Investments and Fair Value of Financial Instruments - Components of Cash Equivalents and Short-Term Investments, Including Unrealized Gains and Losses (Detail) - USD ($)
$ in Thousands |
Dec. 31, 2016 |
Dec. 31, 2015 |
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
| Amortized cost |
$ 11,126
|
$ 24,116
|
| Gross unrealized gains |
0
|
0
|
| Gross unrealized losses |
0
|
0
|
| Fair Value |
11,126
|
24,116
|
| Amortized cost |
23,808
|
17,610
|
| Total cash equivalents and short-term investments, Amortized cost |
34,934
|
41,726
|
| Total cash equivalents and short term investments, Gross unrealized gains |
0
|
0
|
| Total cash equivalents and short term investments, Gross unrealized losses |
0
|
0
|
| Total cash equivalents and short term investments, Fair value |
34,934
|
41,726
|
| Certificates of deposit, 90 days or greater [Member] |
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
| Amortized cost |
23,808
|
17,610
|
| Gross unrealized gains |
0
|
0
|
| Gross unrealized losses |
0
|
0
|
| Fair Value |
23,808
|
17,610
|
| Money market funds [Member] |
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
| Amortized cost |
11,126
|
24,116
|
| Gross unrealized gains |
0
|
0
|
| Gross unrealized losses |
0
|
0
|
| Fair Value |
$ 11,126
|
$ 24,116
|