Financial Commitments (Summary Of Information Related To The Liability And Equity Components Of The Convertible Notes) (Details) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Debt Instrument [Line Items]
Reacquisition of conversion option from repurchase of notes, net of tax	$ (764,000)	$ 0
Deferred taxes	(81,271,000)	(35,116,000)
Convertible Debt
Debt Instrument [Line Items]
Principal	200,000,000
Liability Component
Debt Instrument [Line Items]
Allocated debt issuance costs	(5,100,000)
Liability Component | Convertible Debt
Debt Instrument [Line Items]
Principal	69,918,000	200,000,000
Conversion feature	(46,800,000)	(46,800,000)
Allocated debt issuance costs	(5,051,000)	(5,051,000)
Amortization and extinguishment of discount and debt issuance costs (non-cash interest expense)	49,811,000	34,143,000
Net carrying amount	67,878,000	182,292,000
Equity Component
Debt Instrument [Line Items]
Allocated debt issuance costs	(1,500,000)
Equity Component | Convertible Debt
Debt Instrument [Line Items]
Allocated debt issuance costs	(1,543,000)	(1,543,000)
Net carrying amount	25,678,000	26,442,000
Conversion feature	46,800,000	46,800,000
Deferred taxes	$ (18,815,000)	$ (18,815,000)