Summary Of Significant Accounting Policies (Accounting Changes To Consolidated Statements Of Cash Flows) (Details) - USD ($) $ in Thousands	3 Months Ended										12 Months Ended
	Dec. 31, 2020	[1]	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	[1]	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Net income (loss)	$ (17,663)		$ (19,352)	$ (22,887)	$ (5,955)	$ (27,458)		$ 801	$ 2,294	$ (2,140)	$ (65,857)	$ (26,503)	$ 14,166
Change in net deferred tax assets											401	23,115	(1,841)
Accounts payable and accrued expenses											9,330	508	2,562
Net cash provided by operating activities											$ (30,201)	$ 24,607	32,645
As Reported [Member]
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Net income (loss)	$ (17,663)		$ (19,352)	$ (22,887)	$ (5,955)	$ (27,458)		852	2,357	(2,097)
Adjustments [Member]
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Net income (loss)								$ (51)	$ (63)	$ (43)
Tax Year 2018 [Member]
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Net income (loss)													14,166
Tax Year 2018 [Member] | As Reported [Member]
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Net income (loss)													14,498
Tax Year 2018 [Member] | Adjustments [Member]
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Net income (loss)													(332)
Tax Year 2019 [Member]
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Net income (loss)													14,166
Change in net deferred tax assets													(1,841)
Accounts payable and accrued expenses													2,562
Net cash provided by operating activities													32,645
Tax Year 2019 [Member] | As Reported [Member]
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Net income (loss)													14,498
Change in net deferred tax assets													(1,719)
Accounts payable and accrued expenses													2,107
Net cash provided by operating activities													32,645
Tax Year 2019 [Member] | Adjustments [Member]
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Net income (loss)													(332)
Change in net deferred tax assets													(122)
Accounts payable and accrued expenses													$ 455

[1] Since previously published financial statements have been corrected, there is no impact on the fourth quarter results for 2019 or for the full year of 2020 and so no data is displayed here.