Summary of Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2012

Summary of Significant Accounting Policies

Schedule of changes in the asset retirement obligation

	Years ended December 31,
(Thousands of dollars)	2012	2011
Beginning balance	$  13,109	$      12,028
Accretion expense	1,090	1,007
Liability for additional lagoons placed in service	116	74
Ending balance	$  14,315	$      13,109

Schedule of amounts paid for interest and income taxes

	Years ended December 31,
(Thousands of dollars)	2012		2011		2010
Interest (net of amounts capitalized)	$	11,674	$	6,786	$	8,377
Income taxes (net of refunds)	69,760		126,730		69,626