Investments in and Advances To Joint Ventures (Details 3) (Unconsolidated Joint Ventures [Member], USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Unconsolidated Joint Ventures [Member]
Service fees and income earned by the Company's unconsolidated joint ventures
Management and other fees	$ 6.5	$ 7.3	$ 13.4	$ 14.7
Financing and other fees	0	0.3	0	0.3
Development fees and leasing commissions	1.9	1.9	3.9	3.7
Interest income	$ 0.5		$ 0.5	$ 0.1