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, 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	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					12,000