Related Party Transactions - Additional Information (Detail) - USD ($) |
12 Months Ended | ||
|---|---|---|---|
Dec. 31, 2016 |
Dec. 31, 2015 |
Dec. 31, 2014 |
|
| Related Party Transaction [Line Items] | |||
| Fees paid to related party | $ 0 | $ 0 | |
| Morrison and Foerster LLP | |||
| Related Party Transaction [Line Items] | |||
| Fees paid to related party | $ 275,000 | ||