Investments in Unconsolidated Real Estate Joint Ventures (Management, Leasing and Marketing Fees) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Management, Leasing and Marketing Fees [Line Items]
Fees paid by unconsolidated joint ventures	$ 918	$ 521	$ 1,983	$ 1,053
Development Fee [Member]
Management, Leasing and Marketing Fees [Line Items]
Fees paid by unconsolidated joint ventures	(8)	0	63	0
Loan Guarantee Fee [Member]
Management, Leasing and Marketing Fees [Line Items]
Fees paid by unconsolidated joint ventures	40	0	80	0
Management and Leasing Fee [Member]
Management, Leasing and Marketing Fees [Line Items]
Fees paid by unconsolidated joint ventures	786	474	1,631	953
Marketing Fee [Member]
Management, Leasing and Marketing Fees [Line Items]
Fees paid by unconsolidated joint ventures	$ 100	$ 47	$ 209	$ 100