SIGNIFICANT ACCOUNTING POLICIES: (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Revenue recognition:
Shipping and handling costs	$ 42,619	$ 46,525	$ 45,367
Cash and cash equivalents:
Maximum original maturity period of temporary cash investments classified as cash equivalents	3 months
Investments:
Marketable securities, maximum maturity period	3 years
Inventories:
Inventories at cost, last-in, first-out (LIFO) method	$ 58,413	65,545
Excess of current cost over LIFO cost of inventories	16,864	18,117
Foreign inventories at cost, first-in, first-out (FIFO) method	$ 3,850	$ 4,834