Intangible Assets and Below Market Lease Liabilities (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018
Assets:
Deferred leasing costs (including lease incentives and above market lease and in-place lease acquisition-related intangible assets)	$ 348,197		$ 348,197		$ 344,548
Deferred leasing costs, accumulated amortization	(152,334)		(152,334)		(149,275)
Deferred leasing costs, net/Total scheduled future amortization of intangible assets	195,863		195,863		195,273
Liabilities (in accounts payable, accrued expenses and other liabilities):
Acquisition-related below market lease liabilities, gross	56,355		56,355		57,955
Acquisition-related below market lease liabilities, accumulated amortization	(34,124)		(34,124)		(32,307)
Acquisition-related below market lease liabilities, net	22,231		22,231		$ 25,648
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	182,762		182,762
Amortization of intangible assets and below market lease liabilities [Abstract]
Amortization of intangible assets	8,759	$ 9,207	19,074	$ 18,702
Lease Incentives (in Rental and Other Revenues) [Member]
Assets:
Deferred leasing costs, net/Total scheduled future amortization of intangible assets	8,292		8,292
Amortization of intangible assets and below market lease liabilities [Abstract]
Amortization of intangible assets	460	476	3,308	905
Acquisition-Related Intangible Assets (in Rental and Other Revenues) [Member]
Assets:
Deferred leasing costs, net/Total scheduled future amortization of intangible assets	4,018		4,018
Amortization of intangible assets and below market lease liabilities [Abstract]
Amortization of intangible assets	343	429	700	877
Acquisition-Related Intangible Assets (in Rental Property and Other Expenses) [Member]
Assets:
Deferred leasing costs, net/Total scheduled future amortization of intangible assets	791		791
Amortization of intangible assets and below market lease liabilities [Abstract]
Amortization of intangible assets	139	139	276	276
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	22,231		22,231
Amortization of intangible assets and below market lease liabilities [Abstract]
Amortization of acquisition-related below market lease liabilities	$ (1,763)	$ (1,495)	$ (3,416)	$ (3,018)