Real Estate Investments and Related Intangibles - Intangible Lease Assets and Liabilities (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Intangible lease assets:
Intangible lease assets, net	$ 1,198,506	$ 1,346,758
Intangible lease liabilities:
Accumulated amortization	$ 89,905	73,916
Weighted-Average Useful Life	18 years 9 months 25 days
Intangible lease liabilities, net	$ 173,479	198,551
In-place leases and other intangible assets [Member]
Intangible lease assets:
Weighted-Average Useful Life	15 years 5 months 26 days
Intangible lease assets, net	$ 980,971	1,091,433
Accumulated amortization	$ 703,909	599,680
Leasing Commissions [Member]
Intangible lease assets:
Weighted-Average Useful Life	10 years 8 months 8 days
Intangible lease assets, net	$ 15,660	13,876
Accumulated amortization	$ 4,048	2,902
Above-Market Lease assets and deferred lease incentives [Member]
Intangible lease assets:
Weighted-Average Useful Life	16 years 4 months 26 days
Intangible lease assets, net	$ 201,875	241,449
Accumulated amortization	105,936	88,335
Above‑ And Below-Market Leases and Deferred Lease Incentives [Member]
Finite-Lived Intangible Assets [Line Items]
Amortization expense	4,200	5,400	$ 5,400
In-Place Leases, Leasing Commissions and Other Lease Intangibles [Member]
Finite-Lived Intangible Assets [Line Items]
Amortization expense	$ 139,600	$ 154,200	$ 170,000