Intangible Assets and Below Market Lease Liabilities (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Intangible assets and below market lease liabilities, net [Abstract]
Deferred leasing costs, gross	$ 344,191	$ 353,581
Deferred leasing costs, accumulated amortization	(143,512)	(140,081)
Deferred leasing costs, net/Total scheduled future amortization of intangible assets	200,679	213,500
Acquisition-related below market lease liabilities, gross	59,947	61,221
Acquisition-related below market lease liabilities, accumulated amortization	(28,214)	(23,074)
Acquisition-related below market lease liabilities, net	31,733	38,147
Deferred Leasing Costs and Acquisition-Related Intangible Assets [Member]
Intangible assets and below market lease liabilities, net [Abstract]
Deferred leasing costs, net/Total scheduled future amortization of intangible assets	182,754
Amortization of intangible assets and below market lease liabilities
Amortization of intangible assets	41,187	44,968	$ 43,332
Lease Incentives [Member]
Intangible assets and below market lease liabilities, net [Abstract]
Deferred leasing costs, net/Total scheduled future amortization of intangible assets	9,906
Amortization of intangible assets and below market lease liabilities
Amortization of intangible assets	1,765	1,779	1,493
Acquisition-Related Intangible Assets (in Rental and Other Revenue) [Member]
Intangible assets and below market lease liabilities, net [Abstract]
Deferred leasing costs, net/Total scheduled future amortization of intangible assets	6,395
Amortization of intangible assets and below market lease liabilities
Amortization of intangible assets	2,921	3,851	5,062
Acquisition-Related Intangible Assets (in Rental Property and Other Expenses) [Member]
Intangible assets and below market lease liabilities, net [Abstract]
Deferred leasing costs, net/Total scheduled future amortization of intangible assets	1,624
Amortization of intangible assets and below market lease liabilities
Amortization of intangible assets	557	557	557
Acquisition-Related Below Market Lease Liabilities [Member]
Intangible assets and below market lease liabilities, net [Abstract]
Acquisition-related below market lease liabilities, net	31,733
Amortization of intangible assets and below market lease liabilities
Amortization of acquisition-related below market lease liabilities	$ (6,415)	$ (8,183)	$ (7,065)