Schedule III - Real Estate and Accumulated Depreciation (Activity in Real Estate and Accumulated Depreciation) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Changes in real estate
Balance at beginning of year	$ 8,784,567	$ 8,513,935	$ 10,206,122
Property acquisitions	178,635	0	52,939
Improvements	481,327	251,674	267,726
Retirements/disposals/deconsolidation	(2,089,450)	18,958	(2,012,852)
Balance at end of year	7,355,079	8,784,567	8,513,935
Aggregate cost of land, buildings and improvements before depreciation	9,700,000
Changes in accumulated depreciation
Balance at beginning of year	2,060,560	2,099,137	2,300,116
Depreciation for year	270,843	222,867	245,033
Retirements/disposals/deconsolidation	(375,326)	(261,444)	(446,012)
Balance at end of year	$ 1,956,077	$ 2,060,560	$ 2,099,137