|
Investments - Short-Term and Long-Term Investments in Debt Securities (Details) (USD $)
In Thousands, unless otherwise specified
|
Mar. 31, 2015
|
Dec. 31, 2014
|
| Schedule Of Available For Sale Securities [Line Items] |
|
|
| Short-term investments |
$ 206,085 |
$ 185,783 |
| Long-term investments |
41,158 |
59,197 |
| Short-term Investments |
|
|
| Schedule Of Available For Sale Securities [Line Items] |
|
|
| Cost Basis |
206,078 |
185,812 |
| Unrealized Gains |
47 |
26 |
| Unrealized Losses |
(40) |
(55) |
| Short-term investments |
206,085 |
185,783 |
| Short-term Investments | U.S. Government Securities |
|
|
| Schedule Of Available For Sale Securities [Line Items] |
|
|
| Cost Basis |
32,183 |
26,930 |
| Unrealized Gains |
18 |
7 |
| Unrealized Losses |
|
(2) |
| Short-term investments |
32,201 |
26,935 |
| Short-term Investments | U.S. Government Agency Securities |
|
|
| Schedule Of Available For Sale Securities [Line Items] |
|
|
| Cost Basis |
66,737 |
59,336 |
| Unrealized Gains |
12 |
7 |
| Unrealized Losses |
(5) |
(6) |
| Short-term investments |
66,744 |
59,337 |
| Short-term Investments | Non-U.S. Government Securities |
|
|
| Schedule Of Available For Sale Securities [Line Items] |
|
|
| Cost Basis |
9,556 |
8,764 |
| Unrealized Gains |
|
2 |
| Unrealized Losses |
(1) |
|
| Short-term investments |
9,555 |
8,766 |
| Short-term Investments | Corporate Debt Securities |
|
|
| Schedule Of Available For Sale Securities [Line Items] |
|
|
| Cost Basis |
97,602 |
90,782 |
| Unrealized Gains |
17 |
10 |
| Unrealized Losses |
(34) |
(47) |
| Short-term investments |
97,585 |
90,745 |
| Long-term investments |
|
|
| Schedule Of Available For Sale Securities [Line Items] |
|
|
| Cost Basis |
41,124 |
59,229 |
| Unrealized Gains |
45 |
7 |
| Unrealized Losses |
(11) |
(39) |
| Long-term investments |
41,158 |
59,197 |
| Long-term investments | U.S. Government Securities |
|
|
| Schedule Of Available For Sale Securities [Line Items] |
|
|
| Cost Basis |
15,140 |
25,320 |
| Unrealized Gains |
23 |
4 |
| Unrealized Losses |
|
(10) |
| Long-term investments |
15,163 |
25,314 |
| Long-term investments | U.S. Government Agency Securities |
|
|
| Schedule Of Available For Sale Securities [Line Items] |
|
|
| Cost Basis |
14,040 |
17,369 |
| Unrealized Gains |
13 |
1 |
| Unrealized Losses |
|
(14) |
| Long-term investments |
14,053 |
17,356 |
| Long-term investments | Corporate Debt Securities |
|
|
| Schedule Of Available For Sale Securities [Line Items] |
|
|
| Cost Basis |
11,944 |
16,540 |
| Unrealized Gains |
9 |
2 |
| Unrealized Losses |
(11) |
(15) |
| Long-term investments |
$ 11,942 |
$ 16,527 |