Real Estate and Lease Intangibles - Real Estate Acquisitions and Dispositions (Parenthetical) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2018
Purchase Price	$ 468,050	$ 707,005
Ground Leases [Member] | Other Assets [Member]
Finite-Lived Intangible Asset, Off-market Lease, Favorable, Gross	191,918	191,918
Land [Member]
Purchase Price	68,300	113,700
Depreciable Property [Member]
Purchase Price	386,200	594,400
Rental Properties – Consolidated [Member]
Purchase Price	468,050	$ 707,005
Rental Properties – Consolidated [Member] | Ground Leases [Member] | Other Assets [Member]
Finite-Lived Intangible Asset, Off-market Lease, Favorable, Gross	$ 13,700
Lease expiration year	2113