|
Cash, Cash Equivalents, and Marketable Securities (Details) (USD $)
In Thousands, unless otherwise specified
|
Jun. 30, 2012
|
Dec. 31, 2011
|
| Summary of cash, cash equivalents, restricted cash, and marketable securities |
|
|
| Amortized Cost |
$ 92,435 |
$ 62,533 |
| Unrealized Gains |
|
29 |
| Unrealized Losses |
(2) |
|
| Estimated Fair Value |
92,433 |
62,562 |
|
Cash [Member]
|
|
|
| Summary of cash, cash equivalents, restricted cash, and marketable securities |
|
|
| Amortized Cost |
1,083 |
1,421 |
| Unrealized Losses |
|
|
| Estimated Fair Value |
1,083 |
1,421 |
|
Certificates of Deposit [Member]
|
|
|
| Summary of cash, cash equivalents, restricted cash, and marketable securities |
|
|
| Amortized Cost |
200 |
200 |
| Unrealized Losses |
|
|
| Estimated Fair Value |
200 |
200 |
|
Money Market Funds [Member]
|
|
|
| Summary of cash, cash equivalents, restricted cash, and marketable securities |
|
|
| Amortized Cost |
7,408 |
9,238 |
| Unrealized Losses |
|
|
| Estimated Fair Value |
7,408 |
9,238 |
|
US Treasury Securities [Member]
|
|
|
| Summary of cash, cash equivalents, restricted cash, and marketable securities |
|
|
| Amortized Cost |
83,744 |
51,674 |
| Unrealized Gains |
|
29 |
| Unrealized Losses |
(2) |
|
| Estimated Fair Value |
$ 83,742 |
$ 51,703 |