Changes in Accumulated Other Comprehensive Income (Details) (USD $)	3 Months Ended
	Mar. 31, 2013		Mar. 31, 2012
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	$ 24,946,000
Other comprehensive income before reclassification	(215,000)
Amount reclassified from accumulated other comprehensive income	(683,000)
Net current-period other comprehensive income	(898,000)
Ending balance	24,048,000
Interest rate swap fair value	(919,904)
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Interest Expense	2,201,000		2,727,000
Other revenues	555,000		622,000
Total before tax	(1,958,000)		(8,174,000)
Tax (expense) or benefit	35,000		168,000
Net of tax	(1,653,000)		(7,936,000)
Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net of tax	(683,000)
Oslo Bulk AS [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Equity investee ownership interest (in hundredths)	25.00%
Gains and Losses on Derivatives Fair Value [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	7,352,000	[1]
Other comprehensive income before reclassification	(175,000)	[1]
Amount reclassified from accumulated other comprehensive income	(372,000)	[1]
Net current-period other comprehensive income	(547,000)	[1]
Ending balance	6,805,000	[1]
Gains and Losses on Derivatives Fair Value [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Total before tax	(372,000)
Tax (expense) or benefit	0
Net of tax	(372,000)
Gains and Losses on Derivatives Fair Value [Member] | Foreign Exchange Contracts [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Other revenues	29,000
Gains and Losses on Derivatives Fair Value [Member] | Interest Rate Contract [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Interest Expense	(401,000)
Unrealized Translation Loss [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	350,000
Other comprehensive income before reclassification	(40,000)
Amount reclassified from accumulated other comprehensive income	0
Net current-period other comprehensive income	(40,000)
Ending balance	310,000
Defined Benefit Pension Items [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	17,244,000
Other comprehensive income before reclassification	0
Amount reclassified from accumulated other comprehensive income	(311,000)
Net current-period other comprehensive income	(311,000)
Ending balance	16,933,000
Defined Benefit Pension Items [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Prior service costs	(24,000)
Actuarial losses	(287,000)
Total before tax	(311,000)
Tax (expense) or benefit	0
Net of tax	$ (311,000)

[1] The fair value balance as of March 31, 2013, includes a negative $919,904 balance related to an interest rate swap from our 25% investment in Oslo Bulk AS.