Derivative Instruments (Details) (USD $)	3 Months Ended				3 Months Ended								3 Months Ended			3 Months Ended		3 Months Ended				12 Months Ended	3 Months Ended						3 Months Ended
	Mar. 31, 2013	Jan. 31, 2013 Contract	Dec. 31, 2012 Contract	May 31, 2012 Contract	Mar. 31, 2013 Swap 1 [Member]	Mar. 31, 2013 Swap 2 [Member]	Mar. 31, 2013 Swap 3 [Member]		Mar. 31, 2013 Foreign Exchange Contract 1 [Member]	Jan. 31, 2013 Foreign Exchange Contract 1 [Member]	Dec. 31, 2012 Foreign Exchange Contract 1 [Member]	May 31, 2012 Foreign Exchange Contract 1 [Member]	Mar. 31, 2013 Foreign Exchange Contract 2 [Member]	Dec. 31, 2012 Foreign Exchange Contract 2 [Member]	May 31, 2012 Foreign Exchange Contract 2 [Member]	Mar. 31, 2013 Foreign Exchange Contract 3 [Member]	May 31, 2012 Foreign Exchange Contract 3 [Member]	Mar. 31, 2013 Foreign Exchange Contract 4 [Member]	Mar. 31, 2013 Foreign Exchange Contract 5 [Member]	Mar. 31, 2013 Foreign Exchange Contract 6 [Member]	Mar. 31, 2013 Accumulated Other Comprehensive Loss [Member]	Dec. 31, 2012 Accumulated Other Comprehensive Loss [Member]	Mar. 31, 2013 Interest Rate Swaps [Member]	Mar. 31, 2013 Interest Rate Swaps [Member] Interest Expense [Member]	Mar. 31, 2013 Interest Rate Swap - LT [Member]		Mar. 31, 2013 Interest Rate Swap - LT [Member] Other Liabilities [Member]		Mar. 31, 2013 Foreign Exchange Contracts [Member]	Mar. 31, 2013 Foreign Exchange Contracts [Member] Other Revenues [Member]	Mar. 31, 2013 Foreign Exchange Contracts [Member] Current Liabilities [Member]	Mar. 31, 2013 Foreign Exchange Contracts [Member] Other Assets [Member]
Derivative Instruments [Abstract]
Maximum potential future exposure on derivatives	$ 6,200,000
Derivative posted as collateral	469,500
Derivatives, Fair Value [Line Items]
Unrealized loss related to derivative instruments included in accumulated other comprehensive loss																					6,800,000	7,400,000
Asset derivatives, current notional amount																													3,800,000
Liability derivatives, current notional amount																									67,544,000	[1]			3,000,000
Derivatives, current notional amount	74,344,000
Asset derivatives, fair value	177,000																															177,000
Liability derivatives, fair value	(6,424,000)																										(6,143,000)	[1]			(281,000)
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Recognized in OCI	547,000																						542,000						5,000
Amount of Gain (Loss) Reclassified from AOCI to Income	(449,000)																							(478,000)						29,000
Gain (Loss) Recognized in Income from Ineffective portion	77,000																							77,000						0
Derivative [Line Items]
Effective Date					Sep. 26, 2005	Sep. 26, 2005	Mar. 15, 2009
Termination Date					Sep. 28, 2015	Sep. 28, 2015	Sep. 15, 2020
Current Notional Amount	67,543,763				6,000,000	6,000,000	55,543,763	[2]
Swap Rate (in hundredths)					4.41%	4.41%	2.065%
Type					Variable-to-Fixed	Variable-to-Fixed	Variable-to-Fixed
Exchange rate							94.22			9,910	85.27	13.7787		85.16	14.2939		14.5700
Original funding of vessel's delivery cost (in hundredths)							80.00%
Revised funding of vessel's delivery cost (in hundredths)							65.00%
Reduction in funding of vessel's delivery cost (in hundredths)	15.00%
Change in fair value related to ineffective portion of derivative instrument							77,000
Number of foreign currency derivatives held		1	2	3
Notional amount of forward purchase contracts										3,300,000	1,500,000	750,000		1,500,000	250,000		700,000
Projected Peso exposure represented by Mexican Peso foreign exchange contracts (in hundredths)				50.00%
Projected yen exposure represented by Japanese Yen foreign exchange contract (in hundredths)			7.93%
Projected Rupiah exposure represented by Indonesian Rupiah foreign exchange contract (in hundredths)		80.00%
Transaction Date									May 31, 2012				May 31, 2012			May 31, 2012		Dec. 31, 2012	Dec. 31, 2012	Jan. 31, 2013
Transaction Amount	$ 6,800,000								$ 300,000				$ 100,000			$ 700,000		$ 1,500,000	$ 1,500,000	$ 2,700,000
Effective Date									Jan. 31, 2013				Jan. 31, 2013			Jun. 30, 2013		Dec. 31, 2012	Dec. 31, 2012	Jan. 31, 2013
Expiration Date									May 31, 2013				May 31, 2013			Dec. 31, 2013		Sep. 30, 2013	Dec. 31, 2013	Dec. 31, 2013

[1] We have outstanding a variable-to-fixed interest rate swap with respect to a Yen-based facility for the financing of a PCTC delivered in March 2010. The notional amount under this contract is $55,543,763 (based on a Yen to USD exchange rate of 94.22 as of March 31, 2013). With the bank exercising its option to reduce the underlying Yen loan from 80% to 65% funding of the vessel's delivery cost, the 15% reduction represents the ineffective portion of this swap, which consists of the portion of the derivative instrument that is no longer supported by underlying borrowings. The change in fair value related to the ineffective portion of this swap was a $77,000 gain for the quarter ended March 31, 2013 and this amount was reflected in earnings.

[2] Notional amount converted from Yen at March 31, 2013 at a Yen to USD exchange rate of 94.22