Real Estate Investments and Related Intangibles - Intangible Lease Assets and Liabilities (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Finite-Lived Intangible Assets [Line Items]
Amortization expense	$ 692	$ 1,058	$ 2,034	$ 3,233
Intangible lease assets:
Intangible lease assets, net	1,055,043		1,055,043		$ 1,198,506
Intangible lease liabilities:
Accumulated amortization	96,911		$ 96,911		89,905
Weighted-Average Useful Life			19 years 2 months 12 days
Intangible lease liabilities, net	147,997		$ 147,997		173,479
In-place leases and other intangible assets [Member]
Intangible lease assets:
Weighted-Average Useful Life			14 years 1 month 6 days
Intangible lease assets, net	867,642		$ 867,642		980,971
Accumulated amortization	741,320		$ 741,320		703,909
Leasing commissions [Member]
Intangible lease assets:
Weighted-Average Useful Life			10 years 2 months 12 days
Intangible lease assets, net	15,058		$ 15,058		15,660
Accumulated amortization	5,313		$ 5,313		4,048
Above-market lease assets and deferred lease incentives [Member]
Intangible lease assets:
Weighted-Average Useful Life			13 years 7 months 6 days
Intangible lease assets, net	172,343		$ 172,343		201,875
Accumulated amortization	$ 108,256		108,256		$ 105,936
Above‑ And Below-Market Leases and Deferred Lease Incentives [Member]
Finite-Lived Intangible Assets [Line Items]
Amortization expense			2,000	3,200
In-Place Leases, Leasing Commissions and Other Lease Intangibles [Member]
Finite-Lived Intangible Assets [Line Items]
Amortization expense			$ 96,900	$ 104,500