Investments in Unconsolidated Real Estate Joint Ventures Management, Leasing and Marketing Fees (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Management, Leasing and Marketing Fees [Line Items]
Total Management, Leasing and Marketing Fees Paid by Unconsolidated Joint Ventures	$ 3,042	$ 2,121	$ 2,081
Marketing Fee [Member]
Management, Leasing and Marketing Fees [Line Items]
Total Management, Leasing and Marketing Fees Paid by Unconsolidated Joint Ventures	433	163	154
Development Fee [Member]
Management, Leasing and Marketing Fees [Line Items]
Total Management, Leasing and Marketing Fees Paid by Unconsolidated Joint Ventures	427	0	0
Management and Leasing Fee [Member]
Management, Leasing and Marketing Fees [Line Items]
Total Management, Leasing and Marketing Fees Paid by Unconsolidated Joint Ventures	2,102	1,958	1,927
Loan Guarantee Fee [Member]
Management, Leasing and Marketing Fees [Line Items]
Total Management, Leasing and Marketing Fees Paid by Unconsolidated Joint Ventures	$ 80	$ 0	$ 0