Consolidated Statements of Changes in Stockholders' Equity (USD $) In Thousands, unless otherwise specified	Total	Common Class A [Member]	Common Class B [Member]	Additional Paid-in Capital [Member]	Treasury Stock [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Unearned ESOP Shares [Member]
Balance at at Dec. 31, 2008		$ 218	$ 140	$ 336,454	$ (9,114)	$ 352,978	$ (140)	$ 0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock compensation expense				8,289
Stock options exercises		4		12,557
Conversion Class B to Class A common stock		4	(4)
Contribution of Class A common stock to Employee Stock Ownership Plan		0		4,333
Tax benefit (deficiency) from the exercise of stock options				1,097
Translation adjustments, net of tax	(32)						(32)
Treasury stock acquired					0
Actuarial gain (loss) on defined benefit pension plans, net of tax	0						0
Net income	111,764					111,764
Dividends						0
(Increase) decrease								(1,083)
Balance at at Dec. 31, 2009	817,465	226	136	362,730	(9,114)	464,742	(172)	(1,083)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock compensation expense				7,443
Stock options exercises		4		13,803
Conversion Class B to Class A common stock		3	(3)
Contribution of Class A common stock to Employee Stock Ownership Plan		1		1,796
Tax benefit (deficiency) from the exercise of stock options				(365)
Translation adjustments, net of tax	(70)						(70)
Treasury stock acquired					0
Actuarial gain (loss) on defined benefit pension plans, net of tax	87						87
Net income	125,096					125,096
Dividends						0
(Increase) decrease								1,083
Balance at at Dec. 31, 2010	966,343	234	133	385,407	(9,114)	589,838	(155)	0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock compensation expense				9,170
Stock options exercises		3		8,183
Conversion Class B to Class A common stock		1	(1)
Contribution of Class A common stock to Employee Stock Ownership Plan		1		3,559
Tax benefit (deficiency) from the exercise of stock options				(236)
Translation adjustments, net of tax	(80)						(80)
Treasury stock acquired					(44)
Actuarial gain (loss) on defined benefit pension plans, net of tax	(76)						(76)
Net income	133,306					133,306
Dividends						(30,872)
(Increase) decrease								0
Balance at at Dec. 31, 2011	$ 1,089,257	$ 239	$ 132	$ 406,083	$ (9,158)	$ 692,272	$ (311)	$ 0