Dispositions and Impairment (Details) ft² in Thousands	1 Months Ended	2 Months Ended	12 Months Ended
	Aug. 31, 2018 USD ($) ft² building transaction	Feb. 19, 2020 USD ($)	Dec. 31, 2019 USD ($) ft² building	Dec. 31, 2018 USD ($) ft² building	Dec. 31, 2017 USD ($) portfolio building
Real Estate [Line Items]
Number of assets disposed | building			4	20	4
Proceeds from the sale of real estate			$ 4,900,000	$ 308,600,000	$ 85,200,000
Gross leasable area of real estate disposed (in square feet) | ft²			51	1,200
(Loss) gain on sale of real estate, net			$ (154,000)	$ 165,977,000	37,802,000
Impairment			0	$ 8,887,000	$ 13,922,000
Number of impaired assets | building				6
Number of portfolios impaired | portfolio					1
Land in Miami, FL
Real Estate [Line Items]
Land held for sale			$ 4,000,000.0
Property in Greenville, South Carolina
Real Estate [Line Items]
Number of assets disposed | building	17
Proceeds from the sale of real estate	$ 294,300,000
Gross leasable area of real estate disposed (in square feet) | ft²	1,000
Number of transactions | transaction	2
Medical Office Building in Massachusetts
Real Estate [Line Items]
Number of assets disposed | building				3
Proceeds from the sale of real estate				$ 14,300,000
Gross leasable area of real estate disposed (in square feet) | ft²				200
Medical Office Buildings in Tennessee, Texas and South Carolina
Real Estate [Line Items]
Number of impaired assets | building					2
Subsequent Event | Land in Miami, FL
Real Estate [Line Items]
Proceeds from the sale of real estate		$ 7,600,000
(Loss) gain on sale of real estate, net		$ 2,000,000.0