Fair Value Measurements (Financial Assets And Liabilities Measured At Fair Value) (Details) - USD ($) $ in Thousands	9 Months Ended			12 Months Ended
	Sep. 30, 2017		Sep. 30, 2016	Dec. 31, 2016
Deferred compensation plan investments (1)	$ 116,200	[1]		$ 80,600
Participant Withdrawals From Deferred Compensation Plan Investments	3,000			8,300
Diversification of share awards within deferred compensation plan	23,181		$ 25,406	25,400
Interest Rate Derivative Assets, at Fair Value	1,800			0
Level 1 [Member]
Deferred compensation plan investments (1)	116,200	[1]		80,600
Interest Rate Derivative Assets, at Fair Value	0			0
Level 2 [Member]
Deferred compensation plan investments (1)	0	[1]		0
Interest Rate Derivative Assets, at Fair Value				0
Level 3 [Member]
Deferred compensation plan investments (1)	0	[1]		0
Interest Rate Derivative Assets, at Fair Value	0			$ 0
Interest Rate Swap [Member] | Level 2 [Member]
Interest Rate Derivative Assets, at Fair Value	$ 1,800

[1] Approximately $3.0 million and $8.3 million of participant cash was withdrawn from our deferred compensation plan investments during the nine months ended September 30, 2017 and the year ended December 31, 2016, respectively. Approximately $23.2 million and $25.4 million of shares in the compensation plan were diversified into the deferred compensation plan investments during the nine months ended September 30, 2017 and the year ended December 31, 2016, respectively.