Equity-Based Compensation Profit Sharing and Deferred Compensation Plans (Details Textual) (USD $) In Thousands, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2011 Y	Dec. 31, 2010	Dec. 31, 2009
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Option vesting period, maximum	6
Restricted share units vesting period	over a period of 2 years
Shares available for grant	239,646
Restricted share units exercise price	$ 0.00
Equity-Based Compensation, Profit Sharing and Deferred Compensation Plans (Textual) [Abstract]
Option vesting period, minimum	3
Options outstanding	737,702	1,053,425
Restricted share units outstanding	154,483
Restricted share units weighted average fair value of grants	$ 714.59
Equity-based compensation costs	$ 64,473	$ 53,136	$ 46,302
Tax benefit related to equity-based compensation costs	23,600	19,200	18,000
Pre-tax reversal of stock-based compensation expense attributable to forfeiture estimate	0
Total unrecognized compensation cost for all outstanding options and RSUs	116,672
Weighted-average period over which the unrecognized compensation will be recorded	1.7
Options exercised (shares)	(333,380)	359,765	418,775
Combined plan contributions	$ 6,616	$ 6,567	$ 6,447
Shares contributed to the Employee Stock Ownership Plan	9,300	8,700
Common stock shares held in rabbi trust account	152,964	158,894
Shares of common stock issued from rabbi trust account	5,930
1996 Option Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options authorized under the plan	2,000,000
Option vesting rights	vest annually 25% increments beginning on December 31,2006, or later depending on the grant date.
Number of years for option expiration	10 years
Percentage of option vesting rights	25.00%
Shares available for grant	0
1998 Option Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options authorized under the plan	1,000,000
Option vesting rights	vest 25% increments beginning on December 31,2006, or later depending on the grant date.
Number of years for option expiration	10 years
Percentage of option vesting rights	25.00%
Shares available for grant	0
1998 Directors' Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options authorized under the plan	150,000
Option vesting rights	vest annually in twenty - five - percent (25%) increments beginning on December 31,2006, or later as determined by the date of grant.
Number of years for option expiration	10 years
Percentage of option vesting rights	25.00%
Shares available for grant	0
2000 Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Option distribution limitation for key employees and members of the board	limited to 50% or less of the total option authorized under the plan.
Options authorized under the plan	2,000,000
Option vesting rights	vest annually in 25% increments beginning on December 31,2006, or later as determined by the date of grant.
Number of years for option expiration	10 years
Percentage of option vesting rights	25.00%
Percentage of total options authorized	50.00%
Shares available for grant	0
2010 Equity Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options authorized under the plan	700,000
Option issued under the plan	39,960
Option vesting rights	50% increments ranging from December 31, 2013 through December 31, 2015.
Restricted share units vesting period	10 year period
Shares available for grant	239,646
Restricted share units exercise price	$ 0
RSUs [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options authorized under the plan	240,000
Option issued under the plan	11,394
Option vesting rights	RSUs will vest in 50% increments ranging from December 31, 2011 through December 31, 2015.
Percentage of option vesting rights	50.00%
Shares available for grant	85,517
Restricted share units exercise price	$ 0