Real Estate Properties - Disposition Activities (Details) ft² in Thousands, $ in Thousands	1 Months Ended	9 Months Ended	12 Months Ended
	Nov. 30, 2021 USD ($) property	Sep. 30, 2021 USD ($) property	Dec. 31, 2021 USD ($) ft² property parcel_of_land	Dec. 31, 2020 USD ($) ft² property	Dec. 31, 2019 USD ($) ft² property
Real Estate Properties [Line Items]
Number of properties (in properties) | property			178
Gain on sale of real estate			$ 78,354	$ 10,855	$ 105,131
Loss on Impairment of Real Estate			$ 62,420	$ 2,954	$ 22,255
Rentable Square Feet (in square feet) | ft²			926	163
Disposal Group, Disposed of by Sale
Real Estate Properties [Line Items]
Number of properties (in properties) | property				10	58
Rentable Square Feet | ft²			2,565
Gross Sales Price			$ 226,915
Number of Properties (in properties) | property			6
Gain on sale of real estate			$ 78,354	$ 10,855	$ 105,131
Loss on Impairment of Real Estate			$ 45,196	$ 2,954	$ 12,801
Rentable Square Feet (in square feet) | ft²				906	6,179
Gross Sales Price, excluding closing costs				$ 110,463	$ 848,853
Disposal Group, Disposed of by Sale | Mortgage notes payable, 5.9% interest rate, due in 2021 | Mortgage Note Payable
Real Estate Properties [Line Items]
Extinguishment of debt, amount				$ 13,095
Interest rate (as a percent)				5.90%
Disposal Group, Held-for-sale, Not Discontinued Operations
Real Estate Properties [Line Items]
Number of properties (in properties) | property			4
Loss on Impairment of Real Estate			$ 6,991
Rentable Square Feet (in square feet) | ft²			330
Gross Sales Price, excluding closing costs			$ 29,545
Kansas City, MO | Disposal Group, Disposed of by Sale
Real Estate Properties [Line Items]
Rentable Square Feet | ft²			10
Gross Sales Price			$ 845
Number of Properties (in properties) | property			0
Gain on sale of real estate			$ (63)
Loss on Impairment of Real Estate			$ 0
Richmond, VA | Disposal Group, Disposed of by Sale
Real Estate Properties [Line Items]
Rentable Square Feet | ft²			311
Gross Sales Price			$ 130,000
Number of Properties (in properties) | property			1
Gain on sale of real estate			$ 54,181
Loss on Impairment of Real Estate			$ 0
Huntsville, AL | Disposal Group, Disposed of by Sale
Real Estate Properties [Line Items]
Rentable Square Feet | ft²			1,371
Gross Sales Price			$ 39,000
Number of Properties (in properties) | property			1
Gain on sale of real estate			$ 0
Loss on Impairment of Real Estate			$ 5,383
Fresno, CA | Disposal Group, Disposed of by Sale
Real Estate Properties [Line Items]
Rentable Square Feet | ft²			532
Gross Sales Price			$ 6,000
Number of Properties (in properties) | property			1
Gain on sale of real estate			$ 0
Loss on Impairment of Real Estate			$ 33,902
Liverpool, NY | Disposal Group, Disposed of by Sale
Real Estate Properties [Line Items]
Rentable Square Feet | ft²			38
Gross Sales Price			$ 650
Number of Properties (in properties) | property			1
Gain on sale of real estate			$ 31
Loss on Impairment of Real Estate			$ 0
Memphis, TN | Disposal Group, Disposed of by Sale
Real Estate Properties [Line Items]
Rentable Square Feet | ft²			205
Gross Sales Price			$ 15,270
Number of Properties (in properties) | property			1
Gain on sale of real estate			$ 287
Loss on Impairment of Real Estate			$ 0
Stoneham, MA | Disposal Group, Disposed of by Sale
Real Estate Properties [Line Items]
Rentable Square Feet | ft²			98
Gross Sales Price			$ 6,650
Number of Properties (in properties) | property			1
Gain on sale of real estate			$ (282)
Loss on Impairment of Real Estate			$ 5,911
Sterling, VA | Disposal Group, Disposed of by Sale
Real Estate Properties [Line Items]
Number of Land Parcels | parcel_of_land			2
Rentable Square Feet | ft²			0
Gross Sales Price			$ 28,500
Number of Properties (in properties) | property			0
Gain on sale of real estate			$ 24,200
Loss on Impairment of Real Estate			$ 0
Rockville, MD | Disposal Group, Held-for-sale, Not Discontinued Operations
Real Estate Properties [Line Items]
Number of properties (in properties) | property			1
Loss on Impairment of Real Estate			$ 6,236
Rentable Square Feet (in square feet) | ft²			129
Gross Sales Price, excluding closing costs			$ 6,750
Chesapeake, VA | Disposal Group, Held-for-sale, Not Discontinued Operations
Real Estate Properties [Line Items]
Number of properties (in properties) | property			2
Loss on Impairment of Real Estate			$ 0
Rentable Square Feet (in square feet) | ft²			172
Gross Sales Price, excluding closing costs			$ 18,945
Milwaukee, WI | Disposal Group, Held-for-sale, Not Discontinued Operations
Real Estate Properties [Line Items]
Number of properties (in properties) | property			1
Loss on Impairment of Real Estate			$ 755
Rentable Square Feet (in square feet) | ft²			29
Gross Sales Price, excluding closing costs			$ 3,850
Brookhaven, GA | Disposal Group, Disposed of by Sale
Real Estate Properties [Line Items]
Number of properties (in properties) | property	5	3
Loss on Impairment of Real Estate			$ 425
Gross Sales Price, excluding closing costs	$ 56,000	$ 10,658
Stafford, VA | Disposal Group, Disposed of by Sale | January 2020
Real Estate Properties [Line Items]
Number of properties (in properties) | property				2
Gain on sale of real estate				$ 4,771
Loss on Impairment of Real Estate				$ 0
Rentable Square Feet (in square feet) | ft²				65
Gross Sales Price, excluding closing costs				$ 14,063
Windsor, CT | Disposal Group, Disposed of by Sale | January 2020
Real Estate Properties [Line Items]
Number of properties (in properties) | property				1
Gain on sale of real estate				$ 314
Loss on Impairment of Real Estate				$ 0
Rentable Square Feet (in square feet) | ft²				97
Gross Sales Price, excluding closing costs				$ 7,000
Lincolnshire, IL | Disposal Group, Disposed of by Sale | February 2020
Real Estate Properties [Line Items]
Number of properties (in properties) | property				1
Gain on sale of real estate				$ 1,179
Loss on Impairment of Real Estate				$ 0
Rentable Square Feet (in square feet) | ft²				223
Gross Sales Price, excluding closing costs				$ 12,000
Trenton, NJ | Disposal Group, Disposed of by Sale | March 2020
Real Estate Properties [Line Items]
Number of properties (in properties) | property				1
Gain on sale of real estate				$ (179)
Loss on Impairment of Real Estate				$ 0	$ 9,454
Rentable Square Feet (in square feet) | ft²				267
Gross Sales Price, excluding closing costs				$ 30,100
Fairfax, VA | Disposal Group, Disposed of by Sale | March 2020
Real Estate Properties [Line Items]
Number of properties (in properties) | property				1
Gain on sale of real estate				$ 4,754
Loss on Impairment of Real Estate				$ 0
Rentable Square Feet (in square feet) | ft²				83
Gross Sales Price, excluding closing costs				$ 22,200
Fairfax, VA | Disposal Group, Disposed of by Sale | October 2020
Real Estate Properties [Line Items]
Number of properties (in properties) | property				4
Gain on sale of real estate				$ 16
Loss on Impairment of Real Estate				$ 2,954
Rentable Square Feet (in square feet) | ft²				171
Gross Sales Price, excluding closing costs				$ 25,100
Northern Virginia and Maryland | Disposal Group, Disposed of by Sale
Real Estate Properties [Line Items]
Number of properties (in properties) | property					34
Gain on sale of real estate					$ 0
Loss on Impairment of Real Estate					$ 732
Rentable Square Feet (in square feet) | ft²					1,636
Gross Sales Price, excluding closing costs					$ 198,500
Washington, D.C. | Disposal Group, Disposed of by Sale
Real Estate Properties [Line Items]
Number of properties (in properties) | property					1
Gain on sale of real estate					$ 22,075
Loss on Impairment of Real Estate					$ 0
Rentable Square Feet (in square feet) | ft²					129
Gross Sales Price, excluding closing costs					$ 70,000
Buffalo, NY | Disposal Group, Disposed of by Sale
Real Estate Properties [Line Items]
Number of properties (in properties) | property					1
Gain on sale of real estate					$ 0
Loss on Impairment of Real Estate					$ 5,137
Rentable Square Feet (in square feet) | ft²					122
Gross Sales Price, excluding closing costs					$ 16,900
Maynard, MA | Disposal Group, Disposed of by Sale
Real Estate Properties [Line Items]
Number of properties (in properties) | property					1
Gain on sale of real estate					$ (227)
Loss on Impairment of Real Estate					$ 0
Rentable Square Feet (in square feet) | ft²					287
Gross Sales Price, excluding closing costs					$ 5,000
Kapolei, HI | Disposal Group, Disposed of by Sale
Real Estate Properties [Line Items]
Number of properties (in properties) | property					1
Gain on sale of real estate					$ 0
Loss on Impairment of Real Estate					$ 0
Rentable Square Feet (in square feet) | ft²					417
Gross Sales Price, excluding closing costs					$ 7,100
San Jose, CA | Disposal Group, Disposed of by Sale | July 2019
Real Estate Properties [Line Items]
Number of properties (in properties) | property					1
Gain on sale of real estate					$ (270)
Loss on Impairment of Real Estate					$ 0
Rentable Square Feet (in square feet) | ft²					72
Gross Sales Price, excluding closing costs					$ 14,000
San Jose, CA | Disposal Group, Disposed of by Sale | December 2019
Real Estate Properties [Line Items]
Number of properties (in properties) | property					1
Gain on sale of real estate					$ (333)
Loss on Impairment of Real Estate					$ 0
Rentable Square Feet (in square feet) | ft²					76
Gross Sales Price, excluding closing costs					$ 13,000
Nashua, NH | Disposal Group, Disposed of by Sale
Real Estate Properties [Line Items]
Number of properties (in properties) | property					1
Gain on sale of real estate					$ 8,401
Loss on Impairment of Real Estate					$ 0
Rentable Square Feet (in square feet) | ft²					322
Gross Sales Price, excluding closing costs					$ 25,000
Arlington, TX | Disposal Group, Disposed of by Sale
Real Estate Properties [Line Items]
Number of properties (in properties) | property					1
Gain on sale of real estate					$ 187
Loss on Impairment of Real Estate					$ 0
Rentable Square Feet (in square feet) | ft²					182
Gross Sales Price, excluding closing costs					$ 14,900
Rochester, NY | Disposal Group, Disposed of by Sale
Real Estate Properties [Line Items]
Number of properties (in properties) | property					1
Gain on sale of real estate					$ (104)
Loss on Impairment of Real Estate					$ 0
Rentable Square Feet (in square feet) | ft²					95
Gross Sales Price, excluding closing costs					$ 4,765
Hanover, PA | Disposal Group, Disposed of by Sale
Real Estate Properties [Line Items]
Number of properties (in properties) | property					1
Gain on sale of real estate					$ (417)
Loss on Impairment of Real Estate					$ 0
Rentable Square Feet (in square feet) | ft²					502
Gross Sales Price, excluding closing costs					$ 5,500
San Antonio, TX | Disposal Group, Disposed of by Sale
Real Estate Properties [Line Items]
Number of properties (in properties) | property					1
Gain on sale of real estate					$ 3,869
Loss on Impairment of Real Estate					$ 0
Rentable Square Feet (in square feet) | ft²					618
Gross Sales Price, excluding closing costs					$ 198,000
Topeka, KS | Disposal Group, Disposed of by Sale
Real Estate Properties [Line Items]
Number of properties (in properties) | property					1
Gain on sale of real estate					$ 36
Loss on Impairment of Real Estate					$ 0
Rentable Square Feet (in square feet) | ft²					144
Gross Sales Price, excluding closing costs					$ 15,600
Falling Waters, WV | Disposal Group, Disposed of by Sale
Real Estate Properties [Line Items]
Number of properties (in properties) | property					1
Gain on sale of real estate					$ 0
Loss on Impairment of Real Estate					$ 2,179
Rentable Square Feet (in square feet) | ft²					40
Gross Sales Price, excluding closing costs					$ 650
San Diego, CA | Disposal Group, Disposed of by Sale | September 2019
Real Estate Properties [Line Items]
Number of properties (in properties) | property					1
Gain on sale of real estate					$ 3,062
Loss on Impairment of Real Estate					$ 0
Rentable Square Feet (in square feet) | ft²					44
Gross Sales Price, excluding closing costs					$ 8,950
San Diego, CA | Disposal Group, Disposed of by Sale | December 2019
Real Estate Properties [Line Items]
Number of properties (in properties) | property					1
Gain on sale of real estate					$ 6,823
Loss on Impairment of Real Estate					$ 0
Rentable Square Feet (in square feet) | ft²					148
Gross Sales Price, excluding closing costs					$ 23,750
Columbia, SC | Disposal Group, Disposed of by Sale
Real Estate Properties [Line Items]
Number of properties (in properties) | property					3
Gain on sale of real estate					$ 0
Loss on Impairment of Real Estate					$ 3,581
Rentable Square Feet (in square feet) | ft²					181
Gross Sales Price, excluding closing costs					$ 10,750
Metro DC - MD | Disposal Group, Disposed of by Sale
Real Estate Properties [Line Items]
Number of properties (in properties) | property					3
Gain on sale of real estate					$ 1,177
Loss on Impairment of Real Estate					$ 0
Rentable Square Feet (in square feet) | ft²					373
Gross Sales Price, excluding closing costs					$ 61,938
Phoenix, AZ | Disposal Group, Disposed of by Sale
Real Estate Properties [Line Items]
Number of properties (in properties) | property					1
Gain on sale of real estate					$ 860
Loss on Impairment of Real Estate					$ 0
Rentable Square Feet (in square feet) | ft²					123
Gross Sales Price, excluding closing costs					$ 12,850
Houston, TX | Disposal Group, Disposed of by Sale
Real Estate Properties [Line Items]
Number of properties (in properties) | property					1
Gain on sale of real estate					$ 59,992
Loss on Impairment of Real Estate					$ 0
Rentable Square Feet (in square feet) | ft²					497
Gross Sales Price, excluding closing costs					$ 130,000
Kansas City, KS | Disposal Group, Disposed of by Sale
Real Estate Properties [Line Items]
Number of properties (in properties) | property					1
Gain on sale of real estate					$ 0
Loss on Impairment of Real Estate					$ 1,172
Rentable Square Feet (in square feet) | ft²					171
Gross Sales Price, excluding closing costs					$ 11,700