Financial Commitments (Summary Of Interest Expense As Reported In The Condensed Consolidated Statements of Income) (Details) - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2019	Mar. 31, 2018
Debt Instrument [Line Items]
Interest on debt		$ 13,251	$ 12,138
Other interest		574	757
Total non-cash interest expense	[1]	3,174	2,927
Total interest expense		16,425	15,065
Convertible Notes [Member]
Debt Instrument [Line Items]
Interest on debt		1,438	1,438
Total non-cash interest expense	[1]	$ 2,608	2,376
Effective interest rates		9.39%
2017 Senior Notes [Member] | Senior Notes [Member]
Debt Instrument [Line Items]
Interest on debt		$ 8,594	8,594
Total non-cash interest expense	[1]	$ 205	191
Effective interest rates		7.13%
2017 Credit Facility [Member] | Credit Facility [Member]
Debt Instrument [Line Items]
Interest on debt		$ 2,645	1,349
Total non-cash interest expense	[1]	$ 361	$ 360

[1] The combination of cash and non-cash interest expense produces effective interest rates that are higher than contractual rates. Accordingly, the effective interest rates for the 2017 Senior Notes and the Convertible Notes were 7.13% and 9.39%, respectively, for the three months ended March 31, 2019.