Debt (Details 5) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010
Long-Term Debt
Real estate	$ 1,092.9	$ 1,063.5
Non-recourse mortgages and notes payable
Long-Term Debt
Outstanding principal balances per real estate development, low end of range	5.6	5.8
Outstanding principal balances per real estate development, high end of range	8.7	8.9
Interest rates per real estate development, low end of range (as a percent)	5.50%	5.50%
Interest rates per real estate development, high end of range (as a percent)	5.80%	5.80%
Real estate	29.5	29.6
Other mortgages and notes payable
Long-Term Debt
Long-term debt obligation assumed with purchase of WM Advisors, Inc.	$ 3.5	$ 8.4