Financial Commitments (Reconciliation Of Outstanding Debt Balance To Reported Debt Balance) (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Debt Instrument [Line Items]
Outstanding Long-Term Debt	$ 857,819
Unamortized Discount and Issuance Costs	(23,343)	$ (34,998)
Total debt	834,476	761,504
Convertible Notes [Member]
Debt Instrument [Line Items]
Outstanding Long-Term Debt	200,000	200,000
Unamortized Discount and Issuance Costs	(17,708)	(28,519)
Total debt	182,292	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	(5,635)	(6,479)
Total debt	494,365	493,521
2017 Credit Facility [Member] | Credit Facility [Member]
Debt Instrument [Line Items]
Total debt	$ 114,000	$ 41,000