Investments and Related Party Transactions - Summary of Maximum Exposure to Loss Associated with RS Cogen (Detail) - RS Cogen [Member] - Not a Primary Beneficiary [Member] - Chlorovinyls [Member] - USD ($) |
Dec. 31, 2015 |
Dec. 31, 2014 |
|---|---|---|
| Investment Holdings [Line Items] | ||
| Investment in and net advances to RS Cogen | $ 9,500,000 | $ 4,600,000 |
| Supply contracts | 36,300,000 | 38,500,000 |
| Maximum exposure to loss | $ 45,800,000 | $ 43,100,000 |