Equity Based Compensation Plans Summary of stock options activity (Details) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Shares [Roll Forward]
Beginning balance, outstanding (in shares)	623,434	415,020	300,642
Granted (in shares)	150,325	263,113	197,500
Exercised (in shares)	(52,970)	(41,603)	(83,122)
Forfeited and canceled (in shares)	(25,301)	(13,096)	0
Ending balance, outstanding (in shares)	695,488	623,434	415,020
Options exercisable at year end (in shares)	300,632	250,620	219,820
Weighted-average exercise price [Abstract]
Outstanding at beginning of year (in dollars per share)	$ 125.96	$ 109.71	$ 88.11
Granted (in dollars per share)	$ 153.54	$ 143.95	$ 131.87
Exercised (in dollars per share)	$ 102.43	$ 77.21	$ 84.24
Forfeited and canceled (in dollars per share)	$ 135.25	$ 128.36	$ 0
Outstanding at end of year (in dollars per share)	$ 133.37	$ 125.96	$ 109.71
Options exercisable at year end (in dollars per share)	$ 119.09	$ 107.12	$ 92.31