Commitments and Contingencies - Schedule of Reconciliation of Balances of Accrued Shelton Lease Cease-Use Liability (Detail) - Shelton Operating Lease [Member] - USD ($) $ in Thousands |
12 Months Ended | |
|---|---|---|
May 31, 2016 |
Dec. 31, 2016 |
|
| Restructuring Cost and Reserve [Line Items] | ||
| Additional accruals | $ 1,312 | $ 1,312 |
| Rental payments | (556) | |
| Balance, December 31, 2016 | $ 756 |