Financial Commitments (Summary Of Interest Expense As Reported In The Condensed Consolidated Statements of Income) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Debt Instrument [Line Items]
Interest on debt	$ 14,255	$ 13,011	$ 27,505	$ 25,149
Other interest	541	626	1,116	1,383
Total non-cash interest expense	3,267	2,987	6,442	5,914
Total interest expense	17,522	15,998	33,947	31,063
Convertible Notes [Member]
Debt Instrument [Line Items]
Interest on debt	1,438	1,437	2,875	2,875
Total non-cash interest expense	$ 2,671	2,432	$ 5,279	4,808
Effective interest rates	9.39%		9.39%
2017 Senior Notes [Member] | Senior Notes [Member]
Debt Instrument [Line Items]
Interest on debt	$ 8,594	8,594	$ 17,187	17,187
Total non-cash interest expense	$ 209	195	$ 414	386
Effective interest rates	7.13%		7.13%
2017 Credit Facility [Member] | Credit Facility [Member]
Debt Instrument [Line Items]
Interest on debt	$ 3,682	2,354	$ 6,327	3,704
Total non-cash interest expense	$ 387	$ 360	$ 749	$ 720