CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Statement Of Income And Comprehensive Income [Abstract]
NET INCOME (LOSS)	$ 21,802	$ (11,771)	$ 23,751	$ (10,457)
OTHER COMPREHENSIVE INCOME, NET OF TAX:
Unrealized gain (loss) on available-for-sale securities, net of tax of $37, $11, $47 and $4, respectively	67	19	(84)	4
Employee benefit plan:
Actuarial gain (loss), net of tax of $271, none, $200, and none, respectively	479		(353)
Amortization of prior service cost and actuarial loss for retirement plan included in net periodic pension costs, net of tax of $142, $157, $302 and $258, respectively	254	279	535	420
Net change for employee benefit plan	733	279	182	420
Change in cumulative foreign currency translation adjustment	20		20
TOTAL OTHER COMPREHENSIVE INCOME	820	298	118	424
COMPREHENSIVE INCOME (LOSS)	$ 22,622	$ (11,473)	$ 23,869	$ (10,033)