Real Property Acquisitions and Development - Estimated Fair Value of Allocated Purchase Price of Asset and Liabilities (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019
Business Acquisition [Line Items]
Land and land improvements	$ 59,010	$ 309,418
Buildings and improvements	304,876	2,588,618
Acquired lease intangibles	34,633	165,472
Construction in progress	0	36,174
Real property held for sale	0	17,435
Right of use assets, net	0	58,377
Total net real estate assets	398,519	3,175,494
Receivables and other assets	396	7,161
Total assets acquired	398,915	3,182,655
Secured debt	0	(43,209)
Lease liabilities	0	(47,740)
Accrued expenses and other liabilities	(2,714)	(33,222)
Total liabilities acquired	(2,714)	(124,171)
Noncontrolling interests	(2,827)	(41,827)
Non-cash acquisition related activity	0	(11,889)
Cash disbursed for acquisitions	393,374	3,004,768
Construction in progress additions	142,231	268,472
Less: Capitalized interest	(13,234)	(10,404)
Accruals	(2,298)	45
Cash disbursed for construction in progress	126,699	258,113
Capital improvements to existing properties	183,324	206,413
Total cash invested in real property, net of cash acquired	703,397	3,469,294
Cash acquired from acquisition	580	1,910
Seniors Housing Operating
Business Acquisition [Line Items]
Land and land improvements	15,758	107,945
Buildings and improvements	132,481	1,138,484
Acquired lease intangibles	10,810	61,163
Construction in progress	0	36,174
Real property held for sale	0	17,435
Right of use assets, net	0	0
Total net real estate assets	159,049	1,361,201
Receivables and other assets	257	6,742
Total assets acquired	159,306	1,367,943
Secured debt	0	(43,209)
Lease liabilities	0	0
Accrued expenses and other liabilities	(671)	(9,639)
Total liabilities acquired	(671)	(52,848)
Noncontrolling interests	(2,827)	(39,570)
Non-cash acquisition related activity	0	(11,889)
Cash disbursed for acquisitions	155,808	1,263,636
Construction in progress additions	75,617	188,178
Less: Capitalized interest	(7,760)	(5,972)
Accruals	(1,376)	0
Cash disbursed for construction in progress	66,481	182,206
Capital improvements to existing properties	130,465	160,260
Total cash invested in real property, net of cash acquired	352,754	1,606,102
Triple-net
Business Acquisition [Line Items]
Land and land improvements	0	14,172
Buildings and improvements	765	125,763
Acquired lease intangibles	0	0
Construction in progress	0	0
Real property held for sale	0	0
Right of use assets, net	0	0
Total net real estate assets	765	139,935
Receivables and other assets	0	0
Total assets acquired	765	139,935
Secured debt	0	0
Lease liabilities	0	0
Accrued expenses and other liabilities	0	(100)
Total liabilities acquired	0	(100)
Noncontrolling interests	0	(1,056)
Non-cash acquisition related activity	0	0
Cash disbursed for acquisitions	765	138,779
Construction in progress additions	33,021	37,978
Less: Capitalized interest	(2,569)	(1,565)
Accruals	0	0
Cash disbursed for construction in progress	30,452	36,413
Capital improvements to existing properties	5,971	10,337
Total cash invested in real property, net of cash acquired	37,188	185,529
Outpatient Medical
Business Acquisition [Line Items]
Land and land improvements	43,252	187,301
Buildings and improvements	171,630	1,324,371
Acquired lease intangibles	23,823	104,309
Construction in progress	0	0
Real property held for sale	0	0
Right of use assets, net	0	58,377
Total net real estate assets	238,705	1,674,358
Receivables and other assets	139	419
Total assets acquired	238,844	1,674,777
Secured debt	0	0
Lease liabilities	0	(47,740)
Accrued expenses and other liabilities	(2,043)	(23,483)
Total liabilities acquired	(2,043)	(71,223)
Noncontrolling interests	0	(1,201)
Non-cash acquisition related activity	0	0
Cash disbursed for acquisitions	236,801	1,602,353
Construction in progress additions	33,593	42,316
Less: Capitalized interest	(2,905)	(2,867)
Accruals	(922)	45
Cash disbursed for construction in progress	29,766	39,494
Capital improvements to existing properties	46,888	35,816
Total cash invested in real property, net of cash acquired	$ 313,455	$ 1,677,663