Summary of Significant Accounting Policies - Additional Information (Detail) - USD ($) $ in Millions |
1 Months Ended | 6 Months Ended | |
|---|---|---|---|
Mar. 31, 2018 |
Apr. 30, 2017 |
Jun. 30, 2018 |
|
| Summary Of Significant Accounting Policies [Line Items] | |||
| Prepayment under the agreement | $ 5.0 | ||
| Utilization of prepayment related to hydraulic fracturing services provided | $ 1.2 | ||
| Agreement termination date | Mar. 31, 2018 | ||
| Unused Prepaid Balance [Member] | |||
| Summary Of Significant Accounting Policies [Line Items] | |||
| Proceeds from prepayment under the agreement | $ 3.8 | ||