Summary Of Significant Accounting Policies (Schedule Of Calculation Of Basic And Diluted Earnings Per Share) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended												12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Earnings Per Share Reconciliation [Line Items]
Net income (loss)	$ (6,931)	$ 7,136	$ 9,447	$ 13,773	$ 27,716	$ 7,799	$ 10,943	$ (23,641)	$ (76,361)	$ 17,831	$ 18,074	$ 8,555	$ 23,425	$ 22,817	$ (31,901)
Denominator for basic earnings per share - weighted-average number of common shares outstanding during the period													38,338	46,332	49,680
Denominator for diluted earnings per share													38,763	46,655	49,680
Basic earnings per share	$ (0.19)	$ 0.19	$ 0.25	$ 0.34	$ 0.64	$ 0.17	$ 0.23	$ (0.49)	$ (1.54)	$ 0.36	$ 0.36	$ 0.17	$ 0.61	$ 0.49	$ (0.64)
Diluted earnings per share	$ (0.19)	$ 0.19	$ 0.24	$ 0.34	$ 0.64	$ 0.17	$ 0.23	$ (0.49)	$ (1.54)	$ 0.35	$ 0.36	$ 0.17	$ 0.60	$ 0.49	$ (0.64)
Stock Options [Member]
Earnings Per Share Reconciliation [Line Items]
Incremental common shares attributable to stock-based awards													90	104	0
Restricted Stock Units [Member]
Earnings Per Share Reconciliation [Line Items]
Incremental common shares attributable to stock-based awards													335	219	0