Real Estate and Lease Intangibles - Real Estate Acquisitions and Dispositions (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2017 USD ($) Property	Dec. 31, 2016 USD ($) Property
Real Estate [Line Items]
Properties acquired	4	4
Property Units acquired	947	573
Purchase Price | $	$ 468,050	$ 249,334
Properties disposed	5	99
Property Units disposed	1,194	29,776
Sales Price | $	$ 388,400	$ 6,943,458
Partially Owned Properties – Unconsolidated
Real Estate [Line Items]
Properties disposed		1
Property Units disposed		336
Sales Price | $		$ 74,500
Rental Properties – Consolidated [Member]
Real Estate [Line Items]
Properties acquired	4	4
Property Units acquired	947	573
Purchase Price | $	$ 468,050	$ 249,334
Properties disposed	5	98
Property Units disposed	1,194	29,440
Sales Price | $	$ 354,950	$ 6,811,503
Land [Member]
Real Estate [Line Items]
Purchase Price | $	$ 68,300	$ 98,000
Properties disposed	0	0
Property Units disposed	0	0
Sales Price | $	$ 33,450	$ 57,455