Real Property Acquisitions and Development (Summary of Real Property Investment Activity by Segment) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Jul. 26, 2018
Estimated Fair Value of Allocated Purchase Price of Asset and Liabilities
Land and land improvements	$ 117,466	$ 472,500	$ 542,267	$ 417,983
Buildings and improvements	780,048	3,676,958	3,343,355	2,253,451
Acquired lease intangibles	53,386	259,930	130,007	12,820
Real property held for sale		17,435	418,297	418,297
Construction in progress		36,174
Right of use assets, net		58,377
Total net real estate assets	950,900	4,521,374	4,433,926
Receivables and other assets	1,014	17,220	4,031	1,354
Total assets acquired	951,914	4,538,594	4,437,957
Secured debt		(401,162)	(303,908)
Lease liabilities		(47,740)
Accrued expenses and other liabilities	(2,612)	(44,917)	(46,558)	(13,199)
Total liabilities assumed	(2,612)	(493,819)	(350,466)
Noncontrolling interests	(45,546)	(73,203)	(527,131)	$ (512,741)
Non-cash acquisition related activity		(11,889)
Cash disbursed for acquisitions	903,756	3,959,683	3,560,360
Construction in progress additions	220,034	349,316	164,744
Less: Capitalized interest	(17,472)	(15,272)	(7,905)
Accruals	1,226	(1,035)	(339)
Cash disbursed for construction in progress	201,336	333,009	156,500
Capital improvements to existing properties	244,989	328,824	266,183
Total cash invested in real property, net of cash acquired	1,350,081	4,621,516	3,983,043
Cash acquired from acquisition	580	2,090	395,397
Seniors Housing Operating
Estimated Fair Value of Allocated Purchase Price of Asset and Liabilities
Land and land improvements	55,000	154,470	51,440
Buildings and improvements	527,189	1,518,748	621,731
Acquired lease intangibles	28,668	76,009	69,504
Real property held for sale		17,435	0
Construction in progress		36,174
Right of use assets, net		0
Total net real estate assets	610,857	1,802,836	742,675
Receivables and other assets	746	15,634	1,492
Total assets acquired	611,603	1,818,470	744,167
Secured debt		(194,408)	(134,752)
Lease liabilities		0
Accrued expenses and other liabilities	(1,650)	(12,024)	(18,463)
Total liabilities assumed	(1,650)	(206,432)	(153,215)
Noncontrolling interests	(45,546)	(67,987)	(14,390)
Non-cash acquisition related activity		(11,889)
Cash disbursed for acquisitions	564,407	1,532,162	576,562
Construction in progress additions	134,945	227,018	82,621
Less: Capitalized interest	(10,389)	(8,889)	(3,190)
Accruals	1,226	0	0
Cash disbursed for construction in progress	123,330	218,129	79,431
Capital improvements to existing properties	107,379	260,413	201,001
Total cash invested in real property, net of cash acquired	795,116	2,010,704	856,994
Triple-net
Estimated Fair Value of Allocated Purchase Price of Asset and Liabilities
Land and land improvements	16,876	24,097	413,588
Buildings and improvements	73,855	203,282	2,242,884
Acquired lease intangibles	0	0	9,690
Real property held for sale		0	396,265
Construction in progress		0
Right of use assets, net		0
Total net real estate assets	90,731	227,379	3,062,427
Receivables and other assets	0	0	1,354
Total assets acquired	90,731	227,379	3,063,781
Secured debt		0	0
Lease liabilities		0
Accrued expenses and other liabilities	0	0	(13,199)
Total liabilities assumed	0	0	(13,199)
Noncontrolling interests	0	(4,015)	(512,741)
Non-cash acquisition related activity		0
Cash disbursed for acquisitions	90,731	223,364	2,537,841
Construction in progress additions	45,256	61,414	55,558
Less: Capitalized interest	(3,209)	(2,385)	(2,238)
Accruals	0	0	0
Cash disbursed for construction in progress	42,047	59,029	53,320
Capital improvements to existing properties	76,625	17,426	10,046
Total cash invested in real property, net of cash acquired	209,403	299,819	2,601,207
Outpatient Medical
Estimated Fair Value of Allocated Purchase Price of Asset and Liabilities
Land and land improvements	45,590	293,933	77,239
Buildings and improvements	179,004	1,954,928	478,740
Acquired lease intangibles	24,718	183,921	50,813
Real property held for sale		0	22,032
Construction in progress		0
Right of use assets, net		58,377
Total net real estate assets	249,312	2,491,159	628,824
Receivables and other assets	268	1,586	1,185
Total assets acquired	249,580	2,492,745	630,009
Secured debt		(206,754)	(169,156)
Lease liabilities		(47,740)
Accrued expenses and other liabilities	(962)	(32,893)	(14,896)
Total liabilities assumed	(962)	(287,387)	(184,052)
Noncontrolling interests	0	(1,201)	0
Non-cash acquisition related activity		0
Cash disbursed for acquisitions	248,618	2,204,157	445,957
Construction in progress additions	39,833	60,884	26,565
Less: Capitalized interest	(3,874)	(3,998)	(2,477)
Accruals	0	(1,035)	(339)
Cash disbursed for construction in progress	35,959	55,851	23,749
Capital improvements to existing properties	60,985	50,985	55,136
Total cash invested in real property, net of cash acquired	$ 345,562	$ 2,310,993	$ 524,842