INVESTMENTS: (Fair value due by period) (Details) - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015
Amortized Cost
Due in less than one year	$ 133,643	$ 148,041
Due in one to three years	79,241	99,854
Estimated Fair Value
Due in less than one year	133,686	147,914
Due in one to three years	79,268	99,400
Available-for-sale securities, amortized cost basis	212,884	247,895
Estimated fair value	212,954	247,314
Investment in a privately-held companies accounted for under the cost method	$ 7,800	$ 7,700