Financial Instruments, Fair Value Measurements and Credit Risk (Tables)

12 Months Ended

Dec. 31, 2011

Financial Instruments, Fair Value Measurements and Credit Risk [Abstract]

Realized and Unrealized Gains and Losses on Derivative Instruments

	Year Ended December 31,
(Thousands of U.S. Dollars)	2011			2010			2009
Realized financial derivative (gain) loss	$	(1,522	)	$	-		$	(87	)
Unrealized financial derivative (gain) loss		-			(44	)		277
Derivative financial instruments (gain) loss	$	(1,522	)	$	(44	)	$	190