Real Estate Transactions - Development Activities (Details) $ in Millions	3 Months Ended	6 Months Ended
	Jun. 30, 2020 USD ($) property	Jun. 30, 2020 USD ($)
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Decrease to development commitments		$ 17
Development commitments	$ 344	$ 344
Medical office
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of Properties developed | property	1