Financial Commitments (Reconciliation Of Outstanding Debt Balance To Reported Debt Balance) (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Debt Instrument [Line Items]
Outstanding Long-Term Debt	$ 796,502
Unamortized Discount and Issuance Costs	(34,998)	$ (45,631)
Total debt	761,504	736,276
Convertible Notes [Member]
Debt Instrument [Line Items]
Outstanding Long-Term Debt	200,000	200,000
Unamortized Discount and Issuance Costs	(28,519)	(38,365)
Total debt	171,481	161,635
2017 Senior Notes [Member] | Senior Notes [Member]
Debt Instrument [Line Items]
Outstanding Long-Term Debt	500,000	500,000
Unamortized Discount and Issuance Costs	(6,479)	(7,266)
Total debt	493,521	$ 492,734
2017 Credit Facility [Member] | Credit Facility [Member]
Debt Instrument [Line Items]
Total debt	$ 41,000