Real Estate Investments and Related Intangibles - Intangible Lease Assets and Liabilities (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Intangible lease assets:
Intangible lease assets, net	$ 977,681		$ 977,681		$ 1,037,487
Intangible lease liabilities:
Weighted-Average Useful Life			19 years 2 months 12 days
Intangible lease liabilities, net	130,208		$ 130,208		143,583
Accumulated amortization	106,116		106,116		99,315
Amortization expense	788	$ 611	$ 1,536	$ 1,342
In-place leases and other intangible assets [Member]
Intangible lease assets:
Weighted-Average Useful Life			16 years 1 month 6 days
Intangible lease assets, net	788,686		$ 788,686		854,196
Accumulated amortization	787,231		$ 787,231		748,689
Leasing commissions [Member]
Intangible lease assets:
Weighted-Average Useful Life			7 years 6 months
Intangible lease assets, net	18,790		$ 18,790		17,808
Accumulated amortization	6,409		$ 6,409		6,027
Above-market lease assets and deferred lease incentives [Member]
Intangible lease assets:
Weighted-Average Useful Life			16 years 9 months 18 days
Intangible lease assets, net	170,205		$ 170,205		165,483
Accumulated amortization	$ 120,510		120,510		$ 112,438
Above‑ And Below-Market Leases and Deferred Lease Incentives [Member]
Intangible lease liabilities:
Amortization expense			1,500	1,300
In-Place Leases, Leasing Commissions and Other Lease Intangibles [Member]
Intangible lease liabilities:
Amortization expense			$ 73,300	$ 65,800