CONSOLIDATED STATEMENTS OF COMPREHENSIVE (LOSS) INCOME (Parenthetical) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Other comprehensive (loss) income:
Currency translation adjustment, tax	$ (648)	$ (194)	$ (219)
Unrealized gain on marketable securities arising during the period, tax	(2)	5	90
Change in unfunded SERP liability, tax	$ 71	$ 2	$ (631)