Acquired Intangible Assets and Liabilities (Summary of Acquired Intangible Assets) (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Below Market Lease [Abstract]
Gross amount	$ 294,791	$ 282,670
Accumulated amortization	(193,677)	(178,435)
Net	101,114	104,235
Acquired in place lease value:
Finite-Lived Intangible Assets [Line Items]
Gross amount	901,381	680,419
Accumulated amortization	(472,933)	(452,739)
Net	428,448	227,680
Tenant relationship value:
Finite-Lived Intangible Assets [Line Items]
Gross amount	734,800	0
Accumulated amortization	(14,495)	0
Net	720,305	0
Trade name:
Finite-Lived Intangible Assets [Line Items]
Gross amount	7,300	0
Accumulated amortization	(417)	0
Net	6,883	0
Acquired above market leases:
Finite-Lived Intangible Assets [Line Items]
Gross amount	122,311	126,677
Accumulated amortization	(89,613)	(88,072)
Net	$ 32,698	$ 38,605