CONDENSED CONSOLIDATED STATEMENTS OF EQUITY - USD ($) shares in Thousands, $ in Thousands	Total	Common stock	Additional paid-in capital	Retained earnings	Accumulated other comprehensive income (loss)	Treasury stock, at cost	Non-controlling interests
Balance (in shares) at Dec. 31, 2017		25,413
Balance at Dec. 31, 2017	$ 339,985	$ 25,413	$ 112,475	$ 626,600	$ 733	$ (426,609)	$ 1,373
Increase (Decrease) in Equity
Net (loss) income	(3,607)			(4,132)			525
Distributions to non-controlling interest holders	(672)						(672)
Share-based compensation expense	2,201		2,201
Exercise of stock options and issuance of restricted share units and restricted shares	2,617			(12,500)		15,117
Repurchase of shares	(9,994)					(9,994)
Balance (in shares) at Mar. 31, 2018		25,413
Balance at Mar. 31, 2018	320,082	$ 25,413	114,676	600,253	0	(421,486)	1,226
Balance (in shares) at Dec. 31, 2017		25,413
Balance at Dec. 31, 2017	339,985	$ 25,413	112,475	626,600	733	(426,609)	1,373
Increase (Decrease) in Equity
Net (loss) income	8,169
Balance (in shares) at Sep. 30, 2018		25,413
Balance at Sep. 30, 2018	323,141	$ 25,413	118,625	603,343	0	(425,767)	1,527
Balance (in shares) at Mar. 31, 2018		25,413
Balance at Mar. 31, 2018	320,082	$ 25,413	114,676	600,253	0	(421,486)	1,226
Increase (Decrease) in Equity
Net (loss) income	2,255			1,568			687
Distributions to non-controlling interest holders	(509)						(509)
Share-based compensation expense	1,910		1,910
Exercise of stock options and issuance of restricted share units and restricted shares	90			(4,737)		4,827
Treasury shares withheld for the payment of tax on restricted share unit and restricted share issuances and stock option exercises	(410)			(816)		406
Repurchase of shares	(11,127)					(11,127)
Balance (in shares) at Jun. 30, 2018		25,413
Balance at Jun. 30, 2018	312,291	$ 25,413	116,586	596,268	0	(427,380)	1,404
Increase (Decrease) in Equity
Net (loss) income	9,521			8,667			854
Distributions to non-controlling interest holders	(731)						(731)
Share-based compensation expense	2,039		2,039
Exercise of stock options and issuance of restricted share units and restricted shares	869			(1,287)		2,156
Treasury shares withheld for the payment of tax on restricted share unit and restricted share issuances and stock option exercises	(198)			(305)		107
Repurchase of shares	(650)					(650)
Balance (in shares) at Sep. 30, 2018		25,413
Balance at Sep. 30, 2018	323,141	$ 25,413	118,625	603,343	0	(425,767)	1,527
Balance (in shares) at Dec. 31, 2018		25,413
Balance at Dec. 31, 2018	296,668	$ 25,413	122,667	590,655	0	(443,304)	1,237
Increase (Decrease) in Equity
Net (loss) income	(2,744)			(3,184)			440
Distributions to non-controlling interest holders	(620)						(620)
Share-based compensation expense	2,621		2,621
Exercise of stock options and issuance of restricted share units and restricted shares	28			(1,549)		1,577
Treasury shares withheld for the payment of tax on restricted share unit and restricted share issuances and stock option exercises	(585)			(1,163)		578
Balance (in shares) at Mar. 31, 2019		25,413
Balance at Mar. 31, 2019	295,368	$ 25,413	125,288	584,759	0	(441,149)	1,057
Balance (in shares) at Dec. 31, 2018		25,413
Balance at Dec. 31, 2018	296,668	$ 25,413	122,667	590,655	0	(443,304)	1,237
Increase (Decrease) in Equity
Net (loss) income	228
Balance (in shares) at Sep. 30, 2019		25,413
Balance at Sep. 30, 2019	288,656	$ 25,413	130,951	579,557	0	(448,590)	1,325
Balance (in shares) at Mar. 31, 2019		25,413
Balance at Mar. 31, 2019	295,368	$ 25,413	125,288	584,759	0	(441,149)	1,057
Increase (Decrease) in Equity
Net (loss) income	(4,604)			(5,844)			1,240
Distributions to non-controlling interest holders	(518)						(518)
Share-based compensation expense	2,832		2,832
Exercise of stock options and issuance of restricted share units and restricted shares	207			(3,473)		3,680
Treasury shares withheld for the payment of tax on restricted share unit and restricted share issuances and stock option exercises	(713)			(1,402)		689
Repurchase of shares	(6,700)					(6,700)
Balance (in shares) at Jun. 30, 2019		25,413
Balance at Jun. 30, 2019	285,872	$ 25,413	128,120	574,040	0	(443,480)	1,779
Increase (Decrease) in Equity
Net (loss) income	7,576			7,165			411
Distributions to non-controlling interest holders	(865)						(865)
Share-based compensation expense	2,831		2,831
Exercise of stock options and issuance of restricted share units and restricted shares	157			(1,214)		1,371
Treasury shares withheld for the payment of tax on restricted share unit and restricted share issuances and stock option exercises	(218)			(434)		216
Repurchase of shares	(6,697)					(6,697)
Balance (in shares) at Sep. 30, 2019		25,413
Balance at Sep. 30, 2019	$ 288,656	$ 25,413	$ 130,951	$ 579,557	$ 0	$ (448,590)	$ 1,325