CONSOLIDATED STATEMENTS OF COMPREHENSIVE (LOSS) INCOME (Unaudited) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Statement Of Income and Comprehensive Income [Abstract]
Net (loss) income	$ (34,055)	$ 63,283	$ (26,507)	$ 102,671
Other comprehensive (loss) income:
Pension adjustment and reclassification adjustment, net of taxes	125	84	250	168
Foreign currency translation	153	467	(876)	(4)
Unrealized (loss) gain on securities, net of taxes	(22)	38	(2)	2
Comprehensive (loss) income	$ (33,799)	$ 63,872	$ (27,135)	$ 102,837