Fair Value Measurements and Marketable Securities - Summary of Cash Equivalents and Marketable Securities (Detail) - USD ($)
$ in Thousands |
Dec. 31, 2016 |
Dec. 31, 2015 |
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
| Cash equivalents |
$ 26,588
|
$ 25,927
|
| Marketable securities |
96,842
|
149,484
|
| Total cash equivalents and marketable securities |
123,430
|
175,411
|
| Money Market Funds [Member] |
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
| Cash equivalents |
22,091
|
13,231
|
| U.S. Government Securities [Member] |
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
| Cash equivalents |
|
4,999
|
| Marketable securities |
|
4,500
|
| Corporate Bonds [Member] |
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
| Cash equivalents |
1,500
|
3,000
|
| Marketable securities |
69,622
|
125,516
|
| Commercial Paper [Member] |
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
| Cash equivalents |
2,997
|
4,697
|
| Marketable securities |
27,220
|
19,468
|
| Quoted Prices in Active Markets, (Level 1) [Member] |
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
| Cash equivalents |
22,091
|
13,231
|
| Total cash equivalents and marketable securities |
22,091
|
13,231
|
| Quoted Prices in Active Markets, (Level 1) [Member] | Money Market Funds [Member] |
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
| Cash equivalents |
22,091
|
13,231
|
| Significant Other Observable Inputs (Level 2) [Member] |
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
| Cash equivalents |
4,497
|
12,696
|
| Marketable securities |
96,842
|
149,484
|
| Total cash equivalents and marketable securities |
101,339
|
162,180
|
| Significant Other Observable Inputs (Level 2) [Member] | U.S. Government Securities [Member] |
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
| Cash equivalents |
|
4,999
|
| Marketable securities |
|
4,500
|
| Significant Other Observable Inputs (Level 2) [Member] | Corporate Bonds [Member] |
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
| Cash equivalents |
1,500
|
3,000
|
| Marketable securities |
69,622
|
125,516
|
| Significant Other Observable Inputs (Level 2) [Member] | Commercial Paper [Member] |
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
| Cash equivalents |
2,997
|
4,697
|
| Marketable securities |
$ 27,220
|
$ 19,468
|