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, 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 Equity
Net income	115,911			110,627		5,284
Contributions from non-controlling interest holders	43					43
Distributions to non-controlling interest holders	(7,145)					(7,145)
Stockholders' Equity Note, Spinoff Transaction	(105,000)			(105,000)
Share-based compensation expense	3,644		3,644
Exercise of stock options	3,214			7,661	10,875
Repurchase of shares	(16,781)				(16,781)
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	133,793			129,973		3,820
Contributions from non-controlling interest holders	28					28
Distributions to non-controlling interest holders	(4,176)					(4,176)
Share-based compensation expense	2,400		2,400
Exercise of stock options	6,885			14,539	21,424
Repurchase of shares	(141,018)				(141,018)
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	137,087			134,484		2,603
Distributions to non-controlling interest holders	(2,596)					(2,596)
Share-based compensation expense	2,236		2,236
Exercise of stock options	2,688			6,078	8,766
Repurchase of shares	(255,713)				(255,713)
Balance at Dec. 31, 2014	$ 41,443	$ 25,413	$ 91,509	$ 367,967	$ (444,495)	$ 1,049
Balance (in shares) at Dec. 31, 2014		25,413