CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Statement Of Other Comprehensive Income [Abstract]
NET (LOSS) INCOME	$ (99,561)	$ 245,193	$ 166,895
OTHER COMPREHENSIVE (LOSS) INCOME, NET OF TAXES:
Pension adjustment	1,531	(6,486)	4,928
Foreign currency translation	(1,801)	(1,124)	(778)
Unrealized gain (loss) on securities, net reclassification adjustments	134	(108)	(19)
COMPREHENSIVE (LOSS) INCOME	$ (99,697)	$ 237,475	$ 171,026