Schedule III - Real Estate and Accumulated Depreciation and Amortization Part 5 (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Schedule Of Investments In Real Estate [Line Items]
Total Investment in Real Estate	$ 970,964	$ 782,166	$ 783,233	$ 595,959
Accumulated Depreciation And Amortization Description [Member]
Schedule Of Investments In Real Estate [Line Items]
Initial Cost of Leasehold or Acquisition Investment to Company	914,488
Cost Capitalized Subsequent to Initial Investment	56,476
Land	589,497
Building and Improvements	381,467
Total Investment in Real Estate	970,964
Accumulated Depreciation and Amortization	133,353
CONNECTICUT [Member] | Accumulated Depreciation And Amortization Description [Member] | Farmington One [Member]
Schedule Of Investments In Real Estate [Line Items]
Initial Cost of Leasehold or Acquisition Investment to Company	466
Land	303
Building and Improvements	163
Total Investment in Real Estate	466
Accumulated Depreciation and Amortization	$ 86
Date of Initial Leasehold or Acquisition Investment	2004
CONNECTICUT [Member] | Accumulated Depreciation And Amortization Description [Member] | Franklin One [Member]
Schedule Of Investments In Real Estate [Line Items]
Initial Cost of Leasehold or Acquisition Investment to Company	$ 51
Cost Capitalized Subsequent to Initial Investment	447
Land	20
Building and Improvements	478
Total Investment in Real Estate	498
Accumulated Depreciation and Amortization	$ 284
Date of Initial Leasehold or Acquisition Investment	1982
CONNECTICUT [Member] | Accumulated Depreciation And Amortization Description [Member] | Hartford One [Member]
Schedule Of Investments In Real Estate [Line Items]
Initial Cost of Leasehold or Acquisition Investment to Company	$ 571
Land	371
Building and Improvements	200
Total Investment in Real Estate	571
Accumulated Depreciation and Amortization	$ 105
Date of Initial Leasehold or Acquisition Investment	2004