Stock Options and Incentive Plans (Schedules of Executive Management Share-based Compensation Activity) (Details) - Performance Shares [Member] - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Number of shares
Shares/Share units potentially payable, beginning balance	185,199	185,564	229,361
Forfeitures
Payments	(95,889)	(75,385)	(118,364)
Shares accrued	98,998	75,020	74,567
Shares/Share units potentially payable, ending balance	188,308	185,199	185,564
Weighted average grant date value per share
Shares/Share units potentially payable, beginning balance	$ 30.69	$ 27.51	$ 24.13
Forfeitures
Payments	$ 29.09	$ 28.60	$ 23.05
Shares accrued	38.01	34.65	31.62
Shares/Share units potentially payable, ending balance	$ 35.35	$ 30.69	$ 27.51
Year-end intrinsic value
Shares potentially payable	$ 5,683	$ 6,667	$ 5,202
Shares potentially payable	$ 6,657	$ 5,683	$ 6,667