Financial Commitments (Summary Of Information Related To The Liability And Equity Components Of The Convertible Notes) (Details) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Debt Instrument [Line Items]
Deferred taxes	$ (105,438,000)	$ (108,440,000)
Convertible Notes [Member]
Debt Instrument [Line Items]
Principal	200,000,000
Liability Component [Member]
Debt Instrument [Line Items]
Allocated debt issuance costs	(5,100,000)
Liability Component [Member] | Convertible Notes [Member]
Debt Instrument [Line Items]
Principal	200,000,000	200,000,000
Conversion feature	(46,800,000)	(46,800,000)
Allocated debt issuance costs	(5,051,000)	(5,051,000)
Amortization of discount and debt issuance costs (non-cash interest expense)	23,332,000	13,486,000
Net carrying amount	171,481,000	161,635,000
Equity Component [Member]
Debt Instrument [Line Items]
Allocated debt issuance costs	(1,500,000)
Equity Component [Member] | Convertible Notes [Member]
Debt Instrument [Line Items]
Conversion feature	46,800,000	46,800,000
Allocated debt issuance costs	(1,543,000)	(1,543,000)
Deferred taxes	(18,815,000)	(18,815,000)
Net carrying amount	$ 26,442,000	$ 26,442,000