Schedule III: Real Estate and Accumulated Depreciation - Summary of Activity for Real Estate and Accumulated Depreciation (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Real estate:
Balances at beginning of year	$ 13,974,760	$ 14,330,257	$ 12,931,832
Acquisition of real estate and development and improvements	995,443	987,135	1,930,931
Sales and/or transfers to assets held for sale and discontinued operations	(589,391)	(1,227,614)	(473,057)
Deconsolidation of real estate	(825,074)	(10,306)	0
Impairments	(37,274)	0	(3,118)
Other	(44,891)	(104,712)	(56,331)
Balances at end of year	13,473,573	13,974,760	14,330,257
Accumulated depreciation:
Balances at beginning of year	2,648,930	2,476,015	2,190,486
Depreciation expense	436,085	465,945	418,591
Sales and/or transfers to assets held for sale and discontinued operations	(115,195)	(239,112)	(86,001)
Deconsolidation of real estate	(152,572)	(5,868)	0
Other	(75,553)	(48,050)	(47,061)
Balances at end of year	$ 2,741,695	$ 2,648,930	$ 2,476,015