|
FAIR VALUE (Details) (Recurring basis, USD $)
In Thousands, unless otherwise specified |
Dec. 31, 2012
|
Dec. 31, 2011
|
|---|---|---|
|
Level 1
|
||
| Fair Value | ||
| Assets at Fair Value | $ 23,936 | $ 11,947 |
|
Level 1 | Money market funds
|
||
| Fair Value | ||
| Assets at Fair Value | 23,936 | 11,947 |
|
Level 2
|
||
| Fair Value | ||
| Assets at Fair Value | 274,054 | 235,007 |
|
Level 2 | U. S. treasury bills
|
||
| Fair Value | ||
| Assets at Fair Value | 3,002 | |
|
Level 2 | Government-sponsored enterprise securities
|
||
| Fair Value | ||
| Assets at Fair Value | 77,047 | 144,599 |
|
Level 2 | Corporate bonds and commercial paper
|
||
| Fair Value | ||
| Assets at Fair Value | 197,007 | 87,406 |
|
Total
|
||
| Fair Value | ||
| Assets at Fair Value | 297,990 | 246,954 |
|
Total | Money market funds
|
||
| Fair Value | ||
| Assets at Fair Value | 23,936 | 11,947 |
|
Total | U. S. treasury bills
|
||
| Fair Value | ||
| Assets at Fair Value | 3,002 | |
|
Total | Government-sponsored enterprise securities
|
||
| Fair Value | ||
| Assets at Fair Value | 77,047 | 144,599 |
|
Total | Corporate bonds and commercial paper
|
||
| Fair Value | ||
| Assets at Fair Value | $ 197,007 | $ 87,406 |