Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Jun. 30, 2020	Dec. 31, 2019	Jun. 30, 2019	Dec. 31, 2018
NET EARNINGS (LOSS)	$ (5,591)	$ 105,328	$ 26,988	$ 101,392
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, Net of Tax	0	(1)	0	1,473
OTHER COMPREHENSIVE INCOME (LOSS):
TOTAL COMPREHENSIVE INCOME (LOSS), net of tax	$ (4,841)	108,325	$ 29,238	112,156
Common stock, shares outstanding (in shares)	59,589,770		59,589,770			59,329,431
Stockholders' Equity Attributable to Parent	$ 714,620	480,996	$ 714,620	480,996	$ 496,533	$ 460,342	$ 370,809	$ 436,438
Grant of restricted stock	0	0	0	0
Issuance of common shares, net of withholdings	0	(25)	(1,839)	(1,521)
Stock Issued During Period, Value, Restricted Stock Award, Forfeitures	0	0	0	0
reclassification of liability to equity	221,093		221,093
Amortization of stock awards and restricted stock	1,835	$ 1,887	5,786	$ 5,281
Amazon Warrant AB [Member]
OTHER COMPREHENSIVE INCOME (LOSS):
reclassification of liability to equity	$ 221,093		$ 221,093
Common Stock [Member]
OTHER COMPREHENSIVE INCOME (LOSS):
Common stock, shares outstanding (in shares)	59,589,770	59,368,570	59,589,770	59,368,570	59,589,770	59,329,431	59,363,839	59,134,173
Stockholders' Equity Attributable to Parent	$ 596	$ 594	$ 596	$ 594	$ 596	$ 593	$ 594	$ 591
Grant of restricted stock (in shares)	0	7,500	201,400	151,300
Grant of restricted stock	$ 0	$ 0	$ 2	$ 2
Withholdings of common shares, net of issuances (in shares)	0	(1,069)	59,439	86,097
Issuance of common shares, net of withholdings	$ 0	$ 0	$ 1	$ 1
Stock Issued During Period, Shares, Restricted Stock Award, Forfeited	0	(1,700)	(500)	(3,000)
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	700,757	474,915	700,757	474,915	477,829	475,720	473,053	471,158
Grant of restricted stock	0	0	(2)	(2)
Issuance of common shares, net of withholdings	0	(25)	(1,840)	(1,522)
Stock Issued During Period, Value, Restricted Stock Award, Forfeitures	0	0	0	0
Amortization of stock awards and restricted stock	1,835	1,887	5,786	5,281
Accumulated Deficit [Member]
OTHER COMPREHENSIVE INCOME (LOSS):
TOTAL COMPREHENSIVE INCOME (LOSS), net of tax	(5,591)	105,328	26,988	101,392
Stockholders' Equity Attributable to Parent	72,883	86,085	72,883	86,085	78,474	45,895	(19,243)	56,051
Accumulated Other Comprehensive Income (Loss) [Member]
OTHER COMPREHENSIVE INCOME (LOSS):
TOTAL COMPREHENSIVE INCOME (LOSS), net of tax	750	2,997	2,250	10,764
Stockholders' Equity Attributable to Parent	(59,616)	(80,598)	(59,616)	(80,598)	$ (60,366)	$ (61,866)	$ (83,595)	$ (91,362)
Pension Plans [Member]
Other comprehensive income (loss), net of tax	726	2,965	2,178	9,189
OTHER COMPREHENSIVE INCOME (LOSS):
Income tax (expense) or benefit	(215)	(917)	(645)	(2,457)
Post-Retirement Plans [Member]
Other comprehensive income (loss), net of tax	24	33	72	102
OTHER COMPREHENSIVE INCOME (LOSS):
Income tax (expense) or benefit	$ (7)	$ (10)	$ (21)	$ (27)