Stock-Based Compensation Plans (Details) (USD $)	12 Months Ended					12 Months Ended				12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2012 2009 Plan	May 21, 2009 2009 Plan	Dec. 31, 2012 2009 Plan Stock Options	Dec. 31, 2011 2009 Plan Stock Options	Dec. 31, 2010 2009 Plan Stock Options	Dec. 31, 2012 1994 Plan	Dec. 31, 2012 1994 Plan Stock Options	Dec. 31, 2011 1994 Plan Stock Options	Dec. 31, 2010 1994 Plan Stock Options
Stock-Based Compensation Plans
Common stock authorized for issuance under incentive plan				4,199,822					1,269,822
Common stock shares available for grant					1,269,822
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01		$ 0.01
Common stock authorized under the new plan for issuance under incentive plan				2,930,000
Shares
Options outstanding at the beginning of the period (in shares)						247,403	126,484			1,112,959	2,072,217	2,836,254
Exercised (in shares)	(407,784)					(43,265)	(23,908)			(364,519)	(930,391)	(729,381)
Granted (in shares)	115,303	144,827	126,484			115,303	144,827	126,484
Forfeited (in shares)						(11,887)				(28,610)	(28,867)	(34,656)
Options outstanding at the end of the period (in shares)						307,554	247,403	126,484		719,830	1,112,959	2,072,217
Options exercisable at the end of the period (in shares)						74,618	30,771	3,417		719,830	1,012,304	1,730,978
Weighted average exercise price per share
Options outstanding at the beginning of the period (in dollars per share)						$ 98.42	$ 74.20			$ 94.10	$ 88.50	$ 80.76
Exercised (in dollars per share)						$ 85.09	$ 75.75			$ 68.21	$ 82.43	$ 57.87
Granted (in dollars per share)						$ 133.16	$ 115.83	$ 74.20
Forfeited (in dollars per share)						$ 115.15				$ 139.58	$ 68.29	$ 100.02
Options outstanding at the end of the period (in dollars per share)						$ 112.67	$ 98.42	$ 74.20		$ 105.40	$ 94.10	$ 88.50
Options exercisable at the end of the period (in dollars per share)						$ 97.46	$ 81.54	$ 74.20		$ 105.40	$ 98.62	$ 93.60