Real Property Acquisitions and Development (Summary of Real Property Investment Activity by Segment) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Estimated Fair Value of Allocated Purchase Price of Asset and Liabilities
Land and land improvements	$ 472,500	$ 542,267	$ 116,506
Buildings and improvements	3,676,958	3,343,355	836,879
Acquired lease intangibles	259,930	130,007	87,926
Real property held for sale	17,435	418,297
Construction in progress	36,174
Right of use assets, net	58,377
Receivables and other assets	17,220	4,031	3,969
Total assets acquired	4,538,594	4,437,957	1,045,280
Secured debt	(401,162)	(303,908)	(25,708)
Lease liabilities	(47,740)
Accrued expenses and other liabilities	(44,917)	(46,558)	(70,718)
Total liabilities assumed	(493,819)	(350,466)	(96,426)
Noncontrolling interests	(73,203)	(527,131)	(21,056)
Non-cash acquisition related activity	(11,889)		(122,534)
Cash disbursed for acquisitions	3,959,683	3,560,360	805,264
Construction in progress additions	349,316	164,744	242,765
Capitalized interest	(15,272)	(7,905)	(16,225)
Foreign currency translation	(9,521)	4,206	(7,440)
Accruals	(1,035)	(339)	13,615
Cash disbursed for construction in progress	323,488	160,706	232,715
Capital improvements to existing properties	328,824	266,183	250,276
Total cash invested in real property, net of cash acquired	4,611,995	3,987,249	1,288,255
Cash acquired from acquisition	2,090	395,397	6,591
Seniors Housing Operating
Estimated Fair Value of Allocated Purchase Price of Asset and Liabilities
Land and land improvements	154,470	51,440	42,525
Buildings and improvements	1,518,748	621,731	428,777
Acquired lease intangibles	76,009	69,504	63,912
Real property held for sale	17,435	0
Construction in progress	36,174
Right of use assets, net	0
Receivables and other assets	15,634	1,492	3,959
Total assets acquired	1,818,470	744,167	539,173
Secured debt	(194,408)	(134,752)	0
Lease liabilities	0
Accrued expenses and other liabilities	(12,024)	(18,463)	(46,301)
Total liabilities assumed	(206,432)	(153,215)	(46,301)
Noncontrolling interests	(67,987)	(14,390)	(4,701)
Non-cash acquisition related activity	(11,889)		(67,633)
Cash disbursed for acquisitions	1,532,162	576,562	420,538
Construction in progress additions	227,018	82,621	84,874
Capitalized interest	(8,889)	(3,190)	(9,106)
Foreign currency translation	(8,643)	3,934	(6,830)
Accruals	0	0	0
Cash disbursed for construction in progress	209,486	83,365	68,938
Capital improvements to existing properties	260,413	201,001	185,473
Total cash invested in real property, net of cash acquired	2,002,061	860,928	674,949
Non cash acquisition financed as equity investments			59,665
Non cash acquisition financed as real estate loan receivable			7,968
Triple-net
Estimated Fair Value of Allocated Purchase Price of Asset and Liabilities
Land and land improvements	24,097	413,588	33,416
Buildings and improvements	203,282	2,242,884	248,459
Acquired lease intangibles	0	9,690	0
Real property held for sale	0	396,265
Construction in progress	0
Right of use assets, net	0
Receivables and other assets	0	1,354	0
Total assets acquired	227,379	3,063,781	281,875
Secured debt	0	0	0
Lease liabilities	0
Accrued expenses and other liabilities	0	(13,199)	(21,236)
Total liabilities assumed	0	(13,199)	(21,236)
Noncontrolling interests	(4,015)	(512,741)	(7,275)
Non-cash acquisition related activity	0		(54,901)
Cash disbursed for acquisitions	223,364	2,537,841	198,463
Construction in progress additions	61,414	55,558	120,797
Capitalized interest	(2,385)	(2,238)	(4,713)
Foreign currency translation	(878)	272	(610)
Accruals	0	0	0
Cash disbursed for construction in progress	58,151	53,592	115,474
Capital improvements to existing properties	17,426	10,046	19,989
Total cash invested in real property, net of cash acquired	298,941	2,601,479	333,926
Outpatient Medical
Estimated Fair Value of Allocated Purchase Price of Asset and Liabilities
Land and land improvements	293,933	77,239	40,565
Buildings and improvements	1,954,928	478,740	159,643
Acquired lease intangibles	183,921	50,813	24,014
Real property held for sale	0	22,032
Construction in progress	0
Right of use assets, net	58,377
Receivables and other assets	1,586	1,185	10
Total assets acquired	2,492,745	630,009	224,232
Secured debt	(206,754)	(169,156)	(25,708)
Lease liabilities	(47,740)
Accrued expenses and other liabilities	(32,893)	(14,896)	(3,181)
Total liabilities assumed	(287,387)	(184,052)	(28,889)
Noncontrolling interests	(1,201)	0	(9,080)
Non-cash acquisition related activity	0		0
Cash disbursed for acquisitions	2,204,157	445,957	186,263
Construction in progress additions	60,884	26,565	37,094
Capitalized interest	(3,998)	(2,477)	(2,406)
Foreign currency translation	0	0	0
Accruals	(1,035)	(339)	13,615
Cash disbursed for construction in progress	55,851	23,749	48,303
Capital improvements to existing properties	50,985	55,136	44,814
Total cash invested in real property, net of cash acquired	$ 2,310,993	$ 524,842	$ 279,380