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, 2019	Sep. 30, 2018
Business Acquisition [Line Items]
Land and land improvements	$ 309,418	$ 479,949
Buildings and improvements	2,588,618	2,854,063
Acquired lease intangibles	165,472	91,738
Construction in progress	36,174	0
Real property held for sale	17,435	418,297
Right of use assets, net	58,377
Receivables and other assets	7,161	2,583
Total assets acquired	3,182,655	3,846,630
Secured debt	(43,209)	(104,742)
Lease liabilities	(47,740)
Accrued expenses and other liabilities	(33,222)	(28,795)
Total liabilities acquired	(124,171)	(133,537)
Noncontrolling interests	(41,827)	(522,559)
Non-cash acquisition related activity	(11,889)	0
Cash disbursed for acquisitions	3,004,768	3,190,534
Construction in progress additions	264,546	94,574
Less: Capitalized interest	(10,404)	(6,357)
Foreign currency translation	3,926	2,331
Accruals	45	(2,402)
Cash disbursed for construction in progress	258,113	88,146
Capital improvements to existing properties	206,413	173,635
Total cash invested in real property, net of cash acquired	3,469,294	3,452,315
Cash acquired from acquisition	1,910	391,580
Seniors Housing Operating
Business Acquisition [Line Items]
Land and land improvements	107,945	47,865
Buildings and improvements	1,138,484	535,436
Acquired lease intangibles	61,163	68,084
Construction in progress	36,174	0
Real property held for sale	17,435	0
Right of use assets, net	0
Receivables and other assets	6,742	1,255
Total assets acquired	1,367,943	652,640
Secured debt	(43,209)	(89,973)
Lease liabilities	0
Accrued expenses and other liabilities	(9,639)	(14,686)
Total liabilities acquired	(52,848)	(104,659)
Noncontrolling interests	(39,570)	(9,818)
Non-cash acquisition related activity	(11,889)	0
Cash disbursed for acquisitions	1,263,636	538,163
Construction in progress additions	184,581	28,222
Less: Capitalized interest	(5,972)	(2,608)
Foreign currency translation	3,597	2,151
Accruals	0	0
Cash disbursed for construction in progress	182,206	27,765
Capital improvements to existing properties	160,260	127,274
Total cash invested in real property, net of cash acquired	1,606,102	693,202
Triple-net
Business Acquisition [Line Items]
Land and land improvements	14,172	413,588
Buildings and improvements	125,763	2,239,422
Acquired lease intangibles	0	12,383
Construction in progress	0	0
Real property held for sale	0	396,265
Right of use assets, net	0
Receivables and other assets	0	1,322
Total assets acquired	139,935	3,062,980
Secured debt	0	0
Lease liabilities	0
Accrued expenses and other liabilities	(100)	(13,199)
Total liabilities acquired	(100)	(13,199)
Noncontrolling interests	(1,056)	(512,741)
Non-cash acquisition related activity	0	0
Cash disbursed for acquisitions	138,779	2,537,040
Construction in progress additions	37,649	49,619
Less: Capitalized interest	(1,565)	(1,932)
Foreign currency translation	329	180
Accruals	0	0
Cash disbursed for construction in progress	36,413	47,867
Capital improvements to existing properties	10,337	6,766
Total cash invested in real property, net of cash acquired	185,529	2,591,673
Outpatient Medical
Business Acquisition [Line Items]
Land and land improvements	187,301	18,496
Buildings and improvements	1,324,371	79,205
Acquired lease intangibles	104,309	11,271
Construction in progress	0	0
Real property held for sale	0	22,032
Right of use assets, net	58,377
Receivables and other assets	419	6
Total assets acquired	1,674,777	131,010
Secured debt	0	(14,769)
Lease liabilities	(47,740)
Accrued expenses and other liabilities	(23,483)	(910)
Total liabilities acquired	(71,223)	(15,679)
Noncontrolling interests	(1,201)	0
Non-cash acquisition related activity	0	0
Cash disbursed for acquisitions	1,602,353	115,331
Construction in progress additions	42,316	16,733
Less: Capitalized interest	(2,867)	(1,817)
Foreign currency translation	0	0
Accruals	45	(2,402)
Cash disbursed for construction in progress	39,494	12,514
Capital improvements to existing properties	35,816	39,595
Total cash invested in real property, net of cash acquired	$ 1,677,663	$ 167,440