Variable Interest Entities - Narrative (Details) $ in Millions			1 Months Ended				3 Months Ended		6 Months Ended		12 Months Ended
	Dec. 31, 2020 USD ($) joint_venture loan tenant property investment	Jan. 31, 2020 property	Jun. 30, 2021 joint_venture property loan	May 31, 2021 property	Apr. 30, 2021 property	Jan. 31, 2021 property	Jun. 30, 2021 joint_venture property loan	Jun. 30, 2020 property	Jun. 30, 2021 joint_venture asset property loan facility	Jun. 30, 2020 property	Dec. 31, 2020 USD ($) joint_venture property asset loan tenant
Variable Interest Entity [Line Items]
Number of investments in senior housing development joint ventures | investment	2
Number of loans sold	3		2				2		2		3
Number of properties disposed										18
Term of facility									1 month		1 month
Number of properties acquired | asset									0
Exchange accommodation titleholder, real estate, carrying value | $	$ 813										$ 813
Brookedale MTCA
Variable Interest Entity [Line Items]
Number of properties disposed		18									18
CCRC JV
Variable Interest Entity [Line Items]
Investment ownership percentage	49.00%	49.00%	0.00%	49.00%			0.00%		0.00%		49.00%
CCRC JV | Brookedale MTCA
Variable Interest Entity [Line Items]
Number of assets to be sold				2
VIE tenant - operating leases
Variable Interest Entity [Line Items]
Number of properties leased (in properties)	2										2
Number of VIE tenants (in tenants) | tenant	1										1
Unconsolidated Variable Interest Entities
Variable Interest Entity [Line Items]
Number of unconsolidated joint ventures (in joint ventures) | joint_venture	4		1				1		1		4
Number of VIE borrowers with marketable debt securities (in joint ventures) | joint_venture	1		1				1		1		1
Number of loans to VIE borrowers (in loans) | loan	1		1				1		1		1
Number of properties leased (in properties)	2										2
Hcp Ventures V
Variable Interest Entity [Line Items]
VIE ownership percentage									51.00%
Life science joint ventures
Variable Interest Entity [Line Items]
VIE ownership percentage									99.00%
MSREI JV
Variable Interest Entity [Line Items]
VIE ownership percentage									51.00%
Consolidated Lessees VIE
Variable Interest Entity [Line Items]
Number of properties leased (in properties)			3				3		3
DownREIT Partnerships
Variable Interest Entity [Line Items]
Number of controlling ownership interest entities as a managing member | joint_venture									7
SHOP
Variable Interest Entity [Line Items]
Number of assets to be sold						16	6	2	1	9	23
SHOP | Sunrise Senior Housing Portfolio
Variable Interest Entity [Line Items]
Number of assets to be sold			2			32
SHOP | Discovery SHOP Portfolio
Variable Interest Entity [Line Items]
Number of assets to be sold					10
Number of preferred equity method investments sold					2
SHOP | Discovery SHOP Portfolio | Secured Loans
Variable Interest Entity [Line Items]
Number of loans sold					2
Senior Housing Triple-Net
Variable Interest Entity [Line Items]
Number of assets to be sold							3			18
Senior Housing Triple-Net | Sunrise Senior Housing Portfolio
Variable Interest Entity [Line Items]
Number of assets to be sold			2
Senior Housing Triple-Net | Loans receivable
Variable Interest Entity [Line Items]
Number of properties disposed | facility									7
Term of facility									5 years
Medical office
Variable Interest Entity [Line Items]
Number of assets to be sold							4	3		3	11
Number of properties acquired | asset											7
Medical Office, Hospital
Variable Interest Entity [Line Items]
Number of assets to be sold				1
Number of properties acquired | asset											1
Life science
Variable Interest Entity [Line Items]
Number of properties acquired | asset											3