Fair Value Measurements (Details) - USD ($)
$ in Thousands |
Dec. 31, 2016 |
Dec. 31, 2015 |
| Fair Value Measurements |
|
|
| Fair Value, assets |
$ 0
|
$ 0
|
| Measured on a recurring basis |
|
|
| Fair Value Measurements |
|
|
| Adjusted Cost, assets |
61,806
|
81,068
|
| Unrealized Gains, available-for-sale securities |
|
2
|
| Unrealized Losses, available-for-sale securities |
(15)
|
(63)
|
| Fair Value, assets |
61,791
|
81,007
|
| Measured on a recurring basis | Cash and Cash Equivalents |
|
|
| Fair Value Measurements |
|
|
| Fair Value, assets |
34,813
|
29,530
|
| Measured on a recurring basis | Short-term investments |
|
|
| Fair Value Measurements |
|
|
| Fair Value, available-for-sale investments |
22,970
|
37,761
|
| Measured on a recurring basis | Long-term investments |
|
|
| Fair Value Measurements |
|
|
| Fair Value, available-for-sale investments |
4,008
|
13,716
|
| Measured on a recurring basis | Cash |
|
|
| Fair Value Measurements |
|
|
| Fair value, cash and cash equivalents |
24,708
|
7,593
|
| Measured on a recurring basis | Cash | Cash and Cash Equivalents |
|
|
| Fair Value Measurements |
|
|
| Fair value, cash and cash equivalents |
24,708
|
7,593
|
| Measured on a recurring basis | Level 1 |
|
|
| Fair Value Measurements |
|
|
| Adjusted Cost, assets |
12,106
|
22,935
|
| Unrealized Losses, available-for-sale securities |
(1)
|
(2)
|
| Fair Value, assets |
12,105
|
22,933
|
| Measured on a recurring basis | Level 1 | Cash and Cash Equivalents |
|
|
| Fair Value Measurements |
|
|
| Fair Value, assets |
10,105
|
21,937
|
| Measured on a recurring basis | Level 1 | Short-term investments |
|
|
| Fair Value Measurements |
|
|
| Fair Value, available-for-sale investments |
2,000
|
|
| Measured on a recurring basis | Level 1 | Long-term investments |
|
|
| Fair Value Measurements |
|
|
| Fair Value, available-for-sale investments |
|
996
|
| Measured on a recurring basis | Level 1 | Money market funds |
|
|
| Fair Value Measurements |
|
|
| Fair value, cash and cash equivalents |
10,105
|
21,937
|
| Measured on a recurring basis | Level 1 | Money market funds | Cash and Cash Equivalents |
|
|
| Fair Value Measurements |
|
|
| Fair value, cash and cash equivalents |
10,105
|
21,937
|
| Measured on a recurring basis | Level 1 | U.S. government notes |
|
|
| Fair Value Measurements |
|
|
| Adjusted Cost, available-for-sale securities |
2,001
|
998
|
| Unrealized Losses, available-for-sale securities |
(1)
|
(2)
|
| Fair Value, available-for-sale investments |
2,000
|
996
|
| Measured on a recurring basis | Level 1 | U.S. government notes | Short-term investments |
|
|
| Fair Value Measurements |
|
|
| Fair Value, available-for-sale investments |
2,000
|
|
| Measured on a recurring basis | Level 1 | U.S. government notes | Long-term investments |
|
|
| Fair Value Measurements |
|
|
| Fair Value, available-for-sale investments |
|
996
|
| Measured on a recurring basis | Level 2 |
|
|
| Fair Value Measurements |
|
|
| Adjusted Cost, available-for-sale securities |
24,992
|
50,540
|
| Unrealized Gains, available-for-sale securities |
|
2
|
| Unrealized Losses, available-for-sale securities |
(14)
|
(61)
|
| Fair Value, available-for-sale investments |
24,978
|
50,481
|
| Measured on a recurring basis | Level 2 | Short-term investments |
|
|
| Fair Value Measurements |
|
|
| Fair Value, available-for-sale investments |
20,970
|
37,761
|
| Measured on a recurring basis | Level 2 | Long-term investments |
|
|
| Fair Value Measurements |
|
|
| Fair Value, available-for-sale investments |
4,008
|
12,720
|
| Measured on a recurring basis | Level 2 | Asset-backed securities |
|
|
| Fair Value Measurements |
|
|
| Adjusted Cost, available-for-sale securities |
4,008
|
6,739
|
| Unrealized Losses, available-for-sale securities |
|
(9)
|
| Fair Value, available-for-sale investments |
4,008
|
6,730
|
| Measured on a recurring basis | Level 2 | Asset-backed securities | Long-term investments |
|
|
| Fair Value Measurements |
|
|
| Fair Value, available-for-sale investments |
4,008
|
6,730
|
| Measured on a recurring basis | Level 2 | Corporate bonds |
|
|
| Fair Value Measurements |
|
|
| Adjusted Cost, available-for-sale securities |
13,902
|
39,195
|
| Unrealized Gains, available-for-sale securities |
|
2
|
| Unrealized Losses, available-for-sale securities |
(14)
|
(51)
|
| Fair Value, available-for-sale investments |
13,888
|
39,146
|
| Measured on a recurring basis | Level 2 | Corporate bonds | Short-term investments |
|
|
| Fair Value Measurements |
|
|
| Fair Value, available-for-sale investments |
13,888
|
33,156
|
| Measured on a recurring basis | Level 2 | Corporate bonds | Long-term investments |
|
|
| Fair Value Measurements |
|
|
| Fair Value, available-for-sale investments |
|
5,990
|
| Measured on a recurring basis | Level 2 | Commercial paper |
|
|
| Fair Value Measurements |
|
|
| Adjusted Cost, available-for-sale securities |
7,082
|
1,100
|
| Fair Value, available-for-sale investments |
7,082
|
1,100
|
| Measured on a recurring basis | Level 2 | Commercial paper | Short-term investments |
|
|
| Fair Value Measurements |
|
|
| Fair Value, available-for-sale investments |
$ 7,082
|
1,100
|
| Measured on a recurring basis | Level 2 | U.S. agency securities |
|
|
| Fair Value Measurements |
|
|
| Adjusted Cost, available-for-sale securities |
|
3,506
|
| Unrealized Losses, available-for-sale securities |
|
(1)
|
| Fair Value, available-for-sale investments |
|
3,505
|
| Measured on a recurring basis | Level 2 | U.S. agency securities | Short-term investments |
|
|
| Fair Value Measurements |
|
|
| Fair Value, available-for-sale investments |
|
$ 3,505
|