CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Shipping Revenues:
Time charter revenues	$ 266,193,000	$ 372,149,000	$ 385,206,000
Voyage charter revenues	124,233,000	90,271,000	81,666,000
Shipping revenues	390,426,000	462,420,000	466,872,000
Operating Expenses:
Voyage expenses	29,390,000	16,260,000	17,814,000
Vessel expenses	135,991,000	140,696,000	138,179,000
Charter hire expenses	91,587,000	91,947,000	91,875,000
Depreciation and amortization	58,673,000	89,563,000	76,851,000
General and administrative	27,493,000	41,608,000	61,540,000
Severance costs	16,000	12,996,000	0
Loss on disposal of vessels and other property, including impairments	13,200,000	104,532,000	207,000
Total operating expenses	356,350,000	497,602,000	386,466,000
Income/(loss) from vessel operations	34,076,000	(35,182,000)	80,406,000
Equity in income of affiliated companies	3,747,000	3,642,000	3,783,000
Operating income/(loss)	37,823,000	(31,540,000)	84,189,000
Other expense	(1,881,000)	(2,391,000)	(26,239,000)
Income/(loss) before interest expense, reorganization items and income taxes	35,942,000	(33,931,000)	57,950,000
Interest expense	(37,401,000)	(43,151,000)	(70,365,000)
Loss from continuing operations before reorganization items, net and income taxes	(1,459,000)	(77,082,000)	(12,415,000)
Reorganization items, net	(190,000)	10,925,000	(8,052,000)
Loss from continuing operations before income taxes	(1,649,000)	(66,157,000)	(20,467,000)
Income tax benefit from continuing operations	57,627,000	65,098,000	101,032,000
Net income/(loss) from continuing operations	55,978,000	(1,059,000)	80,565,000
(Loss)/income from discontinued operations	0	(292,555,000)	203,395,000
Net income/(loss)	55,978,000	(293,614,000)	283,960,000
Other Comprehensive Income (Loss), Net of Tax [Abstract]
Net change in unrealized gains on cash flow hedges	907,000	10,311,000	6,927,000
Defined Benefit Plans and Other Postretirement Benefit Plans Disclosures [Abstract]
Net change in unrecognized prior service costs	(157,000)	(60,000)	(211,000)
Net change in unrecognized actuarial losses	948,000	(3,295,000)	3,203,000
Other comprehensive income	1,698,000	6,956,000	9,919,000
Comprehensive income/(loss)	57,676,000	(286,658,000)	293,879,000
Common Class A [Member]
Operating Expenses:
Net income/(loss) from continuing operations	55,957,000	(1,002,000)	79,424,000
(Loss)/income from discontinued operations	$ 0	$ (295,001,000)	$ 200,515,000
Weighted Average Number of Common Shares Outstanding:
Weighted average common shares outstanding, basic	87,834,769	90,949,577	95,584,559
Weighted average common shares outstanding, diluted	88,082,978	90,949,577	95,629,090
Per Share Amounts:
Basic and Diluted net income/(loss) per share, continuing operations	$ 0.64	$ (0.01)	$ 0.83
Basic and Diluted net income/(loss) per share, discontinued operations	0.00	(3.24)	2.10
Basic and diluted net income/(loss)	$ 0.64	$ (3.25)	$ 2.93
Common Class B and Common Stock [Member]
Weighted Average Number of Common Shares Outstanding:
Weighted average common shares outstanding, basic	0	533,758	1,320,337
Weighted average common shares outstanding, diluted	0	533,758	1,320,337
Common Class B [Member]
Operating Expenses:
Net income/(loss) from continuing operations	$ 0	$ (57,000)	$ 1,097,000
(Loss)/income from discontinued operations	$ 0	$ 2,426,000	$ 2,770,000
Weighted Average Number of Common Shares Outstanding:
Weighted average common shares outstanding, basic	0	533,758	1,320,337
Weighted average common shares outstanding, diluted	0	533,758	1,320,337
Per Share Amounts:
Basic and Diluted net income/(loss) per share, continuing operations	$ 0.00	$ (0.11)	$ 0.83
Basic and Diluted net income/(loss) per share, discontinued operations	0.00	4.54	2.10
Basic and diluted net income/(loss)	$ 0.00	$ 4.43	$ 2.93