|
Fair Value (Details) (USD $)
In Thousands, unless otherwise specified |
Jun. 30, 2014
|
Dec. 31, 2013
|
|---|---|---|
| Assets: | ||
| Total assets measured at fair value | $ 386,276 | $ 360,927 |
|
Money Market Funds [Member]
|
||
| Assets: | ||
| Total assets measured at fair value | 91,195 | 98,437 |
|
Commercial Paper [Member]
|
||
| Assets: | ||
| Total assets measured at fair value | 78,684 | 101,773 |
|
Corporate Debt Securities [Member]
|
||
| Assets: | ||
| Total assets measured at fair value | 206,543 | 155,021 |
|
US Government Agencies Debt Securities [Member]
|
||
| Assets: | ||
| Total assets measured at fair value | 9,854 | 5,696 |
|
Fair Value, Inputs, Level 1 [Member]
|
||
| Assets: | ||
| Total assets measured at fair value | 91,195 | 98,437 |
|
Fair Value, Inputs, Level 1 [Member] | Money Market Funds [Member]
|
||
| Assets: | ||
| Total assets measured at fair value | 91,195 | 98,437 |
|
Fair Value, Inputs, Level 2 [Member]
|
||
| Assets: | ||
| Total assets measured at fair value | 295,081 | 262,490 |
|
Fair Value, Inputs, Level 2 [Member] | Commercial Paper [Member]
|
||
| Assets: | ||
| Total assets measured at fair value | 78,684 | 101,773 |
|
Fair Value, Inputs, Level 2 [Member] | Corporate Debt Securities [Member]
|
||
| Assets: | ||
| Total assets measured at fair value | 206,543 | 155,021 |
|
Fair Value, Inputs, Level 2 [Member] | US Government Agencies Debt Securities [Member]
|
||
| Assets: | ||
| Total assets measured at fair value | 9,854 | 5,696 |
|
Estimate of Fair Value Measurement [Member]
|
||
| Assets: | ||
| Total assets measured at fair value | 386,276 | 360,927 |
|
Estimate of Fair Value Measurement [Member] | Money Market Funds [Member]
|
||
| Assets: | ||
| Total assets measured at fair value | 91,195 | 98,437 |
|
Estimate of Fair Value Measurement [Member] | Commercial Paper [Member]
|
||
| Assets: | ||
| Total assets measured at fair value | 78,684 | 101,773 |
|
Estimate of Fair Value Measurement [Member] | Corporate Debt Securities [Member]
|
||
| Assets: | ||
| Total assets measured at fair value | 206,543 | 155,021 |
|
Estimate of Fair Value Measurement [Member] | US Government Agencies Debt Securities [Member]
|
||
| Assets: | ||
| Total assets measured at fair value | 9,854 | 5,696 |
|
Fair Value, Inputs, Level 3 [Member]
|
||
| Assets: | ||
| Total assets measured at fair value | 0 | 0 |
| Liabilities: | ||
| Liabilities measured at fair value | $ 0 | $ 0 |