Non-Controlling Interests, Preferred Shares, Common Shares and Common Shares in Treasury - Fair Value Hierarchy of Valuation Techniques Used by Company (Detail) (USD $) In Millions, unless otherwise specified	Mar. 18, 2011	Dec. 31, 2010 Fair Value, Measurements, Recurring [Member] Warrants [Member]	Dec. 31, 2010 Level 1 [Member] Fair Value, Measurements, Recurring [Member] Warrants [Member]	Dec. 31, 2010 Level 2 [Member] Fair Value, Measurements, Recurring [Member] Warrants [Member]	Dec. 31, 2010 Level 3 [Member] Fair Value, Measurements, Recurring [Member] Warrants [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Derivative instrument liability, fair value	$ 74.3	$ 96.2	$ 0	$ 0	$ 96.2