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)		151,300
Issuance of common shares, net of withholdings	(1,521)	$ 1	(1,522)
Withholdings of common shares, net of issuances (in shares)		86,097
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)		3,000
Amortization of stock awards and restricted stock	5,281		5,281
Total comprehensive income (loss)	112,156			101,392	10,764
Balance at at Sep. 30, 2019	480,996	$ 594	474,915	86,085	(80,598)
Balance at (in shares) at Sep. 30, 2019		59,368,570
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
Stock-based compensation plans
Grant of restricted stock	0	$ 0	0
Grant of restricted stock (in shares)		7,500
Issuance of common shares, net of withholdings	(25)	$ 0	(25)
Withholdings of common shares, net of issuances (in shares)		(1,069)
Forfeited restricted stock	0	$ 0	0
Forfeited restricted stock (in shares)		1,700
Amortization of stock awards and restricted stock	1,887		1,887
Total comprehensive income (loss)	108,325			105,328	2,997
Balance at at Sep. 30, 2019	480,996	$ 594	474,915	86,085	(80,598)
Balance at (in shares) at Sep. 30, 2019		59,368,570
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	5,786		5,786
Total comprehensive income (loss)	29,238			26,988	2,250
Balance at at Sep. 30, 2020	$ 714,620	$ 596	700,757	72,883	(59,616)
Balance at (in shares) at Sep. 30, 2020	59,589,770	59,589,770
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
Stock-based compensation plans
Grant of restricted stock	0	$ 0	0
Grant of restricted stock (in shares)		0
Issuance of common shares, net of withholdings	0	$ 0	0
Withholdings of common shares, net of issuances (in shares)		0
Forfeited restricted stock	0	$ 0	0
Forfeited restricted stock (in shares)		0
Amortization of stock awards and restricted stock	1,835		1,835
Total comprehensive income (loss)	(4,841)			(5,591)	750
Balance at at Sep. 30, 2020	$ 714,620	$ 596	$ 700,757	$ 72,883	$ (59,616)
Balance at (in shares) at Sep. 30, 2020	59,589,770	59,589,770