Marketable Investments - Summary of Company's Fair Value Hierarchy for its Financial Assets (Detail) - USD ($)
$ in Thousands |
Dec. 31, 2016 |
Dec. 31, 2015 |
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
| Fair value of assets on recurring basis |
$ 63,669
|
$ 48,100
|
| Money Market Funds [Member] |
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
| Fair value of assets on recurring basis |
2,522
|
325
|
| Level 1 [Member] |
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
| Fair value of assets on recurring basis |
2,522
|
325
|
| Level 1 [Member] | Money Market Funds [Member] |
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
| Fair value of assets on recurring basis |
2,522
|
325
|
| Level 2 [Member] |
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
| Fair value of assets on recurring basis |
61,147
|
47,775
|
| Federal Agency Obligations [Member] |
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
| Fair value of assets on recurring basis |
1,793
|
|
| Federal Agency Obligations [Member] | Level 2 [Member] |
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
| Fair value of assets on recurring basis |
1,793
|
|
| Corporate Obligations [Member] |
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
| Fair value of assets on recurring basis |
59,354
|
47,775
|
| Corporate Obligations [Member] | Level 2 [Member] |
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
| Fair value of assets on recurring basis |
$ 59,354
|
$ 47,775
|