Investments (Cost And Estimated Fair Value Of Investments) (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Schedule of Available-for-sale Securities [Line Items]
Cost	$ 3,054	$ 8,052
Gross unrealized gain	2	1
Gross unrealized loss	0	(12)
Fair value, investments	3,056	8,041
Less cash equivalents, Carrying amount	6,713	1,090	$ 8,785
Commercial Paper [Member]
Schedule of Available-for-sale Securities [Line Items]
Cost	1,520	718
Gross unrealized gain	0	0
Gross unrealized loss	0	0
Fair value, investments	1,520	718
Treasury Bills [Member]
Schedule of Available-for-sale Securities [Line Items]
Cost	8,000	7,998
Gross unrealized gain	0	1
Gross unrealized loss	0	0
Fair value, investments	8,000	7,999
Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Cost	54	54
Gross unrealized gain	2	0
Gross unrealized loss	0	(12)
Fair value, investments	56	42
Debt and Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Cost	9,574	8,770
Gross unrealized gain	2	1
Gross unrealized loss	0	(12)
Fair value, investments	9,576	8,759
Less Cash Equivalents [Member]
Schedule of Available-for-sale Securities [Line Items]
Gross unrealized gain	0	0
Gross unrealized loss	0	0
Less cash equivalents, Carrying amount	6,520	718
Less cash equivalents, Fair value	$ 6,520	$ 718