Acquisitions of Real Estate Property - 2020 Acquisitions (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2020 USD ($) property	Dec. 31, 2019 USD ($) property	Dec. 31, 2018 USD ($) property
Business Acquisition [Line Items]
Number of real estate properties	1,200
Payments to acquire real estate | $	$ 78,648	$ 958,125	$ 265,907
2020 Acquisitions
Business Acquisition [Line Items]
Payments to acquire real estate | $	$ 249,500
Other 2019 Acquisitions
Business Acquisition [Line Items]
Number of real estate properties		2
Payments to acquire real estate | $		$ 237,000
Office operations
Business Acquisition [Line Items]
Number of real estate properties acquired			5
Office operations | Other 2019 Acquisitions
Business Acquisition [Line Items]
Number of real estate properties		1
Office operations | Research and Innovation Center
Business Acquisition [Line Items]
Number of real estate properties acquired	2		1
Senior living operations | 2020 Acquisitions
Business Acquisition [Line Items]
Number of real estate properties	7
Senior living operations | Other 2019 Acquisitions
Business Acquisition [Line Items]
Number of real estate properties		2
Triple-net leased properties | LTAC [Member] | 2020 Acquisitions
Business Acquisition [Line Items]
Number of real estate properties	1