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	60,595			58,449		2,146
Contributions from non-controlling interest holders	15					15
Distributions to non-controlling interest holders	(1,889)					(1,889)
Share-based compensation expense	1,519		1,519
Exercise of stock options	2,914			(3,639)	6,553
Repurchase of shares	(51,573)				(51,573)
Balance at Jun. 30, 2013	171,410	25,413	88,392	178,937	(122,974)	1,642
Balance (in shares) at Jun. 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	94,878			93,732		1,146
Distributions to non-controlling interest holders	(1,207)					(1,207)
Share-based compensation expense	1,130		1,130
Exercise of stock options	639			(2,932)	3,571
Repurchase of shares	(80,702)				(80,702)
Balance at Jun. 30, 2014	$ 172,479	$ 25,413	$ 90,403	$ 330,361	$ (274,679)	$ 981
Balance (in shares) at Jun. 30, 2014		25,413