Related Party Transactions Related Party Revenue (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Sponsors [Member] | Family Office Services [Member]
Related Party Transaction [Line Items]
Revenue from related parties	$ 1.10	$ 0.80	$ 0.80
Accounts and Notes Receivable, Net [Member] | Partners and Shareholders [Member]
Related Party Transaction [Line Items]
Due from related parties	0.08	0.50	0.50
Third party management and other fees [Member] | Sponsors [Member] | Supervisory Fee Revenue [Member]
Related Party Transaction [Line Items]
Revenue from related parties	2.80	1.90	2.10
Third party management and other fees [Member] | Sponsors [Member] | Property Management Fee Revenue [Member]
Related Party Transaction [Line Items]
Revenue from related parties	1.60	1.00	0.90
Third party management and other fees [Member] | Sponsors [Member] | Lease Commissions [Member]
Related Party Transaction [Line Items]
Revenue from related parties	0	0.20	0
Third party management and other fees [Member] | Equity Method Investee [Member] | Supervisory Fee Revenue [Member]
Related Party Transaction [Line Items]
Revenue from related parties	0.60	0.80	1.20
Third party management and other fees [Member] | Equity Method Investee [Member] | Property Management Fee Revenue [Member]
Related Party Transaction [Line Items]
Revenue from related parties	0.10	1.20	0.70
Other income and fees [Member] | Sponsors [Member] | Profit Share [Member]
Related Party Transaction [Line Items]
Revenue from related parties	3.30	0.70	0.80
Other income and fees [Member] | Sponsors [Member] | Other Fees and Disbursements from Non-Controlled Affiliates [Member]
Related Party Transaction [Line Items]
Revenue from related parties	0.02	0.60	0.90
Other income and fees [Member] | Equity Method Investee [Member] | Profit Share [Member]
Related Party Transaction [Line Items]
Revenue from related parties	0.40	0.90	0.90
Other income and fees [Member] | Equity Method Investee [Member] | Other Fees and Disbursements from Non-Controlled Affiliates [Member]
Related Party Transaction [Line Items]
Revenue from related parties	1.10	1.30	1.20
Due from related parties	0	0.40	0.90
Other income and fees [Member] | Equity Method Investee [Member] | Other Fees Reimbursed on the Equity Method for Offering Costs Related to Offering [Member]
Related Party Transaction [Line Items]
Revenue from related parties	$ 1.10	$ 1.30	$ 1.20