Intangible Assets and Below Market Lease Liabilities - Scheduled Future Amortization (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2018	Dec. 31, 2017
Scheduled future amortization of intangible assets [Abstract]
Deferred leasing costs, net/Total scheduled future amortization of intangible assets	$ 193,796	$ 200,679
Scheduled future amortization of below market lease liabilities [Abstract]
Total scheduled future amortization of acquisition-related below market lease liabilities	(27,179)	$ (31,733)
Deferred Leasing Costs and Acquisition-Related Intangible Assets (in Depreciation and Amortization) [Member]
Scheduled future amortization of intangible assets [Abstract]
October 1 through December 31, 2018	9,395
2019	34,011
2020	29,391
2021	24,873
2022	20,584
Thereafter	58,398
Deferred leasing costs, net/Total scheduled future amortization of intangible assets	$ 176,652
Weighted average remaining amortization periods for intangible assets and below market lease liabilities [Abstract]
Finite-lived intangible assets, average useful life (in years)	7 years 4 months 25 days
Lease Incentives (in Rental and Other Revenues) [Member]
Scheduled future amortization of intangible assets [Abstract]
October 1 through December 31, 2018	$ 453
2019	1,647
2020	1,360
2021	1,132
2022	915
Thereafter	5,327
Deferred leasing costs, net/Total scheduled future amortization of intangible assets	$ 10,834
Weighted average remaining amortization periods for intangible assets and below market lease liabilities [Abstract]
Finite-lived intangible assets, average useful life (in years)	10 years 1 month 5 days
Acquisition-Related Intangible Assets (in Rental and Other Revenues) [Member]
Scheduled future amortization of intangible assets [Abstract]
October 1 through December 31, 2018	$ 369
2019	1,273
2020	959
2021	632
2022	462
Thereafter	1,408
Deferred leasing costs, net/Total scheduled future amortization of intangible assets	$ 5,103
Weighted average remaining amortization periods for intangible assets and below market lease liabilities [Abstract]
Finite-lived intangible assets, average useful life (in years)	6 years 6 months
Acquisition-Related Intangible Assets (in Rental Property and Other Expenses) [Member]
Scheduled future amortization of intangible assets [Abstract]
October 1 through December 31, 2018	$ 136
2019	553
2020	518
2021	0
2022	0
Thereafter	0
Deferred leasing costs, net/Total scheduled future amortization of intangible assets	$ 1,207
Weighted average remaining amortization periods for intangible assets and below market lease liabilities [Abstract]
Finite-lived intangible assets, average useful life (in years)	2 years 2 months 15 days
Acquisition-Related Below Market Lease Liabilities (in Rental and Other Revenues) [Member]
Scheduled future amortization of below market lease liabilities [Abstract]
October 1 through December 31, 2018	$ (1,442)
2019	(5,425)
2020	(5,169)
2021	(4,362)
2022	(3,258)
Thereafter	(7,523)
Total scheduled future amortization of acquisition-related below market lease liabilities	$ (27,179)
Weighted average remaining amortization periods for intangible assets and below market lease liabilities [Abstract]
Finite-lived below market lease liabilities, average useful life (in years)	6 years 1 month 10 days