Discontinued Operations - Depreciation, Amortization and Capital Expenditures Associated with Discontinued Operations (Detail) - Aromatics [Member] - Discontinued Operations Disposed of by Sale [Member] - USD ($) $ in Millions |
3 Months Ended | 6 Months Ended | |
|---|---|---|---|
Jun. 30, 2015 |
Jun. 30, 2016 |
Jun. 30, 2015 |
|
| Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items] | |||
| Depreciation and amortization | $ 2.9 | $ 2.1 | $ 5.7 |
| Capital expenditures | $ 1.9 | $ 1.0 | $ 3.6 |