Debt (Schedule Of Long Term Debt) (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Debt Instrument [Line Items]
Total debt, gross	$ 1,300,000	$ 1,300,000
Unamortized debt issuance costs	(18,286)	(15,400)
Total debt, net	1,281,714	1,284,600
Unsecured Senior Notes Due 2024 [Member]
Debt Instrument [Line Items]
Total debt, gross	500,000
Unsecured Senior Notes Due 2021 [Member]
Debt Instrument [Line Items]
Total debt, gross	$ 800,000	800,000
Unsecured Senior Notes Due 2019 [Member]
Debt Instrument [Line Items]
Total debt, gross		$ 500,000