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, 2020	Jun. 30, 2019
Business Acquisition [Line Items]
Land and land improvements	$ 56,605	$ 243,996
Buildings and improvements	304,702	2,404,818
Acquired lease intangibles	34,633	144,265
Construction in progress	0	36,174
Right of use assets, net	0	56,073
Receivables and other assets	396	4,936
Total assets acquired	396,336	2,890,262
Secured debt	0	(43,209)
Lease liabilities	0	(45,287)
Accrued expenses and other liabilities	(2,707)	(31,183)
Total liabilities acquired	(2,707)	(119,679)
Noncontrolling interests	(2,827)	(39,886)
Non-cash acquisition related activity	0	(11,889)
Cash disbursed for acquisitions	390,802	2,718,808
Construction in progress additions	106,644	161,620
Less: Capitalized interest	(9,287)	(6,256)
Accruals	(4,326)	45
Cash disbursed for construction in progress	93,031	155,409
Capital improvements to existing properties	122,103	124,176
Total cash invested in real property, net of cash acquired	605,936	2,998,393
Cash acquired from acquisition	580	1,910
Seniors Housing Operating
Business Acquisition [Line Items]
Land and land improvements	15,758	103,743
Buildings and improvements	132,480	1,109,966
Acquired lease intangibles	10,810	58,773
Construction in progress	0	36,174
Right of use assets, net	0	0
Receivables and other assets	257	4,560
Total assets acquired	159,305	1,313,216
Secured debt	0	(43,209)
Lease liabilities	0	0
Accrued expenses and other liabilities	(671)	(8,677)
Total liabilities acquired	(671)	(51,886)
Noncontrolling interests	(2,827)	(38,830)
Non-cash acquisition related activity	0	(11,889)
Cash disbursed for acquisitions	155,807	1,210,611
Construction in progress additions	53,705	110,902
Less: Capitalized interest	(5,470)	(3,560)
Accruals	(1,343)	0
Cash disbursed for construction in progress	46,892	107,342
Capital improvements to existing properties	87,002	97,867
Total cash invested in real property, net of cash acquired	289,701	1,415,820
Triple-net
Business Acquisition [Line Items]
Land and land improvements	0	8,099
Buildings and improvements	765	96,244
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	765	104,343
Secured debt	0	0
Lease liabilities	0	0
Accrued expenses and other liabilities	0	0
Total liabilities acquired	0	0
Noncontrolling interests	0	(1,056)
Non-cash acquisition related activity	0	0
Cash disbursed for acquisitions	765	103,287
Construction in progress additions	26,262	24,131
Less: Capitalized interest	(1,826)	(908)
Accruals	0	0
Cash disbursed for construction in progress	24,436	23,223
Capital improvements to existing properties	4,700	7,423
Total cash invested in real property, net of cash acquired	29,901	133,933
Outpatient Medical
Business Acquisition [Line Items]
Land and land improvements	40,847	132,154
Buildings and improvements	171,457	1,198,608
Acquired lease intangibles	23,823	85,492
Construction in progress	0	0
Right of use assets, net	0	56,073
Receivables and other assets	139	376
Total assets acquired	236,266	1,472,703
Secured debt	0	0
Lease liabilities	0	(45,287)
Accrued expenses and other liabilities	(2,036)	(22,506)
Total liabilities acquired	(2,036)	(67,793)
Noncontrolling interests	0	0
Non-cash acquisition related activity	0	0
Cash disbursed for acquisitions	234,230	1,404,910
Construction in progress additions	26,677	26,587
Less: Capitalized interest	(1,991)	(1,788)
Accruals	(2,983)	45
Cash disbursed for construction in progress	21,703	24,844
Capital improvements to existing properties	30,401	18,886
Total cash invested in real property, net of cash acquired	$ 286,334	$ 1,448,640