Investments (Cost And Estimated Fair Value Of Investments) (Details) - USD ($)
$ in Thousands |
Mar. 31, 2021 |
Dec. 31, 2020 |
Mar. 31, 2020 |
Dec. 31, 2019 |
| Schedule of Available-for-sale Securities [Line Items] |
|
|
|
|
| Cost |
$ 8,052
|
$ 8,052
|
|
|
| Gross unrealized gain |
2
|
1
|
|
|
| Gross unrealized loss |
(12)
|
(12)
|
|
|
| Fair value, investments |
8,042
|
8,041
|
|
|
| Cash equivalents, Carrying amount |
1,045
|
1,090
|
$ 7,850
|
$ 8,785
|
| Commercial Paper [Member] |
|
|
|
|
| Schedule of Available-for-sale Securities [Line Items] |
|
|
|
|
| Cost |
719
|
718
|
|
|
| Gross unrealized gain |
0
|
0
|
|
|
| Gross unrealized loss |
0
|
0
|
|
|
| Fair value, investments |
719
|
718
|
|
|
| Treasury Bills [Member] |
|
|
|
|
| Schedule of Available-for-sale Securities [Line Items] |
|
|
|
|
| Cost |
7,998
|
7,998
|
|
|
| Gross unrealized gain |
2
|
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 |
0
|
0
|
|
|
| Gross unrealized loss |
(12)
|
(12)
|
|
|
| Fair value, investments |
42
|
42
|
|
|
| Debt and Equity Securities [Member] |
|
|
|
|
| Schedule of Available-for-sale Securities [Line Items] |
|
|
|
|
| Cost |
8,771
|
8,770
|
|
|
| Gross unrealized gain |
2
|
1
|
|
|
| Gross unrealized loss |
(12)
|
(12)
|
|
|
| Fair value, investments |
8,761
|
8,759
|
|
|
| Less Cash Equivalents [Member] |
|
|
|
|
| Schedule of Available-for-sale Securities [Line Items] |
|
|
|
|
| Gross unrealized gain |
0
|
0
|
|
|
| Gross unrealized loss |
0
|
0
|
|
|
| Cash equivalents, Carrying amount |
719
|
718
|
|
|
| Cash equivalents, Fair value |
$ 719
|
$ 718
|
|
|