Stock Based Compensation (Summary Of Non-Vested Stock Award Activity Under Incentive Plan) (Details) - $ / shares shares in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Stock-Based Compensation [Abstract]
Outstanding, beginning of year, Shares	116	70	71
Outstanding, beginning of year, Grant Date Fair Value	$ 511.88	$ 525.60	$ 520.27
Shares granted	90	47	2
Granted, Grant Date Fair Value	$ 509.05	$ 785.32	$ 495.92
Vested, Shares	(7)	(1)	(2)
Vested, Grant Date Fair Value	$ 605.83	$ 413.07	$ 284.11
Forfeited, Shares	(74)	0	(1)
Forfeited, Grant Date Fair Value	$ 529.54	$ 534.55	$ 410.55
Outstanding, end of year, Shares	125	116	70
Outstanding, end of year, Grant Date Fair Value	$ 606.24	$ 511.88	$ 525.60