Schedule III Real Estate and Accumulated Depreciation - Changes in Accumulated Depreciation (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Reconciliation of real estate accumulated depreciation
Accumulated Depreciation, Beginning Balance	$ 1,776,224	$ 1,631,888	$ 1,516,694
Depreciation expense	157,673	153,893	137,209
Properties held for sale	0	0	(14,547)
Dispositions and other	(9,312)	(9,557)	(7,468)
Accumulated Depreciation, Ending Balance	$ 1,924,585	$ 1,776,224	$ 1,631,888