Schedule III - Real Estate and Accumulated Depreciation (Activity in Real Estate and Accumulated Depreciation) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Changes in real estate
Balance at beginning of year	$ 8,513,935	$ 10,206,122	$ 12,743,332
Property acquisitions	0	52,939	13,323
Improvements	251,674	267,726	342,014
Retirements/disposals/deconsolidation	18,958	(2,012,852)	(2,892,547)
Balance at end of year	8,784,567	8,513,935	10,206,122
Aggregate cost of land, buildings and improvements before depreciation	10,300,000
Changes in accumulated depreciation
Balance at beginning of year	2,099,137	2,300,116	2,264,694
Depreciation for year	222,867	245,033	347,015
Retirements/disposals/deconsolidation	(261,444)	(446,012)	(311,593)
Balance at end of year	$ 2,060,560	$ 2,099,137	$ 2,300,116