Condensed Consolidated Statements of Equity - Unaudited - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Accumulated Deficit	Accumulated Other Comprehensive Income	Treasury Stock	Noncontrolling Interest
Beginning balance (in shares) at Dec. 31, 2016		23,125,000
Beginning balance at Dec. 31, 2016	$ 427,569	$ 23	$ 495,468	$ (173,231)	$ 6,661	$ (927)	$ 99,575
Beginning balance, treasury stock (in shares) at Dec. 31, 2016						55,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation expense	2,022		1,723				299
Exercise of restricted stock units (in shares)		71,000
Exercise of restricted stock units	0
Withholding taxes paid on vested restricted stock units	(844)		(723)				(121)
Changes in ownership of noncontrolling interest	0		(465)				465
Acquisition of interests held by noncontrolling owners	0
Distribution of treasury stock to deferred compensation plan participants (in shares)						(54,000)
Distribution of treasury stock to deferred compensation plan participants	796		(106)			$ 902
Distribution to noncontrolling interest	(26)						(26)
Purchases of treasury stock (in shares)						47,000
Purchases of treasury stock	(690)					$ (690)
Retirement of treasury stock (in shares)		(47,000)				(47,000)
Retirement of treasury stock	0		(690)			$ 690
Deconsolidation of noncontrolling interest in conjunction with sale of consolidated subsidiary	(101,342)						(101,342)
Net income (loss)	2,729			1,579			1,150
Unrealized loss on investments, net of deferred income tax of $3,385 and reclassification adjustments of $9,781	(6,286)				(6,286)
Foreign currency translation	32				32
Ending balance (in shares) at Sep. 30, 2017		23,149,000
Ending balance at Sep. 30, 2017	323,960	$ 23	495,207	(171,652)	407	$ (25)	0
Ending balance, treasury stock (in shares) at Sep. 30, 2017						1,000
Beginning balance at Jun. 30, 2017					788
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	(6,284)
Ending balance (in shares) at Sep. 30, 2017		23,149,000
Ending balance at Sep. 30, 2017	323,960	$ 23	495,207	(171,652)	407	$ (25)	$ 0
Ending balance, treasury stock (in shares) at Sep. 30, 2017						1,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Reclassification of unrealized gain on investments to accumulated deficit	$ 16			560	(544)
Beginning balance (in shares) at Dec. 31, 2017	23,153,000	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					1,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation expense	$ 380		380
Exercise of restricted stock units (in shares)		23,000
Exercise of restricted stock units	0
Distribution of treasury stock to deferred compensation plan participants (in shares)						2,000
Distribution of treasury stock to deferred compensation plan participants	26					$ 26
Purchases of treasury stock (in shares)						1,716,000
Purchases of treasury stock	(19,853)					$ (19,853)
Retirement of treasury stock (in shares)		(1,492,000)				(1,492,000)
Retirement of treasury stock	(1)	$ (1)	(17,117)			$ 17,117
Net income (loss)	$ (3,229)			(3,229)
Ending balance (in shares) at Sep. 30, 2018	21,685,000	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					223,000