Summary of Significant Accounting Policies (Details) $ in Thousands		12 Months Ended
	Jan. 01, 2019 USD ($)	Dec. 31, 2019 USD ($) property Segments	Dec. 31, 2018 USD ($) property	Dec. 31, 2017 USD ($) property
Impairment of consolidated properties		$ 12,298	$ 2,079	$ 67,003
Occupancy percentage for stabilization		90.00%
Number of properties held for sale | property		0	0
Balance in accumulated other comprehensive loss relating to derivatives		$ 12,288	$ 1,522
Percentage rent		2,555	3,426	4,451
Lease termination fee income		2,024	1,721	2,021
Taxes remitted to governmental authorities and reimbursed by tenants		$ 634	545	$ 1,414
Number of properties sold | property				47
Number of reportable segments | Segments		1
Lease liabilities and ROU assets recognized		$ 103,840	0	$ 0
Straight-line ground rent liabilities	$ 31,030
Acquired ground lease intangible liability	11,898
Rental income			370,638	414,804
Tenant recovery income			105,170	115,944
Other property income			6,689	7,391
Intangible Assets, Amortization Expense, Fiscal Year Maturity
Total		79,832	97,090
Total		(63,578)	(86,543)
Acquired in-place lease value intangibles
Amortization expense		14,728	21,014	25,284
Intangible Assets, Amortization Expense, Fiscal Year Maturity
2020		10,461
2021		9,471
2022		8,267
2023		7,105
2024		6,291
Thereafter		29,584
Total		71,179
Acquired above market lease intangibles
Amortization expense		3,197	4,403	4,696
Intangible Assets, Amortization Expense, Fiscal Year Maturity
2020		1,910
2021		1,418
2022		1,150
2023		1,010
2024		772
Thereafter		2,393
Total		8,653
Acquired below market lease intangibles
Amortization expense		8,626	9,870	8,009
Intangible Assets, Amortization Expense, Fiscal Year Maturity
2020		(5,513)
2021		(5,147)
2022		(4,830)
2023		(4,600)
2024		(4,384)
Thereafter		(39,104)
Total		(63,578)
Acquired ground lease intangibles
Amortization expense			560	560
Acquired lease intangible assets, net
Accumulated amortization, acquired lease intangible assets		280,530
Intangible Assets, Amortization Expense, Fiscal Year Maturity
2020		12,371
2021		10,889
2022		9,417
2023		8,115
2024		7,063
Thereafter		31,977
Total		79,832
Acquired lease intangible liabilities, net
Accumulated amortization, acquired lease intangible liabilities		53,018
Intangible Assets, Amortization Expense, Fiscal Year Maturity
2020		(5,513)
2021		(5,147)
2022		(4,830)
2023		(4,600)
2024		(4,384)
Thereafter		(39,104)
Total		$ (63,578)
Building and associated improvements
Estimated useful life (in years)		30 years
Capitalized internal salaries and related benefits		$ 2,685	2,032	1,187
Site improvements and most other capital improvements
Estimated useful life (in years)		15 years
Capitalized internal leasing incentives
Capitalized internal leasing incentives		$ 359	384	368
Consolidated properties
Impairment of consolidated properties		$ 12,298	$ 2,079	$ 67,003
Number of properties sold | property		2	10	47
Redevelopment properties
Capitalized internal salaries and related benefits		$ 1,414	$ 1,123	$ 268
Capitalized indirect project costs		3,730	2,128	1,202
Capitalized interest		$ 1,594	$ 462	$ 485
ASU 2016-02
Lease liabilities and ROU assets recognized	$ 103,432