Investments - Schedule of Lease Intangible Assets and Liabilities, Net of Accumulated Amortization (Details) - USD ($)
$ in Thousands
Sep. 30, 2019
Dec. 31, 2018
Lessor, Lease, Description [Line Items]    
Less: accumulated amortization $ (160,275) $ (149,582)
Intangible lease assets, net 311,597 294,463
Below-market leases 164,001 167,527
Less: accumulated amortization (47,486) (47,365)
Intangible lease liabilities, net 116,515 120,162
In-place leases    
Lessor, Lease, Description [Line Items]    
Intangible lease assets, gross 402,902 381,143
Above-market leases    
Lessor, Lease, Description [Line Items]    
Intangible lease assets, gross $ 68,970 $ 62,902