Investment in Kronos Worldwide, Inc. - Additional Information (Detail) - Kronos - USD ($) $ / shares in Units, shares in Millions, $ in Millions	Sep. 30, 2016	Dec. 31, 2015
Schedule Of Equity Method Investments [Line Items]
Outstanding common stock, shares	35.2	35.2
Aggregate market value	$ 292.0	$ 198.6
Common stock quoted market price per share	$ 8.29	$ 5.64

Balance held at close of period in number of shares.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 946
-SubTopic 320
-Section S99
-Paragraph 4
-Subparagraph (SX 210.12-12C.Column B)
-URI http://asc.fasb.org/extlink&oid=50485924&loc=d3e611225-123010

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 946
-SubTopic 320
-Section S99
-Paragraph 6
-Subparagraph (SX 210.12-14.Column B)
-URI http://asc.fasb.org/extlink&oid=50485924&loc=d3e611322-123010

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 946
-SubTopic 320
-Section S99
-Paragraph 1
-Subparagraph (SX 210.12-12.Column B)
-URI http://asc.fasb.org/extlink&oid=50485924&loc=d3e611133-123010

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant