Investments (Tables)

6 Months Ended

Jun. 30, 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	$	134,965	$	136,258	$	88,589	$	89,146
Money market funds and deposit accounts	101,011		101,011		139,420		139,420
Enhanced cash mutual fund	50,000		50,072		-		-
Collateralized mortgage obligations	24,859		24,944		14,915		15,011
Fixed rate municipal notes and bonds	23,553		23,592		17,718		17,788
U.S. Government agency securities	22,424		22,572		9,720		9,757
U.S. Treasury securities	20,458		20,526		4,848		4,905
Emerging markets debt mutual fund	17,693		17,035		17,693		16,399
Asset backed debt securities	15,499		15,514		3,533		3,533
Other	680		683		1,480		1,484
Total available-for-sale short-term investments	411,142		412,207		297,916		297,443
High yield trading debt securities	21,129		22,084		20,155		20,750
Emerging markets trading debt mutual fund	2,966		2,919		2,620		2,487
Emerging markets trading debt securities	2,004		2,073		2,444		2,355
Other trading debt securities	684		754		218		221
Total available-for-sale and trading short-term investments	$	437,925	$	440,037	$	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	$	44,983
Due after one year through three years	88,072
Due after three years	67,516
Total fixed rate securities	$	200,571