Schedule III Real Estate Rollforward (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Real Estate and Accumulated Depreciation [Line Items]
Real Estate, Gross	$ 7,248,346	$ 6,612,229	$ 6,523,281
Real Estate, Other Acquisitions	205,390	327,318	945,912
Real Estate, Improvements	635,173	683,284	716,627
Real Estate, Cost of Real Estate Sold	(176,603)	(336,327)	(1,538,680)
Impairment Charges	0	0	(859)
Write Off of Fully Depreciated Assets	(61,028)	(38,158)	(34,052)
Real Estate, Gross	7,851,278	7,248,346	6,612,229
Total Land, Land Improvements, Buildings and Tenant Improvements Held-for-Sale	(23,401)	0	(18,662)
SEC Schedule III, Real Estate, Excluding Held-for-Sale	7,827,877	7,248,346	6,593,567
Real Estate Accumulated Depreciation	1,487,593	1,345,060	1,196,458	$ 1,302,210
Real Estate Accumulated Depreciation, Depreciation Expense	272,422	256,250	242,606
Real Estate Accumulated Depreciation, Real Estate Sold	(68,861)	(69,490)	(314,306)
Real Estate Accumulated Depreciation, Other Deductions	(61,028)	(38,158)	(34,052)
Schedule III - Accumulated Depreciation of Assets Held-for-Sale	(7,132)	(884)	(2,553)
Real Estate Investment Property, Accumulated Depreciation	1,480,461	1,344,176	$ 1,193,905
Other real estate investments	8,931,914	8,197,119
Real Estate Assets	$ 7,993,377	$ 7,248,346