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, 2012	$ 159,829	$ 25,413	$ 86,873	$ 124,127	$ (77,954)	$ 1,370
Balance (in shares) at Dec. 31, 2012		25,413
Increase (Decrease) in Equity
Net income	97,550			94,457		3,093
Contributions from non-controlling interest holders	18					18
Distributions to non-controlling interest holders	(3,234)					(3,234)
Share-based compensation expense	2,076		2,076
Exercise of stock options	4,710			(8,801)	13,511
Repurchase of shares	(87,418)				(87,418)
Balance at Sep. 30, 2013	173,531	25,413	88,949	209,783	(151,861)	1,247
Balance (in shares) at Sep. 30, 2013		25,413
Balance at Dec. 31, 2013	157,741	25,413	89,273	239,561	(197,548)	1,042
Balance (in shares) at Dec. 31, 2013		25,413
Increase (Decrease) in Equity
Net income	137,993			136,019		1,974
Distributions to non-controlling interest holders	(1,813)					(1,813)
Share-based compensation expense	1,638		1,638
Exercise of stock options	2,523			(5,628)	8,151
Repurchase of shares	(208,820)				(208,820)
Balance at Sep. 30, 2014	$ 89,262	$ 25,413	$ 90,911	$ 369,952	$ (398,217)	$ 1,203
Balance (in shares) at Sep. 30, 2014		25,413