|
Fair Value (Details) (USD $)
In Thousands, unless otherwise specified |
Sep. 30, 2014
|
Dec. 31, 2013
|
|---|---|---|
| Assets: | ||
| Total assets measured at fair value | $ 386,334 | $ 360,927 |
|
Money Market Funds
|
||
| Assets: | ||
| Total assets measured at fair value | 91,780 | 98,437 |
|
Commercial Paper
|
||
| Assets: | ||
| Total assets measured at fair value | 60,743 | 101,773 |
|
Corporate Debt Securities
|
||
| Assets: | ||
| Total assets measured at fair value | 220,707 | 155,021 |
|
US Government Agencies Debt Securities
|
||
| Assets: | ||
| Total assets measured at fair value | 13,104 | 5,696 |
|
Estimate of Fair Value Measurement
|
||
| Assets: | ||
| Total assets measured at fair value | 386,334 | 360,927 |
|
Estimate of Fair Value Measurement | Money Market Funds
|
||
| Assets: | ||
| Total assets measured at fair value | 91,780 | 98,437 |
|
Estimate of Fair Value Measurement | Commercial Paper
|
||
| Assets: | ||
| Total assets measured at fair value | 60,743 | 101,773 |
|
Estimate of Fair Value Measurement | Corporate Debt Securities
|
||
| Assets: | ||
| Total assets measured at fair value | 220,707 | 155,021 |
|
Estimate of Fair Value Measurement | US Government Agencies Debt Securities
|
||
| Assets: | ||
| Total assets measured at fair value | 13,104 | 5,696 |
|
Fair Value, Inputs, Level 1
|
||
| Assets: | ||
| Total assets measured at fair value | 91,780 | 98,437 |
|
Fair Value, Inputs, Level 1 | Money Market Funds
|
||
| Assets: | ||
| Total assets measured at fair value | 91,780 | 98,437 |
|
Fair Value, Inputs, Level 1 | Commercial Paper
|
||
| Assets: | ||
| Total assets measured at fair value | 0 | 0 |
|
Fair Value, Inputs, Level 1 | Corporate Debt Securities
|
||
| Assets: | ||
| Total assets measured at fair value | 0 | 0 |
|
Fair Value, Inputs, Level 1 | US Government Agencies Debt Securities
|
||
| Assets: | ||
| Total assets measured at fair value | 0 | 0 |
|
Fair Value, Inputs, Level 2
|
||
| Assets: | ||
| Total assets measured at fair value | 294,554 | 262,490 |
|
Fair Value, Inputs, Level 2 | Money Market Funds
|
||
| Assets: | ||
| Total assets measured at fair value | 0 | 0 |
|
Fair Value, Inputs, Level 2 | Commercial Paper
|
||
| Assets: | ||
| Total assets measured at fair value | 60,743 | 101,773 |
|
Fair Value, Inputs, Level 2 | Corporate Debt Securities
|
||
| Assets: | ||
| Total assets measured at fair value | 220,707 | 155,021 |
|
Fair Value, Inputs, Level 2 | US Government Agencies Debt Securities
|
||
| Assets: | ||
| Total assets measured at fair value | 13,104 | 5,696 |
|
Fair Value, Inputs, Level 3
|
||
| Assets: | ||
| Total assets measured at fair value | 0 | 0 |
| Liabilities: | ||
| Liabilities measured at fair value | $ 0 | $ 0 |