Condensed Consolidated Statements of Comprehensive Income (Loss) (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Statement of Comprehensive Income [Abstract]
Net (loss) earnings	$ (3,277)	$ (4,967)	$ (21,798)	$ (9,622)
Unrealized gain (loss) on short-term investments	41	(494)	370	523
Changes in pension plan assets and benefit obligations	(24)	1	(2)	3
Tax effect of the above-listed adjustments	(8)	178	(134)	(229)
Total comprehensive (loss) income	$ (3,268)	$ (5,282)	$ (21,564)	$ (9,325)