Stock Based Compensation (Restricted Stock Units Activity) (Details) - Restricted Stock Units (RSUs) [Member] - $ / shares	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Shares, Outstanding at Beginning of Year	213,899
Shares, Granted	277,261
Shares, Vested	(220,105)
Shares, Canceled	(13,472)
Shares, Outstanding at End of Year	257,583	213,899
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Roll Forward]
Shares, Outstanding at Beginning of Year, Weighted Average Grant Date Fair Value	$ 42.32
Shares, Granted, Weighted Average Grant Date Fair Value	49.34	$ 44.33	$ 42.28
Shares, Vested, Weighted Average Grant Date Fair Value	46.02
Shares, Canceled, Weighted Average Grant Date Fair Value	44.94
Shares, Outstanding at End of Year, Weighted Average Grant Date Fair Value	$ 46.58	$ 42.32
Shares, Outstanding at End of Year, Weighted Average Remaining Years Contractual Term	1 year 2 months 24 days
Shares, Outstanding at End of Year, Aggregate Intrinsic Value	$ 13,407,195