Stock-Based Compensation (Schedule Of Activity For Non-Vested Restricted Stock) (Details) - Restricted Stock [Member] - $ / shares	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Non-vested at beginning of period, Shares	26,587	23,668	16,301
Granted, Shares	3,162	5,779	7,367
Vested, Shares	(1,284)	(2,570)	0
Forfeited, Shares	0	(290)	0
Non-vested at end of period, Shares	28,465	26,587	23,668
Non-vested at beginning of period, Weighted Average Fair Value at Grant Date	$ 78.00	$ 79.02	$ 84.96
Granted, Weighted Average Fair Value at Grant Date	89.10	84.90	65.87
Vested, Weighted Average Fair Value at Grant Date	106.92	103.65
Forfeited, Weighted Average Fair Value at Grant Date		78.12
Non-vested at end of period, Weighted Average Fair Value at Grant Date	$ 77.93	$ 78.00	$ 79.02