Schedule III - Real Estate and Accumulated Depreciation and Amortization Part 4 (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Schedule Of Investments In Real Estate [Line Items]
Total Investment in Real Estate	$ 1,043,106	$ 970,964	$ 782,166	$ 783,233
CONNECTICUT [Member] | Accumulated Depreciation And Amortization Description [Member] | Bridgeport Three [Member]
Schedule Of Investments In Real Estate [Line Items]
Initial Cost of Leasehold or Acquisition Investment to Company	350
Cost Capitalized Subsequent to Initial Investment	330
Land	228
Building and Improvements	452
Total Investment in Real Estate	680
Accumulated Depreciation and Amortization	$ 268
Date of Initial Leasehold or Acquisition Investment	1985
CONNECTICUT [Member] | Accumulated Depreciation And Amortization Description [Member] | Bridgeport Four [Member]
Schedule Of Investments In Real Estate [Line Items]
Initial Cost of Leasehold or Acquisition Investment to Company	$ 377
Cost Capitalized Subsequent to Initial Investment	391
Land	246
Building and Improvements	522
Total Investment in Real Estate	768
Accumulated Depreciation and Amortization	$ 326
Date of Initial Leasehold or Acquisition Investment	1985
CONNECTICUT [Member] | Accumulated Depreciation And Amortization Description [Member] | Bristol One [Member]
Schedule Of Investments In Real Estate [Line Items]
Initial Cost of Leasehold or Acquisition Investment to Company	$ 1,594
Land	1,036
Building and Improvements	558
Total Investment in Real Estate	1,594
Accumulated Depreciation and Amortization	$ 316
Date of Initial Leasehold or Acquisition Investment	2004
CONNECTICUT [Member] | Accumulated Depreciation And Amortization Description [Member] | Brookfield One [Member]
Schedule Of Investments In Real Estate [Line Items]
Initial Cost of Leasehold or Acquisition Investment to Company	$ 58
Cost Capitalized Subsequent to Initial Investment	432
Land	20
Building and Improvements	470
Total Investment in Real Estate	490
Accumulated Depreciation and Amortization	$ 305
Date of Initial Leasehold or Acquisition Investment	1985
CONNECTICUT [Member] | Accumulated Depreciation And Amortization Description [Member] | Darien One [Member]
Schedule Of Investments In Real Estate [Line Items]
Initial Cost of Leasehold or Acquisition Investment to Company	$ 667
Cost Capitalized Subsequent to Initial Investment	285
Land	434
Building and Improvements	518
Total Investment in Real Estate	952
Accumulated Depreciation and Amortization	$ 424
Date of Initial Leasehold or Acquisition Investment	1985
CONNECTICUT [Member] | Accumulated Depreciation And Amortization Description [Member] | Durham Two [Member]
Schedule Of Investments In Real Estate [Line Items]
Initial Cost of Leasehold or Acquisition Investment to Company	$ 994
Building and Improvements	994
Total Investment in Real Estate	994
Accumulated Depreciation and Amortization	$ 994
Date of Initial Leasehold or Acquisition Investment	2004