Investments (Cost And Estimated Fair Value Of Investments) (Details) - USD ($)
$ in Thousands |
Sep. 30, 2017 |
Dec. 31, 2016 |
Sep. 30, 2016 |
Dec. 31, 2015 |
| Schedule of Available-for-sale Securities [Line Items] |
|
|
|
|
| Cost |
$ 7,450
|
$ 7,473
|
|
|
| Gross unrealized gain |
24
|
8
|
|
|
| Gross unrealized loss |
(54)
|
(54)
|
|
|
| Fair value, investments |
7,420
|
7,427
|
|
|
| Cash equivalents, Carrying amount |
1,185
|
840
|
$ 792
|
$ 569
|
| Commercial Paper [Member] |
|
|
|
|
| Schedule of Available-for-sale Securities [Line Items] |
|
|
|
|
| Cost |
693
|
348
|
|
|
| Gross unrealized gain |
0
|
0
|
|
|
| Gross unrealized loss |
0
|
0
|
|
|
| Fair value, investments |
693
|
348
|
|
|
| Treasury Bills [Member] |
|
|
|
|
| Schedule of Available-for-sale Securities [Line Items] |
|
|
|
|
| Cost |
7,396
|
7,419
|
|
|
| Gross unrealized gain |
24
|
8
|
|
|
| Gross unrealized loss |
0
|
0
|
|
|
| Fair value, investments |
7,420
|
7,427
|
|
|
| Equity Securities [Member] |
|
|
|
|
| Schedule of Available-for-sale Securities [Line Items] |
|
|
|
|
| Cost |
54
|
54
|
|
|
| Gross unrealized gain |
0
|
0
|
|
|
| Gross unrealized loss |
(54)
|
(54)
|
|
|
| Fair value, investments |
0
|
0
|
|
|
| Debt and Equity Securities [Member] |
|
|
|
|
| Schedule of Available-for-sale Securities [Line Items] |
|
|
|
|
| Cost |
8,143
|
7,821
|
|
|
| Gross unrealized gain |
24
|
8
|
|
|
| Gross unrealized loss |
(54)
|
(54)
|
|
|
| Fair value, investments |
8,113
|
7,775
|
|
|
| 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 |
693
|
348
|
|
|
| Cash equivalents, Fair value |
$ 693
|
$ 348
|
|
|