Financial Commitments (Reconciliation Of Outstanding Debt Balance To Reported Debt Balance) (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Debt Instrument [Line Items]
Unamortized Discount and Issuance Costs	$ (20,259)	$ (23,343)
Total debt	902,333	834,476
Convertible Notes [Member]
Debt Instrument [Line Items]
Outstanding Long-Term Debt	200,000	200,000
Unamortized Discount and Issuance Costs	(14,844)	(17,708)
Total debt	185,156	182,292
2017 Senior Notes [Member] | Senior Notes [Member]
Debt Instrument [Line Items]
Outstanding Long-Term Debt	500,000	500,000
Unamortized Discount and Issuance Costs	(5,415)	(5,635)
Total debt	$ 494,585	$ 494,365