Investments (Cost And Estimated Fair Value Of Investments) (Details) - USD ($)
$ in Thousands |
Sep. 30, 2018 |
Dec. 31, 2017 |
Sep. 30, 2017 |
Dec. 31, 2016 |
| Schedule of Available-for-sale Securities [Line Items] |
|
|
|
|
| Cost |
$ 7,725
|
$ 7,741
|
|
|
| Gross unrealized gain |
33
|
24
|
|
|
| Gross unrealized loss |
(9)
|
(9)
|
|
|
| Fair value, investments |
7,749
|
7,756
|
|
|
| Cash equivalents, Carrying amount |
853
|
963
|
$ 1,185
|
$ 840
|
| Commercial Paper [Member] |
|
|
|
|
| Schedule of Available-for-sale Securities [Line Items] |
|
|
|
|
| Cost |
316
|
568
|
|
|
| Gross unrealized gain |
0
|
0
|
|
|
| Gross unrealized loss |
0
|
0
|
|
|
| Fair value, investments |
316
|
568
|
|
|
| Treasury Bills [Member] |
|
|
|
|
| Schedule of Available-for-sale Securities [Line Items] |
|
|
|
|
| Cost |
7,671
|
7,687
|
|
|
| Gross unrealized gain |
33
|
24
|
|
|
| Gross unrealized loss |
0
|
0
|
|
|
| Fair value, investments |
7,704
|
7,711
|
|
|
| Equity Securities [Member] |
|
|
|
|
| Schedule of Available-for-sale Securities [Line Items] |
|
|
|
|
| Cost |
54
|
54
|
|
|
| Gross unrealized gain |
0
|
0
|
|
|
| Gross unrealized loss |
(9)
|
(9)
|
|
|
| Fair value, investments |
45
|
45
|
|
|
| Debt and Equity Securities [Member] |
|
|
|
|
| Schedule of Available-for-sale Securities [Line Items] |
|
|
|
|
| Cost |
8,041
|
8,309
|
|
|
| Gross unrealized gain |
33
|
24
|
|
|
| Gross unrealized loss |
(9)
|
(9)
|
|
|
| Fair value, investments |
8,065
|
8,324
|
|
|
| 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 |
316
|
568
|
|
|
| Cash equivalents, Fair value |
$ 316
|
$ 568
|
|
|