Stock Option and Incentive Plan Schedule of Stock Options Status (Details) - $ / shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Beginning Outstanding, Shares	547,129	547,129	553,312
Beginning Oustanding, Weighted Average Exercise Price	$ 96.38	$ 96.38	$ 97.21
Exercised, Shares	(6,688)	0	(11,447)
Exercised, Weighted Averge Exercise Price	$ 99.15	$ 0.00	$ 92.50
Special dividend adjustment (shares)			5,264
Special dividend adjustment weighted average exercise price			$ 96.38
Ending Outstanding, Shares	540,441	547,129	547,129
Ending Oustanding, Weighted Average Exercise Pric	$ 96.35	$ 96.38	$ 96.38