XML 47 R34.htm IDEA: XBRL DOCUMENT v3.8.0.1
SHORT-TERM INVESTMENTS: (Details) - USD ($)
$ in Millions
3 Months Ended 9 Months Ended 12 Months Ended
Sep. 30, 2017
Sep. 30, 2016
Sep. 30, 2017
Sep. 30, 2016
Dec. 31, 2016
Short-term investment:          
Trading securities $ 29.5   $ 29.5   $ 49.2
Weighted average interest rate (as a percent)     1.40%   2.20%
Available-for-sale 1.0   $ 1.0   $ 2.1
Weighted average interest rate (as a percent)     0.70%   0.78%
Total 30.5   $ 30.5   $ 51.3
Trading securities:          
Interest earned 0.2 $ 0.3 0.6 $ 1.0  
Unrealized gain (loss) at the end of the period 0.1 0.3 0.1 0.3  
Available-for-sale:          
Investment redeemed 0.1 0.3 1.1 0.8  
Maximum          
Available-for-sale:          
Interest earned $ 0.1 $ 0.1 $ 0.1 $ 0.1