Real Estate Investments - Dispositions (Details) - Real Estate Dispositions $ in Thousands						6 Months Ended
	May 19, 2021 USD ($) ft²	May 18, 2021 USD ($) ft² property	Apr. 12, 2021 USD ($) ft²	Mar. 11, 2021 USD ($) ft² transaction	Mar. 11, 2021 USD ($) ft² property	Jun. 30, 2021 USD ($) ft²
Real Estate Dispositions [Line Items]
SALE PRICE						$ 91,550
CLOSING ADJUSTMENTS						(1,421)
NET PROCEEDS						90,129
NET REAL ESTATE INVESTMENT						47,049
Other (including receivables)						4,105
GAIN/(IMPAIRMENT)						$ 38,975
SQUARE FOOTAGE | ft²						356,686
Los Angeles, CA
Real Estate Dispositions [Line Items]
SALE PRICE				$ 26,000	$ 26,000
CLOSING ADJUSTMENTS				(555)	(555)
NET PROCEEDS					25,445
NET REAL ESTATE INVESTMENT				6,046	6,046
Other (including receivables)				$ 509	509
GAIN/(IMPAIRMENT)					$ 18,890
SQUARE FOOTAGE | ft²				73,906	73,906
Number of properties sold | property					2
Number of transactions | transaction				2
Atlanta, GA
Real Estate Dispositions [Line Items]
SALE PRICE			$ 8,050
CLOSING ADJUSTMENTS			(272)
NET PROCEEDS			7,778
NET REAL ESTATE INVESTMENT			5,675
Other (including receivables)			151
GAIN/(IMPAIRMENT)			$ 1,952
SQUARE FOOTAGE | ft²			19,732
Richmond, VA
Real Estate Dispositions [Line Items]
SALE PRICE		$ 52,000
CLOSING ADJUSTMENTS		(314)
NET PROCEEDS		51,686
NET REAL ESTATE INVESTMENT		29,414
Other (including receivables)		3,270
GAIN/(IMPAIRMENT)		$ 19,002
SQUARE FOOTAGE | ft²		142,856
Gadsden, AL
Real Estate Dispositions [Line Items]
SALE PRICE	$ 5,500
CLOSING ADJUSTMENTS	(280)
NET PROCEEDS	5,220
NET REAL ESTATE INVESTMENT	5,914
Other (including receivables)	175
GAIN/(IMPAIRMENT)	$ (869)
SQUARE FOOTAGE | ft²	120,192
Number of transactions | property		3