|
Fair Value (Details) (USD $)
In Thousands, unless otherwise specified |
Mar. 31, 2014
|
Dec. 31, 2013
|
|---|---|---|
| Assets: | ||
| Total assets measured at fair value | $ 385,765 | $ 360,927 |
|
Money market funds
|
||
| Assets: | ||
| Total assets measured at fair value | 90,531 | 98,437 |
|
Commercial paper
|
||
| Assets: | ||
| Total assets measured at fair value | 82,424 | 101,773 |
|
Corporate debt securities
|
||
| Assets: | ||
| Total assets measured at fair value | 201,869 | 155,021 |
|
U.S. government and government agency debt securities
|
||
| Assets: | ||
| Total assets measured at fair value | 10,941 | 5,696 |
|
Quoted Prices in Active Markets for Identical Instruments (Level 1)
|
||
| Assets: | ||
| Total assets measured at fair value | 90,531 | 98,437 |
|
Quoted Prices in Active Markets for Identical Instruments (Level 1) | Money market funds
|
||
| Assets: | ||
| Total assets measured at fair value | 90,531 | 98,437 |
|
Significant Other Observable Inputs (Level 2)
|
||
| Assets: | ||
| Total assets measured at fair value | 295,234 | 262,490 |
|
Significant Other Observable Inputs (Level 2) | Commercial paper
|
||
| Assets: | ||
| Total assets measured at fair value | 82,424 | 101,773 |
|
Significant Other Observable Inputs (Level 2) | Corporate debt securities
|
||
| Assets: | ||
| Total assets measured at fair value | 201,869 | 155,021 |
|
Significant Other Observable Inputs (Level 2) | U.S. government and government agency debt securities
|
||
| Assets: | ||
| Total assets measured at fair value | 10,941 | 5,696 |
|
Total
|
||
| Assets: | ||
| Total assets measured at fair value | 385,765 | 360,927 |
|
Total | Money market funds
|
||
| Assets: | ||
| Total assets measured at fair value | 90,531 | 98,437 |
|
Total | Commercial paper
|
||
| Assets: | ||
| Total assets measured at fair value | 82,424 | 101,773 |
|
Total | Corporate debt securities
|
||
| Assets: | ||
| Total assets measured at fair value | 201,869 | 155,021 |
|
Total | U.S. government and government agency debt securities
|
||
| Assets: | ||
| Total assets measured at fair value | 10,941 | 5,696 |
|
Level 3
|
||
| Assets: | ||
| Total assets measured at fair value | 0 | 0 |
| Liabilities: | ||
| Liabilities measured at fair value | $ 0 | $ 0 |