Stock Award Plans, Employee Plan Stock Option Activity (Details) - Employee Stock Award Plan [Member] - $ / shares	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Stock Award Plan Information [Abstract]
Shares available for future grants (in shares)	1,575,948
Stock Options [Member]
Stock Award Plan Information [Abstract]
Term of grant	7 years
Vesting period	3 years
Outstanding Non-Qualified or Nonincentive Stock Awards [Roll Forward]
Outstanding at Period Start (in shares)	654,655	601,121	430,432
Granted (in shares)	115,797	123,141	186,706
Exercised (in shares)	(283,886)	(36,616)
Forfeited (in shares)	(21,864)	(32,991)	(16,017)
Outstanding at Period End (in shares)	464,702	654,655	601,121
Weighted Average Exercise Price [Abstract]
Outstanding at Period Start (in dollars per share)	$ 66.45	$ 65.33	$ 71.01
Granted (in dollars per share)	75.50	68.46	53.50
Exercised (in dollars per share)	61.81	47.95
Forfeited (in dollars per share)	102.42	74.07	80.17
Outstanding at Period End (in dollars per share)	$ 69.85	$ 66.45	$ 65.33
Stock options exercisable (in shares)	230,254	380,608	321,942
Stock Appreciation Rights [Member]
Outstanding Non-Qualified or Nonincentive Stock Awards [Roll Forward]
Outstanding at Period End (in shares)	0