Schedule III - Real Estate and Accumulated Depreciation and Amortization Part 7 (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Schedule Of Investments In Real Estate [Line Items]
Total Investment in Real Estate	$ 782,166	$ 783,233	$ 595,959	$ 570,275
Accumulated Depreciation And Amortization Description [Member]
Schedule Of Investments In Real Estate [Line Items]
Initial Cost of Leasehold or Acquisition Investment to Company	720,099
Cost Capitalized Subsequent to Initial Investment	62,067
Land	474,232
Building and Improvements	307,934
Total Investment in Real Estate	782,166
Accumulated Depreciation and Amortization	120,576
CONNECTICUT | Accumulated Depreciation And Amortization Description [Member] | Waterbury One [Member]
Schedule Of Investments In Real Estate [Line Items]
Initial Cost of Leasehold or Acquisition Investment to Company	469
Land	305
Building and Improvements	164
Total Investment in Real Estate	469
Accumulated Depreciation and Amortization	$ 80
Date of Initial Leasehold or Acquisition Investment	2004
CONNECTICUT | Accumulated Depreciation And Amortization Description [Member] | Waterbury Two [Member]
Schedule Of Investments In Real Estate [Line Items]
Initial Cost of Leasehold or Acquisition Investment to Company	$ 515
Land	335
Building and Improvements	180
Total Investment in Real Estate	515
Accumulated Depreciation and Amortization	$ 88
Date of Initial Leasehold or Acquisition Investment	2004
CONNECTICUT | Accumulated Depreciation And Amortization Description [Member] | Waterbury Three [Member]
Schedule Of Investments In Real Estate [Line Items]
Initial Cost of Leasehold or Acquisition Investment to Company	$ 804
Land	516
Building and Improvements	288
Total Investment in Real Estate	804
Accumulated Depreciation and Amortization	$ 145
Date of Initial Leasehold or Acquisition Investment	2004
CONNECTICUT | Accumulated Depreciation And Amortization Description [Member] | Watertown Five [Member]
Schedule Of Investments In Real Estate [Line Items]
Initial Cost of Leasehold or Acquisition Investment to Company	$ 352
Cost Capitalized Subsequent to Initial Investment	343
Land	204
Building and Improvements	491
Total Investment in Real Estate	695
Accumulated Depreciation and Amortization	$ 215
Date of Initial Leasehold or Acquisition Investment	1992
CONNECTICUT | Accumulated Depreciation And Amortization Description [Member] | Watertown Six [Member]
Schedule Of Investments In Real Estate [Line Items]
Initial Cost of Leasehold or Acquisition Investment to Company	$ 925
Land	567
Building and Improvements	358
Total Investment in Real Estate	925
Accumulated Depreciation and Amortization	$ 201
Date of Initial Leasehold or Acquisition Investment	2004
CONNECTICUT | Accumulated Depreciation And Amortization Description [Member] | West Haven One [Member]
Schedule Of Investments In Real Estate [Line Items]
Initial Cost of Leasehold or Acquisition Investment to Company	$ 185
Cost Capitalized Subsequent to Initial Investment	322
Land	74
Building and Improvements	433
Total Investment in Real Estate	507
Accumulated Depreciation and Amortization	$ 214
Date of Initial Leasehold or Acquisition Investment	1982
CONNECTICUT | Accumulated Depreciation And Amortization Description [Member] | West Haven Two [Member]
Schedule Of Investments In Real Estate [Line Items]
Initial Cost of Leasehold or Acquisition Investment to Company	$ 1,215
Land	790
Building and Improvements	425
Total Investment in Real Estate	1,215
Accumulated Depreciation and Amortization	$ 207
Date of Initial Leasehold or Acquisition Investment	2004
CONNECTICUT | Accumulated Depreciation And Amortization Description [Member] | Westbrook One [Member]
Schedule Of Investments In Real Estate [Line Items]
Initial Cost of Leasehold or Acquisition Investment to Company	$ 345
Building and Improvements	345
Total Investment in Real Estate	345
Accumulated Depreciation and Amortization	$ 345
Date of Initial Leasehold or Acquisition Investment	2004
CONNECTICUT | Accumulated Depreciation And Amortization Description [Member] | Westport One [Member]
Schedule Of Investments In Real Estate [Line Items]
Initial Cost of Leasehold or Acquisition Investment to Company	$ 604
Cost Capitalized Subsequent to Initial Investment	12
Land	393
Building and Improvements	223
Total Investment in Real Estate	616
Accumulated Depreciation and Amortization	$ 172
Date of Initial Leasehold or Acquisition Investment	1985
CONNECTICUT | Accumulated Depreciation And Amortization Description [Member] | Wethersfield One [Member]
Schedule Of Investments In Real Estate [Line Items]
Initial Cost of Leasehold or Acquisition Investment to Company	$ 447
Building and Improvements	447
Total Investment in Real Estate	447
Accumulated Depreciation and Amortization	$ 447
Date of Initial Leasehold or Acquisition Investment	2004
CONNECTICUT | Accumulated Depreciation And Amortization Description [Member] | Willimantic One [Member]
Schedule Of Investments In Real Estate [Line Items]
Initial Cost of Leasehold or Acquisition Investment to Company	$ 717
Land	466
Building and Improvements	251
Total Investment in Real Estate	717
Accumulated Depreciation and Amortization	$ 122
Date of Initial Leasehold or Acquisition Investment	2004
CONNECTICUT | Accumulated Depreciation And Amortization Description [Member] | Wilton One [Member]
Schedule Of Investments In Real Estate [Line Items]
Initial Cost of Leasehold or Acquisition Investment to Company	$ 519
Cost Capitalized Subsequent to Initial Investment	364
Land	338
Building and Improvements	545
Total Investment in Real Estate	883
Accumulated Depreciation and Amortization	$ 242
Date of Initial Leasehold or Acquisition Investment	1985
CONNECTICUT | Accumulated Depreciation And Amortization Description [Member] | Windsor Locks One [Member]
Schedule Of Investments In Real Estate [Line Items]
Initial Cost of Leasehold or Acquisition Investment to Company	$ 1,031
Land	670
Building and Improvements	361
Total Investment in Real Estate	1,031
Accumulated Depreciation and Amortization	$ 176
Date of Initial Leasehold or Acquisition Investment	2004
CONNECTICUT | Accumulated Depreciation And Amortization Description [Member] | Windsor Locks Two [Member]
Schedule Of Investments In Real Estate [Line Items]
Initial Cost of Leasehold or Acquisition Investment to Company	$ 1,434
Cost Capitalized Subsequent to Initial Investment	1,400
Land	1,055
Building and Improvements	1,779
Total Investment in Real Estate	2,834
Accumulated Depreciation and Amortization	$ 1,453
Date of Initial Leasehold or Acquisition Investment	2004
DISTRICT OF COLUMBIA | Accumulated Depreciation And Amortization Description [Member] | Washington One [Member]
Schedule Of Investments In Real Estate [Line Items]
Initial Cost of Leasehold or Acquisition Investment to Company	$ 848
Land	418
Building and Improvements	430
Total Investment in Real Estate	848
Accumulated Depreciation and Amortization	$ 79
Date of Initial Leasehold or Acquisition Investment	2013
DISTRICT OF COLUMBIA | Accumulated Depreciation And Amortization Description [Member] | Washington Two [Member]
Schedule Of Investments In Real Estate [Line Items]
Initial Cost of Leasehold or Acquisition Investment to Company	$ 941
Land	664
Building and Improvements	277
Total Investment in Real Estate	941
Accumulated Depreciation and Amortization	$ 58
Date of Initial Leasehold or Acquisition Investment	2013
FLORIDA | Accumulated Depreciation And Amortization Description [Member] | Orlando One [Member]
Schedule Of Investments In Real Estate [Line Items]
Initial Cost of Leasehold or Acquisition Investment to Company	$ 868
Cost Capitalized Subsequent to Initial Investment	33
Land	401
Building and Improvements	500
Total Investment in Real Estate	901
Accumulated Depreciation and Amortization	$ 333
Date of Initial Leasehold or Acquisition Investment	2000