Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
NET EARNINGS (LOSS)	$ (53,726)	$ 11,575	$ (43,738)	$ 19,793
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, Net of Tax	99	53	136	310
OTHER COMPREHENSIVE INCOME:
TOTAL COMPREHENSIVE INCOME (LOSS), NET OF TAXES	(52,355)	13,783	(41,059)	24,413
Pension Plans [Member]
Other comprehensive income, net of tax	1,235	2,146	2,469	4,292
OTHER COMPREHENSIVE INCOME:
Income tax (expense) or benefit	(702)	(1,222)	(1,405)	(2,444)
Post-Retirement Plans [Member]
Other comprehensive income, net of tax	37	9	74	18
OTHER COMPREHENSIVE INCOME:
Income tax (expense) or benefit	$ (21)	$ (5)	$ (42)	$ (10)