|
Fair Value Measurements (Details) (USD $)
|
12 Months Ended |
|
Dec. 31, 2014
|
Dec. 31, 2013
|
Dec. 31, 2012
|
| Assets: |
|
|
|
| Total, Estimated Fair Value |
$ 56,901,000 |
$ 26,419,000 |
|
| Transfer of assets between levels |
0 |
0 |
|
| Transfer of liabilities between levels |
|
0 |
0 |
| U.S. treasury notes |
|
|
|
| Assets: |
|
|
|
| Available for sale securities |
|
11,188,000 |
|
| U.S. government agency securities |
|
|
|
| Assets: |
|
|
|
| Available for sale securities |
|
9,637,000 |
|
| Certificates of deposit |
|
|
|
| Assets: |
|
|
|
| Available for sale securities |
|
238,000 |
|
| Level 1 | U.S. treasury notes |
|
|
|
| Assets: |
|
|
|
| Available for sale securities |
|
11,188,000 |
|
| Level 1 | Certificates of deposit |
|
|
|
| Assets: |
|
|
|
| Available for sale securities |
|
238,000 |
|
| Level 2 |
|
|
|
| Assets: |
|
|
|
| Total, Estimated Fair Value |
|
9,637,000 |
|
| Level 2 | U.S. government agency securities |
|
|
|
| Assets: |
|
|
|
| Available for sale securities |
|
9,637,000 |
|
| Recurring fair value measurement | Level 1 |
|
|
|
| Assets: |
|
|
|
| Money market fund |
357,000 |
5,356,000 |
|
| Total, Estimated Fair Value |
16,652,000 |
16,782,000 |
|
| Recurring fair value measurement | Level 1 | U.S. treasury notes |
|
|
|
| Assets: |
|
|
|
| Available for sale securities |
11,513,000 |
|
|
| Recurring fair value measurement | Level 1 | Certificates of deposit |
|
|
|
| Assets: |
|
|
|
| Available for sale securities |
4,782,000 |
|
|
| Recurring fair value measurement | Level 2 |
|
|
|
| Assets: |
|
|
|
| Total, Estimated Fair Value |
40,249,000 |
|
|
| Recurring fair value measurement | Level 2 | U.S. government agency securities |
|
|
|
| Assets: |
|
|
|
| Available for sale securities |
40,249,000 |
|
|
| Recurring fair value measurement | Total |
|
|
|
| Assets: |
|
|
|
| Money market fund |
357,000 |
5,356,000 |
|
| Total, Estimated Fair Value |
56,901,000 |
26,419,000 |
|
| Recurring fair value measurement | Total | U.S. treasury notes |
|
|
|
| Assets: |
|
|
|
| Available for sale securities |
11,513,000 |
|
|
| Recurring fair value measurement | Total | U.S. government agency securities |
|
|
|
| Assets: |
|
|
|
| Available for sale securities |
40,249,000 |
|
|
| Recurring fair value measurement | Total | Certificates of deposit |
|
|
|
| Assets: |
|
|
|
| Available for sale securities |
$ 4,782,000 |
|
|