Investments (Narrative) (Details) |
3 Months Ended |
|---|---|
Mar. 31, 2021 | |
| Minimum [Member] | |
| Schedule of Available-for-sale Securities [Line Items] | |
| Treasury Bills, term | 1 month |
| Maximum [Member] | |
| Schedule of Available-for-sale Securities [Line Items] | |
| Treasury Bills, term | 5 months |