Real Property Acquisitions and Development - Estimated Fair Value of Allocated Purchase Price of Asset and Liabilities (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018
Business Acquisition [Line Items]
Land and land improvements	$ 243,996	$ 56,925
Buildings and improvements	2,404,818	578,594
Acquired lease intangibles	144,265	73,936
Construction in progress	36,174	0
Right of use assets, net	56,073	0
Receivables and other assets	4,936	1,256
Total assets acquired	2,890,262	710,711
Secured debt	(43,209)	(89,973)
Lease liabilities	(45,287)
Accrued expenses and other liabilities	(31,183)	(15,324)
Total liabilities acquired	(119,679)	(105,297)
Noncontrolling interests	(39,886)	(9,818)
Non-cash acquisition related activity	(11,889)	0
Cash disbursed for acquisitions	2,718,808	595,596
Construction in progress additions	161,414	70,261
Less: Capitalized interest	(6,256)	(4,436)
Foreign currency translation	206	1,308
Accruals	45	(4,155)
Cash disbursed for construction in progress	155,409	62,978
Capital improvements to existing properties	124,176	111,332
Total cash invested in real property, net of cash acquired	2,998,393	769,906
Cash acquired from acquisition	1,910	4,392,000
Seniors Housing Operating
Business Acquisition [Line Items]
Land and land improvements	103,743	47,865
Buildings and improvements	1,109,966	535,921
Acquired lease intangibles	58,773	68,084
Construction in progress	36,174	0
Right of use assets, net	0	0
Receivables and other assets	4,560	1,255
Total assets acquired	1,313,216	653,125
Secured debt	(43,209)	(89,973)
Lease liabilities	0
Accrued expenses and other liabilities	(8,677)	(14,686)
Total liabilities acquired	(51,886)	(104,659)
Noncontrolling interests	(38,830)	(9,818)
Non-cash acquisition related activity	(11,889)	0
Cash disbursed for acquisitions	1,210,611	538,648
Construction in progress additions	110,761	20,704
Less: Capitalized interest	(3,560)	(1,783)
Foreign currency translation	141	1,176
Accruals	0	0
Cash disbursed for construction in progress	107,342	20,097
Capital improvements to existing properties	97,867	76,237
Total cash invested in real property, net of cash acquired	1,415,820	634,982
Triple-net
Business Acquisition [Line Items]
Land and land improvements	8,099	1,691
Buildings and improvements	96,244	0
Acquired lease intangibles	0	0
Construction in progress	0	0
Right of use assets, net	0	0
Receivables and other assets	0	0
Total assets acquired	104,343	1,691
Secured debt	0	0
Lease liabilities	0
Accrued expenses and other liabilities	0	(6)
Total liabilities acquired	0	(6)
Noncontrolling interests	(1,056)	0
Non-cash acquisition related activity	0	0
Cash disbursed for acquisitions	103,287	1,685
Construction in progress additions	24,066	38,238
Less: Capitalized interest	(908)	(1,432)
Foreign currency translation	65	132
Accruals	0	0
Cash disbursed for construction in progress	23,223	36,938
Capital improvements to existing properties	7,423	8,569
Total cash invested in real property, net of cash acquired	133,933	47,192
Outpatient Medical
Business Acquisition [Line Items]
Land and land improvements	132,154	7,369
Buildings and improvements	1,198,608	42,673
Acquired lease intangibles	85,492	5,852
Construction in progress	0	0
Right of use assets, net	56,073	0
Receivables and other assets	376	1
Total assets acquired	1,472,703	55,895
Secured debt	0	0
Lease liabilities	(45,287)
Accrued expenses and other liabilities	(22,506)	(632)
Total liabilities acquired	(67,793)	(632)
Noncontrolling interests	0	0
Non-cash acquisition related activity	0	0
Cash disbursed for acquisitions	1,404,910	55,263
Construction in progress additions	26,587	11,319
Less: Capitalized interest	(1,788)	(1,221)
Foreign currency translation	0	0
Accruals	45	(4,155)
Cash disbursed for construction in progress	24,844	5,943
Capital improvements to existing properties	18,886	26,526
Total cash invested in real property, net of cash acquired	$ 1,448,640	$ 87,732