Acquired Intangible Assets and Liabilities (Schedule of Estimated Annual Amortization of Leases) (Details) (USD $) In Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Acquired Above-Market Leases [Member]
Estimated annual amortization expense	$ 4,208	$ 5,088	$ 5,754	$ 7,115	$ 6,546
Acquired in Place Lease Value [Member]
Estimated annual amortization expense	$ 16,371	$ 24,816	$ 33,062	$ 37,960	$ 42,321