SHORT-TERM INVESTMENTS: (Tables)

3 Months Ended

Mar. 31, 2020

SHORT-TERM INVESTMENTS:

Schedule of short-term investments

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

	At March 31,			At December 31,
	2020			2019
Trading securities	$	40.1		$	80.0
Weighted average interest rate		1.9	%		2.0	%
Available-for-sale	$	0.6		$	0.7
Weighted average interest rate		0.7	%		0.7	%
Total	$	40.7		$	80.7

Summary of activity investments

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

	Three months ended
	March 31,
	2020		2019
Trading:
Interest earned	$	0.7	$	0.1
Unrealized gain (loss) at the end of the period	$	(*)	$	(0.1)
Available-for-sale:
Interest earned		(*)		(*)
Investment redeemed	$	0.1	$	—

(*) Less than $0.1 million.