Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Mar. 31, 2020	Dec. 31, 2019	Mar. 31, 2019	Dec. 31, 2018
NET EARNINGS (LOSS)	$ (104,926)	$ (26,601)	$ 32,579	$ (3,936)
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, Net of Tax	0	1,479	0	1,474
OTHER COMPREHENSIVE INCOME (LOSS):
TOTAL COMPREHENSIVE INCOME (LOSS), net of tax	$ (104,176)	(21,813)	$ 34,079	3,831
Common stock, shares outstanding (in shares)	59,589,770		59,589,770			59,329,431
Stockholders' Equity Attributable to Parent	$ 496,533	370,809	$ 496,533	370,809	$ 599,303	$ 460,342	$ 390,814	$ 436,438
Grant of restricted stock	0	0	0	0
Issuance of common shares, net of withholdings	(724)	(112)	(1,839)	(1,496)
Stock Issued During Period, Value, Restricted Stock Award, Forfeitures	0	0	0	0
Amortization of stock awards and restricted stock	$ 2,130	$ 1,920	$ 3,951	$ 3,394
Common Stock [Member]
OTHER COMPREHENSIVE INCOME (LOSS):
Common stock, shares outstanding (in shares)	59,589,770	59,363,839	59,589,770	59,363,839	59,623,195	59,329,431	59,351,326	59,134,173
Stockholders' Equity Attributable to Parent	$ 596	$ 594	$ 596	$ 594	$ 596	$ 593	$ 594	$ 591
Grant of restricted stock (in shares)	900	18,600	201,400	143,800
Grant of restricted stock	$ 0	$ 0	$ 2	$ 2
Withholdings of common shares, net of issuances (in shares)	(33,825)	(4,787)	59,439	87,166
Issuance of common shares, net of withholdings	$ 0	$ 0	$ 1	$ 1
Stock Issued During Period, Shares, Restricted Stock Award, Forfeited	(500)	(1,300)	(500)	(1,300)
Stock Issued During Period, Value, Restricted Stock Award, Forfeitures	$ 0	$ 0	$ 0	$ 0
Additional Paid-in Capital [Member]
OTHER COMPREHENSIVE INCOME (LOSS):
Stockholders' Equity Attributable to Parent	477,829	473,053	477,829	473,053	476,423	475,720	471,245	471,158
Grant of restricted stock	0	0	(2)	(2)
Issuance of common shares, net of withholdings	(724)	(112)	(1,840)	(1,497)
Stock Issued During Period, Value, Restricted Stock Award, Forfeitures	0	0	0	0
Amortization of stock awards and restricted stock	2,130	1,920	3,951	3,394
Accumulated Deficit [Member]
OTHER COMPREHENSIVE INCOME (LOSS):
TOTAL COMPREHENSIVE INCOME (LOSS), net of tax	(104,926)	(26,601)	32,579	(3,936)
Stockholders' Equity Attributable to Parent	78,474	(19,243)	78,474	(19,243)	183,400	45,895	7,358	56,051
Accumulated Other Comprehensive Income (Loss) [Member]
OTHER COMPREHENSIVE INCOME (LOSS):
TOTAL COMPREHENSIVE INCOME (LOSS), net of tax	750	4,788	1,500	7,767
Stockholders' Equity Attributable to Parent	(60,366)	(83,595)	(60,366)	(83,595)	$ (61,116)	$ (61,866)	$ (88,383)	$ (91,362)
Pension Plans [Member]
Other comprehensive income (loss), net of tax	726	3,273	1,452	6,224
OTHER COMPREHENSIVE INCOME (LOSS):
Income tax (expense) or benefit	(215)	(609)	(430)	(1,540)
Post-Retirement Plans [Member]
Other comprehensive income (loss), net of tax	24	36	48	69
OTHER COMPREHENSIVE INCOME (LOSS):
Income tax (expense) or benefit	$ (7)	$ (7)	$ (14)	$ (17)