Employee Benefit Plans (Summary Of Stock Option Activity) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Shares
Outstanding, beginning balance (in shares)			2,478
Granted (in shares)	0	63	0	608
Exercised (in shares)			(54)
Forfeited (in shares)			(195)
Outstanding, ending balance (in shares)	2,229		2,229		2,478
Vested and expected to vest (in shares)	2,191		2,191
Exercisable (in shares)	1,783		1,783
Weighted average exercise price
Outstanding, beginning balance (in dollars per share)			$ 47.24
Granted (in dollars per share)			0.00
Exercised (in dollars per share)			26.10
Forfeited (in dollars per share)			60.71
Outstanding, ending balance (in dollars per share)	$ 46.56		46.56		$ 47.24
Vested and expected to vest (in dollars per share)	46.34		46.34
Exercisable (in dollars per share)	$ 43.29		$ 43.29
Remaining contractual term (years)
Outstanding			5 years 4 months 10 days		7 years 2 months 19 days
Vested and expected to vest			5 years 3 months 22 days
Exercisable			4 years 9 months 4 days
Aggregate intrinsic value
Outstanding	$ 12,383		$ 12,383		$ 42,324
Vested and expected to vest	12,387		12,387
Exercisable	$ 12,386		$ 12,386