Investments in Real Estate - Acquisitions (Details) ft² in Thousands, $ in Thousands	1 Months Ended	3 Months Ended
	Apr. 27, 2017 USD ($) ft²	Mar. 31, 2017 USD ($) market shares	Mar. 31, 2016 USD ($)
Business Acquisition [Line Items]
Closing costs		$ 300
Land		4,934	$ 17,315
Building and improvements		29,762	128,945
In place leases		3,185	15,919
Below market leases		(65)	(5,382)
Above market leases		0	840
Below market leasehold interests		0	1,099
Above market leasehold interests		0	(50)
Net assets acquired		37,816	158,686
Other, net		1,230	3,321
Aggregate purchase price		$ 39,046	$ 162,007
Minimum
Business Acquisition [Line Items]
Number of markets where the Company is concentrated | market		15
Maximum
Business Acquisition [Line Items]
Number of markets where the Company is concentrated | market		20
Subsequent Event
Business Acquisition [Line Items]
Aggregate purchase price	$ 150,000
Gross leasable area to be sold (in square feet) | ft²	592
Healthcare Trust of America Holdings, LP (HTALP)
Business Acquisition [Line Items]
Number of operating partnership units issued in acquisition (shares) | shares		20,687
Market value of operating partnership units issued in acquisition		$ 600