Common Stock (Narrative) (Details) (USD $)	1 Months Ended	3 Months Ended								12 Months Ended															12 Months Ended				12 Months Ended											12 Months Ended				12 Months Ended				12 Months Ended					12 Months Ended				12 Months Ended
	Nov. 30, 2009	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2010	Sep. 30, 2010	Jun. 30, 2010	Mar. 31, 2010	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2011 Class B Common [Member]	Dec. 31, 2011 Outstanding Stock Options [Member]	Dec. 31, 2010 Outstanding Stock Options [Member]	Dec. 31, 2009 Outstanding Stock Options [Member]	Dec. 31, 2011 Restricted Stock [Member]	Dec. 31, 2010 Restricted Stock [Member]	Dec. 31, 2009 Restricted Stock [Member]	Dec. 31, 2011 Amended And Restated 1992 Stock Option Plan [Member]	Dec. 31, 2011 Stock Incentive Plan [Member]	Dec. 31, 2010 Stock Incentive Plan [Member]	Dec. 31, 2009 Stock Incentive Plan [Member]	Dec. 31, 2011 Stock Incentive Plan [Member] Class B Common [Member]	Dec. 31, 2011 2001 Plan [Member]	Dec. 31, 2010 2001 Plan [Member]	Dec. 31, 2009 2001 Plan [Member]	Dec. 31, 2010 2001 Plan [Member] Class B Common [Member]	Dec. 31, 2011 2010 Plan [Member]	Dec. 31, 2011 Employee Stock Purchase Plan [Member]	Dec. 31, 2010 Employee Stock Purchase Plan [Member]	Dec. 31, 2009 Employee Stock Purchase Plan [Member]	Dec. 31, 2011 Long-Term Incentive Plans [Member]	Dec. 31, 2010 Long-Term Incentive Plans [Member]	Dec. 31, 2009 Long-Term Incentive Plans [Member]	Dec. 31, 2011 Chief Executive Officer ("CEO") And Chairman Of The Board [Member]	Dec. 31, 2011 Chief Executive Officer ("CEO") And Chairman Of The Board [Member] Class B Common Stock 2010 [Member]	Dec. 31, 2010 Chief Executive Officer ("CEO") And Chairman Of The Board [Member] Class B Common Stock 2010 [Member]	Mar. 31, 2010 Chief Executive Officer ("CEO") And Chairman Of The Board [Member] Class B Common Stock 2010 [Member]	Dec. 31, 2011 Chief Executive Officer [Member] Class B Common Stock 2009 [Member]	Dec. 31, 2010 Chief Executive Officer [Member] Class B Common Stock 2009 [Member]	Dec. 31, 2009 Chief Executive Officer [Member] Class B Common Stock 2009 [Member]	Mar. 31, 2009 Chief Executive Officer [Member] Class B Common Stock 2009 [Member]	Dec. 31, 2011 Chief Executive Officer [Member] Class B Common Stock 2008 [Member]	Dec. 31, 2010 Chief Executive Officer [Member] Class B Common Stock 2008 [Member]	Dec. 31, 2009 Chief Executive Officer [Member] Class B Common Stock 2008 [Member]	Mar. 31, 2008 Chief Executive Officer [Member] Class B Common Stock 2008 [Member]	Dec. 31, 2011 Chief Executive Officer [Member] Class B Common Stock 2007 [Member]	Dec. 31, 2010 Chief Executive Officer [Member] Class B Common Stock 2007 [Member]	Dec. 31, 2009 Chief Executive Officer [Member] Class B Common Stock 2007 [Member]	Dec. 31, 2008 Chief Executive Officer [Member] Class B Common Stock 2007 [Member]	Dec. 31, 2007 Chief Executive Officer [Member] Class B Common Stock 2007 [Member]	Dec. 31, 2011 Various Employees [Member] Class B Common Stock 2007 [Member]	Dec. 31, 2010 Various Employees [Member] Class B Common Stock 2007 [Member]	Dec. 31, 2009 Various Employees [Member] Class B Common Stock 2007 [Member]	Dec. 31, 2007 Various Employees [Member] Class B Common Stock 2007 [Member]	Dec. 31, 2010 Various Officers And Employees [Member] Class B Common Stock 2006 [Member]	Dec. 31, 2009 Various Officers And Employees [Member] Class B Common Stock 2006 [Member]	Dec. 31, 2006 Various Officers And Employees [Member] Class B Common Stock 2006 [Member]
Percentage of stock dividend	100.00%
Dividends declared and paid, per share										$ 0.20	$ 0.2	$ 0.17
Dividends declared and paid										$ 19,000,000	$ 19,000,000	$ 17,000,000
Stock repurchase programs authorized to purchase, shares		10,000,000								10,000,000
Excess tax benefit										0	0	0
Compensation cost recognized										18,200,000	16,800,000	13,100,000		15,800,000	13,300,000	9,900,000	2,000,000	3,100,000	2,800,000										198,000	461,000	339,000	316,000	2,400,000	3,500,000	3,200,000		375,000	355,000		556,000	556,000	482,000		375,000	375,000	375,000		333,000	375,000				120,000	135,000	135,000		1,300,000	1,500,000
Compensation cost recognized, pre-tax charge														15,800,000	13,300,000	9,900,000
Compensation cost recognized, after-tax														9,800,000	8,300,000	6,200,000	1,200,000	2,000,000	1,800,000										947,000
Stock-based compensation plans expired																				July of 2005						March, 2010
Earnings per share diluted		$ 0.98	$ 0.86	$ 1.04	$ 1.15	$ 0.38	$ 0.57	$ 0.67	$ 0.73	$ 4.04	$ 2.34	$ 2.64		$ 0.10	$ 0.08	$ 0.06
Shares reserved													6,000,000											23,000,000				2,400,000
Stock options granted during period (net of cancellations)										2,894,500	94,000	2,635,000									2,747,500	82,750	2,400,500
Weighted-average grant date fair value of option granted																					$ 11.62	$ 7.84	$ 7.93
Percentage of discount provided to eligible employees for purchase of shares under employee stock purchase plan										10.00%
Stock issued under employee stock purchase plan																														98,366	94,955	138,870
Stock issued during period, net of cancellations										700,000																1,200,000
Fully vested shares										1,757,500															78,133	313,770	31,638									12,368				27,462	27,463			15,546	15,548	15,548		15,341	15,341	15,340	15,340
Issuance of restricted shares approved, shares													21,500																										49,472				109,850				62,190					61,362				22,250			247,000
Restricted shares price, per share													$ 53.21																										$ 30.32				$ 20.26				$ 24.12					$ 24.45				$ 29.62			$ 25.71
Issuance of restricted shares, value													1,100,000																										1,500,000				2,200,000				1,500,000					1,500,000				659,000			6,400,000
Estimated compensation cost																																					770,000			630,000				15,000									42,000
Total in-the-money value of all stock options exercised during the year										$ 28,900,000	$ 26,800,000	$ 10,200,000
Issuance upon conversion of shares													31,167,268