Fair Value Measurements (Investments in Joint Ventures) (Details) (USD $)	Mar. 31, 2013 Investment	Dec. 31, 2012 Investment
Equity Method Investments [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
FV Option	$ 42,568,000	$ 42,568,000
Fair value option, number of investments	2	2
Equity Method Investments [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Funds	25,792,000	25,795,000
Joint venture investments recorded at fair value	68,360,000	68,363,000
Fair Value, Measurements, Recurring [Member] | Level 3 [Member] | Real Estate Funds [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Funds	25,792,000	25,795,000
The funds, unfunded commitments	$ 5,200,000