Investments (Tables)

3 Months Ended

Mar. 31, 2012

Investments

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

	2012				2011
	Amortized		Fair		Amortized		Fair
(Thousands of dollars)	Cost		Value		Cost		Value
Corporate bonds	$	132,726	$	133,989	$	88,589	$	89,146
Money market funds	69,867		69,867		139,420		139,420
U.S. Treasury securities	36,110		36,095		4,848		4,905
Collateralized mortgage obligations	22,677		22,720		14,915		15,011
Fixed rate municipal notes and bonds	21,275		21,335		17,718		17,788
U.S. Government agency securities	18,534		18,603		9,720		9,757
Emerging markets debt mutual fund	17,693		17,687		17,693		16,399
Asset backed debt securities	10,530		10,536		3,533		3,533
Other	1,480		1,483		1,480		1,484
Total available-for-sale short-term investments	330,892		332,315		297,916		297,443
High yield trading debt securities	21,217		22,349		20,155		20,750
Emerging markets trading debt mutual funds	2,651		2,686		2,620		2,487
Emerging markets trading debt securities	2,099		2,246		2,444		2,355
Other trading debt securities	217		238		218		221
Total available-for-sale and trading short-term investments	$	357,076	$	359,834	$	323,353	$	323,256

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)	2012
Due within one year	$	53,083
Due after one year through three years	90,771
Due after three years	66,844
Total fixed rate securities	$	210,698