Real Estate Transactions (Fair Value of Assets and Liabilities Acquired) (Details) $ in Thousands	Dec. 31, 2014 USD ($)
Northpark Town Center
Tangible assets:
Land and improvements	$ 24,577
Building	274,151
Tenant improvements	21,674
Other assets	0
Tangible assets	320,402
Intangible assets:
Total intangible assets	33,005
Tangible liabilities:
Accounts payable and accrued expenses	0
Total tangible liabilities	0
Intangible liabilities:
Total intangible liabilities	(8,018)
Total purchase price	345,389
Northpark Town Center | Above-market leases
Intangible assets:
Total intangible assets	2,846
Northpark Town Center | In-place leases
Intangible assets:
Total intangible assets	30,159
Northpark Town Center | Below-market ground leases
Intangible assets:
Total intangible assets	0
Fifth Third Center
Tangible assets:
Land and improvements	22,863
Building	163,649
Tenant improvements	16,781
Other assets	1,014
Tangible assets	204,307
Intangible assets:
Total intangible assets	18,066
Tangible liabilities:
Accounts payable and accrued expenses	(1,026)
Total tangible liabilities	(1,026)
Intangible liabilities:
Total intangible liabilities	(9,374)
Total purchase price	211,973
Fifth Third Center | Above-market leases
Intangible assets:
Total intangible assets	632
Fifth Third Center | In-place leases
Intangible assets:
Total intangible assets	17,096
Fifth Third Center | Below-market ground leases
Intangible assets:
Total intangible assets	$ 338