Non-Controlling Interests, Preferred Shares, Common Shares and Common Shares in Treasury - Reconciliation of Beginning and Ending Balances of Equity Derivative Instruments (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011
Fair Value Measurements Disclosure [Line Items]
Balance of Level 3, Beginning value	$ 96.2
Unrealized gain	(21.9)
Transfer out of liability to paid-in capital	(74.3)
Balance of Level 3, Ending value	$ 0