Schedule III - Reconciliation of Gross Real Estate Activity (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
SEC Schedule III, Reconciliation of Carrying Amount of Real Estate Investments [Roll Forward]
Balance, beginning of year	$ 14,566,343	$ 15,857,507	$ 6,699,547
Additions:
Acquisitions	91,052	33,695	11,095,559
Improvements	25,781	60,321	114,070
Deductions:
Dispositions	(878,552)	(1,261,724)	(1,945,186)
Impairments	(228,750)	(106,064)	(105,367)
Reclassification to assets held for sale	(36,722)	(16,761)	(1,116)
Other	769	(631)	0
Balance, end of year	$ 13,539,921	$ 14,566,343	$ 15,857,507