Real Estate and Lease Intangibles - Real Estate Acquisitions and Dispositions (Parenthetical) (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2017	Dec. 31, 2016
Purchase Price	$ 468,050
Ground Lease [Member] | Other Assets [Member]
Acquired ground lease intangibles – below market	191,918	$ 178,251
Land [Member]
Purchase Price	68,300
Depreciable Property [Member]
Purchase Price	386,200
Rental Properties – Consolidated [Member]
Purchase Price	$ 468,050
Rental Properties – Consolidated [Member] | Ground Lease [Member]
Lease expiration year	2113
Rental Properties – Consolidated [Member] | Ground Lease [Member] | Other Assets [Member]
Acquired ground lease intangibles – below market	$ 13,700