SHORT-TERM INVESTMENTS: (Tables)

12 Months Ended

Dec. 31, 2013

SHORT-TERM INVESTMENTS:

Schedule of short-term investments

Short-term investments were as follows ($ in millions):

	At December 31,
	2013			2012
Trading securities	$	202.6		$	127.8
Weighted average interest rate	3.78		%	1.87		%
Available-for-sale	5.7			6.5
Weighted average interest rate	0.42		%	0.43		%
Total	$	208.3		$	134.3

Summary of activities in short-term investments

The following table summarizes the activity of these investments by category (in millions):

	Years ended December 31,
	2013			2012
Trading:
Interest earned	$	5.2		$	3.1
Unrealized gain (loss) at December 31,	$	(1.9	)	$	2.4
Available-for-sale:
Interest earned	(*		)	$	0.1
Investment redeemed	$	0.8		$	1.9

(*) Less than $0.1 million

Schedule of contractual maturities of the Company's available for sale debt securities

At December 31, 2013 and 2012, contractual maturities of the available-for-sale debt securities are as follows (in millions):

	2013		2012
One year or less	$	0.4	$	0.4
Maturing after one year through five years	—		—
Maturing after five years through ten years	0.2		—
Due after 10 years	5.1		6.1
Total debt securities	$	5.7	$	6.5