Acquisitions (Details) (USD $)	3 Months Ended					3 Months Ended				3 Months Ended
	Mar. 31, 2012	Mar. 31, 2013		Dec. 31, 2012		Mar. 31, 2013 U.S. United Ocean Services, LLC Acquisition [Member]	Dec. 31, 2012 U.S. United Ocean Services, LLC Acquisition [Member]	Nov. 30, 2012 U.S. United Ocean Services, LLC Acquisition [Member] Handysizebulker Tugbarge Ton		Mar. 31, 2013 Frascati Shops, Inc. and Tower, LLC [Member]	Sep. 30, 2012 Frascati Shops, Inc. and Tower, LLC [Member]	Aug. 06, 2012 Frascati Shops, Inc. and Tower, LLC [Member]
Business Acquisition [Line Items]
Acquisition date						Nov. 30, 2012				Aug. 06, 2012
Subsidiary ownership interest acquired (in hundredths)								100.00%
Amount of total consideration								$ 114,700,000				$ 4,500,000
Cash payment included in purchase price								112,200,000				623,000
Post-closing settlement payment								2,500,000
Acquisition expenses							1,800,000				40,000
Weight of U.S. Flag Jones Act dry bulk fleet								131,000
Number of handysize bulkers controlled by acquiree								2
Number of tug/barge units controlled by acquiree								4
Assumption of miscellaneous payables												383,000
Summary of the amounts recognized for assets acquired and liabilities assumed [Abstract]
Working Capital including Cash Acquired								8,512,000				18,000
Inventory								6,510,000				231,000
Property, Plant, & Equipment								60,037,000				3,411,000
Identifiable Intangible Assets								45,131,000				490,000
Total Assets Acquired								120,190,000				4,150,000
Misc. Payables & Accrued Expenses								(5,469,000)				(412,000)
Other Long Term Liability								(1,945,000)				(3,490,000)
Deferred Tax Liability												(453,000)
Total Liabilities Assumed								(7,414,000)				(4,355,000)
Net Assets Acquired and Liabilities Assumed								112,776,000				(205,000)
Total Consideration Transferred								(114,717,000)				(623,000)
Goodwill		2,771,000	[1]	2,700,000	[1]			1,943,000	[2]			828,000	[3]
Business acquisition, pro forma information [Abstract]
Revenues	82,270,000
Net earnings attributable to ISH	$ 7,691,000
Net earnings per share attributable to ISH common stockholders [Abstract]
Basic (in dollars per share)	$ 1.07
Diluted (in dollars per share)	$ 1.07

[1] The addition of $71,000 in goodwill is associated with post acquisition settlement adjustments on our 2012 acquistiions. FSI was increased by $29,000 and UOS was increased by $42,000.

[2] Goodwill is calculated as the excess of the consideration transferred over the net assets acquired and represents the future economic benefits arising from other assets acquired that could not be individually identified and separately recognized. Our above-described goodwill will not be amortized nor do we expect it to be deductible for tax purposes. Specifically, the goodwill recorded as part of the acquisition of UOS includes the following: • the expected synergies and other benefits that we believe will result from combining the operations of UOS withour existing Jones Act operations. • any intangible assets that do not qualify for separate recognition, including an assembled workforce of theacquired company, and • the anticipated higher rate of return of UOS's existing businesses as going concerns compared to the anticipatedrate of return if we had acquired all of the net assets separately.

[3] Goodwill is calculated as the excess of the consideration transferred over the net assets acquired and represents the future economic benefits arising from other assets acquired that could not be individually identified and separately recognized. Our above-described goodwill will not be amortized nor do we expect it to be deductible for tax purposes. Specifically, the goodwill recorded as part of the acquisition of the Acquired Companies includes the following: • the expected synergies and other benefits that we believe will result from combining the operations of UOS withour existing Jones Act operations. • any intangible assets that do not qualify for separate recognition, including an assembled workforce of theacquired company, and • the anticipated higher rate of return of UOS's existing businesses as going concerns compared to the anticipatedrate of return if we had acquired all of the net assets separately.