Earnings Per Share (Schedule Of Basic And Diluted Earnings Per Share) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Net income	$ 43,789	$ 10,414	$ 69,962	$ 2,018
Weighted average basic common shares outstanding	77,416	78,047	77,376	78,044
Dilutive effect of restricted and performance stock units	625	1,782	632	1,715
Dilutive effect of convertible debt instruments	5,815	11,268	6,499	11,343
Dilutive effect of employee share purchase plan	3	3	7	5
Weighted average dilutive common shares outstanding	83,859	91,100	84,514	91,107
Basic	$ 0.57	$ 0.13	$ 0.90	$ 0.03
Diluted	$ 0.52	$ 0.11	$ 0.83	$ 0.02
Convertible Notes And Warrants [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive shares (excluded from per-share calculations)	3,610	6,002	3,910	6,035