Investments in Unconsolidated Real Estate Joint Ventures (Joint Venture Fees) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Management, Leasing and Marketing Fees [Line Items]
Fees paid by unconsolidated joint ventures	$ 888	$ 639	$ 2,870	$ 1,692
Development Fee [Member]
Management, Leasing and Marketing Fees [Line Items]
Fees paid by unconsolidated joint ventures	(6)	8	57	8
Loan Guarantee Fee [Member]
Management, Leasing and Marketing Fees [Line Items]
Fees paid by unconsolidated joint ventures	40	16	121	16
Management and Leasing Fee [Member]
Management, Leasing and Marketing Fees [Line Items]
Fees paid by unconsolidated joint ventures	761	554	2,391	1,507
Marketing Fee [Member]
Management, Leasing and Marketing Fees [Line Items]
Fees paid by unconsolidated joint ventures	$ 93	$ 61	$ 301	$ 161