Financial Instruments (Tables)

6 Months Ended

Jun. 30, 2011

Financial Instruments [Abstract]

Financial Instruments

(Thousands of dollars)
	June 30, 2011				June 30, 2010
	Carrying		Fair		Carrying		Fair
	Amount		Value		Amount		Value
Publicly traded debt	$	632,400	$	676,031	$	686,990	$	740,514
Non-traded debt		21,362		20,309		22,094		21,094