Summary of Significant Accounting Policies (Details) - USD ($)		3 Months Ended		9 Months Ended		10 Months Ended
		Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Oct. 28, 2020	Dec. 31, 2019	Dec. 31, 2018
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents [Abstract]
Cash and cash equivalents		$ 227,138,000	$ 12,748,000	$ 227,138,000	$ 12,748,000		$ 32,713,000
Restricted cash		4,108,000	5,068,000	4,108,000	5,068,000		4,903,000
Total cash, cash equivalents and restricted cash		231,246,000	17,816,000	$ 231,246,000	17,816,000		$ 37,616,000	$ 133,530,000
Leases [Abstract]
Deferred rent period				3 months
Net income attributable to noncontrolling interests	[1]	$ (105,000)	(114,000)	$ 438,000	486,000
Unconsolidated Joint Ventures [Abstract]
Investment in unconsolidated joint ventures, ownership percentage		50.00%		50.00%			50.00%
Investment in unconsolidated joint venture		$ 64,756,000		$ 64,756,000			$ 65,888,000
Income (loss) from unconsolidated joint venture		$ 422,000	422,000	1,223,000	1,456,000
Subsequent Event
Leases [Abstract]
Amount of rent deferrals						$ 11,000,000.0
Amount of repayment of rent deferrals						$ 3,700,000
Secured Debt
Leases [Abstract]
Debt term		1 year
Debt instrument, face amount		$ 6,000,000		$ 6,000,000
Minimum
Leases [Abstract]
Lessor, term of contract		3 years		3 years
Deferred rent payback period				12 months
Maximum
Leases [Abstract]
Lessor, term of contract		7 years		7 years
Deferred rent payback period				3 months
Building and Building Improvements
Real estate investments [Abstract]
Depreciation expense		$ 59,200,000	54,900,000	$ 176,400,000	158,900,000
Healthcare Trust of America Holdings, LP (HTALP)
Partners' Capital Notes [Abstract]
Limited partner's capital, units issued (in shares)		3,533,826		3,533,826			3,834,279
Limited partner's capital, units outstanding (in shares)		3,533,826		3,533,826			3,834,279
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents [Abstract]
Cash and cash equivalents		$ 227,138,000		$ 227,138,000			$ 32,713,000
Restricted cash		4,108,000		4,108,000			4,903,000
Total cash, cash equivalents and restricted cash		231,246,000	17,816,000	231,246,000	17,816,000		37,616,000	$ 133,530,000
Leases [Abstract]
Net income attributable to noncontrolling interests		0	0	0	66,000
Unconsolidated Joint Ventures [Abstract]
Investment in unconsolidated joint venture		64,756,000		64,756,000			$ 65,888,000
Income (loss) from unconsolidated joint venture		$ 422,000	$ 422,000	$ 1,223,000	$ 1,456,000

[1] Includes amounts attributable to redeemable noncontrolling interests for the nine months ended September 30, 2019.