Employee Benefit Plans (Summary Of Restricted Stock Units) (Details) - $ / shares	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018
Service-based Restricted Stock
Shares
Unvested, Beginning balance (in shares)			304,000
Granted (in shares)			0
Vested (in shares)			(73,000)
Forfeited (in shares)			(31,000)
Unvested, Ending balance (in shares)	200,000		200,000
Weighted-Average Grant Date Fair Value
Unvested, beginning balance (in dollars per share)			$ 61.61
Granted (in dollars per share)			0.00
Vested (in dollars per share)			58.67
Forfeitures (in dollars per share)			63.27
Unvested, ending balance (in dollars per share)	$ 62.42		$ 62.42
Performance-Based Restricted Stock Units
Shares
Unvested, Beginning balance (in shares)			725,000
Granted (in shares)	0	0	0
Vested (in shares)			(221,000)
Forfeited (in shares)			(304,000)
Unvested, Ending balance (in shares)	200,000		200,000
Weighted-Average Grant Date Fair Value
Unvested, beginning balance (in dollars per share)			$ 60.21
Granted (in dollars per share)			0.00
Vested (in dollars per share)			58.45
Forfeitures (in dollars per share)			61.65
Unvested, ending balance (in dollars per share)	$ 59.98		$ 59.98