ACCUMULATED OTHER COMPREHENSIVE LOSS, Components of Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Accumulated other comprehensive loss [Abstract]
Foreign currency translation adjustment, net of taxes of ($699) at September 30, 2017 and ($984) at December 31, 2016	$ (17,929)	$ (28,976)
Unrealized holding gains on available-for-sale securities, net of taxes of $71 at September 30, 2017 and $263 at December 31, 2016	124	424
Unfunded SERP liability, net of taxes of ($1,300) at September 30, 2017 and ($1,398) at December 31, 2016	(2,561)	(2,745)
Accumulated other comprehensive loss	(20,366)	(31,297)
Accumulated other comprehensive loss, tax [Abstract]
Foreign currency translation adjustment, tax	(699)	(984)
Unrealized holding gains on available-for-sale securities, tax	71	263
Change in unfunded SERP liability, tax	$ (1,300)	$ (1,398)