Fair Value Measurements (Financial Assets And Liabilities Measured At Fair Value) (Details) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2019		Dec. 31, 2018
Deferred compensation plan investments (1)	$ 138,000	[1]	$ 144,700
Participant Withdrawals From Deferred Compensation Plan Investments	19,000		12,700
Diversification of share awards within deferred compensation plan	52,674		40,300
Interest Rate Derivative Liabilities, at Fair Value	13,400		7,400
Level 1 [Member]
Deferred compensation plan investments (1)	138,000	[1]	144,700
Interest Rate Derivative Liabilities, at Fair Value	0		0
Level 2 [Member]
Deferred compensation plan investments (1)	0	[1]	0
Level 3 [Member]
Deferred compensation plan investments (1)	0	[1]	0
Interest Rate Derivative Liabilities, at Fair Value	0		0
Interest Rate Swap [Member]
Interest Rate Derivative Assets, at Fair Value	0		0
Interest Rate Derivative Liabilities, at Fair Value	13,400		7,400
Interest Rate Swap [Member] | Level 2 [Member]
Interest Rate Derivative Liabilities, at Fair Value	$ 13,400		$ 7,400

[1] Approximately $19.0 million and $12.7 million of participant cash was withdrawn from our deferred compensation plan investments during the three months ended March 31, 2019 and the year ended December 31, 2018, respectively. Approximately $40.3 million of participant restricted share units in the compensation plan were diversified into deferred compensation plan investments during the year ended December 31, 2018.