Investment in Affiliate and Other Assets - Summary of Financial Information (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Financial Information [Line Items]
Current assets	$ 1,062.0				$ 949.0				$ 1,062.0	$ 949.0
Property and equipment, net	733.6				796.4				733.6	796.4	763.1
Total assets	2,967.2				2,967.2				2,967.2	2,967.2	3,170.5
Other liabilities, primarily current	40.4				51.3				40.4	51.3
Total liabilities and equity	2,967.2				2,967.2				2,967.2	2,967.2
Net sales	432.0	476.5	491.7	462.4	400.1	448.2	516.1	499.2	1,862.6	1,863.6	2,087.3
Cost of sales									1,459.8	1,729.4	1,512.1
General and administrative									276.1	375.1	273.3
Total costs and expenses									1,792.6	2,169.5	1,856.5
Net income (loss)	13.7	37.5	23.7	4.6	10.8	(40.9)	(48.6)	(48.2)	79.5	(126.9)	222.1
Loss before income taxes									112.0	(217.9)	301.4
LPC
Financial Information [Line Items]
Current assets	107.4				127.2				107.4	127.2
Property and equipment, net	110.6				114.1				110.6	114.1
Total assets	218.0				241.3				218.0	241.3
Other liabilities, primarily current	37.3				33.9				37.3	33.9
Partners’ equity	180.7				207.4				180.7	207.4
Total liabilities and equity	218.0				241.3				218.0	241.3
Net sales									386.9	449.1	477.7
Cost of sales									386.4	448.7	477.3
General and administrative									0.5	0.4	0.4
Total costs and expenses									386.9	449.1	477.7
LPC | Kronos Worldwide, Inc.
Financial Information [Line Items]
Net sales									193.1	224.5	250.2
LPC | Tioxide
Financial Information [Line Items]
Net sales									193.8	224.6	227.5
Basic Management Inc And Landwell
Financial Information [Line Items]
Net sales										9.5	10.4
Net income (loss)										(3.7)	(1.4)
Loss before income taxes										$ (3.9)	$ (1.2)