Acquired Intangible Assets and Liabilities (Summary of Acquired Intangible Assets) (Details) - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015
Finite-Lived Intangible Assets [Line Items]
Below-market lease, gross amount	$ 291,430	$ 294,791
Below-market lease, accumulated amortization	(200,607)	(193,677)
Total	90,823	101,114
Acquired in-place lease value
Finite-Lived Intangible Assets [Line Items]
Gross amount	887,175	901,381
Accumulated amortization	(492,236)	(472,933)
Net	394,939	428,448
Tenant relationship value
Finite-Lived Intangible Assets [Line Items]
Gross amount	734,800	734,800
Accumulated amortization	(46,213)	(14,495)
Net	688,587	720,305
Trade name
Finite-Lived Intangible Assets [Line Items]
Gross amount	7,300	7,300
Accumulated amortization	(7,300)	(417)
Net	0	6,883
Acquired above-market leases
Finite-Lived Intangible Assets [Line Items]
Gross amount	118,309	122,311
Accumulated amortization	(91,524)	(89,613)
Net	$ 26,785	$ 32,698