Consolidated Statements of Changes in Stockholders Equity and Comprehensive Income (USD $) In Thousands	Common Class A [Member]	Common Class B [Member]	Additional Paid-in Capital [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Retained Earnings [Member]	Total
Balance at December 31, 2008 at Dec. 31, 2008	$ 234,522	$ 468	$ 9,275	$ (5,810)	$ 9,888	$ 248,343
Balance at December 31, 2008 (in Shares) at Dec. 31, 2008	16,717	3,762
Net income (loss)					9,151	9,151
Fair value of interest rate swap agreements, net of tax expense (benefit)				1,960		1,960
Comprehensive income						11,111
Issuance of stock in connection with employee stock plans	2,426					2,426
Issuance of stock in connection with employee stock plans (in Shares)	635
Issuance of restricted stock to employees and directors (in Shares)	110
Shares forfeited by employees (in Shares)	(26)
Issuance of Class A common stock	43,150					43,150
Issuance of Class A common stock (in Shares)	4,600
Repurchase of Class A common stock	(1)					(1)
Compensation for stock and stock option issuances and excess tax benefits from option exercises	783		1,226			2,009
Balance at Dec. 31, 2009	280,880	468	10,501	(3,850)	19,039	307,038
Balance (in Shares) at Dec. 31, 2009	22,036	3,762
Net income (loss)					13,719	13,719
Fair value of interest rate swap agreements, net of tax expense (benefit)				(1,019)		(1,019)
Comprehensive income						12,700
Issuance of stock in connection with employee stock plans	4,192					4,192
Issuance of stock in connection with employee stock plans (in Shares)	658
Shares forfeited by employees (in Shares)	(9)
Repurchase of Class A common stock	(1,626)					(1,626)
Repurchase of Class A common stock (in Shares)	(162)
Compensation for stock and stock option issuances and excess tax benefits from option exercises	1,361		471			1,832
Dividends paid					(3,919)	(3,919)
Balance at Dec. 31, 2010	284,807	468	10,972	(4,869)	28,839	320,217
Balance (in Shares) at Dec. 31, 2010	22,523	3,762
Net income (loss)					58,860	58,860
Fair value of interest rate swap agreements, net of tax expense (benefit)				361		361
Comprehensive income						59,221
Issuance of stock in connection with employee stock plans	5,654					5,654
Issuance of stock in connection with employee stock plans (in Shares)	438
Issuance of restricted stock to employees and directors (in Shares)	11
Shares forfeited by employees (in Shares)	(5)
Repurchase of Class A common stock	(13,568)					(13,568)
Repurchase of Class A common stock (in Shares)	(772)
Compensation for stock and stock option issuances and excess tax benefits from option exercises	2,473		(54)			2,419
Dividends paid					(6,822)	(6,822)
Balance at Dec. 31, 2011	$ 279,366	$ 468	$ 10,918	$ (4,508)	$ 80,877	$ 367,121
Balance (in Shares) at Dec. 31, 2011	22,195	3,762