Schedule III - Real Estate and Accumulated Depreciation - Summary (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Initial cost of encumbrances	$ 2,202,312
Initial cost of land and land improvements	3,629,663
Initial cost of building and improvements	28,865,012
Cost Capitalized Subsequent to Acquisition	5,167,480
Carrying amount of land and land improvements	3,968,430
Carrying amount of building and improvements	33,637,317
Accumulated depreciation	6,910,114	$ 6,104,297	$ 5,715,459	$ 5,499,958
Construction in progress
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Initial cost of encumbrances	0
Initial cost of land and land improvements	0
Initial cost of building and improvements	651,389
Cost Capitalized Subsequent to Acquisition	0
Carrying amount of land and land improvements	0
Carrying amount of building and improvements	651,389
Accumulated depreciation	0
Seniors Housing Operating
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Initial cost of encumbrances	1,599,522
Initial cost of land and land improvements	1,958,208
Initial cost of building and improvements	15,959,072
Cost Capitalized Subsequent to Acquisition	2,969,135
Carrying amount of land and land improvements	2,110,813
Carrying amount of building and improvements	18,775,602
Accumulated depreciation	4,123,782
Seniors Housing Operating | Operating Segments
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Initial cost of encumbrances	1,599,522
Initial cost of land and land improvements	1,958,208
Initial cost of building and improvements	15,959,072
Cost Capitalized Subsequent to Acquisition	2,969,135
Carrying amount of land and land improvements	2,110,813
Carrying amount of building and improvements	18,775,602
Accumulated depreciation	4,123,782
Triple-net
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Initial cost of encumbrances	72,536
Initial cost of land and land improvements	911,678
Initial cost of building and improvements	7,485,316
Cost Capitalized Subsequent to Acquisition	592,881
Carrying amount of land and land improvements	955,620
Carrying amount of building and improvements	8,034,255
Accumulated depreciation	1,459,518
Triple-net | Operating Segments
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Initial cost of encumbrances	72,536
Initial cost of land and land improvements	911,678
Initial cost of building and improvements	7,485,316
Cost Capitalized Subsequent to Acquisition	592,881
Carrying amount of land and land improvements	955,620
Carrying amount of building and improvements	8,034,255
Accumulated depreciation	1,459,518
Outpatient Medical
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Initial cost of encumbrances	530,254
Initial cost of land and land improvements	728,837
Initial cost of building and improvements	4,612,615
Cost Capitalized Subsequent to Acquisition	1,602,519
Carrying amount of land and land improvements	901,997
Carrying amount of building and improvements	6,041,974
Accumulated depreciation	1,326,814
Outpatient Medical | Operating Segments
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Initial cost of encumbrances	530,254
Initial cost of land and land improvements	728,837
Initial cost of building and improvements	4,612,615
Cost Capitalized Subsequent to Acquisition	1,602,519
Carrying amount of land and land improvements	901,997
Carrying amount of building and improvements	6,041,974
Accumulated depreciation	1,326,814
Total continuing operating properties
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Initial cost of encumbrances	2,202,312
Initial cost of land and land improvements	3,598,723
Initial cost of building and improvements	28,708,392
Cost Capitalized Subsequent to Acquisition	5,164,535
Carrying amount of land and land improvements	3,968,430
Carrying amount of building and improvements	33,503,220
Accumulated depreciation	6,910,114
Assets held for sale
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Initial cost of encumbrances	0
Initial cost of land and land improvements	30,940
Initial cost of building and improvements	156,620
Cost Capitalized Subsequent to Acquisition	2,945
Carrying amount of land and land improvements	0
Carrying amount of building and improvements	134,097
Accumulated depreciation	$ 0