CONSOLIDATED STATEMENTS OF STOCKHOLDERS EQUITY - USD ($) $ in Thousands	Total	Class A and B Common Stock [Member]	Additional Paid-in Capital [Member]	Purchase Price Of Excess Of Predecessor Basis, Net Of Tax [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income [Member]	Treasury Stock [Member]
Beginning Balance at Dec. 31, 2013	$ 561,527	$ 419	$ 167,357	$ (15,458)	$ 538,251	$ (85)	$ (128,957)
Beginning Balance (in shares) at Dec. 31, 2013		41,887,088					(4,598,408)
Purchase of treasury shares	(18,024)						$ (18,024)
Purchase of treasury shares (in shares)							(501,271)
Stock tendered for payments of withholding taxes	(3,195)						$ (3,195)
Stock tendered for payments of withholding taxes (in shares)							(80,772)
Issuance of restricted stock awards, net of forfeitures			(5,032)				$ 5,032
Issuance of restricted stock awards, net of forfeitures (in shares)							202,983
Share-based compensation expense	8,258		8,258
Tax benefit of share-based compensation plans	652		652
Net income	51,558				51,558
Foreign currency translation adjustment	8					8
Ending Balance at Dec. 31, 2014	600,784	$ 419	171,235	(15,458)	589,809	(77)	$ (145,144)
Ending Balance (in shares) at Dec. 31, 2014		41,887,088					(4,977,468)
Purchase of treasury shares	(28,823)						$ (28,823)
Purchase of treasury shares (in shares)							(735,524)
Stock tendered for payments of withholding taxes	(2,916)						$ (2,916)
Stock tendered for payments of withholding taxes (in shares)							(77,732)
Issuance of restricted stock awards, net of forfeitures			(4,897)				$ 4,897
Issuance of restricted stock awards, net of forfeitures (in shares)							199,893
Share-based compensation expense	7,833		7,833
Tax benefit of share-based compensation plans	114		114
Net income	70,949				70,949
Foreign currency translation adjustment	(101)					(101)
Ending Balance at Dec. 31, 2015	647,840	$ 419	174,285	(15,458)	660,758	(178)	$ (171,986)
Ending Balance (in shares) at Dec. 31, 2015		41,887,088					(5,590,831)
Purchase of treasury shares	$ (100,000)						$ (100,000)
Purchase of treasury shares (in shares)	(2,672,227)						(2,672,227)
Stock tendered for payments of withholding taxes	$ (2,489)						$ (2,489)
Stock tendered for payments of withholding taxes (in shares)							(73,546)
Issuance of restricted stock awards, net of forfeitures			(8,838)				$ 8,838
Issuance of restricted stock awards, net of forfeitures (in shares)							304,794
Share-based compensation expense	8,479		8,479
Tax benefit of share-based compensation plans	(361)		(361)
Net income	74,805				74,805
Foreign currency translation adjustment	(95)					(95)
Ending Balance at Dec. 31, 2016	$ 628,179	$ 419	$ 173,565	$ (15,458)	$ 735,563	$ (273)	$ (265,637)
Ending Balance (in shares) at Dec. 31, 2016		41,887,088					(8,031,810)