| Fair Value, Marketable Securities Measured on a Recurring Basis [Table Text Block] |
| | | Fair Value Measurements Using Inputs Considered as of: | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Government securities | | $ | 6,352 | | | $ | — | | | $ | 6,352 | | | $ | — | | | $ | 1,998 | | | $ | — | | | $ | 1,998 | | | $ | — | | | Bank certificates of deposit | | | 1,998 | | | | — | | | | 1,998 | | | | — | | | | — | | | | — | | | | — | | | | — | | | Commercial paper and corporate bonds | | | 998 | | | | — | | | | 998 | | | | — | | | | 1,997 | | | | — | | | | 1,997 | | | | — | | | Total | | $ | 9,348 | | | $ | — | | | $ | 9,348 | | | $ | — | | | $ | 3,995 | | | $ | — | | | $ | 3,995 | | | $ | — | | |