Information Related to Reportable Segment (Parenthetical) (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Investment in Homesite
Segment Reporting Information [Line Items]
Equity in (losses) earnings	$ (20.2)	$ (3.2)	$ (1.1)
ORX Exploration, Inc.
Segment Reporting Information [Line Items]
Equity in (losses) earnings	$ (1.6)	$ (2.0)	$ (21.9)

This item represents the entity's proportionate share for the period of the net income (loss) of its investee (such as unconsolidated subsidiaries and joint ventures) to which the equity method of accounting is applied. This item includes income or expense related to stock-based compensation based on the investor's grant of stock to employees of an equity method investee.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

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+ Details