Intangible Assets and Liabilities - Summary of Intangible Assets and Liabilities (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2016	Dec. 31, 2015
Assets:
Gross	$ 507,420	$ 490,329
Accumulated amortization	(230,271)	(219,334)
Total	$ 277,149	$ 270,995
Weighted Average Remaining Amortization in Years	16 years 6 months	16 years 7 months 6 days
Liabilities:
Gross	$ 39,254	$ 33,822
Accumulated amortization	(7,716)	(7,211)
Total	$ 31,538	$ 26,611
Weighted Average Remaining Amortization in Years	33 years 2 months 12 days	38 years
Below market leases
Liabilities:
Gross	$ 27,622	$ 22,240
Weighted Average Remaining Amortization in Years	22 years 6 months	27 years 2 months 12 days
Above market leasehold interests
Liabilities:
Gross	$ 11,632	$ 11,582
Weighted Average Remaining Amortization in Years	53 years 7 months 6 days	53 years 8 months 12 days
In place leases
Assets:
Gross	$ 265,666	$ 249,824
Weighted Average Remaining Amortization in Years	10 years 6 months	11 years
Tenant relationships
Assets:
Gross	$ 180,845	$ 180,925
Weighted Average Remaining Amortization in Years	10 years 4 months 24 days	10 years 4 months 24 days
Above market leases
Assets:
Gross	$ 25,203	$ 24,974
Weighted Average Remaining Amortization in Years	6 years	6 years
Below market leasehold interests
Assets:
Gross	$ 35,706	$ 34,606
Weighted Average Remaining Amortization in Years	63 years 2 months 12 days	63 years