Investments - Additional Information (Detail)	12 Months Ended												12 Months Ended
	Dec. 31, 2014 USD ($)		Dec. 31, 2013 USD ($)		Dec. 31, 2012 USD ($)	Dec. 31, 2014 Significant Unconsolidated Joint Venture USD ($)	Dec. 31, 2013 Significant Unconsolidated Joint Venture USD ($)	Dec. 31, 2012 Significant Unconsolidated Joint Venture USD ($)	Dec. 31, 2014 Joint Venture Saudi Organometallic Chemicals Company SAR	Dec. 31, 2012 Joint Venture Saudi Organometallic Chemicals Company USD ($)	Dec. 31, 2014 Joint Venture Saudi Organometallic Chemicals Company USD ($)	Dec. 31, 2013 Joint Venture Saudi Organometallic Chemicals Company	Dec. 31, 2012 Eurecat S.A. EUR (€)	Dec. 31, 2014 Eurecat S.A. USD ($)	Dec. 31, 2013 Eurecat S.A. USD ($)	Dec. 31, 2014 Nippon Aluminum Alkyls	Dec. 31, 2013 Nippon Aluminum Alkyls	Dec. 31, 2012 Nippon Aluminum Alkyls	Dec. 31, 2014 Magnifin Magnesiaprodukte GmbH & Co. KG	Dec. 31, 2013 Magnifin Magnesiaprodukte GmbH & Co. KG	Dec. 31, 2012 Magnifin Magnesiaprodukte GmbH & Co. KG	Dec. 31, 2014 Nippon Ketjen Company Limited	Dec. 31, 2013 Nippon Ketjen Company Limited	Dec. 31, 2012 Nippon Ketjen Company Limited	Dec. 31, 2014 Eurecat S.A.	Dec. 31, 2013 Eurecat S.A.	Dec. 31, 2012 Eurecat S.A.	Dec. 31, 2014 Fabrica Carioca de Catalisadores S.A.	Dec. 31, 2013 Fabrica Carioca de Catalisadores S.A.	Dec. 31, 2012 Fabrica Carioca de Catalisadores S.A.	Dec. 31, 2014 Stannica, LLC	Dec. 31, 2013 Stannica, LLC	Dec. 31, 2012 Stannica, LLC	Dec. 31, 2014 Stannica Llc USD ($)	Dec. 31, 2013 Stannica Llc USD ($)	Dec. 31, 2014 Benefit Protection Trust USD ($)	Dec. 31, 2013 Benefit Protection Trust USD ($)
Schedule of Investments [Line Items]
Investment in significant unconsolidated joint ventures						$ 154,400,000	$ 172,900,000
Equity in net income of unconsolidated investments (net of tax)	35,742,000		31,729,000		38,067,000	35,400,000	31,500,000	37,000,000
Undistributed earnings from equity method investees						112,900,000	117,100,000
Dividends received from unconsolidated investments	40,688,000		21,632,000		26,908,000	39,600,000	20,500,000	25,600,000
Investments in unconsolidated joint ventures exceeded the amount of underlying equity in net assets	7,000,000		8,400,000
Excess amount paid for joint ventures remaining to be amortized	1,000,000		1,400,000
Carrying value of unconsolidated investment	0		0																															6,200,000	5,500,000
Marketable equity securities	23,974,000		23,801,000																																	22,200,000	23,000,000
Long-term advances to joint ventures	7,499,000		0		24,959,000				28,100,000	22,500,000			1,900,000
Long-term advances to joint ventures	$ 34,084,000	[1]	$ 25,124,000	[1]							$ 7,500,000			$ 2,300,000	$ 2,600,000
Ownership percentage											50.00%			50.00%		50.00%	50.00%	50.00%	50.00%	50.00%	50.00%	50.00%	50.00%	50.00%	50.00%	50.00%	50.00%	50.00%	50.00%	50.00%	50.00%	50.00%	50.00%
Interest rate margin over LIBOR											1.275%
Interest rate percentage											1.53%	1.52%
Long-term advances to joint venture, maturity date									Dec. 31, 2021

[1] See Note 9, “Investments.”