Schedule III Real Estate Rollforward (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Real Estate and Accumulated Depreciation [Line Items]
Real Estate, Gross	$ 7,851,278	$ 7,248,346	$ 6,612,229
Real Estate, Other Acquisitions	410,003	205,390	327,318
Real Estate, Improvements	796,312	635,173	683,284
Real Estate, Cost of Real Estate Sold	(203,502)	(176,603)	(336,327)
Write Off of Fully Depreciated Assets	(85,659)	(61,028)	(38,158)
Real Estate, Gross	8,768,432	7,851,278	7,248,346
Total Land, Land Improvements, Buildings and Tenant Improvements Held-for-Sale	(72,754)	(23,401)	0
SEC Schedule III, Real Estate, Excluding Held-for-Sale	8,695,678	7,827,877	7,248,346
Real Estate Accumulated Depreciation	1,665,284	1,487,593	1,345,060	$ 1,196,458
Real Estate Accumulated Depreciation, Depreciation Expense	297,158	272,422	256,250
Real Estate Accumulated Depreciation, Real Estate Sold	(33,808)	(68,861)	(69,490)
Real Estate Accumulated Depreciation, Other Deductions	(85,659)	(61,028)	(38,158)
Schedule III - Accumulated Depreciation of Assets Held-for-Sale	(5,976)	(7,132)	(884)
Real Estate Investment Property, Accumulated Depreciation	1,659,308	1,480,461	$ 1,344,176
Other real estate investments	9,863,886	8,931,914
Real Estate Assets	$ 8,745,155	$ 7,993,377