Debt (Schedule Of Credit Facilities) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Line of Credit Facility [Line Items]
Balance outstanding	$ 40,000
Maximum balance outstanding during the period	497,000	$ 5,000
Weighted average balance	$ 74,311	$ 123
Year-to-date weighted average interest rate (excluding facility fee)	1.00%	3.30%
Unsecured Revolving Credit Facility [Member]
Line of Credit Facility [Line Items]
Balance outstanding	$ 40,000
Available balance	$ 458,068	$ 497,946
Variable interest rate (excluding facility fee)	0.94%
Letters of Credit [Member]
Line of Credit Facility [Line Items]
Letters of credit outstanding under facility	$ 1,932	$ 2,054