Selected Balance Sheet Data (Summary Of Intangible Assets) (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 13,125	$ 13,125
Accumulated Amortization	(2,837)	(2,340)
Net Carrying Amount	10,288	10,785
Customer List [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	6,400	6,400
Accumulated Amortization	(667)	(467)
Net Carrying Amount	5,733	5,933
Technology Intangibles [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	6,725	6,725
Accumulated Amortization	(2,170)	(1,873)
Net Carrying Amount	$ 4,555	$ 4,852