Financial Commitments (Summary Of Interest Expense As Reported In The Consolidated Statements of Operations) (Details) - USD ($) $ in Thousands		3 Months Ended		6 Months Ended
		Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Other interest		$ 535	$ 541	$ 1,039	$ 1,116
Total cash interest expense		12,904	14,255	25,854	27,505
Total non-cash interest expense	[1]	3,560	3,267	7,046	6,442
Total interest expense		16,464	17,522	32,900	33,947
Convertible Notes [Member]
Total cash interest expense		1,438	1,438	2,875	2,875
Total non-cash interest expense	[1]	$ 2,933	2,671	$ 5,797	5,279
Effective interest rates		9.39%		9.39%
2017 Senior Notes [Member] | Senior Notes [Member]
Total cash interest expense		$ 8,593	8,594	$ 17,187	17,187
Total non-cash interest expense	[1]	$ 225	209	$ 445	414
Effective interest rates		7.13%		7.13%
2017 Credit Facility [Member] | Revolving Credit Facility [Member]
Total cash interest expense		$ 2,338	3,682	$ 4,753	6,327
Total non-cash interest expense	[1]	$ 402	$ 387	$ 804	$ 749

[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 six months ended June 30, 2020.