Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Accumulated Deficit [Member]	Accumulated Other Comprehensive Income (Loss) [Member]
Balance at at Dec. 31, 2018	$ 436,438	$ 591	$ 471,158	$ 56,051	$ (91,362)
Balance at (in shares) at Dec. 31, 2018		59,134,173
Stock-based compensation plans
Grant of restricted stock	0	$ 2	(2)
Grant of restricted stock (in shares)		143,800
Issuance of common shares, net of withholdings	(1,496)	$ 1	(1,497)
Withholdings of common shares, net of issuances (in shares)		87,166
Forfeited restricted stock	0	$ 0	0
New Accounting Pronouncement or Change in Accounting Principle, Effect of Adoption, Quantification | Accounting Standards Update 2016-02 [Member]	(71,358)			(71,358)
Forfeited restricted stock (in shares)		1,300
Amortization of stock awards and restricted stock	3,394		3,394
Total comprehensive income (loss)	3,831			(3,936)	7,767
Balance at at Jun. 30, 2019	370,809	$ 594	473,053	(19,243)	(83,595)
Balance at (in shares) at Jun. 30, 2019		59,363,839
Balance at at Mar. 31, 2019	390,814	$ 594	471,245	7,358	(88,383)
Balance at (in shares) at Mar. 31, 2019		59,351,326
Stock-based compensation plans
Grant of restricted stock	0	$ 0	0
Grant of restricted stock (in shares)		18,600
Issuance of common shares, net of withholdings	(112)	$ 0	(112)
Withholdings of common shares, net of issuances (in shares)		(4,787)
Forfeited restricted stock	0	$ 0	0
Forfeited restricted stock (in shares)		1,300
Amortization of stock awards and restricted stock	1,920		1,920
Total comprehensive income (loss)	(21,813)			(26,601)	4,788
Balance at at Jun. 30, 2019	370,809	$ 594	473,053	(19,243)	(83,595)
Balance at (in shares) at Jun. 30, 2019		59,363,839
Balance at at Dec. 31, 2019	$ 460,342	$ 593	475,720	45,895	(61,866)
Balance at (in shares) at Dec. 31, 2019	59,329,431	59,329,431
Stock-based compensation plans
Grant of restricted stock	$ 0	$ 2	(2)
Grant of restricted stock (in shares)		201,400
Issuance of common shares, net of withholdings	(1,839)	$ 1	(1,840)
Withholdings of common shares, net of issuances (in shares)		59,439
Forfeited restricted stock	0	$ 0	0
Forfeited restricted stock (in shares)		500
Amortization of stock awards and restricted stock	3,951		3,951
Total comprehensive income (loss)	34,079			32,579	1,500
Balance at at Jun. 30, 2020	$ 496,533	$ 596	477,829	78,474	(60,366)
Balance at (in shares) at Jun. 30, 2020	59,589,770	59,589,770
Balance at at Mar. 31, 2020	$ 599,303	$ 596	476,423	183,400	(61,116)
Balance at (in shares) at Mar. 31, 2020		59,623,195
Stock-based compensation plans
Grant of restricted stock	0	$ 0	0
Grant of restricted stock (in shares)		900
Issuance of common shares, net of withholdings	(724)	$ 0	(724)
Withholdings of common shares, net of issuances (in shares)		(33,825)
Forfeited restricted stock	0	$ 0	0
Forfeited restricted stock (in shares)		500
Amortization of stock awards and restricted stock	2,130		2,130
Total comprehensive income (loss)	(104,176)			(104,926)	750
Balance at at Jun. 30, 2020	$ 496,533	$ 596	$ 477,829	$ 78,474	$ (60,366)
Balance at (in shares) at Jun. 30, 2020	59,589,770	59,589,770