Intangible Assets and Below Market Lease Liabilities - Scheduled Future Amortization (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Scheduled future amortization of intangible assets [Abstract]
Deferred leasing costs, net/Total scheduled future amortization of intangible assets	$ 195,273	$ 200,679
Scheduled future amortization of below market lease liabilites [Abstract]
Total scheduled future amortization of below market lease liabilities	(25,648)	$ (31,733)
Deferred Leasing Costs and Acquisition-Related Intangible Assets [Member]
Scheduled future amortization of intangible assets [Abstract]
2019	35,862
2020	31,285
2021	26,702
2022	22,392
2023	18,972
Thereafter	43,147
Deferred leasing costs, net/Total scheduled future amortization of intangible assets	$ 178,360
Weighted average remaining amortization periods for intangible assets and liabilities [Abstract]
Intangible assets, weighted average useful life (in years)	7 years 3 months 20 days
Lease Incentives [Member]
Scheduled future amortization of intangible assets [Abstract]
2019	$ 1,730
2020	1,445
2021	1,205
2022	982
2023	914
Thereafter	4,851
Deferred leasing costs, net/Total scheduled future amortization of intangible assets	$ 11,127
Weighted average remaining amortization periods for intangible assets and liabilities [Abstract]
Intangible assets, weighted average useful life (in years)	10 years 1 month 10 days
Acquisition-Related Intangible Assets (in Rental and Other Revenue) [Member]
Scheduled future amortization of intangible assets [Abstract]
2019	$ 1,261
2020	957
2021	631
2022	462
2023	308
Thereafter	1,100
Deferred leasing costs, net/Total scheduled future amortization of intangible assets	$ 4,719
Weighted average remaining amortization periods for intangible assets and liabilities [Abstract]
Intangible assets, weighted 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]
2019	$ 553
2020	514
2021	0
2022	0
2023	0
Thereafter	0
Deferred leasing costs, net/Total scheduled future amortization of intangible assets	$ 1,067
Weighted average remaining amortization periods for intangible assets and liabilities [Abstract]
Intangible assets, weighted average useful life (in years)	2 years
Acquisition-Related Below Market Lease Liabilities [Member]
Scheduled future amortization of below market lease liabilites [Abstract]
2019	$ (5,405)
2020	(5,135)
2021	(4,331)
2022	(3,258)
2023	(2,878)
Thereafter	(4,641)
Total scheduled future amortization of below market lease liabilities	$ (25,648)
Weighted average remaining amortization periods for intangible assets and liabilities [Abstract]
Below market lease liabilities, weighted average useful life (in years)	5 years 11 months