Leases (Narrative) (Details) $ in Thousands	3 Months Ended	12 Months Ended
	Dec. 31, 2020 USD ($) building	Dec. 31, 2020 USD ($) building	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)
Lessee, Lease, Description [Line Items]
Pricing period		30 years
Number of buildings subleased | building	7	7
Straight line rent receivables	$ 146,508
Rental and other revenues related to operating lease payments		$ 1,443,360	$ 1,588,400	$ 1,380,422
Rental and other revenues related to operating lease payments, variable leases		203,348	$ 200,564
Avery Healthcare
Lessee, Lease, Description [Line Items]
Straight line rent receivables		$ 91,025
Minimum
Lessee, Lease, Description [Line Items]
Lease term extension period		1 year
Maximum
Lessee, Lease, Description [Line Items]
Lease term extension period		25 years