Intangible Assets (Detail) - USD ($) $ in Thousands |
9 Months Ended | 12 Months Ended |
|---|---|---|
Sep. 30, 2016 |
Dec. 31, 2015 |
|
| Finite-Lived Intangible Assets [Line Items] | ||
| Gross Carrying Amount | $ 30,352 | $ 30,352 |
| Accumulated Amortization | (15,447) | (13,485) |
| Net | $ 14,905 | $ 16,867 |
| Remaining Useful Life (Years) | 8 years 7 months | 9 years 3 months |
| Customer relationships | ||
| Finite-Lived Intangible Assets [Line Items] | ||
| Gross Carrying Amount | $ 11,731 | $ 11,731 |
| Accumulated Amortization | (7,932) | (6,865) |
| Net | $ 3,799 | $ 4,866 |
| Remaining Useful Life (Years) | 5 years 8 months | 6 years |
| Disposal permits | ||
| Finite-Lived Intangible Assets [Line Items] | ||
| Gross Carrying Amount | $ 1,269 | $ 1,269 |
| Accumulated Amortization | (572) | (451) |
| Net | $ 697 | $ 818 |
| Remaining Useful Life (Years) | 4 years 5 months | 5 years 2 months |
| Customer contracts | ||
| Finite-Lived Intangible Assets [Line Items] | ||
| Gross Carrying Amount | $ 17,352 | $ 17,352 |
| Accumulated Amortization | (6,943) | (6,169) |
| Net | $ 10,409 | $ 11,183 |
| Remaining Useful Life (Years) | 10 years | 11 years |