ACCUMULATED OTHER COMPREHENSIVE LOSS, Components of Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Accumulated other comprehensive loss [Abstract]
Foreign currency translation adjustment, net of taxes of ($800) at June 30, 2017 and ($984) at December 31, 2016	$ (21,405)	$ (28,976)
Unrealized holding gains on available-for-sale securities, net of taxes of $92 at June 30, 2017 and $263 at December 31, 2016	157	424
Unfunded SERP liability, net of taxes of ($1,333) at June 30, 2017 and ($1,398) at December 31, 2016	(2,622)	(2,745)
Accumulated other comprehensive loss	(23,870)	(31,297)
Accumulated other comprehensive loss, tax [Abstract]
Foreign currency translation adjustment, tax	(800)	(984)
Unrealized holding gains on available-for-sale securities, tax	92	263
Change in unfunded SERP liability, tax	$ (1,333)	$ (1,398)