Condensed Consolidated Statements of Equity - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Accumulated Deficit	Accumulated Other Comprehensive Income	Treasury Stock	Noncontrolling Interest
Beginning balance (shares) at Dec. 31, 2015		23,116
Beginning balance at Dec. 31, 2015	$ 434,004	$ 23	$ 494,207	$ (151,366)	$ 4,961	$ (1,413)	$ 87,592
Beginning balance, treasury stock (shares) at Dec. 31, 2015						78
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation expense	2,050		1,730				320
Exercise of restricted stock units (shares)		9
Exercise of restricted stock units	0
Withholding taxes paid on vested restricted stock units	(46)		(26)				(20)
Changes in ownership of noncontrolling interest	1		(1,898)				1,899
Acquisition of interests held by noncontrolling owners	(1,000)						(1,000)
Distribution of treasury stock to deferred compensation plan participant (former CEO) (shares)						(23)
Distribution of treasury stock to deferred compensation plan participant (former CEO)	217		(269)			$ 486
Net income	(11,424)			(13,100)			1,676
Unrealized loss on investments, net of deferred income tax of $3,385 and reclassification adjustments of $9,781	1,484				1,484
Foreign currency translation	57				57
Ending balance (shares) at Sep. 30, 2016		23,125
Ending balance at Sep. 30, 2016	425,343	$ 23	493,744	(164,466)	6,502	$ (927)	90,467
Ending balance, treasury stock (shares) at Sep. 30, 2016						55
Beginning balance (shares) at Dec. 31, 2015		23,116
Beginning balance at Dec. 31, 2015	$ 434,004	$ 23	494,207	(151,366)	4,961	$ (1,413)	87,592
Beginning balance, treasury stock (shares) at Dec. 31, 2015						78
Ending balance (shares) at Dec. 31, 2016	23,125	23,125
Ending balance at Dec. 31, 2016	$ 427,569	$ 23	495,468	(173,231)	6,661	$ (927)	99,575
Ending balance, treasury stock (shares) at Dec. 31, 2016	55					55
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation expense	$ 2,022		1,723				299
Exercise of restricted stock units (shares)		71
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
Distribution to noncontrolling interest	(26)						(26)
Purchases of treasury stock (shares)						47
Purchases of treasury stock	(690)					$ (690)
Retirement of treasury stock (shares)		(47)				(47)
Retirement of treasury stock	0		(690)			$ 690
Distribution of treasury stock to deferred compensation plan participant (former CEO) (shares)						(54)
Distribution of treasury stock to deferred compensation plan participant (former CEO)	796		(106)			$ 902
Deconsolidation of noncontrolling interest in conjunction with sale of consolidated subsidiary	(101,342)						(101,342)
Net income	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 (shares) at Sep. 30, 2017	23,148	23,149
Ending balance at Sep. 30, 2017	$ 323,960	$ 23	$ 495,207	$ (171,652)	$ 407	$ (25)	$ 0
Ending balance, treasury stock (shares) at Sep. 30, 2017	1					1