Business and Segment Reporting (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012		Dec. 31, 2012
Shipping revenues	$ 247,438	$ 292,378
Time charter equivalent revenues	195,645	214,029
Depreciation and amortization	43,271	49,262
Income/(loss) from vessel operations	20,547	(1,707)
Equity in income of affiliated companies	10,290	6,908	[1]
Total assets	4,031,162	4,156,332	[2]	4,043,535
Expenditures for vessels	12,203	29,343
Payments for drydocking	3,834	10,829
International Crude Tankers Segment [Member]
Shipping revenues	67,648	94,441
Time charter equivalent revenues	52,770	75,500
Depreciation and amortization	18,299	20,371
Gain/(loss) on disposal of vessels	0	(394)
Income/(loss) from vessel operations	(6,811)	(8,619)
Equity in income of affiliated companies	7,687	4,450	[3]
Investments in affiliated companies	249,183	232,866	[3]
Total assets	1,710,728	1,910,431	[3]
Expenditures for vessels	1,637	16,819
Payments for drydocking	489	4,280
International Product Carriers Segment [Member]
Shipping revenues	72,669	91,423
Time charter equivalent revenues	45,888	46,707
Depreciation and amortization	6,992	10,796
Gain/(loss) on disposal of vessels	0	0
Income/(loss) from vessel operations	4,670	(11,295)
Equity in income of affiliated companies	0	0	[3]
Investments in affiliated companies	4,501	3,855	[3]
Total assets	603,657	835,122	[3]
Expenditures for vessels	10,571	12,238
Payments for drydocking	290	2,920
International Other Segment [Member]
Shipping revenues	1,077	3,165
Time charter equivalent revenues	1,064	3,140
Depreciation and amortization	853	1,489
Gain/(loss) on disposal of vessels	6	7
Income/(loss) from vessel operations	(858)	(506)
Equity in income of affiliated companies	2,121	2,116	[3]
Investments in affiliated companies	10,864	5,773	[3]
Total assets	11,072	12,146	[3]
Expenditures for vessels	(5)	3
Payments for drydocking	0	0
Us Flag [Member]
Shipping revenues	106,044	103,349
Time charter equivalent revenues	95,923	88,682
Depreciation and amortization	17,127	16,606
Gain/(loss) on disposal of vessels	(28)	493
Income/(loss) from vessel operations	23,546	18,713
Equity in income of affiliated companies	482	342	[3]
Investments in affiliated companies	411	392	[3]
Total assets	1,103,300	1,121,448	[3]
Expenditures for vessels	0	283
Payments for drydocking	3,055	3,629
Reportable Segment [Member]
Shipping revenues	247,438	292,378
Time charter equivalent revenues	195,645	214,029
Depreciation and amortization	43,271	49,262
Gain/(loss) on disposal of vessels	(22)	106
Income/(loss) from vessel operations	20,547	(1,707)
Equity in income of affiliated companies	10,290	6,908	[3]
Investments in affiliated companies	264,959	242,886	[3]
Total assets	3,428,757	3,879,147	[3]
Expenditures for vessels	12,203	29,343
Payments for drydocking	$ 3,834	$ 10,829

[1] Equity in income of affiliated companies has been restated for the three months ended March 31, 2012 as more fully described in Note 2.

[2] Total assets have been restated as of March 31, 2012 as more fully described in Note 2.

[3] Equity in income of affiliated companies has been restated for the three months ended March 31, 2012 and investments in affiliated companies and total assets have been restated as of March 31, 2012 as more fully described in Note 2.