CONSOLIDATED STATEMENTS OF EQUITY - USD ($) shares in Thousands, $ in Thousands	Total	Common stock	Additional paid-in capital	Retained earnings	Accumulated other comprehensive income (loss)	Treasury stock, at cost	Non-controlling interests
Balance at Dec. 31, 2014	$ 41,443	$ 25,413	$ 91,509	$ 367,967	$ 0	$ (444,495)	$ 1,049
Balance (in shares) at Dec. 31, 2014		25,413
Increase (Decrease) in Equity
Net income	44,800			41,598			3,202
Other comprehensive income (loss), net of tax	0
Distributions to non-controlling interest holders	(2,959)						(2,959)
Share-based compensation expense	4,812		4,812
Exercise of stock options and issuance of restricted shares	1,390			(8,292)		9,682
Issuance of restricted shares for acquisitions	21,733			(32,003)		53,736
Repurchase of shares	(58,949)					(58,949)
Balance at Dec. 31, 2015	52,270	$ 25,413	96,321	369,270	0	(440,026)	1,292
Balance (in shares) at Dec. 31, 2015		25,413
Increase (Decrease) in Equity
Net income	31,386			28,693			2,693
Other comprehensive income (loss), net of tax	(1,745)				(1,745)
Distributions to non-controlling interest holders	(2,580)						(2,580)
Share-based compensation expense	6,188		6,188
Excess tax benefit on stock-based compensation	4,779		4,779
Exercise of stock options and issuance of restricted shares	9,558			(64,177)		73,735
Repurchase of shares	(37,662)					(37,662)
Balance at Dec. 31, 2016	62,194	$ 25,413	107,288	333,786	(1,745)	(403,953)	1,405
Balance (in shares) at Dec. 31, 2016		25,413
Increase (Decrease) in Equity
Net income	311,631			308,891			2,740
Other comprehensive income (loss), net of tax	2,478				2,478
Distributions to non-controlling interest holders	(2,772)						(2,772)
Share-based compensation expense	4,255		4,255
Exercise of stock options and issuance of restricted shares	2,374			(13,491)		15,865
Treasury shares withheld for the payment of tax on restricted share issuances	(1,164)			(1,654)		490
Repurchase of shares	(39,011)					(39,011)
Balance at Dec. 31, 2017	$ 339,985	$ 25,413	$ 112,475	$ 626,600	$ 733	$ (426,609)	$ 1,373
Balance (in shares) at Dec. 31, 2017		25,413