Summary of Significant Accounting Policies - Non-Cash Financing Activities (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2009	Jun. 30, 2009
Non Cash Activities [Line Items]
Mortgages Assumed	$ 112.7	$ 35.8
Business Acquisition, Percentage of Voting Interests Acquired		50.00%
Retirement of Exchangeable Notes, Principal Amount		142.3
Retirement of Exchangeable Notes, Carrying Value		135.3
Retirement of Exchangeable Notes, Number of Common Shares Issued		9.7
Tax Increment Financing Liability			2.6
Debt Assumed Adjustments [Member]
Non Cash Activities [Line Items]
Fair Value of Assets Acquired		1.5
Rental Property Adjustment [Member]
Non Cash Activities [Line Items]
Fair Value of Assets Acquired		$ 32.0