Investments (Tables)

12 Months Ended

Dec. 31, 2011

Investments

Summary of the amortized cost and estimated fair value of short-term investments for both available-for-sale and trading securities

	2011				2010
	Amortized		Fair		Amortized		Fair
(Thousands of dollars)	Cost		Value		Cost		Value
Money market funds	$	139,420	$	139,420	$	110,164	$	110,164
Corporate bonds	88,589		89,146		81,214		82,351
Fixed rate municipal notes and bonds	17,718		17,788		20,564		20,648
Emerging markets debt mutual fund	17,693		16,399		–		–
Collateralized mortgage obligations	14,915		15,011		12,329		12,380
U.S. Government agency securities	9,720		9,757		10,142		10,184
U.S. Treasury securities	4,848		4,905		7,139		7,148
Asset backed debt securities	3,533		3,533		2,847		2,848
Enhanced cash mutual fund	–		–		60,256		60,302
Other	1,480		1,484		2,360		2,355
Total available-for-sale short-term investments	297,916		297,443		307,015		308,380
High yield trading debt securities	20,155		20,750		19,447		20,783
Emerging markets trading debt mutual funds	2,620		2,487		–		–
Emerging markets trading debt securities	2,444		2,355		1,918		2,072
Other trading debt securities	218		221		889		970
Total short-term investments	$	323,353	$	323,256	$	329,269	$	332,205

Summary of estimated fair value of fixed rate securities designated as available-for-sale, classified by the contractual maturity date of the security

(Thousands of dollars)	2011
Due within one year	$	31,349
Due after one year through three years	60,281
Due after three years	23,892
Total fixed rate securities	$	115,522