]
Debt Instrument [Line Items]
Less than one year		5,926,000
One to two years		6,222,000
Two to three years		6,532,000
Three to four years		6,858,000
Four to five years		7,200,000
Over five years		56,410,000
Total debt		89,148,000	$ 94,792,000
Current maturities		(5,926,000)
Long-term Debt, Excluding Current Maturities, Gross		83,222,000
Long-term debt, less current maturities		83,222,000
Debt instrument, maturity date	February 2027
Convertible Senior Notes 2032 [Member]
Debt Instrument [Line Items]
Over five years		200,000,000
Total debt		200,000,000		$ 200,000,000
Long-term Debt, Excluding Current Maturities, Gross		200,000,000
Long-term debt, less current maturities		183,489,000
Unamortized debt discount		$ (16,511,000)		$ (35,400,000)
Debt instrument, maturity date		March 2032