Accounting for Stock-Based Compensation (Schedule of Share-based Compensation, Stock Options, Activity) (Details) - Employee Stock Option [Member] - $ / shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Beginning Balance, shares	1,185,320	1,232,158	1,953,727
Exercised, Shares			(711,568)
Forfeited and Cancelled, Shares	(69,653)	(46,838)	(10,001)
Ending Balance, shares	1,115,667	1,185,320	1,232,158
Beginning of Period, Weighted Average Exercise Price	$ 28.12	$ 31.65	$ 32.94
Exercised, Weighted Average Exercise Price			35.15
Forfeited and Cancelled, Weighted Average Exercise Price	33.52	27.44	34.96
End of Period, Weighted Average Exercise Price	$ 31.56	$ 28.12	$ 31.65
Weighted Average Remaining Contractual Term	2 years
Exercisable, Shares	1,115,667
Exercisable, Weighted Average Exercise Price	$ 31.56
Exercisable, Weighted Average Remaining Contractual Term	2 years