Investments - Summary of Maximum Exposure to Loss Associated with RS Cogen (Detail) - RS Cogen [Member] - Not a Primary Beneficiary [Member] - Chlorovinyls [Member] - USD ($)	Jun. 30, 2016	Dec. 31, 2015
Investment Holdings [Line Items]
Investment in and net advances to RS Cogen	$ 9,900,000	$ 9,500,000
Supply contracts	35,300,000	36,300,000
Maximum exposure to loss	$ 45,200,000	$ 45,800,000