Condensed Consolidated Statements of Equity - Unaudited - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Accumulated Deficit	Accumulated Other Comprehensive Income	Treasury Stock
Beginning balance (in shares) at Dec. 31, 2017		23,154,000
Beginning balance at Dec. 31, 2017	$ 207,163	$ 23	$ 379,388	$ (172,767)	$ 544	$ (25)
Beginning balance, treasury stock (in shares) at Dec. 31, 2017						1,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation expense	124		124
Purchases of treasury stock (in shares)						442,000
Purchases of treasury stock	(4,985)					$ (4,985)
Retirement of treasury stock (in shares)		(336,000)				(336,000)
Retirement of treasury stock	0		(3,776)			$ 3,776
Net income (loss)	(2,863)			(2,863)
Reclassification of unrealized gain on investments to accumulated deficit	17			561	(544)
Ending balance (in shares) at Mar. 31, 2018		22,818,000
Ending balance at Mar. 31, 2018	199,456	$ 23	375,736	(175,069)	0	$ (1,234)
Ending balance, treasury stock (in shares) at Mar. 31, 2018						107,000
Beginning balance (in shares) at Dec. 31, 2017		23,154,000
Beginning balance at Dec. 31, 2017	207,163	$ 23	379,388	(172,767)	544	$ (25)
Beginning balance, treasury stock (in shares) at Dec. 31, 2017						1,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	(3,229)
Ending balance (in shares) at Sep. 30, 2018		21,685,000
Ending balance at Sep. 30, 2018	184,502	$ 22	362,651	(175,436)	0	$ (2,735)
Ending balance, treasury stock (in shares) at Sep. 30, 2018						223,000
Beginning balance (in shares) at Mar. 31, 2018		22,818,000
Beginning balance at Mar. 31, 2018	199,456	$ 23	375,736	(175,069)	0	$ (1,234)
Beginning balance, treasury stock (in shares) at Mar. 31, 2018						107,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation expense	176		176
Exercise of restricted stock units (in shares)		23,000
Exercise of restricted stock units	0
Purchases of treasury stock (in shares)						713,000
Purchases of treasury stock	(7,960)					$ (7,960)
Retirement of treasury stock (in shares)		(819,000)				(819,000)
Retirement of treasury stock	0	$ (1)	(9,168)			$ 9,169
Net income (loss)	4,302			4,302
Ending balance (in shares) at Jun. 30, 2018		22,022,000
Ending balance at Jun. 30, 2018	195,974	$ 22	366,744	(170,767)	0	$ (25)
Ending balance, treasury stock (in shares) at Jun. 30, 2018						1,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation expense	80		80
Purchases of treasury stock (in shares)						561,000
Purchases of treasury stock	(6,908)					$ (6,908)
Retirement of treasury stock (in shares)		(337,000)				(337,000)
Retirement of treasury stock	(1)	$ 0	(4,173)			$ 4,172
Distribution of treasury stock to deferred compensation plan participant (in shares)						(2,000)
Distribution of treasury stock to deferred compensation plan participant	26					$ 26
Net income (loss)	(4,669)			(4,669)
Ending balance (in shares) at Sep. 30, 2018		21,685,000
Ending balance at Sep. 30, 2018	$ 184,502	$ 22	362,651	(175,436)	$ 0	$ (2,735)
Ending balance, treasury stock (in shares) at Sep. 30, 2018						223,000
Beginning balance (in shares) at Dec. 31, 2018	20,848,000	20,848,000
Beginning balance at Dec. 31, 2018	$ 176,624	$ 21	353,250	(175,536)		$ (1,111)
Beginning balance, treasury stock (in shares) at Dec. 31, 2018	121,000					121,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation expense	$ 22		22
Purchases of treasury stock (in shares)						420,000
Purchases of treasury stock	(4,340)					$ (4,340)
Retirement of treasury stock (in shares)		(529,000)				(529,000)
Retirement of treasury stock	0	$ (1)	(5,328)			$ 5,329
Net income (loss)	6,684			6,684
Ending balance (in shares) at Mar. 31, 2019		20,319,000
Ending balance at Mar. 31, 2019	$ 178,990	$ 20	347,944	(168,852)		$ (122)
Ending balance, treasury stock (in shares) at Mar. 31, 2019						12,000
Beginning balance (in shares) at Dec. 31, 2018	20,848,000	20,848,000
Beginning balance at Dec. 31, 2018	$ 176,624	$ 21	353,250	(175,536)		$ (1,111)
Beginning balance, treasury stock (in shares) at Dec. 31, 2018	121,000					121,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	$ 6,945
Ending balance (in shares) at Sep. 30, 2019	19,968,000	19,968,000
Ending balance at Sep. 30, 2019	$ 175,552	$ 20	344,193	(168,591)		$ (70)
Ending balance, treasury stock (in shares) at Sep. 30, 2019	7,000					7,000
Beginning balance (in shares) at Mar. 31, 2019		20,319,000
Beginning balance at Mar. 31, 2019	$ 178,990	$ 20	347,944	(168,852)		$ (122)
Beginning balance, treasury stock (in shares) at Mar. 31, 2019						12,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation expense	22		22
Exercise of restricted stock units	(5)		(5)
Purchases of treasury stock (in shares)						245,000
Purchases of treasury stock	(2,704)					$ (2,704)
Retirement of treasury stock (in shares)		(252,000)				(252,000)
Retirement of treasury stock	0		(2,771)			$ 2,771
Net income (loss)	(1,118)			(1,118)
Ending balance (in shares) at Jun. 30, 2019		20,067,000
Ending balance at Jun. 30, 2019	175,185	$ 20	345,190	(169,970)		$ (55)
Ending balance, treasury stock (in shares) at Jun. 30, 2019						5,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation expense	22		22
Purchases of treasury stock (in shares)						101,000
Purchases of treasury stock	(1,034)					$ (1,034)
Retirement of treasury stock (in shares)		(99,000)				(99,000)
Retirement of treasury stock	0		(1,019)			$ 1,019
Net income (loss)	$ 1,379			1,379
Ending balance (in shares) at Sep. 30, 2019	19,968,000	19,968,000
Ending balance at Sep. 30, 2019	$ 175,552	$ 20	$ 344,193	$ (168,591)		$ (70)
Ending balance, treasury stock (in shares) at Sep. 30, 2019	7,000					7,000