Acquisitions - Reconciliation of Purchase Price (Details) - USD ($) $ in Thousands				3 Months Ended		9 Months Ended
	Feb. 17, 2015	Nov. 14, 2014	Jun. 04, 2014	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014
Acquisition
Distributions in excess of investment				$ (1,278,216)		$ (1,278,216)		$ (984,132)
Gain on remeasurement of assets				$ 0	$ 0	$ 22,089	$ 0
Cascade Mall
Acquisition
Purchase price			$ 15,233
Distributions in excess of investment			(15,767)
Fair value of acquired net assets (at 100% ownership)			$ 31,000
Ownership interest at completion of acquisition (as a percent)			100.00%
PPRLP Queens Portfolio
Acquisition
Purchase price		$ 1,838,886
Less debt assumed		(672,109)
Distributions in excess of investment		(208,735)
Gain on remeasurement of assets		1,423,136
Fair value of acquired net assets (at 100% ownership)		$ 2,381,178
Ownership interest at completion of acquisition (as a percent)		100.00%
Inland Center
Acquisition
Purchase price	$ 51,250
Less debt assumed	(25,000)
Distributions in excess of investment	(4,161)
Gain on remeasurement of assets	22,089
Fair value of acquired net assets (at 100% ownership)	$ 52,500
Ownership interest at completion of acquisition (as a percent)	100.00%