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Schedule III Real Estate Assets and Accumulated Depreciation and Amortization - Schedule III (Details) - USD ($)
$ in Thousands
 12 Months Ended
Dec. 31, 2019
Dec. 31, 2018
Dec. 31, 2017
Dec. 31, 2016
Real Estate Properties [Line Items]        
Encumbrances $ 1,017,571      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Initial Cost [Abstract]        
Land 463,960      
Building and Improvements 3,622,552      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Cost Capitalized Subsequent to Acquisition [Abstract]        
Building and Improvements 191,921      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Land 458,339      
Building and Improvements 3,820,094      
Total 4,278,433 $ 3,073,364 $ 2,869,328 $ 3,024,389
Accumulated Depreciation and Amortization 668,104 $ 538,412 $ 426,752 $ 338,552
Loan valuation discount 1,100      
Aggregate cost of real estate owned for income tax purposes $ 4,200,000      
Minimum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 5 years      
Maximum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 40 years      
Plainfield | Minimum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 5 years      
Plainfield | Maximum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 40 years      
Renfro | Minimum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 5 years      
Renfro | Maximum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 40 years      
Emporia Partners | Minimum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 5 years      
Emporia Partners | Maximum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 40 years      
AT&T | Minimum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 5 years      
AT&T | Maximum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 40 years      
Westinghouse | Minimum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 5 years      
Westinghouse | Maximum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 40 years      
TransDigm | Minimum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 5 years      
TransDigm | Maximum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 40 years      
Atrium II | Minimum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 5 years      
Atrium II | Maximum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 40 years      
Zeller Plastik | Minimum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 5 years      
Zeller Plastik | Maximum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 40 years      
Northrop Grumman | Minimum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 5 years      
Northrop Grumman | Maximum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 40 years      
Health Net | Minimum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 5 years      
Health Net | Maximum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 40 years      
Comcast | Minimum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 5 years      
Comcast | Maximum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 40 years      
500 Rivertech | Minimum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 5 years      
500 Rivertech | Maximum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 40 years      
Schlumberger | Minimum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 5 years      
Schlumberger | Maximum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 40 years      
UTC | Minimum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 5 years      
UTC | Maximum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 40 years      
Avnet | Minimum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 5 years      
Avnet | Maximum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 40 years      
Cigna | Minimum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 5 years      
Cigna | Maximum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 40 years      
Nokia | Minimum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 5 years      
Nokia | Maximum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 40 years      
Verizon | Minimum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 5 years      
Verizon | Maximum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 40 years      
Fox Head | Minimum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 5 years      
Fox Head | Maximum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 40 years      
2500 Windy Ridge | Minimum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 5 years      
2500 Windy Ridge | Maximum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 40 years      
General Electric | Minimum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 5 years      
General Electric | Maximum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 40 years      
Atlanta Wildwood | Minimum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 5 years      
Atlanta Wildwood | Maximum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 40 years      
Community Insurance | Minimum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 5 years      
Community Insurance | Maximum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 40 years      
Anthem | Minimum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 5 years      
Anthem | Maximum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 40 years      
JPMorgan Chase | Minimum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 5 years      
JPMorgan Chase | Maximum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 40 years      
Sterling Commerce Center | Minimum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 5 years      
Sterling Commerce Center | Maximum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 40 years      
Aetna. | Minimum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 5 years      
Aetna. | Maximum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 40 years      
CHRISTUS Health | Minimum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 5 years      
CHRISTUS Health | Maximum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 40 years      
Roush Industries | Minimum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 5 years      
Roush Industries | Maximum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 40 years      
Parkland Center | Minimum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 5 years      
Parkland Center | Maximum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 40 years      
1200 Morris | Minimum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 5 years      
1200 Morris | Maximum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 40 years      
United HealthCare | Minimum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 5 years      
United HealthCare | Maximum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 40 years      
Intermec (Northpointe Corporate Center II) | Minimum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 5 years      
Intermec (Northpointe Corporate Center II) | Maximum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 40 years      
Comcast (Northpointe Corporate Center I) | Minimum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 5 years      
Comcast (Northpointe Corporate Center I) | Maximum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 40 years      
Farmers | Minimum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 5 years      
Farmers | Maximum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 40 years      
2200 Channahon Road | Minimum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 5 years      
2200 Channahon Road | Maximum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 40 years      
Digital Globe | Minimum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 5 years      
Digital Globe | Maximum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 40 years      
Waste Management | Minimum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 5 years      
Waste Management | Maximum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 40 years      
Wyndham Worldwide | Minimum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 5 years      
Wyndham Worldwide | Maximum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 40 years      
ACE Hardware Corporation HQ | Minimum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 5 years      
ACE Hardware Corporation HQ | Maximum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 40 years      
Equifax | Minimum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 5 years      
Equifax | Maximum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 40 years      
American Express | Minimum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 5 years      
American Express | Maximum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 40 years      
SoftBank | Minimum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 5 years      
SoftBank | Maximum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 40 years      
Vanguard | Minimum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 5 years      
Vanguard | Maximum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 40 years      
Parallon | Minimum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 5 years      
Parallon | Maximum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 40 years      
TW Telecom | Minimum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 5 years      
TW Telecom | Maximum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 40 years      
Equifax II | Minimum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 5 years      
Equifax II | Maximum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 40 years      
Mason I | Minimum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 5 years      
Mason I | Maximum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 40 years      
Wells Fargo. | Minimum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 5 years      
Wells Fargo. | Maximum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 40 years      
GE Aviation | Minimum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 5 years      
GE Aviation | Maximum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 40 years      
Westgate III | Minimum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 5 years      
Westgate III | Maximum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 40 years      
2275 Cabot Drive | Minimum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 5 years      
2275 Cabot Drive | Maximum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 40 years      
Franklin Center | Minimum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 5 years      
Franklin Center | Maximum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 40 years      
4650 Lakehurst Court | Minimum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 5 years      
4650 Lakehurst Court | Maximum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 40 years      
Miramar | Minimum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 5 years      
Miramar | Maximum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 40 years      
Royal Ridge V | Minimum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 5 years      
Royal Ridge V | Maximum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 40 years      
Duke Bridges | Minimum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 5 years      
Duke Bridges | Maximum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 40 years      
Houston Westway II | Minimum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 5 years      
Houston Westway II | Maximum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 40 years      
Houston Westway I | Minimum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 5 years      
Houston Westway I | Maximum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 40 years      
Atlanta Perimeter | Minimum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 5 years      
Atlanta Perimeter | Maximum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 40 years      
South Lake at Dulles | Minimum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 5 years      
South Lake at Dulles | Maximum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 40 years      
Four Parkway | Minimum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 5 years      
Four Parkway | Maximum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 40 years      
Highway 94 | Minimum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 5 years      
Highway 94 | Maximum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 40 years      
Heritage IV | Minimum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 5 years      
Heritage IV | Maximum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 40 years      
Samsonite | Minimum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 5 years      
Samsonite | Maximum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 40 years      
Restoration Hardware | Minimum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 5 years      
Restoration Hardware | Maximum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 40 years      
HealthSpring | Minimum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 5 years      
HealthSpring | Maximum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 40 years      
LPL | Minimum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 5 years      
LPL | Maximum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 40 years      
LPL | Minimum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 5 years      
LPL | Maximum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 40 years      
Quaker | Minimum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 5 years      
Quaker | Maximum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 40 years      
Operating Properties        
Real Estate Properties [Line Items]        
Encumbrances $ 0      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Initial Cost [Abstract]        
Land 1,955      
Building and Improvements 15,540      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Cost Capitalized Subsequent to Acquisition [Abstract]        
Building and Improvements 1,362      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Land 1,955      
Building and Improvements 16,902      
Total 18,857      
Accumulated Depreciation and Amortization 3,395      
Operating Properties | Plainfield        
Real Estate Properties [Line Items]        
Encumbrances 0      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Initial Cost [Abstract]        
Land 3,709      
Building and Improvements 22,209      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Cost Capitalized Subsequent to Acquisition [Abstract]        
Building and Improvements 7,344      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Land 3,709      
Building and Improvements 29,553      
Total 33,262      
Accumulated Depreciation and Amortization 14,206      
Operating Properties | Renfro        
Real Estate Properties [Line Items]        
Encumbrances 12,816      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Initial Cost [Abstract]        
Land 1,400      
Building and Improvements 18,182      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Cost Capitalized Subsequent to Acquisition [Abstract]        
Building and Improvements 2,012      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Land 1,400      
Building and Improvements 20,194      
Total 21,594      
Accumulated Depreciation and Amortization 8,757      
Operating Properties | Emporia Partners        
Real Estate Properties [Line Items]        
Encumbrances 2,104      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Initial Cost [Abstract]        
Land 274      
Building and Improvements 7,567      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Cost Capitalized Subsequent to Acquisition [Abstract]        
Building and Improvements 0      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Land 274      
Building and Improvements 7,567      
Total 7,841      
Accumulated Depreciation and Amortization 3,025      
Operating Properties | AT&T        
Real Estate Properties [Line Items]        
Encumbrances 24,683      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Initial Cost [Abstract]        
Land 6,770      
Building and Improvements 32,420      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Cost Capitalized Subsequent to Acquisition [Abstract]        
Building and Improvements 718      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Land 6,770      
Building and Improvements 33,138      
Total 39,908      
Accumulated Depreciation and Amortization 10,234      
Operating Properties | Westinghouse        
Real Estate Properties [Line Items]        
Encumbrances 20,885      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Initial Cost [Abstract]        
Land 2,650      
Building and Improvements 26,745      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Cost Capitalized Subsequent to Acquisition [Abstract]        
Building and Improvements 0      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Land 2,650      
Building and Improvements 26,745      
Total 29,395      
Accumulated Depreciation and Amortization 8,430      
Operating Properties | TransDigm        
Real Estate Properties [Line Items]        
Encumbrances 4,367      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Initial Cost [Abstract]        
Land 3,773      
Building and Improvements 9,030      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Cost Capitalized Subsequent to Acquisition [Abstract]        
Building and Improvements 411      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Land 3,773      
Building and Improvements 9,441      
Total 13,214      
Accumulated Depreciation and Amortization 2,839      
Operating Properties | Atrium II        
Real Estate Properties [Line Items]        
Encumbrances 9,019      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Initial Cost [Abstract]        
Land 2,600      
Building and Improvements 13,500      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Cost Capitalized Subsequent to Acquisition [Abstract]        
Building and Improvements 8,087      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Land 2,600      
Building and Improvements 21,587      
Total 24,187      
Accumulated Depreciation and Amortization 6,393      
Operating Properties | Zeller Plastik        
Real Estate Properties [Line Items]        
Encumbrances 8,543      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Initial Cost [Abstract]        
Land 2,674      
Building and Improvements 13,229      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Cost Capitalized Subsequent to Acquisition [Abstract]        
Building and Improvements 651      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Land 2,674      
Building and Improvements 13,880      
Total 16,554      
Accumulated Depreciation and Amortization 3,710      
Operating Properties | Northrop Grumman        
Real Estate Properties [Line Items]        
Encumbrances 10,324      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Initial Cost [Abstract]        
Land 1,300      
Building and Improvements 16,188      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Cost Capitalized Subsequent to Acquisition [Abstract]        
Building and Improvements 39      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Land 1,300      
Building and Improvements 16,227      
Total 17,527      
Accumulated Depreciation and Amortization 6,542      
Operating Properties | Health Net        
Real Estate Properties [Line Items]        
Encumbrances 12,815      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Initial Cost [Abstract]        
Land 4,182      
Building and Improvements 18,072      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Cost Capitalized Subsequent to Acquisition [Abstract]        
Building and Improvements 324      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Land 4,182      
Building and Improvements 18,396      
Total 22,578      
Accumulated Depreciation and Amortization 7,730      
Operating Properties | Comcast        
Real Estate Properties [Line Items]        
Encumbrances 14,105      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Initial Cost [Abstract]        
Land 3,146      
Building and Improvements 22,826      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Cost Capitalized Subsequent to Acquisition [Abstract]        
Building and Improvements 1,593      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Land 3,146      
Building and Improvements 24,419      
Total 27,565      
Accumulated Depreciation and Amortization 9,578      
Operating Properties | 500 Rivertech        
Real Estate Properties [Line Items]        
Encumbrances 0      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Initial Cost [Abstract]        
Land 3,000      
Building and Improvements 9,000      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Cost Capitalized Subsequent to Acquisition [Abstract]        
Building and Improvements 6,982      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Land 3,000      
Building and Improvements 15,982      
Total 18,982      
Accumulated Depreciation and Amortization 4,920      
Operating Properties | Schlumberger        
Real Estate Properties [Line Items]        
Encumbrances 28,735      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Initial Cost [Abstract]        
Land 2,800      
Building and Improvements 47,752      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Cost Capitalized Subsequent to Acquisition [Abstract]        
Building and Improvements 829      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Land 2,800      
Building and Improvements 48,581      
Total 51,381      
Accumulated Depreciation and Amortization 11,624      
Operating Properties | UTC        
Real Estate Properties [Line Items]        
Encumbrances 22,712      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Initial Cost [Abstract]        
Land 1,330      
Building and Improvements 37,858      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Cost Capitalized Subsequent to Acquisition [Abstract]        
Building and Improvements 0      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Land 1,330      
Building and Improvements 37,858      
Total 39,188      
Accumulated Depreciation and Amortization 9,973      
Operating Properties | Avnet        
Real Estate Properties [Line Items]        
Encumbrances 18,984      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Initial Cost [Abstract]        
Land 1,860      
Building and Improvements 31,481      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Cost Capitalized Subsequent to Acquisition [Abstract]        
Building and Improvements 47      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Land 1,860      
Building and Improvements 31,528      
Total 33,388      
Accumulated Depreciation and Amortization 7,341      
Operating Properties | Cigna        
Real Estate Properties [Line Items]        
Encumbrances 39,000      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Initial Cost [Abstract]        
Land 8,600      
Building and Improvements 48,102      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Cost Capitalized Subsequent to Acquisition [Abstract]        
Building and Improvements 133      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Land 8,600      
Building and Improvements 48,235      
Total 56,835      
Accumulated Depreciation and Amortization 12,717      
Operating Properties | Nokia        
Real Estate Properties [Line Items]        
Encumbrances 0      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Initial Cost [Abstract]        
Land 7,697      
Building and Improvements 21,843      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Cost Capitalized Subsequent to Acquisition [Abstract]        
Building and Improvements 0      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Land 7,697      
Building and Improvements 21,843      
Total 29,540      
Accumulated Depreciation and Amortization 4,894      
Operating Properties | Verizon        
Real Estate Properties [Line Items]        
Encumbrances 25,007      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Initial Cost [Abstract]        
Land 5,300      
Building and Improvements 36,768      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Cost Capitalized Subsequent to Acquisition [Abstract]        
Building and Improvements 5,681      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Land 5,300      
Building and Improvements 42,449      
Total 47,749      
Accumulated Depreciation and Amortization 16,429      
Operating Properties | Fox Head        
Real Estate Properties [Line Items]        
Encumbrances 0      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Initial Cost [Abstract]        
Land 3,672      
Building and Improvements 23,230      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Cost Capitalized Subsequent to Acquisition [Abstract]        
Building and Improvements 0      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Land 3,672      
Building and Improvements 23,230      
Total 26,902      
Accumulated Depreciation and Amortization 5,090      
Operating Properties | 2500 Windy Ridge        
Real Estate Properties [Line Items]        
Encumbrances 0      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Initial Cost [Abstract]        
Land 5,000      
Building and Improvements 50,227      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Cost Capitalized Subsequent to Acquisition [Abstract]        
Building and Improvements 17,824      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Land 5,000      
Building and Improvements 68,051      
Total 73,051      
Accumulated Depreciation and Amortization 14,882      
Operating Properties | General Electric        
Real Estate Properties [Line Items]        
Encumbrances 0      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Initial Cost [Abstract]        
Land 5,050      
Building and Improvements 51,396      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Cost Capitalized Subsequent to Acquisition [Abstract]        
Building and Improvements 148      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Land 5,050      
Building and Improvements 51,544      
Total 56,594      
Accumulated Depreciation and Amortization 10,959      
Operating Properties | Atlanta Wildwood        
Real Estate Properties [Line Items]        
Encumbrances 0      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Initial Cost [Abstract]        
Land 4,241      
Building and Improvements 23,414      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Cost Capitalized Subsequent to Acquisition [Abstract]        
Building and Improvements 5,445      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Land 4,241      
Building and Improvements 28,859      
Total 33,100      
Accumulated Depreciation and Amortization 9,008      
Operating Properties | Community Insurance        
Real Estate Properties [Line Items]        
Encumbrances 0      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Initial Cost [Abstract]        
Land 1,177      
Building and Improvements 22,323      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Cost Capitalized Subsequent to Acquisition [Abstract]        
Building and Improvements 0      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Land 1,177      
Building and Improvements 22,323      
Total 23,500      
Accumulated Depreciation and Amortization 5,188      
Operating Properties | Anthem        
Real Estate Properties [Line Items]        
Encumbrances 0      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Initial Cost [Abstract]        
Land 850      
Building and Improvements 8,892      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Cost Capitalized Subsequent to Acquisition [Abstract]        
Building and Improvements 175      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Land 850      
Building and Improvements 9,067      
Total 9,917      
Accumulated Depreciation and Amortization 2,808      
Operating Properties | JPMorgan Chase        
Real Estate Properties [Line Items]        
Encumbrances 0      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Initial Cost [Abstract]        
Land 5,500      
Building and Improvements 39,000      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Cost Capitalized Subsequent to Acquisition [Abstract]        
Building and Improvements 586      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Land 5,500      
Building and Improvements 39,586      
Total 45,086      
Accumulated Depreciation and Amortization 9,696      
Operating Properties | Sterling Commerce Center        
Real Estate Properties [Line Items]        
Encumbrances 0      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Initial Cost [Abstract]        
Land 4,750      
Building and Improvements 32,769      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Cost Capitalized Subsequent to Acquisition [Abstract]        
Building and Improvements 4,307      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Land 4,750      
Building and Improvements 37,076      
Total 41,826      
Accumulated Depreciation and Amortization 12,021      
Operating Properties | Aetna.        
Real Estate Properties [Line Items]        
Encumbrances 36,199      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Initial Cost [Abstract]        
Land 3,000      
Building and Improvements 12,330      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Cost Capitalized Subsequent to Acquisition [Abstract]        
Building and Improvements 624      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Land 3,000      
Building and Improvements 12,954      
Total 15,954      
Accumulated Depreciation and Amortization 4,518      
Operating Properties | CHRISTUS Health        
Real Estate Properties [Line Items]        
Encumbrances 0      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Initial Cost [Abstract]        
Land 1,950      
Building and Improvements 46,922      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Cost Capitalized Subsequent to Acquisition [Abstract]        
Building and Improvements 357      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Land 1,950      
Building and Improvements 47,279      
Total 49,229      
Accumulated Depreciation and Amortization 13,580      
Operating Properties | Roush Industries        
Real Estate Properties [Line Items]        
Encumbrances 0      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Initial Cost [Abstract]        
Land 875      
Building and Improvements 11,375      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Cost Capitalized Subsequent to Acquisition [Abstract]        
Building and Improvements 2,449      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Land 875      
Building and Improvements 13,824      
Total 14,699      
Accumulated Depreciation and Amortization 3,593      
Operating Properties | Parkland Center        
Real Estate Properties [Line Items]        
Encumbrances 0      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Initial Cost [Abstract]        
Land 3,100      
Building and Improvements 26,348      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Cost Capitalized Subsequent to Acquisition [Abstract]        
Building and Improvements 10,825      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Land 3,100      
Building and Improvements 37,173      
Total 40,273      
Accumulated Depreciation and Amortization 16,544      
Operating Properties | 1200 Morris        
Real Estate Properties [Line Items]        
Encumbrances 0      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Initial Cost [Abstract]        
Land 2,925      
Building and Improvements 18,935      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Cost Capitalized Subsequent to Acquisition [Abstract]        
Building and Improvements 2,278      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Land 2,925      
Building and Improvements 21,213      
Total 24,138      
Accumulated Depreciation and Amortization 7,724      
Operating Properties | United HealthCare        
Real Estate Properties [Line Items]        
Encumbrances 0      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Initial Cost [Abstract]        
Land 2,920      
Building and Improvements 23,510      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Cost Capitalized Subsequent to Acquisition [Abstract]        
Building and Improvements 6,764      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Land 2,920      
Building and Improvements 30,274      
Total 33,194      
Accumulated Depreciation and Amortization 7,431      
Operating Properties | Intermec (Northpointe Corporate Center II)        
Real Estate Properties [Line Items]        
Encumbrances 0      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Initial Cost [Abstract]        
Land 1,109      
Building and Improvements 6,066      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Cost Capitalized Subsequent to Acquisition [Abstract]        
Building and Improvements 4,576      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Land 1,109      
Building and Improvements 10,642      
Total 11,751      
Accumulated Depreciation and Amortization 3,221      
Operating Properties | Comcast (Northpointe Corporate Center I)        
Real Estate Properties [Line Items]        
Encumbrances 39,650      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Initial Cost [Abstract]        
Land 2,292      
Building and Improvements 16,930      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Cost Capitalized Subsequent to Acquisition [Abstract]        
Building and Improvements 2,324      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Land 2,292      
Building and Improvements 19,254      
Total 21,546      
Accumulated Depreciation and Amortization 4,829      
Operating Properties | Farmers        
Real Estate Properties [Line Items]        
Encumbrances 0      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Initial Cost [Abstract]        
Land 2,750      
Building and Improvements 17,106      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Cost Capitalized Subsequent to Acquisition [Abstract]        
Building and Improvements 816      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Land 2,750      
Building and Improvements 17,922      
Total 20,672      
Accumulated Depreciation and Amortization 5,366      
Operating Properties | 2200 Channahon Road        
Real Estate Properties [Line Items]        
Encumbrances 0      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Initial Cost [Abstract]        
Land 6,000      
Building and Improvements 46,511      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Cost Capitalized Subsequent to Acquisition [Abstract]        
Building and Improvements (15,695)      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Land 3,537      
Building and Improvements 33,279      
Total 36,816      
Accumulated Depreciation and Amortization 14,276      
Operating Properties | Digital Globe        
Real Estate Properties [Line Items]        
Encumbrances 0      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Initial Cost [Abstract]        
Land 8,600      
Building and Improvements 83,400      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Cost Capitalized Subsequent to Acquisition [Abstract]        
Building and Improvements 0      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Land 8,600      
Building and Improvements 83,400      
Total 92,000      
Accumulated Depreciation and Amortization 19,091      
Operating Properties | Waste Management        
Real Estate Properties [Line Items]        
Encumbrances 0      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Initial Cost [Abstract]        
Land 0      
Building and Improvements 16,515      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Cost Capitalized Subsequent to Acquisition [Abstract]        
Building and Improvements 82      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Land 0      
Building and Improvements 16,597      
Total 16,597      
Accumulated Depreciation and Amortization 4,607      
Operating Properties | Wyndham Worldwide        
Real Estate Properties [Line Items]        
Encumbrances 0      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Initial Cost [Abstract]        
Land 6,200      
Building and Improvements 91,153      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Cost Capitalized Subsequent to Acquisition [Abstract]        
Building and Improvements 1,171      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Land 6,200      
Building and Improvements 92,324      
Total 98,524      
Accumulated Depreciation and Amortization 16,350      
Operating Properties | ACE Hardware Corporation HQ        
Real Estate Properties [Line Items]        
Encumbrances 22,750      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Initial Cost [Abstract]        
Land 6,900      
Building and Improvements 33,945      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Cost Capitalized Subsequent to Acquisition [Abstract]        
Building and Improvements 0      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Land 6,900      
Building and Improvements 33,945      
Total 40,845      
Accumulated Depreciation and Amortization 7,392      
Operating Properties | Equifax        
Real Estate Properties [Line Items]        
Encumbrances 0      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Initial Cost [Abstract]        
Land 1,850      
Building and Improvements 12,709      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Cost Capitalized Subsequent to Acquisition [Abstract]        
Building and Improvements 194      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Land 1,850      
Building and Improvements 12,903      
Total 14,753      
Accumulated Depreciation and Amortization 3,913      
Operating Properties | American Express        
Real Estate Properties [Line Items]        
Encumbrances 0      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Initial Cost [Abstract]        
Land 15,000      
Building and Improvements 45,893      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Cost Capitalized Subsequent to Acquisition [Abstract]        
Building and Improvements 375      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Land 15,000      
Building and Improvements 46,268      
Total 61,268      
Accumulated Depreciation and Amortization 18,300      
Operating Properties | SoftBank        
Real Estate Properties [Line Items]        
Encumbrances 0      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Initial Cost [Abstract]        
Land 22,789      
Building and Improvements 68,950      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Cost Capitalized Subsequent to Acquisition [Abstract]        
Building and Improvements 4,231      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Land 22,789      
Building and Improvements 73,181      
Total 95,970      
Accumulated Depreciation and Amortization 22,758      
Operating Properties | Vanguard        
Real Estate Properties [Line Items]        
Encumbrances 0      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Initial Cost [Abstract]        
Land 2,230      
Building and Improvements 31,062      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Cost Capitalized Subsequent to Acquisition [Abstract]        
Building and Improvements 0      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Land 2,230      
Building and Improvements 31,062      
Total 33,292      
Accumulated Depreciation and Amortization 7,152      
Operating Properties | Parallon        
Real Estate Properties [Line Items]        
Encumbrances 7,120      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Initial Cost [Abstract]        
Land 1,000      
Building and Improvements 16,772      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Cost Capitalized Subsequent to Acquisition [Abstract]        
Building and Improvements 0      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Land 1,000      
Building and Improvements 16,772      
Total 17,772      
Accumulated Depreciation and Amortization 3,828      
Operating Properties | TW Telecom        
Real Estate Properties [Line Items]        
Encumbrances 0      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Initial Cost [Abstract]        
Land 10,554      
Building and Improvements 35,817      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Cost Capitalized Subsequent to Acquisition [Abstract]        
Building and Improvements 1,474      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Land 10,554      
Building and Improvements 37,291      
Total 47,845      
Accumulated Depreciation and Amortization 9,166      
Operating Properties | Equifax II        
Real Estate Properties [Line Items]        
Encumbrances 0      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Initial Cost [Abstract]        
Land 2,200      
Building and Improvements 12,755      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Cost Capitalized Subsequent to Acquisition [Abstract]        
Building and Improvements 70      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Land 2,200      
Building and Improvements 12,825      
Total 15,025      
Accumulated Depreciation and Amortization 3,288      
Operating Properties | Mason I        
Real Estate Properties [Line Items]        
Encumbrances 0      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Initial Cost [Abstract]        
Land 4,777      
Building and Improvements 18,489      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Cost Capitalized Subsequent to Acquisition [Abstract]        
Building and Improvements 0      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Land 4,777      
Building and Improvements 18,489      
Total 23,266      
Accumulated Depreciation and Amortization 2,380      
Operating Properties | Wells Fargo.        
Real Estate Properties [Line Items]        
Encumbrances 26,975      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Initial Cost [Abstract]        
Land 2,150      
Building and Improvements 40,806      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Cost Capitalized Subsequent to Acquisition [Abstract]        
Building and Improvements 46      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Land 2,150      
Building and Improvements 40,852      
Total 43,002      
Accumulated Depreciation and Amortization 8,128      
Operating Properties | GE Aviation        
Real Estate Properties [Line Items]        
Encumbrances 0      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Initial Cost [Abstract]        
Land 4,400      
Building and Improvements 61,681      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Cost Capitalized Subsequent to Acquisition [Abstract]        
Building and Improvements 0      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Land 4,400      
Building and Improvements 61,681      
Total 66,081      
Accumulated Depreciation and Amortization 14,077      
Operating Properties | Westgate III        
Real Estate Properties [Line Items]        
Encumbrances 0      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Initial Cost [Abstract]        
Land 3,209      
Building and Improvements 75,937      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Cost Capitalized Subsequent to Acquisition [Abstract]        
Building and Improvements 0      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Land 3,209      
Building and Improvements 75,937      
Total 79,146      
Accumulated Depreciation and Amortization 13,333      
Operating Properties | 2275 Cabot Drive        
Real Estate Properties [Line Items]        
Encumbrances 0      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Initial Cost [Abstract]        
Land 2,788      
Building and Improvements 16,200      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Cost Capitalized Subsequent to Acquisition [Abstract]        
Building and Improvements 53      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Land 2,788      
Building and Improvements 16,253      
Total 19,041      
Accumulated Depreciation and Amortization 6,276      
Operating Properties | Franklin Center        
Real Estate Properties [Line Items]        
Encumbrances 0      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Initial Cost [Abstract]        
Land 6,989      
Building and Improvements 46,875      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Cost Capitalized Subsequent to Acquisition [Abstract]        
Building and Improvements 1,386      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Land 6,989      
Building and Improvements 48,261      
Total 55,250      
Accumulated Depreciation and Amortization 8,403      
Operating Properties | 4650 Lakehurst Court        
Real Estate Properties [Line Items]        
Encumbrances 0      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Initial Cost [Abstract]        
Land 2,943      
Building and Improvements 22,651      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Cost Capitalized Subsequent to Acquisition [Abstract]        
Building and Improvements 808      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Land 2,943      
Building and Improvements 23,459      
Total 26,402      
Accumulated Depreciation and Amortization 6,781      
Operating Properties | Miramar        
Real Estate Properties [Line Items]        
Encumbrances 0      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Initial Cost [Abstract]        
Land 4,488      
Building and Improvements 19,979      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Cost Capitalized Subsequent to Acquisition [Abstract]        
Building and Improvements 2,221      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Land 4,488      
Building and Improvements 22,200      
Total 26,688      
Accumulated Depreciation and Amortization 4,268      
Operating Properties | Royal Ridge V        
Real Estate Properties [Line Items]        
Encumbrances 21,385      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Initial Cost [Abstract]        
Land 1,842      
Building and Improvements 22,052      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Cost Capitalized Subsequent to Acquisition [Abstract]        
Building and Improvements 3,622      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Land 1,842      
Building and Improvements 25,674      
Total 27,516      
Accumulated Depreciation and Amortization 4,373      
Operating Properties | Duke Bridges        
Real Estate Properties [Line Items]        
Encumbrances 27,475      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Initial Cost [Abstract]        
Land 8,239      
Building and Improvements 51,395      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Cost Capitalized Subsequent to Acquisition [Abstract]        
Building and Improvements 7,458      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Land 8,239      
Building and Improvements 58,853      
Total 67,092      
Accumulated Depreciation and Amortization 9,221      
Operating Properties | Houston Westway II        
Real Estate Properties [Line Items]        
Encumbrances 0      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Initial Cost [Abstract]        
Land 3,961      
Building and Improvements 78,668      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Cost Capitalized Subsequent to Acquisition [Abstract]        
Building and Improvements 507      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Land 3,961      
Building and Improvements 79,175      
Total 83,136      
Accumulated Depreciation and Amortization 17,452      
Operating Properties | Houston Westway I        
Real Estate Properties [Line Items]        
Encumbrances 0      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Initial Cost [Abstract]        
Land 6,540      
Building and Improvements 30,703      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Cost Capitalized Subsequent to Acquisition [Abstract]        
Building and Improvements (15,039)      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Land 3,382      
Building and Improvements 18,822      
Total 22,204      
Accumulated Depreciation and Amortization 6,104      
Operating Properties | Atlanta Perimeter        
Real Estate Properties [Line Items]        
Encumbrances 69,461      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Initial Cost [Abstract]        
Land 8,382      
Building and Improvements 96,718      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Cost Capitalized Subsequent to Acquisition [Abstract]        
Building and Improvements 679      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Land 8,382      
Building and Improvements 97,397      
Total 105,779      
Accumulated Depreciation and Amortization 25,393      
Operating Properties | South Lake at Dulles        
Real Estate Properties [Line Items]        
Encumbrances 0      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Initial Cost [Abstract]        
Land 9,666      
Building and Improvements 74,098      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Cost Capitalized Subsequent to Acquisition [Abstract]        
Building and Improvements 2,814      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Land 9,666      
Building and Improvements 76,912      
Total 86,578      
Accumulated Depreciation and Amortization 15,410      
Operating Properties | Four Parkway        
Real Estate Properties [Line Items]        
Encumbrances 0      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Initial Cost [Abstract]        
Land 4,339      
Building and Improvements 37,298      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Cost Capitalized Subsequent to Acquisition [Abstract]        
Building and Improvements 2,692      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Land 4,339      
Building and Improvements 39,990      
Total 44,329      
Accumulated Depreciation and Amortization 10,514      
Operating Properties | Highway 94        
Real Estate Properties [Line Items]        
Encumbrances 15,610      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Initial Cost [Abstract]        
Land 5,637      
Building and Improvements 25,280      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Cost Capitalized Subsequent to Acquisition [Abstract]        
Building and Improvements 0      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Land 5,637      
Building and Improvements 25,280      
Total 30,917      
Accumulated Depreciation and Amortization 5,080      
Operating Properties | Heritage IV        
Real Estate Properties [Line Items]        
Encumbrances 0      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Initial Cost [Abstract]        
Land 2,330      
Building and Improvements 26,376      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Cost Capitalized Subsequent to Acquisition [Abstract]        
Building and Improvements 0      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Land 2,330      
Building and Improvements 26,376      
Total 28,706      
Accumulated Depreciation and Amortization 5,328      
Operating Properties | Samsonite        
Real Estate Properties [Line Items]        
Encumbrances 21,154      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Initial Cost [Abstract]        
Land 5,040      
Building and Improvements 42,490      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Cost Capitalized Subsequent to Acquisition [Abstract]        
Building and Improvements 0      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Land 5,040      
Building and Improvements 42,490      
Total 47,530      
Accumulated Depreciation and Amortization 6,183      
Operating Properties | Restoration Hardware        
Real Estate Properties [Line Items]        
Encumbrances 78,000      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Initial Cost [Abstract]        
Land 15,463      
Building and Improvements 36,613      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Cost Capitalized Subsequent to Acquisition [Abstract]        
Building and Improvements 37,693      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Land 15,463      
Building and Improvements 74,306      
Total 89,769      
Accumulated Depreciation and Amortization 14,996      
Operating Properties | HealthSpring        
Real Estate Properties [Line Items]        
Encumbrances 20,723      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Initial Cost [Abstract]        
Land 8,126      
Building and Improvements 31,447      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Cost Capitalized Subsequent to Acquisition [Abstract]        
Building and Improvements 0      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Land 8,126      
Building and Improvements 31,447      
Total 39,573      
Accumulated Depreciation and Amortization 5,478      
Operating Properties | LPL        
Real Estate Properties [Line Items]        
Encumbrances 0      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Initial Cost [Abstract]        
Land 4,612      
Building and Improvements 86,352      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Cost Capitalized Subsequent to Acquisition [Abstract]        
Building and Improvements 0      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Land 4,612      
Building and Improvements 86,352      
Total 90,964      
Accumulated Depreciation and Amortization 5,283      
Operating Properties | LPL        
Real Estate Properties [Line Items]        
Encumbrances 0      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Initial Cost [Abstract]        
Land 1,274      
Building and Improvements 41,509      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Cost Capitalized Subsequent to Acquisition [Abstract]        
Building and Improvements 0      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Land 1,274      
Building and Improvements 41,509      
Total 42,783      
Accumulated Depreciation and Amortization 2,541      
Operating Properties | Quaker        
Real Estate Properties [Line Items]        
Encumbrances 0      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Initial Cost [Abstract]        
Land 5,433      
Building and Improvements 55,341      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Cost Capitalized Subsequent to Acquisition [Abstract]        
Building and Improvements 0      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Land 5,433      
Building and Improvements 55,341      
Total 60,774      
Accumulated Depreciation and Amortization 3,060      
Operating Properties | McKesson        
Real Estate Properties [Line Items]        
Encumbrances 0      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Initial Cost [Abstract]        
Land 312      
Building and Improvements 69,760      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Cost Capitalized Subsequent to Acquisition [Abstract]        
Building and Improvements 0      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Land 312      
Building and Improvements 69,760      
Total 70,072      
Accumulated Depreciation and Amortization $ 6,252      
Operating Properties | McKesson | Minimum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 5 years      
Operating Properties | McKesson | Maximum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 40 years      
Operating Properties | Shaw Industries        
Real Estate Properties [Line Items]        
Encumbrances $ 0      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Initial Cost [Abstract]        
Land 5,465      
Building and Improvements 57,116      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Cost Capitalized Subsequent to Acquisition [Abstract]        
Building and Improvements 0      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Land 5,465      
Building and Improvements 57,116      
Total 62,581      
Accumulated Depreciation and Amortization $ 2,957      
Operating Properties | Shaw Industries | Minimum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 5 years      
Operating Properties | Shaw Industries | Maximum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 40 years      
Operating Properties | GEAR Entities        
Real Estate Properties [Line Items]        
Encumbrances $ 0      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Initial Cost [Abstract]        
Land 1,584      
Building and Improvements 0      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Cost Capitalized Subsequent to Acquisition [Abstract]        
Building and Improvements 0      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Land 1,584      
Building and Improvements 0      
Total 1,584      
Accumulated Depreciation and Amortization $ 0      
Operating Properties | GEAR Entities | Minimum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 5 years      
Operating Properties | GEAR Entities | Maximum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 40 years      
Operating Properties | Owens Corning        
Real Estate Properties [Line Items]        
Encumbrances $ 3,300      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Initial Cost [Abstract]        
Land 867      
Building and Improvements 4,418      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Cost Capitalized Subsequent to Acquisition [Abstract]        
Building and Improvements 555      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Land 867      
Building and Improvements 4,973      
Total 5,840      
Accumulated Depreciation and Amortization $ 200      
Operating Properties | Owens Corning | Minimum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 5 years      
Operating Properties | Owens Corning | Maximum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 40 years      
Operating Properties | Westgate II        
Real Estate Properties [Line Items]        
Encumbrances $ 34,200      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Initial Cost [Abstract]        
Land 7,716      
Building and Improvements 48,422      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Cost Capitalized Subsequent to Acquisition [Abstract]        
Building and Improvements 870      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Land 7,716      
Building and Improvements 49,292      
Total 57,008      
Accumulated Depreciation and Amortization $ 2,023      
Operating Properties | Westgate II | Minimum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 5 years      
Operating Properties | Westgate II | Maximum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 40 years      
Operating Properties | Administrative Office of Pennsylvania Courts        
Real Estate Properties [Line Items]        
Encumbrances $ 6,070      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Initial Cost [Abstract]        
Land 1,246      
Building and Improvements 9,626      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Cost Capitalized Subsequent to Acquisition [Abstract]        
Building and Improvements 498      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Land 1,246      
Building and Improvements 10,124      
Total 11,370      
Accumulated Depreciation and Amortization $ 390      
Operating Properties | Administrative Office of Pennsylvania Courts | Minimum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 5 years      
Operating Properties | Administrative Office of Pennsylvania Courts | Maximum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 40 years      
Operating Properties | American Express Center        
Real Estate Properties [Line Items]        
Encumbrances $ 54,900      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Initial Cost [Abstract]        
Land 10,595      
Building and Improvements 82,098      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Cost Capitalized Subsequent to Acquisition [Abstract]        
Building and Improvements 3,109      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Land 10,595      
Building and Improvements 85,207      
Total 95,802      
Accumulated Depreciation and Amortization $ 3,962      
Operating Properties | American Express Center | Minimum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 5 years      
Operating Properties | American Express Center | Maximum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 40 years      
Operating Properties | MGM Corporate Center        
Real Estate Properties [Line Items]        
Encumbrances $ 18,180      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Initial Cost [Abstract]        
Land 4,546      
Building and Improvements 25,825      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Cost Capitalized Subsequent to Acquisition [Abstract]        
Building and Improvements 1,076      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Land 4,546      
Building and Improvements 26,901      
Total 31,447      
Accumulated Depreciation and Amortization $ 1,123      
Operating Properties | MGM Corporate Center | Minimum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 5 years      
Operating Properties | MGM Corporate Center | Maximum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 40 years      
Operating Properties | American Showa        
Real Estate Properties [Line Items]        
Encumbrances $ 10,320      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Initial Cost [Abstract]        
Land 1,214      
Building and Improvements 16,538      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Cost Capitalized Subsequent to Acquisition [Abstract]        
Building and Improvements 2,427      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Land 1,214      
Building and Improvements 18,965      
Total 20,179      
Accumulated Depreciation and Amortization $ 637      
Operating Properties | American Showa | Minimum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 5 years      
Operating Properties | American Showa | Maximum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 40 years      
Operating Properties | Huntington Ingalls        
Real Estate Properties [Line Items]        
Encumbrances $ 0      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Initial Cost [Abstract]        
Land 6,213      
Building and Improvements 29,219      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Cost Capitalized Subsequent to Acquisition [Abstract]        
Building and Improvements 2,651      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Land 6,213      
Building and Improvements 31,870      
Total 38,083      
Accumulated Depreciation and Amortization $ 1,087      
Operating Properties | Huntington Ingalls | Minimum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 5 years      
Operating Properties | Huntington Ingalls | Maximum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 40 years      
Operating Properties | Wyndham        
Real Estate Properties [Line Items]        
Encumbrances $ 0      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Initial Cost [Abstract]        
Land 9,677      
Building and Improvements 71,316      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Cost Capitalized Subsequent to Acquisition [Abstract]        
Building and Improvements 1,742      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Land 9,677      
Building and Improvements 73,058      
Total 82,735      
Accumulated Depreciation and Amortization $ 2,276      
Operating Properties | Wyndham | Minimum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 5 years      
Operating Properties | Wyndham | Maximum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 40 years      
Operating Properties | Exel        
Real Estate Properties [Line Items]        
Encumbrances $ 0      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Initial Cost [Abstract]        
Land 978      
Building and Improvements 14,137      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Cost Capitalized Subsequent to Acquisition [Abstract]        
Building and Improvements 2,568      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Land 978      
Building and Improvements 16,705      
Total 17,683      
Accumulated Depreciation and Amortization $ 778      
Operating Properties | Exel | Minimum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 5 years      
Operating Properties | Exel | Maximum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 40 years      
Operating Properties | Morpho Detection        
Real Estate Properties [Line Items]        
Encumbrances $ 0      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Initial Cost [Abstract]        
Land 2,006      
Building and Improvements 10,270      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Cost Capitalized Subsequent to Acquisition [Abstract]        
Building and Improvements 484      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Land 2,006      
Building and Improvements 10,754      
Total 12,760      
Accumulated Depreciation and Amortization $ 406      
Operating Properties | Morpho Detection | Minimum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 5 years      
Operating Properties | Morpho Detection | Maximum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 40 years      
Operating Properties | Aetna        
Real Estate Properties [Line Items]        
Encumbrances $ 0      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Initial Cost [Abstract]        
Land 2,332      
Building and Improvements 18,486      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Cost Capitalized Subsequent to Acquisition [Abstract]        
Building and Improvements 1,598      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Land 2,332      
Building and Improvements 20,084      
Total 22,416      
Accumulated Depreciation and Amortization $ 803      
Operating Properties | Aetna | Minimum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 5 years      
Operating Properties | Aetna | Maximum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 40 years      
Operating Properties | Bank of America I        
Real Estate Properties [Line Items]        
Encumbrances $ 0      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Initial Cost [Abstract]        
Land 5,737      
Building and Improvements 22,479      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Cost Capitalized Subsequent to Acquisition [Abstract]        
Building and Improvements 1,318      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Land 5,737      
Building and Improvements 23,797      
Total 29,534      
Accumulated Depreciation and Amortization $ 1,332      
Operating Properties | Bank of America I | Minimum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 5 years      
Operating Properties | Bank of America I | Maximum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 40 years      
Operating Properties | Bank of America II        
Real Estate Properties [Line Items]        
Encumbrances $ 0      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Initial Cost [Abstract]        
Land 5,735      
Building and Improvements 15,461      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Cost Capitalized Subsequent to Acquisition [Abstract]        
Building and Improvements 2,217      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Land 5,735      
Building and Improvements 17,678      
Total 23,413      
Accumulated Depreciation and Amortization $ 2,498      
Operating Properties | Bank of America II | Minimum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 5 years      
Operating Properties | Bank of America II | Maximum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 40 years      
Operating Properties | Atlas Copco        
Real Estate Properties [Line Items]        
Encumbrances $ 0      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Initial Cost [Abstract]        
Land 1,156      
Building and Improvements 18,297      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Cost Capitalized Subsequent to Acquisition [Abstract]        
Building and Improvements 1,505      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Land 1,156      
Building and Improvements 19,802      
Total 20,958      
Accumulated Depreciation and Amortization $ 693      
Operating Properties | Atlas Copco | Minimum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 5 years      
Operating Properties | Atlas Copco | Maximum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 40 years      
Operating Properties | Toshiba TEC        
Real Estate Properties [Line Items]        
Encumbrances $ 0      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Initial Cost [Abstract]        
Land 1,916      
Building and Improvements 36,374      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Cost Capitalized Subsequent to Acquisition [Abstract]        
Building and Improvements 2,423      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Land 1,916      
Building and Improvements 38,797      
Total 40,713      
Accumulated Depreciation and Amortization $ 1,301      
Operating Properties | Toshiba TEC | Minimum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 5 years      
Operating Properties | Toshiba TEC | Maximum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 40 years      
Operating Properties | NETGEAR        
Real Estate Properties [Line Items]        
Encumbrances $ 0      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Initial Cost [Abstract]        
Land 22,600      
Building and Improvements 28,859      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Cost Capitalized Subsequent to Acquisition [Abstract]        
Building and Improvements 1,700      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Land 22,600      
Building and Improvements 30,559      
Total 53,159      
Accumulated Depreciation and Amortization $ 1,521      
Operating Properties | NETGEAR | Minimum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 5 years      
Operating Properties | NETGEAR | Maximum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 40 years      
Operating Properties | Nike        
Real Estate Properties [Line Items]        
Encumbrances $ 0      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Initial Cost [Abstract]        
Land 8,186      
Building and Improvements 41,184      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Cost Capitalized Subsequent to Acquisition [Abstract]        
Building and Improvements 2,164      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Land 8,186      
Building and Improvements 43,348      
Total 51,534      
Accumulated Depreciation and Amortization $ 3,132      
Operating Properties | Nike | Minimum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 5 years      
Operating Properties | Nike | Maximum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 40 years      
Operating Properties | Zebra Technologies        
Real Estate Properties [Line Items]        
Encumbrances $ 0      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Initial Cost [Abstract]        
Land 5,927      
Building and Improvements 58,688      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Cost Capitalized Subsequent to Acquisition [Abstract]        
Building and Improvements 1,234      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Land 5,927      
Building and Improvements 59,922      
Total 65,849      
Accumulated Depreciation and Amortization $ 2,472      
Operating Properties | Zebra Technologies | Minimum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 5 years      
Operating Properties | Zebra Technologies | Maximum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 40 years      
Operating Properties | WABCO        
Real Estate Properties [Line Items]        
Encumbrances $ 0      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Initial Cost [Abstract]        
Land 1,226      
Building and Improvements 13,902      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Cost Capitalized Subsequent to Acquisition [Abstract]        
Building and Improvements 779      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Land 1,226      
Building and Improvements 14,681      
Total 15,907      
Accumulated Depreciation and Amortization $ 345      
Operating Properties | WABCO | Minimum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 5 years      
Operating Properties | WABCO | Maximum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 40 years      
Operating Properties | IGT        
Real Estate Properties [Line Items]        
Encumbrances $ 45,300      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Initial Cost [Abstract]        
Land 5,673      
Building and Improvements 67,610      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Cost Capitalized Subsequent to Acquisition [Abstract]        
Building and Improvements 2,021      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Land 5,673      
Building and Improvements 69,631      
Total 75,304      
Accumulated Depreciation and Amortization $ 1,804      
Operating Properties | IGT | Minimum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 5 years      
Operating Properties | IGT | Maximum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 40 years      
Operating Properties | 3M        
Real Estate Properties [Line Items]        
Encumbrances $ 43,600      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Initial Cost [Abstract]        
Land 5,802      
Building and Improvements 75,758      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Cost Capitalized Subsequent to Acquisition [Abstract]        
Building and Improvements 6,391      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Land 5,802      
Building and Improvements 82,149      
Total 87,951      
Accumulated Depreciation and Amortization $ 1,759      
Operating Properties | 3M | Minimum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 5 years      
Operating Properties | 3M | Maximum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 40 years      
Operating Properties | Amazon        
Real Estate Properties [Line Items]        
Encumbrances $ 61,500      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Initial Cost [Abstract]        
Land 4,773      
Building and Improvements 95,475      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Cost Capitalized Subsequent to Acquisition [Abstract]        
Building and Improvements 11,546      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Land 4,773      
Building and Improvements 107,021      
Total 111,794      
Accumulated Depreciation and Amortization $ 2,725      
Operating Properties | Amazon | Minimum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 5 years      
Operating Properties | Amazon | Maximum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 40 years      
Operating Properties | Zoetis        
Real Estate Properties [Line Items]        
Encumbrances $ 0      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Initial Cost [Abstract]        
Land 3,718      
Building and Improvements 44,082      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Cost Capitalized Subsequent to Acquisition [Abstract]        
Building and Improvements 735      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Land 3,718      
Building and Improvements 44,817      
Total 48,535      
Accumulated Depreciation and Amortization $ 1,310      
Operating Properties | Zoetis | Minimum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 5 years      
Operating Properties | Zoetis | Maximum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 40 years      
Operating Properties | Southern Company        
Real Estate Properties [Line Items]        
Encumbrances $ 99,600      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Initial Cost [Abstract]        
Land 7,794      
Building and Improvements 157,724      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Cost Capitalized Subsequent to Acquisition [Abstract]        
Building and Improvements 1,457      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Land 7,794      
Building and Improvements 159,181      
Total 166,975      
Accumulated Depreciation and Amortization $ 3,051      
Life on which depreciation in latest income statement is computed 38 years      
Operating Properties | Allstate        
Real Estate Properties [Line Items]        
Encumbrances $ 0      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Initial Cost [Abstract]        
Land 3,109      
Building and Improvements 13,096      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Cost Capitalized Subsequent to Acquisition [Abstract]        
Building and Improvements 553      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Land 3,109      
Building and Improvements 13,649      
Total 16,758      
Accumulated Depreciation and Amortization $ 487      
Operating Properties | Allstate | Minimum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 5 years      
Operating Properties | Allstate | Maximum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 40 years      
Operating Properties | MISO        
Real Estate Properties [Line Items]        
Encumbrances $ 0      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Initial Cost [Abstract]        
Land 3,725      
Building and Improvements 25,848      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Cost Capitalized Subsequent to Acquisition [Abstract]        
Building and Improvements 971      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Land 3,725      
Building and Improvements 26,819      
Total 30,544      
Accumulated Depreciation and Amortization $ 831      
Operating Properties | MISO | Minimum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 5 years      
Operating Properties | MISO | Maximum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 40 years      
Operating Properties | McKesson II        
Real Estate Properties [Line Items]        
Encumbrances $ 0      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Initial Cost [Abstract]        
Land 0      
Building and Improvements 36,959      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Cost Capitalized Subsequent to Acquisition [Abstract]        
Building and Improvements 4,681      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Land 0      
Building and Improvements 41,640      
Total 41,640      
Accumulated Depreciation and Amortization $ 561      
Operating Properties | McKesson II | Minimum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 5 years      
Operating Properties | McKesson II | Maximum        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Life on which depreciation in latest income statement is computed 40 years      
Operating Properties | Others        
Real Estate Properties [Line Items]        
Encumbrances $ 0      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Initial Cost [Abstract]        
Land 0      
Building and Improvements 0      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Cost Capitalized Subsequent to Acquisition [Abstract]        
Building and Improvements 95      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Investment Property, Net [Abstract]        
Land 0      
Building and Improvements 95      
Total 95      
Accumulated Depreciation and Amortization $ 10