Stock Benefit Plan (Tables)

12 Months Ended

Dec. 31, 2011

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Awards Granted To Employees And Non-Employee Directors

	Employee Awards						Non-Employee Director Awards
Name of Plan	Stock Options Granted		Restricted Stock Granted		Total Granted		Stock Options Granted		Restricted Stock Granted		Total Granted		Available for Future Grant of Awards
1994 Plan		1,542,381		—		1,542,381		153,654		—		153,654		—
2000 Plan		2,101,220		350,702		2,451,922		163,760		2,700		166,460		—
2003 Plan		2,737,142		96,822		2,833,964		217,723		28,935		246,658		—
2008 Plan		1,354,837		290,131		1,644,968		134,146		36,313		170,459		—
2011 Plan		166,810		87,913		254,723		—		9,464		9,464		2,931,962

Schedule Of Weighted Average Assumptions

Assumption	2011			2010			2009
Expected dividend yield		4.32	%		5.87	%		6.93	%
Expected volatility		25.98	%		19.31	%		31.33	%
Expected lives of the employee options		6.0 Years			5.7 Years			5.7 Years
Expected lives of the director options		—			6.7 Years			4.9 Years
Risk free interest rate		2.36	%		2.75	%		2.46	%

Stock Options [Member]

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Summary Of Stock Option Activity

	Number of Options			Weighted Average Exercise Price Per Option		Weighted Average Remaining Contractual Term in Years		Aggregate Intrinsic Value
Options outstanding at December 31, 2010		3,169,105		$	44.98
Granted		166,810			62.09
Exercised		(540,667	)		44.10
Cancelled		(20,876	)		50.10
Options outstanding at December 31, 2011		2,774,372		$	46.14		5.6	$	31,711
Options exercisable at December 31, 2011		1,695,451		$	45.28		4.4	$	20,837

Schedule Of Cash Proceeds Received From Stock Option Activity

	2011		2010		2009
Stock-based compensation costs recognized	$	2,813	$	2,818	$	3,289
Fair value of options vested		2,562		2,457		2,385
Cash received from the exercise of options		23,843		14,090		5,904
Intrinsic value of options exercised		9,288		5,723		1,348
Number of options granted to employees		166,810		352,454		535,056
Number of options granted to Directors		—		48,490		54,000
Grant date fair value of options granted to employees, per share	$	9.95	$	4.14	$	4.76
Grant date fair value of options granted to Directors, per share		—		4.33		4.72

Unvested Stock Option [Member]

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Summary Of Stock Option Activity

	Number of Options			Weighted Average Exercise Price Per Option
Unvested stock options at December 31, 2010		1,391,013		$	45.75
Granted		166,810			62.09
Vested		(458,026	)		47.43
Cancelled		(20,876	)		50.10
Unvested stock options at December 31, 2011		1,078,921		$	47.48

Restricted Stock [Member]

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Summary Of Restricted Stock Activity

	Number of Shares			Weighted Average Grant Date  Fair Value Per Share
Restricted stock outstanding and unvested at December 31, 2010		283,215		$	44.58
Granted		97,377			62.09
Vested and issued		(85,327	)		45.26
Cancelled		(5,817	)		43.64
Restricted stock outstanding and unvested at December 31, 2011		289,448		$	50.29

Schedule Of Cash Proceeds Received From Restricted Stock Activity

	2011		2010		2009
Stock-based compensation costs recognized	$	6,226	$	4,527	$	3,549
Fair value of restricted shares vested		5,246		3,447		1,749
Number of restricted shares granted to employees		87,913		108,252		114,078
Number of restricted shares granted to Directors		9,464		12,760		14,769
Weighted average price of shares granted, per share	$	62.09	$	49.35	$	33.90