Impact of Recently Issued Accounting Standards - Additional Information (Detail) $ in Millions |
6 Months Ended |
|---|---|
|
Jun. 30, 2017
USD ($)
| |
| Accounting Standards Update 2016-09 [Member] | Retained Earnings (Deficit) | |
| New Accounting Pronouncements Or Change In Accounting Principle [Line Items] | |
| New accounting pronouncement or change in accounting principle, effect of adoption, quantification | $ 18.5 |