CONSOLIDATED STATEMENTS OF COMPREHENSIVE (LOSS) INCOME (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Statement Of Income and Comprehensive Income [Abstract]
Net (loss) income	$ (35,173)	$ 64,885	$ (61,680)	$ 167,556
Other comprehensive (loss) income:
Pension adjustment and reclassification adjustment, net of taxes	126	85	376	253
Foreign currency translation	(598)	(649)	(1,474)	(653)
Unrealized loss on securities, net of taxes	(27)	(38)	(29)	(36)
Comprehensive (loss) income	$ (35,672)	$ 64,283	$ (62,807)	$ 167,120