|
Financial Instruments and Fair Value Measurement (Details) (USD $)
In Thousands, unless otherwise specified
|
Sep. 30, 2012
|
Dec. 31, 2011
|
| Schedule of assets measured at fair value on a recurring basis |
|
|
| Assets at fair value |
$ 160,385 |
$ 138,285 |
|
Money market [Member]
|
|
|
| Schedule of assets measured at fair value on a recurring basis |
|
|
| Assets at fair value |
160,385 |
136,273 |
|
U.S. agency obligations [Member]
|
|
|
| Schedule of assets measured at fair value on a recurring basis |
|
|
| Assets at fair value |
|
2,012 |
|
Level 1 [Member]
|
|
|
| Schedule of assets measured at fair value on a recurring basis |
|
|
| Assets at fair value |
160,385 |
136,273 |
|
Level 1 [Member] | Money market [Member]
|
|
|
| Schedule of assets measured at fair value on a recurring basis |
|
|
| Assets at fair value |
160,385 |
136,273 |
|
Level 1 [Member] | U.S. agency obligations [Member]
|
|
|
| Schedule of assets measured at fair value on a recurring basis |
|
|
| Assets at fair value |
|
|
|
Level 2 [Member]
|
|
|
| Schedule of assets measured at fair value on a recurring basis |
|
|
| Assets at fair value |
|
2,012 |
|
Level 2 [Member] | Money market [Member]
|
|
|
| Schedule of assets measured at fair value on a recurring basis |
|
|
| Assets at fair value |
|
|
|
Level 2 [Member] | U.S. agency obligations [Member]
|
|
|
| Schedule of assets measured at fair value on a recurring basis |
|
|
| Assets at fair value |
|
2,012 |
|
Level 3 [Member]
|
|
|
| Schedule of assets measured at fair value on a recurring basis |
|
|
| Assets at fair value |
|
|
|
Level 3 [Member] | Money market [Member]
|
|
|
| Schedule of assets measured at fair value on a recurring basis |
|
|
| Assets at fair value |
|
|
|
Level 3 [Member] | U.S. agency obligations [Member]
|
|
|
| Schedule of assets measured at fair value on a recurring basis |
|
|
| Assets at fair value |
|
|