Schedule III - Real Estate and Accumulated Depreciation and Amortization Part 9 (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Schedule Of Investments In Real Estate [Line Items]
Total Investment in Real Estate	$ 1,113,651	$ 1,043,106	$ 970,964	$ 782,166
Accumulated Depreciation And Amortization Description [Member]
Schedule Of Investments In Real Estate [Line Items]
Initial Cost of Leasehold or Acquisition Investment to Company	1,049,787
Cost Capitalized Subsequent to Initial Investment	63,864
Land	669,351
Building and Improvements	444,300
Total Investment in Real Estate	1,113,651
Accumulated Depreciation and Amortization	165,892
Accumulated Depreciation And Amortization Description [Member] | NEW YORK | East Hampton One [Member]
Schedule Of Investments In Real Estate [Line Items]
Initial Cost of Leasehold or Acquisition Investment to Company	660
Cost Capitalized Subsequent to Initial Investment	39
Land	428
Building and Improvements	271
Total Investment in Real Estate	699
Accumulated Depreciation and Amortization	$ 242
Date of Initial Leasehold or Acquisition Investment	1985
Accumulated Depreciation And Amortization Description [Member] | NEW YORK | East Meadow One [Member]
Schedule Of Investments In Real Estate [Line Items]
Cost Capitalized Subsequent to Initial Investment	$ 1,903
Land	1,670
Building and Improvements	233
Total Investment in Real Estate	1,903
Accumulated Depreciation and Amortization	$ 52
Date of Initial Leasehold or Acquisition Investment	1988
Accumulated Depreciation And Amortization Description [Member] | NEW YORK | East Pembroke [Member]
Schedule Of Investments In Real Estate [Line Items]
Initial Cost of Leasehold or Acquisition Investment to Company	$ 787
Land	537
Building and Improvements	250
Total Investment in Real Estate	787
Accumulated Depreciation and Amortization	$ 138
Date of Initial Leasehold or Acquisition Investment	2006
Accumulated Depreciation And Amortization Description [Member] | NEW YORK | Eastchester One [Member]
Schedule Of Investments In Real Estate [Line Items]
Initial Cost of Leasehold or Acquisition Investment to Company	$ 1,724
Cost Capitalized Subsequent to Initial Investment	993
Land	2,302
Building and Improvements	415
Total Investment in Real Estate	2,717
Accumulated Depreciation and Amortization	$ 68
Date of Initial Leasehold or Acquisition Investment	2011
Accumulated Depreciation And Amortization Description [Member] | NEW YORK | Elmont One [Member]
Schedule Of Investments In Real Estate [Line Items]
Initial Cost of Leasehold or Acquisition Investment to Company	$ 389
Cost Capitalized Subsequent to Initial Investment	319
Land	231
Building and Improvements	477
Total Investment in Real Estate	708
Accumulated Depreciation and Amortization	$ 357
Date of Initial Leasehold or Acquisition Investment	1978
Accumulated Depreciation And Amortization Description [Member] | NEW YORK | Elmsford One [Member]
Schedule Of Investments In Real Estate [Line Items]
Cost Capitalized Subsequent to Initial Investment	$ 948
Land	581
Building and Improvements	367
Total Investment in Real Estate	948
Accumulated Depreciation and Amortization	$ 268
Date of Initial Leasehold or Acquisition Investment	1971
Accumulated Depreciation And Amortization Description [Member] | NEW YORK | Elmsford Two [Member]
Schedule Of Investments In Real Estate [Line Items]
Initial Cost of Leasehold or Acquisition Investment to Company	$ 1,453
Land	1,453
Total Investment in Real Estate	$ 1,453
Date of Initial Leasehold or Acquisition Investment	2011
Accumulated Depreciation And Amortization Description [Member] | NEW YORK | Fishkill One [Member]
Schedule Of Investments In Real Estate [Line Items]
Initial Cost of Leasehold or Acquisition Investment to Company	$ 1,793
Land	1,793
Total Investment in Real Estate	$ 1,793
Date of Initial Leasehold or Acquisition Investment	2011
Accumulated Depreciation And Amortization Description [Member] | NEW YORK | Floral Park One [Member]
Schedule Of Investments In Real Estate [Line Items]
Initial Cost of Leasehold or Acquisition Investment to Company	$ 616
Cost Capitalized Subsequent to Initial Investment	170
Land	356
Building and Improvements	430
Total Investment in Real Estate	786
Accumulated Depreciation and Amortization	$ 302
Date of Initial Leasehold or Acquisition Investment	1998
Accumulated Depreciation And Amortization Description [Member] | NEW YORK | Flushing One [Member]
Schedule Of Investments In Real Estate [Line Items]
Initial Cost of Leasehold or Acquisition Investment to Company	$ 516
Cost Capitalized Subsequent to Initial Investment	241
Land	320
Building and Improvements	437
Total Investment in Real Estate	757
Accumulated Depreciation and Amortization	$ 290
Date of Initial Leasehold or Acquisition Investment	1998
Accumulated Depreciation And Amortization Description [Member] | NEW YORK | Flushing Two [Member]
Schedule Of Investments In Real Estate [Line Items]
Initial Cost of Leasehold or Acquisition Investment to Company	$ 1,947
Land	1,405
Building and Improvements	542
Total Investment in Real Estate	1,947
Accumulated Depreciation and Amortization	$ 191
Date of Initial Leasehold or Acquisition Investment	2013
Accumulated Depreciation And Amortization Description [Member] | NEW YORK | Flushing Three [Member]
Schedule Of Investments In Real Estate [Line Items]
Initial Cost of Leasehold or Acquisition Investment to Company	$ 2,478
Land	1,801
Building and Improvements	677
Total Investment in Real Estate	2,478
Accumulated Depreciation and Amortization	$ 239
Date of Initial Leasehold or Acquisition Investment	2013
Accumulated Depreciation And Amortization Description [Member] | NEW YORK | Flushing Four [Member]
Schedule Of Investments In Real Estate [Line Items]
Initial Cost of Leasehold or Acquisition Investment to Company	$ 1,936
Land	1,413
Building and Improvements	523
Total Investment in Real Estate	1,936
Accumulated Depreciation and Amortization	$ 200
Date of Initial Leasehold or Acquisition Investment	2013
Accumulated Depreciation And Amortization Description [Member] | NEW YORK | Forest Hills One [Member]
Schedule Of Investments In Real Estate [Line Items]
Initial Cost of Leasehold or Acquisition Investment to Company	$ 1,273
Land	1,273
Total Investment in Real Estate	$ 1,273
Date of Initial Leasehold or Acquisition Investment	2013
Accumulated Depreciation And Amortization Description [Member] | NEW YORK | Franklin Square One [Member]
Schedule Of Investments In Real Estate [Line Items]
Initial Cost of Leasehold or Acquisition Investment to Company	$ 153
Cost Capitalized Subsequent to Initial Investment	331
Land	137
Building and Improvements	347
Total Investment in Real Estate	484
Accumulated Depreciation and Amortization	$ 220
Date of Initial Leasehold or Acquisition Investment	1978
Accumulated Depreciation And Amortization Description [Member] | NEW YORK | Garden City One [Member]
Schedule Of Investments In Real Estate [Line Items]
Initial Cost of Leasehold or Acquisition Investment to Company	$ 362
Cost Capitalized Subsequent to Initial Investment	242
Land	236
Building and Improvements	368
Total Investment in Real Estate	604
Accumulated Depreciation and Amortization	$ 238
Date of Initial Leasehold or Acquisition Investment	1985
Accumulated Depreciation And Amortization Description [Member] | NEW YORK | Garnerville One [Member]
Schedule Of Investments In Real Estate [Line Items]
Initial Cost of Leasehold or Acquisition Investment to Company	$ 1,508
Land	1,508
Total Investment in Real Estate	$ 1,508
Date of Initial Leasehold or Acquisition Investment	2011
Accumulated Depreciation And Amortization Description [Member] | NEW YORK | Glen Head One [Member]
Schedule Of Investments In Real Estate [Line Items]
Initial Cost of Leasehold or Acquisition Investment to Company	$ 235
Cost Capitalized Subsequent to Initial Investment	216
Land	103
Building and Improvements	348
Total Investment in Real Estate	451
Accumulated Depreciation and Amortization	$ 348
Date of Initial Leasehold or Acquisition Investment	1982
Accumulated Depreciation And Amortization Description [Member] | NEW YORK | Glen Head Two [Member]
Schedule Of Investments In Real Estate [Line Items]
Initial Cost of Leasehold or Acquisition Investment to Company	$ 463
Cost Capitalized Subsequent to Initial Investment	282
Land	301
Building and Improvements	444
Total Investment in Real Estate	745
Accumulated Depreciation and Amortization	$ 305
Date of Initial Leasehold or Acquisition Investment	1985
Accumulated Depreciation And Amortization Description [Member] | NEW YORK | Great Neck One [Member]
Schedule Of Investments In Real Estate [Line Items]
Initial Cost of Leasehold or Acquisition Investment to Company	$ 500
Cost Capitalized Subsequent to Initial Investment	252
Land	450
Building and Improvements	302
Total Investment in Real Estate	752
Accumulated Depreciation and Amortization	$ 188
Date of Initial Leasehold or Acquisition Investment	1985
Accumulated Depreciation And Amortization Description [Member] | NEW YORK | Hartsdale One [Member]
Schedule Of Investments In Real Estate [Line Items]
Initial Cost of Leasehold or Acquisition Investment to Company	$ 1,626
Land	1,626
Total Investment in Real Estate	$ 1,626
Date of Initial Leasehold or Acquisition Investment	2011
Accumulated Depreciation And Amortization Description [Member] | NEW YORK | Hawthorne One [Member]
Schedule Of Investments In Real Estate [Line Items]
Initial Cost of Leasehold or Acquisition Investment to Company	$ 2,084
Land	2,084
Total Investment in Real Estate	$ 2,084
Date of Initial Leasehold or Acquisition Investment	2011
Accumulated Depreciation And Amortization Description [Member] | NEW YORK | Hopewell Junction One [Member]
Schedule Of Investments In Real Estate [Line Items]
Initial Cost of Leasehold or Acquisition Investment to Company	$ 1,163
Land	1,163
Total Investment in Real Estate	$ 1,163
Date of Initial Leasehold or Acquisition Investment	2011
Accumulated Depreciation And Amortization Description [Member] | NEW YORK | Huntington Station One [Member]
Schedule Of Investments In Real Estate [Line Items]
Initial Cost of Leasehold or Acquisition Investment to Company	$ 141
Cost Capitalized Subsequent to Initial Investment	284
Land	84
Building and Improvements	341
Total Investment in Real Estate	425
Accumulated Depreciation and Amortization	$ 225
Date of Initial Leasehold or Acquisition Investment	1978
Accumulated Depreciation And Amortization Description [Member] | NEW YORK | Hyde Park One [Member]
Schedule Of Investments In Real Estate [Line Items]
Initial Cost of Leasehold or Acquisition Investment to Company	$ 990
Land	990
Total Investment in Real Estate	$ 990
Date of Initial Leasehold or Acquisition Investment	2011
Accumulated Depreciation And Amortization Description [Member] | NEW YORK | Katonah One [Member]
Schedule Of Investments In Real Estate [Line Items]
Initial Cost of Leasehold or Acquisition Investment to Company	$ 1,084
Land	1,084
Total Investment in Real Estate	$ 1,084
Date of Initial Leasehold or Acquisition Investment	2011
Accumulated Depreciation And Amortization Description [Member] | NEW YORK | Lakeville One [Member]
Schedule Of Investments In Real Estate [Line Items]
Initial Cost of Leasehold or Acquisition Investment to Company	$ 1,028
Land	203
Building and Improvements	825
Total Investment in Real Estate	1,028
Accumulated Depreciation and Amortization	$ 557
Date of Initial Leasehold or Acquisition Investment	2008
Accumulated Depreciation And Amortization Description [Member] | NEW YORK | Levittown One [Member]
Schedule Of Investments In Real Estate [Line Items]
Initial Cost of Leasehold or Acquisition Investment to Company	$ 503
Cost Capitalized Subsequent to Initial Investment	42
Land	327
Building and Improvements	218
Total Investment in Real Estate	545
Accumulated Depreciation and Amortization	$ 196
Date of Initial Leasehold or Acquisition Investment	1985
Accumulated Depreciation And Amortization Description [Member] | NEW YORK | Levittown Two [Member]
Schedule Of Investments In Real Estate [Line Items]
Initial Cost of Leasehold or Acquisition Investment to Company	$ 547
Cost Capitalized Subsequent to Initial Investment	86
Land	356
Building and Improvements	277
Total Investment in Real Estate	633
Accumulated Depreciation and Amortization	$ 242
Date of Initial Leasehold or Acquisition Investment	1985
Accumulated Depreciation And Amortization Description [Member] | NEW YORK | Long Island City One [Member]
Schedule Of Investments In Real Estate [Line Items]
Initial Cost of Leasehold or Acquisition Investment to Company	$ 2,717
Land	1,183
Building and Improvements	1,534
Total Investment in Real Estate	2,717
Accumulated Depreciation and Amortization	$ 490
Date of Initial Leasehold or Acquisition Investment	2013
Accumulated Depreciation And Amortization Description [Member] | NEW YORK | Mamaroneck One [Member]
Schedule Of Investments In Real Estate [Line Items]
Initial Cost of Leasehold or Acquisition Investment to Company	$ 1,429
Land	1,429
Total Investment in Real Estate	$ 1,429
Date of Initial Leasehold or Acquisition Investment	2011
Accumulated Depreciation And Amortization Description [Member] | NEW YORK | Massapequa One [Member]
Schedule Of Investments In Real Estate [Line Items]
Initial Cost of Leasehold or Acquisition Investment to Company	$ 333
Cost Capitalized Subsequent to Initial Investment	285
Land	217
Building and Improvements	401
Total Investment in Real Estate	618
Accumulated Depreciation and Amortization	$ 259
Date of Initial Leasehold or Acquisition Investment	1985
Accumulated Depreciation And Amortization Description [Member] | NEW YORK | Mastic One [Member]
Schedule Of Investments In Real Estate [Line Items]
Initial Cost of Leasehold or Acquisition Investment to Company	$ 313
Cost Capitalized Subsequent to Initial Investment	110
Land	204
Building and Improvements	219
Total Investment in Real Estate	423
Accumulated Depreciation and Amortization	$ 206
Date of Initial Leasehold or Acquisition Investment	1985
Accumulated Depreciation And Amortization Description [Member] | NEW YORK | Middletown One [Member]
Schedule Of Investments In Real Estate [Line Items]
Initial Cost of Leasehold or Acquisition Investment to Company	$ 751
Cost Capitalized Subsequent to Initial Investment	274
Land	489
Building and Improvements	536
Total Investment in Real Estate	1,025
Accumulated Depreciation and Amortization	$ 383
Date of Initial Leasehold or Acquisition Investment	1985
Accumulated Depreciation And Amortization Description [Member] | NEW YORK | Middletown Two [Member]
Schedule Of Investments In Real Estate [Line Items]
Initial Cost of Leasehold or Acquisition Investment to Company	$ 1,281
Land	1,281
Total Investment in Real Estate	$ 1,281
Date of Initial Leasehold or Acquisition Investment	2011
Accumulated Depreciation And Amortization Description [Member] | NEW YORK | Middletown Three [Member]
Schedule Of Investments In Real Estate [Line Items]
Initial Cost of Leasehold or Acquisition Investment to Company	$ 719
Land	719
Total Investment in Real Estate	$ 719
Date of Initial Leasehold or Acquisition Investment	2011
Accumulated Depreciation And Amortization Description [Member] | NEW YORK | Millwood One [Member]
Schedule Of Investments In Real Estate [Line Items]
Initial Cost of Leasehold or Acquisition Investment to Company	$ 1,448
Land	1,448
Total Investment in Real Estate	$ 1,448
Date of Initial Leasehold or Acquisition Investment	2011
Accumulated Depreciation And Amortization Description [Member] | NEW YORK | Mount Kisco One [Member]
Schedule Of Investments In Real Estate [Line Items]
Initial Cost of Leasehold or Acquisition Investment to Company	$ 1,907
Land	1,907
Total Investment in Real Estate	$ 1,907
Date of Initial Leasehold or Acquisition Investment	2011
Accumulated Depreciation And Amortization Description [Member] | NEW YORK | Mount Vernon One [Member]
Schedule Of Investments In Real Estate [Line Items]
Initial Cost of Leasehold or Acquisition Investment to Company	$ 985
Land	985
Total Investment in Real Estate	$ 985
Date of Initial Leasehold or Acquisition Investment	2011
Accumulated Depreciation And Amortization Description [Member] | NEW YORK | Nanuet One [Member]
Schedule Of Investments In Real Estate [Line Items]
Initial Cost of Leasehold or Acquisition Investment to Company	$ 2,316
Land	2,316
Total Investment in Real Estate	$ 2,316
Date of Initial Leasehold or Acquisition Investment	2011
Accumulated Depreciation And Amortization Description [Member] | NEW YORK | Naples One [Member]
Schedule Of Investments In Real Estate [Line Items]
Initial Cost of Leasehold or Acquisition Investment to Company	$ 1,257
Land	827
Building and Improvements	430
Total Investment in Real Estate	1,257
Accumulated Depreciation and Amortization	$ 238
Date of Initial Leasehold or Acquisition Investment	2006
Accumulated Depreciation And Amortization Description [Member] | NEW YORK | New Paltz One [Member]
Schedule Of Investments In Real Estate [Line Items]
Initial Cost of Leasehold or Acquisition Investment to Company	$ 971
Land	971
Total Investment in Real Estate	$ 971
Date of Initial Leasehold or Acquisition Investment	2011
Accumulated Depreciation And Amortization Description [Member] | NEW YORK | New Rochelle One [Member]
Schedule Of Investments In Real Estate [Line Items]
Initial Cost of Leasehold or Acquisition Investment to Company	$ 189
Cost Capitalized Subsequent to Initial Investment	380
Land	104
Building and Improvements	465
Total Investment in Real Estate	569
Accumulated Depreciation and Amortization	$ 273
Date of Initial Leasehold or Acquisition Investment	1982
Accumulated Depreciation And Amortization Description [Member] | NEW YORK | New Rochelle Two [Member]
Schedule Of Investments In Real Estate [Line Items]
Initial Cost of Leasehold or Acquisition Investment to Company	$ 1,887
Land	1,887
Total Investment in Real Estate	$ 1,887
Date of Initial Leasehold or Acquisition Investment	2011
Accumulated Depreciation And Amortization Description [Member] | NEW YORK | New Windsor One [Member]
Schedule Of Investments In Real Estate [Line Items]
Initial Cost of Leasehold or Acquisition Investment to Company	$ 1,084
Land	1,084
Total Investment in Real Estate	$ 1,084
Date of Initial Leasehold or Acquisition Investment	2011
Accumulated Depreciation And Amortization Description [Member] | NEW YORK | New York One [Member]
Schedule Of Investments In Real Estate [Line Items]
Initial Cost of Leasehold or Acquisition Investment to Company	$ 126
Cost Capitalized Subsequent to Initial Investment	399
Land	78
Building and Improvements	447
Total Investment in Real Estate	525
Accumulated Depreciation and Amortization	$ 332
Date of Initial Leasehold or Acquisition Investment	1972
Accumulated Depreciation And Amortization Description [Member] | NEW YORK | Newburgh One [Member]
Schedule Of Investments In Real Estate [Line Items]
Initial Cost of Leasehold or Acquisition Investment to Company	$ 527
Land	527
Total Investment in Real Estate	$ 527
Date of Initial Leasehold or Acquisition Investment	2011
Accumulated Depreciation And Amortization Description [Member] | NEW YORK | Newburgh Two [Member]
Schedule Of Investments In Real Estate [Line Items]
Initial Cost of Leasehold or Acquisition Investment to Company	$ 1,192
Land	1,192
Total Investment in Real Estate	$ 1,192
Date of Initial Leasehold or Acquisition Investment	2011