Investments (Tables)

12 Months Ended

Dec. 31, 2014

Investments

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

	2014				2013
	Amortized		Fair		Amortized		Fair
(Thousands of dollars)	Cost		Value		Cost		Value
Money market funds	$	142,432	$	142,432	$	88,430	$	88,430
Corporate bonds	11,000		11,015		69,591		70,258
U.S. Government agency securities	9,684		9,666		27,299		27,147
Asset backed debt securities	2,260		2,291		8,446		8,477
Collateralized mortgage obligations	1,150		1,170		7,597		7,600
U.S. Treasury securities	523		522		5,258		5,223
Emerging markets debt mutual fund	-		-		17,693		16,941
Total available-for-sale short-term investments	167,049		167,096		224,314		224,076
High yield trading debt securities	187,491		181,483		49,352		50,428
Equity mutual fund	83,809		82,542		-		-
Domestic equity ETF	31,307		32,651		-		-
Money market funds held in trading accounts	21,401		21,401		11,033		11,033
Emerging markets trading debt mutual fund	3,323		2,614		3,202		2,858
Other trading investments	2,850		2,779		2,141		2,254
Total trading short-term investments	330,181		323,470		65,728		66,573
Total short-term investments	$	497,230	$	490,566	$	290,042	$	290,649

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)	2014
Due within one year	$	546
Due after one year through three years	9,956
Due after three years	11,105
Total fixed rate securities	$	21,607