Acquired Intangible Assets and Liabilities (Summary of Acquired Intangible Assets) (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Acquired below-market leases
Gross amount	$ 283,899	$ 294,791
Accumulated amortization	(202,000)	(193,677)
Net	81,899	101,114
Acquired in-place lease value
Finite-Lived Intangible Assets [Line Items]
Gross amount	896,693	901,381
Accumulated amortization	(517,443)	(472,933)
Net	379,250	428,448
Tenant relationship value
Finite-Lived Intangible Assets [Line Items]
Gross amount	971,519	734,800
Accumulated amortization	(82,069)	(14,495)
Net	889,450	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	110,142	122,311
Accumulated amortization	(87,961)	(89,613)
Net	$ 22,181	$ 32,698