CONSOLIDATED STATEMENTS OF CHANGES IN EQUITY (USD $) In Thousands, unless otherwise specified	Total	Common stock [Member]	Additional paid-in Capital [Member]	Retained earnings [Member]	Accumulated other comprehensive income [Member]	Treasury stock [Member]	Noncontrolling interest [Member]
Beginning Balance at Dec. 31, 2010	$ 299,946	$ 30	$ 48,887	$ 205,453	$ 14,757	$ (34,151)	$ 64,970
Comprehensive income:
Net income	37,052			28,185			8,867
Foreign currency translation adjustment	2,346				1,973		373
Net derivative instrument gain (loss), net of tax	15				12		3
Shares issued upon exercise of stock options	958	1	957
Purchase of subsidiary shares from noncontrolling interests	(750)		(417)				(333)
Sale of subsidiary shares to noncontrolling interests	2,844		611				2,233
Dividends	(10,473)			(7,324)			(3,149)
Stock compensation	712		528	136			48
Ending Balance at Sep. 30, 2011	332,650	31	52,408	252,471	7,854	(34,151)	80,323
Beginning Balance at Dec. 31, 2011	324,350	31	50,883	228,164	7,747	(34,151)	71,676
Comprehensive income:
Net income	40,912			31,523			9,389
Foreign currency translation adjustment	152				142		10
Net derivative instrument gain (loss), net of tax	(45)				(35)		(10)
Shares issued upon exercise of stock options	416		416
Sale of subsidiary shares to noncontrolling interests	3,284		737				2,547
Dividends	(10,669)			(7,336)			(3,333)
Stock compensation	536		372	120			44
Ending Balance at Sep. 30, 2012	$ 358,936	$ 31	$ 52,408	$ 252,471	$ 7,854	$ (34,151)	$ 80,323