CONDENSED CONSOLIDATED STATEMENTS OF EQUITY (USD $) In Thousands, unless otherwise specified	Total	Common Stock	Additional Paid-in Capital	Retained Earnings	Treasury Stock, at Cost	Non-controlling Interests
Balance at Dec. 31, 2010	$ 151,898	$ 25,413	$ 79,297	$ 58,546	$ (14,418)	$ 3,060
Balance (in shares) at Dec. 31, 2010		25,413
Increase (Decrease) in Stockholders' Equity
Net income	30,814			28,210		2,604
Contributions from non-controlling interest holders	14					14
Distributions to non-controlling interest holders	(4,193)					(4,193)
Share-based compensation expense	1,379		1,379
Exercise of stock options	510			(2,012)	2,522
Repurchase of shares	(12,546)				(12,546)
Balance at Jun. 30, 2011	167,876	25,413	80,676	84,744	(24,442)	1,485
Balance (in shares) at Jun. 30, 2011		25,413
Balance at Dec. 31, 2011	165,943	25,413	83,229	126,161	(72,048)	3,188
Balance (in shares) at Dec. 31, 2011		25,413
Increase (Decrease) in Stockholders' Equity
Net income	56,473			53,310		3,163
Contributions from non-controlling interest holders	24					24
Distributions to non-controlling interest holders	(4,830)					(4,830)
Share-based compensation expense	892		892
Exercise of stock options	2,018			(4,397)	6,415
Repurchase of shares	(16,781)				(16,781)
Balance at Jun. 30, 2012	$ 203,739	$ 25,413	$ 84,121	$ 175,074	$ (82,414)	$ 1,545
Balance (in shares) at Jun. 30, 2012		25,413