Financial Commitments (Reconciliation Of Outstanding Debt Balance To Reported Debt Balance) (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Debt Instrument [Line Items]
Unamortized Discount and Issuance Costs	$ (29,305)	$ (34,998)
Total debt	956,177	761,504
Convertible Notes [Member]
Debt Instrument [Line Items]
Outstanding Long-Term Debt	200,000	200,000
Unamortized Discount and Issuance Costs	(23,240)	(28,519)
Total debt	176,760	171,481
2017 Senior Notes [Member] | Senior Notes [Member]
Debt Instrument [Line Items]
Outstanding Long-Term Debt	500,000	500,000
Unamortized Discount and Issuance Costs	(6,065)	(6,479)
Total debt	$ 493,935	$ 493,521