Intangible Assets and Below Market Lease Liabilities (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Assets:
Deferred leasing costs (including lease incentives and above market lease and in-place lease acquisition-related intangible assets)	$ 341,384		$ 341,384		$ 344,191
Deferred leasing costs, accumulated amortization	(147,588)		(147,588)		(143,512)
Deferred leasing costs, net/Total scheduled future amortization of intangible assets	193,796		193,796		200,679
Liabilities (in accounts payable, accrued expenses and other liabilities):
Acquisition-related below market lease liabilities, gross	58,698		58,698		59,947
Acquisition-related below market lease liabilities, accumulated amortization	(31,519)		(31,519)		(28,214)
Acquisition-related below market lease liabilities, net	27,179		27,179		$ 31,733
Deferred Leasing Costs and Acquisition-Related Intangible Assets (in Depreciation and Amortization) [Member]
Assets:
Deferred leasing costs, net/Total scheduled future amortization of intangible assets	176,652		176,652
Amortization of intangible assets and below market lease liabilities [Abstract]
Amortization of intangible assets	8,969	$ 10,130	27,671	$ 30,882
Lease Incentives (in Rental and Other Revenues) [Member]
Assets:
Deferred leasing costs, net/Total scheduled future amortization of intangible assets	10,834		10,834
Amortization of intangible assets and below market lease liabilities [Abstract]
Amortization of intangible assets	452	444	1,357	1,284
Acquisition-Related Intangible Assets (in Rental and Other Revenues) [Member]
Assets:
Deferred leasing costs, net/Total scheduled future amortization of intangible assets	5,103		5,103
Amortization of intangible assets and below market lease liabilities [Abstract]
Amortization of intangible assets	415	671	1,292	2,382
Acquisition-Related Intangible Assets (in Rental Property and Other Expenses) [Member]
Assets:
Deferred leasing costs, net/Total scheduled future amortization of intangible assets	1,207		1,207
Amortization of intangible assets and below market lease liabilities [Abstract]
Amortization of intangible assets	140	140	416	416
Acquisition-Related Below Market Lease Liabilities (in Rental and Other Revenues) [Member]
Liabilities (in accounts payable, accrued expenses and other liabilities):
Acquisition-related below market lease liabilities, net	27,179		27,179
Amortization of intangible assets and below market lease liabilities [Abstract]
Amortization of acquisition-related below market lease liabilities	$ (1,535)	$ (1,576)	$ (4,553)	$ (4,748)