Impairment of Lift Venture Investment - Additional Information (Detail) - USD ($) |
3 Months Ended | 12 Months Ended | |
|---|---|---|---|
Sep. 30, 2016 |
Dec. 31, 2015 |
Nov. 30, 2014 |
|
| Investment [Line Items] | |||
| Investment impairment charge | $ 0 | $ 0 | |
| Lift Ventures LLC [Member] | |||
| Investment [Line Items] | |||
| Investment impairment charge | $ 5,647,000 | ||