SHORT-TERM INVESTMENTS: (Tables)

6 Months Ended

Jun. 30, 2020

SHORT-TERM INVESTMENTS:

Schedule of short-term investments

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

	At June 30,			At December 31,
	2020			2019
Trading securities	$	30.1		$	80.0
Weighted average interest rate		0.1	%		2.0	%
Available-for-sale	$	0.6		$	0.7
Weighted average interest rate		0.7	%		0.7	%
Total	$	30.7		$	80.7

Summary of activity investments

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

	Three months ended				Six months ended
	June 30,				June 30,
	2020		2019		2020		2019
Trading:
Interest earned	$	(*)	$	(*)	$	0.4	$	0.1
Unrealized gain (loss) at the end of the period	$	(*)	$	(*)	$	(*)	$	(*)
Available-for-sale:
Interest earned		(*)		(*)				(*)
Investment redeemed	$	—	$	—	$	0.1	$	—

(*) Less than $0.1 million.