Acquired Intangible Assets and Liabilities (Details) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Acquired Intangible Assets and Liabilities
New intangible assets added		$ 2,900,000
New intangible liabilities added		200,000
Weighted average life of intangible assets		4 years 4 months 24 days
Weighted average life of intangible liabilities		6 months
Below-market lease contract value, gross	11,000,000	18,600,000
Accumulated amortization of below-market lease	4,400,000	10,100,000
Acquired Intangible Assets and Liabilities
Increase to rental income	800,000	1,500,000	1,700,000
Amortization of all other identified intangible assets	(823,000)	(1,505,000)	(1,650,000)
Estimated amortization of acquired below-market leases, net of acquired above-market leases
2014	434,000
2015	548,000
2016	565,000
2017	596,000
2018	597,000
Thereafter	2,590,000
Total	5,330,000
Estimated amortization of all other identified intangible assets
2014	3,168,000
2015	2,071,000
2016	1,665,000
2017	1,172,000
2018	656,000
Thereafter	945,000
Total	9,677,000
Lease contracts value, gross	24,500,000	45,700,000
Accumulated amortization	14,800,000	28,600,000
Above-market leases
Estimated amortization of all other identified intangible assets
Lease contracts value, gross	4,100,000	6,800,000
Accumulated amortization	2,800,000	4,500,000
Other identified intangible assets
Acquired Intangible Assets and Liabilities
Amortization of all other identified intangible assets	$ 7,400,000	$ 18,100,000	$ 32,200,000