Real Estate and Accumulated Depreciation Activity of Real Estate and Accumulated Depreciation (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Reconciliation of Carrying Amount of Real Estate Investments [Roll Forward]
Real Estate, Balance at the beginning of the year	$ 21,058,714	$ 20,114,576	$ 19,451,683
Real Estate, Additions to / improvements of real estate	1,043,379	1,099,286	977,287
Real Estate, Assets sold / written off	(496,548)	(155,148)	(314,394)
Real Estate, Balance at the end of the year	21,605,545	21,058,714	20,114,576
Reconciliation of Real Estate Accumulated Depreciation [Roll Forward]
Accumulated depreciation, Balance at beginning of the year	4,566,570	4,201,891	3,905,940
Accumulated depreciation, Depreciation expense	533,342	497,059	560,024
Accumulated depreciation, Assets sold / written off	(228,810)	(132,380)	(264,073)
Accumulated depreciation, Balance at end of the year	$ 4,871,102	$ 4,566,570	$ 4,201,891

Real Estate Accumulated Depreciation Depreciation Expense Excluding Furniture Fixtures And Equipment

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Real estate accumulated depreciation excluding furniture fixtures and equipment

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Real Estate Accumulated Depreciation Real Estate Sold Excluding Furniture Fixtures And Equipment

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Real Estate Cost Of Real Estate Sold Excluding Furniture Fixtures And Equipment

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Real Estate Gross At Carrying Value Excluding Furniture Fixtures And Equipment

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Real Estate Improvements Excluding Furniture Fixtures And Equipment

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A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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