Stock-Based Compensation Plans (Details) (USD $)	9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012
Shares
Exercised (in shares)	(33,900)
Granted (in shares)	215,230	115,303
2009 Plan | Stock Options
Shares
Options outstanding at the beginning of the period (in shares)	307,554
Exercised (in shares)	(9,939)
Granted (in shares)	215,230
Forfeited (in shares)	(1,267)
Options outstanding at the end of the period (in shares)	511,578
Options exercisable at the end of the period (in shares)	194,177
Weighted average exercise price per share
Options outstanding at the beginning of the period (in dollars per share)	$ 112.67
Exercised (in dollars per share)	$ 94.73
Granted (in dollars per share)	$ 129.03
Forfeited (in dollars per share)	$ 131.56
Options outstanding at the end of the period (in dollars per share)	$ 119.85
Options exercisable at the end of the period (in dollars per share)	$ 105.48
1994 Plan | Stock Options
Shares
Options outstanding at the beginning of the period (in shares)	719,830
Exercised (in shares)	(23,961)
Forfeited (in shares)	(4,012)
Options outstanding at the end of the period (in shares)	691,857
Options exercisable at the end of the period (in shares)	691,857
Weighted average exercise price per share
Options outstanding at the beginning of the period (in dollars per share)	$ 105.40
Exercised (in dollars per share)	$ 79.84
Forfeited (in dollars per share)	$ 127.56
Options outstanding at the end of the period (in dollars per share)	$ 106.16
Options exercisable at the end of the period (in dollars per share)	$ 106.16