Investments (Tables)

12 Months Ended

Dec. 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
Money market funds	$	126,537	$	126,537	$	139,420	$	139,420
Corporate bonds	67,275		69,214		88,589		89,146
U.S. Government agency securities	23,647		23,775		9,720		9,757
Emerging markets debt mutual fund	17,693		18,734		17,693		16,399
U.S. Treasury securities	17,165		17,169		4,848		4,905
Collateralized mortgage obligations	15,059		15,162		14,915		15,011
Asset backed debt securities	12,180		12,238		3,533		3,533
Fixed rate municipal notes and bonds	-		-		17,718		17,788
Other	-		-		1,480		1,484
Total available-for-sale short-term investments	279,556		282,829		297,916		297,443
High yield trading debt securities	21,839		23,406		20,155		20,750
Emerging markets trading debt mutual funds	3,046		3,237		2,620		2,487
Emerging markets trading debt securities	2,361		2,600		2,444		2,355
Other trading investments	1,262		1,307		218		221
Total short-term investments	$	308,064	$	313,379	$	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	$    2,587
Due after one year through three years	52,411
Due after three years	60,721
Total fixed rate securities	$115,719