Intangible Assets and Below Market Lease Liabilities - Scheduled Future Amortization (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Scheduled future amortization of intangible assets [Abstract]
Deferred leasing costs, net/Total scheduled future amortization of intangible assets	$ 200,679	$ 213,500
Scheduled future amortization of below market lease liabilites [Abstract]
Total scheduled future amortization of below market lease liabilities	(31,733)	$ (38,147)
Deferred Leasing Costs and Acquisition-Related Intangible Assets [Member]
Scheduled future amortization of intangible assets [Abstract]
2018	36,566
2019	31,032
2020	26,614
2021	22,262
2022	18,098
Thereafter	48,182
Deferred leasing costs, net/Total scheduled future amortization of intangible assets	$ 182,754
Weighted average remaining amortization periods for intangible assets and liabilities [Abstract]
Intangible assets, weighted average useful life (in years)	7 years 7 months 9 days
Lease Incentives [Member]
Scheduled future amortization of intangible assets [Abstract]
2018	$ 1,586
2019	1,434
2020	1,171
2021	948
2022	734
Thereafter	4,033
Deferred leasing costs, net/Total scheduled future amortization of intangible assets	$ 9,906
Weighted average remaining amortization periods for intangible assets and liabilities [Abstract]
Intangible assets, weighted average useful life (in years)	9 years 11 months
Acquisition-Related Intangible Assets (in Rental and Other Revenue) [Member]
Scheduled future amortization of intangible assets [Abstract]
2018	$ 1,659
2019	1,275
2020	959
2021	632
2022	462
Thereafter	1,408
Deferred leasing costs, net/Total scheduled future amortization of intangible assets	$ 6,395
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]
2018	$ 553
2019	553
2020	518
2021	0
2022	0
Thereafter	0
Deferred leasing costs, net/Total scheduled future amortization of intangible assets	$ 1,624
Weighted average remaining amortization periods for intangible assets and liabilities [Abstract]
Intangible assets, weighted average useful life (in years)	3 years
Acquisition-Related Below Market Lease Liabilities [Member]
Scheduled future amortization of below market lease liabilites [Abstract]
2018	$ (5,911)
2019	(5,454)
2020	(5,193)
2021	(4,383)
2022	(3,269)
Thereafter	(7,523)
Total scheduled future amortization of below market lease liabilities	$ (31,733)
Weighted average remaining amortization periods for intangible assets and liabilities [Abstract]
Below market lease liabilities, weighted average useful life (in years)	6 years 7 months 12 days