Schedule III - Real Estate and Accumulated Depreciation and Amortization Part 8 (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] | NJ [Member] | Somerset One [Member]
Schedule Of Investments In Real Estate [Line Items]
Initial Cost of Leasehold or Acquisition Investment to Company	683
Cost Capitalized Subsequent to Initial Investment	231
Land	445
Building and Improvements	469
Total Investment in Real Estate	914
Accumulated Depreciation and Amortization	$ 381
Date of Initial Leasehold or Acquisition Investment	1985
Accumulated Depreciation And Amortization Description [Member] | NJ [Member] | Union One [Member]
Schedule Of Investments In Real Estate [Line Items]
Initial Cost of Leasehold or Acquisition Investment to Company	$ 437
Cost Capitalized Subsequent to Initial Investment	212
Land	239
Building and Improvements	410
Total Investment in Real Estate	649
Accumulated Depreciation and Amortization	$ 234
Date of Initial Leasehold or Acquisition Investment	1985
Accumulated Depreciation And Amortization Description [Member] | NJ [Member] | Vernon One [Member]
Schedule Of Investments In Real Estate [Line Items]
Initial Cost of Leasehold or Acquisition Investment to Company	$ 671
Cost Capitalized Subsequent to Initial Investment	444
Land	437
Building and Improvements	678
Total Investment in Real Estate	1,115
Accumulated Depreciation and Amortization	$ 395
Date of Initial Leasehold or Acquisition Investment	1985
Accumulated Depreciation And Amortization Description [Member] | NJ [Member] | Washington Township One [Member]
Schedule Of Investments In Real Estate [Line Items]
Initial Cost of Leasehold or Acquisition Investment to Company	$ 913
Cost Capitalized Subsequent to Initial Investment	365
Land	594
Building and Improvements	684
Total Investment in Real Estate	1,278
Accumulated Depreciation and Amortization	$ 439
Date of Initial Leasehold or Acquisition Investment	1985
Accumulated Depreciation And Amortization Description [Member] | NJ [Member] | Watchung One [Member]
Schedule Of Investments In Real Estate [Line Items]
Initial Cost of Leasehold or Acquisition Investment to Company	$ 450
Cost Capitalized Subsequent to Initial Investment	118
Land	226
Building and Improvements	342
Total Investment in Real Estate	568
Accumulated Depreciation and Amortization	$ 174
Date of Initial Leasehold or Acquisition Investment	1985
Accumulated Depreciation And Amortization Description [Member] | NJ [Member] | West Orange One [Member]
Schedule Of Investments In Real Estate [Line Items]
Initial Cost of Leasehold or Acquisition Investment to Company	$ 800
Cost Capitalized Subsequent to Initial Investment	423
Land	521
Building and Improvements	702
Total Investment in Real Estate	1,223
Accumulated Depreciation and Amortization	$ 524
Date of Initial Leasehold or Acquisition Investment	1985
Accumulated Depreciation And Amortization Description [Member] | NEW MEXICO [Member] | Albuquerque One [Member]
Schedule Of Investments In Real Estate [Line Items]
Initial Cost of Leasehold or Acquisition Investment to Company	$ 2,308
Land	1,830
Building and Improvements	478
Total Investment in Real Estate	2,308
Accumulated Depreciation and Amortization	$ 74
Date of Initial Leasehold or Acquisition Investment	2017
Accumulated Depreciation And Amortization Description [Member] | NEW MEXICO [Member] | Albuquerque Two [Member]
Schedule Of Investments In Real Estate [Line Items]
Initial Cost of Leasehold or Acquisition Investment to Company	$ 3,682
Land	3,141
Building and Improvements	541
Total Investment in Real Estate	3,682
Accumulated Depreciation and Amortization	$ 84
Date of Initial Leasehold or Acquisition Investment	2017
Accumulated Depreciation And Amortization Description [Member] | NEW MEXICO [Member] | Albuquerque Three [Member]
Schedule Of Investments In Real Estate [Line Items]
Initial Cost of Leasehold or Acquisition Investment to Company	$ 1,829
Land	1,382
Building and Improvements	447
Total Investment in Real Estate	1,829
Accumulated Depreciation and Amortization	$ 65
Date of Initial Leasehold or Acquisition Investment	2017
Accumulated Depreciation And Amortization Description [Member] | NEW MEXICO [Member] | Albuquerque Four [Member]
Schedule Of Investments In Real Estate [Line Items]
Initial Cost of Leasehold or Acquisition Investment to Company	$ 2,322
Land	1,796
Building and Improvements	526
Total Investment in Real Estate	2,322
Accumulated Depreciation and Amortization	$ 80
Date of Initial Leasehold or Acquisition Investment	2017
Accumulated Depreciation And Amortization Description [Member] | NEW MEXICO [Member] | Las Cruces One [Member]
Schedule Of Investments In Real Estate [Line Items]
Initial Cost of Leasehold or Acquisition Investment to Company	$ 1,842
Land	1,374
Building and Improvements	468
Total Investment in Real Estate	1,842
Accumulated Depreciation and Amortization	$ 69
Date of Initial Leasehold or Acquisition Investment	2017
Accumulated Depreciation And Amortization Description [Member] | NEVADA [Member] | Fernley One [Member]
Schedule Of Investments In Real Estate [Line Items]
Initial Cost of Leasehold or Acquisition Investment to Company	$ 1,665
Land	221
Building and Improvements	1,444
Total Investment in Real Estate	1,665
Accumulated Depreciation and Amortization	$ 468
Date of Initial Leasehold or Acquisition Investment	2015
Accumulated Depreciation And Amortization Description [Member] | NEVADA [Member] | Las Vegas One [Member]
Schedule Of Investments In Real Estate [Line Items]
Initial Cost of Leasehold or Acquisition Investment to Company	$ 3,472
Land	655
Building and Improvements	2,817
Total Investment in Real Estate	3,472
Accumulated Depreciation and Amortization	$ 20
Date of Initial Leasehold or Acquisition Investment	2019
Accumulated Depreciation And Amortization Description [Member] | NEVADA [Member] | Las Vegas Two [Member]
Schedule Of Investments In Real Estate [Line Items]
Initial Cost of Leasehold or Acquisition Investment to Company	$ 2,814
Land	563
Building and Improvements	2,251
Total Investment in Real Estate	2,814
Accumulated Depreciation and Amortization	$ 16
Date of Initial Leasehold or Acquisition Investment	2019
Accumulated Depreciation And Amortization Description [Member] | NEVADA [Member] | Las Vegas Three [Member]
Schedule Of Investments In Real Estate [Line Items]
Initial Cost of Leasehold or Acquisition Investment to Company	$ 3,752
Land	615
Building and Improvements	3,137
Total Investment in Real Estate	3,752
Accumulated Depreciation and Amortization	$ 23
Date of Initial Leasehold or Acquisition Investment	2019
Accumulated Depreciation And Amortization Description [Member] | NEVADA [Member] | Las Vegas Four [Member]
Schedule Of Investments In Real Estate [Line Items]
Initial Cost of Leasehold or Acquisition Investment to Company	$ 3,094
Land	830
Building and Improvements	2,264
Total Investment in Real Estate	3,094
Accumulated Depreciation and Amortization	$ 17
Date of Initial Leasehold or Acquisition Investment	2019
Accumulated Depreciation And Amortization Description [Member] | NEW YORK | Alfred Station One [Member]
Schedule Of Investments In Real Estate [Line Items]
Initial Cost of Leasehold or Acquisition Investment to Company	$ 714
Land	414
Building and Improvements	300
Total Investment in Real Estate	714
Accumulated Depreciation and Amortization	$ 166
Date of Initial Leasehold or Acquisition Investment	2006
Accumulated Depreciation And Amortization Description [Member] | NEW YORK | Amherst One [Member]
Schedule Of Investments In Real Estate [Line Items]
Initial Cost of Leasehold or Acquisition Investment to Company	$ 223
Cost Capitalized Subsequent to Initial Investment	246
Land	173
Building and Improvements	296
Total Investment in Real Estate	469
Accumulated Depreciation and Amortization	$ 167
Date of Initial Leasehold or Acquisition Investment	2000
Accumulated Depreciation And Amortization Description [Member] | NEW YORK | Astoria One [Member]
Schedule Of Investments In Real Estate [Line Items]
Initial Cost of Leasehold or Acquisition Investment to Company	$ 1,684
Land	1,105
Building and Improvements	579
Total Investment in Real Estate	1,684
Accumulated Depreciation and Amortization	$ 221
Date of Initial Leasehold or Acquisition Investment	2013
Accumulated Depreciation And Amortization Description [Member] | NEW YORK | Avoca One [Member]
Schedule Of Investments In Real Estate [Line Items]
Initial Cost of Leasehold or Acquisition Investment to Company	$ 936
Cost Capitalized Subsequent to Initial Investment	(1)
Land	635
Building and Improvements	300
Total Investment in Real Estate	935
Accumulated Depreciation and Amortization	$ 166
Date of Initial Leasehold or Acquisition Investment	2006
Accumulated Depreciation And Amortization Description [Member] | NEW YORK | Batavia One [Member]
Schedule Of Investments In Real Estate [Line Items]
Initial Cost of Leasehold or Acquisition Investment to Company	$ 684
Land	364
Building and Improvements	320
Total Investment in Real Estate	684
Accumulated Depreciation and Amortization	$ 177
Date of Initial Leasehold or Acquisition Investment	2006
Accumulated Depreciation And Amortization Description [Member] | NEW YORK | Bay Shore One [Member]
Schedule Of Investments In Real Estate [Line Items]
Initial Cost of Leasehold or Acquisition Investment to Company	$ 157
Cost Capitalized Subsequent to Initial Investment	355
Land	86
Building and Improvements	426
Total Investment in Real Estate	512
Accumulated Depreciation and Amortization	$ 310
Date of Initial Leasehold or Acquisition Investment	1981
Accumulated Depreciation And Amortization Description [Member] | NEW YORK | Bayside One [Member]
Schedule Of Investments In Real Estate [Line Items]
Initial Cost of Leasehold or Acquisition Investment to Company	$ 470
Cost Capitalized Subsequent to Initial Investment	254
Land	306
Building and Improvements	418
Total Investment in Real Estate	724
Accumulated Depreciation and Amortization	$ 255
Date of Initial Leasehold or Acquisition Investment	1985
Accumulated Depreciation And Amortization Description [Member] | NEW YORK | Brewster One [Member]
Schedule Of Investments In Real Estate [Line Items]
Initial Cost of Leasehold or Acquisition Investment to Company	$ 789
Land	789
Total Investment in Real Estate	$ 789
Date of Initial Leasehold or Acquisition Investment	2011
Accumulated Depreciation And Amortization Description [Member] | NEW YORK | Briarcliff Manor One [Member]
Schedule Of Investments In Real Estate [Line Items]
Initial Cost of Leasehold or Acquisition Investment to Company	$ 652
Cost Capitalized Subsequent to Initial Investment	552
Land	502
Building and Improvements	702
Total Investment in Real Estate	1,204
Accumulated Depreciation and Amortization	$ 563
Date of Initial Leasehold or Acquisition Investment	1976
Accumulated Depreciation And Amortization Description [Member] | NEW YORK | Bronx One [Member]
Schedule Of Investments In Real Estate [Line Items]
Initial Cost of Leasehold or Acquisition Investment to Company	$ 390
Cost Capitalized Subsequent to Initial Investment	54
Land	251
Building and Improvements	193
Total Investment in Real Estate	444
Accumulated Depreciation and Amortization	$ 176
Date of Initial Leasehold or Acquisition Investment	1985
Accumulated Depreciation And Amortization Description [Member] | NEW YORK | Bronx Two [Member]
Schedule Of Investments In Real Estate [Line Items]
Initial Cost of Leasehold or Acquisition Investment to Company	$ 423
Land	423
Total Investment in Real Estate	$ 423
Date of Initial Leasehold or Acquisition Investment	2013
Accumulated Depreciation And Amortization Description [Member] | NEW YORK | Bronx Three [Member]
Schedule Of Investments In Real Estate [Line Items]
Initial Cost of Leasehold or Acquisition Investment to Company	$ 1,049
Land	485
Building and Improvements	564
Total Investment in Real Estate	1,049
Accumulated Depreciation and Amortization	$ 217
Date of Initial Leasehold or Acquisition Investment	2013
Accumulated Depreciation And Amortization Description [Member] | NEW YORK | Bronx Four [Member]
Schedule Of Investments In Real Estate [Line Items]
Initial Cost of Leasehold or Acquisition Investment to Company	$ 1,910
Land	1,349
Building and Improvements	561
Total Investment in Real Estate	1,910
Accumulated Depreciation and Amortization	$ 225
Date of Initial Leasehold or Acquisition Investment	2013
Accumulated Depreciation And Amortization Description [Member] | NEW YORK | Bronx Five [Member]
Schedule Of Investments In Real Estate [Line Items]
Initial Cost of Leasehold or Acquisition Investment to Company	$ 953
Land	953
Total Investment in Real Estate	$ 953
Date of Initial Leasehold or Acquisition Investment	2013
Accumulated Depreciation And Amortization Description [Member] | NEW YORK | Bronx Six [Member]
Schedule Of Investments In Real Estate [Line Items]
Initial Cost of Leasehold or Acquisition Investment to Company	$ 884
Land	884
Total Investment in Real Estate	$ 884
Date of Initial Leasehold or Acquisition Investment	2013
Accumulated Depreciation And Amortization Description [Member] | NEW YORK | Bronx Seven [Member]
Schedule Of Investments In Real Estate [Line Items]
Initial Cost of Leasehold or Acquisition Investment to Company	$ 2,408
Land	1,712
Building and Improvements	696
Total Investment in Real Estate	2,408
Accumulated Depreciation and Amortization	$ 252
Date of Initial Leasehold or Acquisition Investment	2013
Accumulated Depreciation And Amortization Description [Member] | NEW YORK | Bronx Eight [Member]
Schedule Of Investments In Real Estate [Line Items]
Initial Cost of Leasehold or Acquisition Investment to Company	$ 877
Land	877
Total Investment in Real Estate	$ 877
Date of Initial Leasehold or Acquisition Investment	2013
Accumulated Depreciation And Amortization Description [Member] | NEW YORK | Bronxville [Member]
Schedule Of Investments In Real Estate [Line Items]
Initial Cost of Leasehold or Acquisition Investment to Company	$ 1,232
Land	1,232
Total Investment in Real Estate	$ 1,232
Date of Initial Leasehold or Acquisition Investment	2011
Accumulated Depreciation And Amortization Description [Member] | NEW YORK | Brooklyn One [Member]
Schedule Of Investments In Real Estate [Line Items]
Initial Cost of Leasehold or Acquisition Investment to Company	$ 282
Cost Capitalized Subsequent to Initial Investment	222
Land	176
Building and Improvements	328
Total Investment in Real Estate	504
Accumulated Depreciation and Amortization	$ 315
Date of Initial Leasehold or Acquisition Investment	1967
Accumulated Depreciation And Amortization Description [Member] | NEW YORK | Brooklyn Two [Member]
Schedule Of Investments In Real Estate [Line Items]
Initial Cost of Leasehold or Acquisition Investment to Company	$ 75
Cost Capitalized Subsequent to Initial Investment	382
Land	31
Building and Improvements	426
Total Investment in Real Estate	457
Accumulated Depreciation and Amortization	$ 290
Date of Initial Leasehold or Acquisition Investment	1967
Accumulated Depreciation And Amortization Description [Member] | NEW YORK | Brooklyn Three [Member]
Schedule Of Investments In Real Estate [Line Items]
Initial Cost of Leasehold or Acquisition Investment to Company	$ 627
Cost Capitalized Subsequent to Initial Investment	313
Land	408
Building and Improvements	532
Total Investment in Real Estate	940
Accumulated Depreciation and Amortization	$ 377
Date of Initial Leasehold or Acquisition Investment	1985
Accumulated Depreciation And Amortization Description [Member] | NEW YORK | Brooklyn Four [Member]
Schedule Of Investments In Real Estate [Line Items]
Initial Cost of Leasehold or Acquisition Investment to Company	$ 476
Cost Capitalized Subsequent to Initial Investment	320
Land	306
Building and Improvements	490
Total Investment in Real Estate	796
Accumulated Depreciation and Amortization	$ 347
Date of Initial Leasehold or Acquisition Investment	1985
Accumulated Depreciation And Amortization Description [Member] | NEW YORK | Brooklyn Five [Member]
Schedule Of Investments In Real Estate [Line Items]
Initial Cost of Leasehold or Acquisition Investment to Company	$ 422
Cost Capitalized Subsequent to Initial Investment	3
Land	275
Building and Improvements	150
Total Investment in Real Estate	425
Accumulated Depreciation and Amortization	$ 9
Date of Initial Leasehold or Acquisition Investment	1985
Accumulated Depreciation And Amortization Description [Member] | NEW YORK | Brooklyn Six [Member]
Schedule Of Investments In Real Estate [Line Items]
Initial Cost of Leasehold or Acquisition Investment to Company	$ 236
Cost Capitalized Subsequent to Initial Investment	372
Land	154
Building and Improvements	454
Total Investment in Real Estate	608
Accumulated Depreciation and Amortization	$ 271
Date of Initial Leasehold or Acquisition Investment	1985
Accumulated Depreciation And Amortization Description [Member] | NEW YORK | Buffalo [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	241
Land	151
Building and Improvements	403
Total Investment in Real Estate	554
Accumulated Depreciation and Amortization	$ 258
Date of Initial Leasehold or Acquisition Investment	2000
Accumulated Depreciation And Amortization Description [Member] | NEW YORK | Byron [Member]
Schedule Of Investments In Real Estate [Line Items]
Initial Cost of Leasehold or Acquisition Investment to Company	$ 969
Land	669
Building and Improvements	300
Total Investment in Real Estate	969
Accumulated Depreciation and Amortization	$ 166
Date of Initial Leasehold or Acquisition Investment	2006
Accumulated Depreciation And Amortization Description [Member] | NEW YORK | Chester [Member]
Schedule Of Investments In Real Estate [Line Items]
Initial Cost of Leasehold or Acquisition Investment to Company	$ 1,158
Land	1,158
Total Investment in Real Estate	$ 1,158
Date of Initial Leasehold or Acquisition Investment	2011
Accumulated Depreciation And Amortization Description [Member] | NEW YORK | Churchville [Member]
Schedule Of Investments In Real Estate [Line Items]
Initial Cost of Leasehold or Acquisition Investment to Company	$ 1,012
Land	602
Building and Improvements	410
Total Investment in Real Estate	1,012
Accumulated Depreciation and Amortization	$ 227
Date of Initial Leasehold or Acquisition Investment	2006
Accumulated Depreciation And Amortization Description [Member] | NEW YORK | Corona One [Member]
Schedule Of Investments In Real Estate [Line Items]
Initial Cost of Leasehold or Acquisition Investment to Company	$ 2,543
Land	1,903
Building and Improvements	640
Total Investment in Real Estate	2,543
Accumulated Depreciation and Amortization	$ 235
Date of Initial Leasehold or Acquisition Investment	2013
Accumulated Depreciation And Amortization Description [Member] | NEW YORK | Cortlandt Manor [Member]
Schedule Of Investments In Real Estate [Line Items]
Initial Cost of Leasehold or Acquisition Investment to Company	$ 1,872
Land	1,872
Total Investment in Real Estate	$ 1,872
Date of Initial Leasehold or Acquisition Investment	2011
Accumulated Depreciation And Amortization Description [Member] | NEW YORK | Dobbs Ferry One [Member]
Schedule Of Investments In Real Estate [Line Items]
Initial Cost of Leasehold or Acquisition Investment to Company	$ 670
Cost Capitalized Subsequent to Initial Investment	34
Land	434
Building and Improvements	270
Total Investment in Real Estate	704
Accumulated Depreciation and Amortization	$ 242
Date of Initial Leasehold or Acquisition Investment	1985
Accumulated Depreciation And Amortization Description [Member] | NEW YORK | Dobbs Ferry Two [Member]
Schedule Of Investments In Real Estate [Line Items]
Initial Cost of Leasehold or Acquisition Investment to Company	$ 1,345
Land	1,345
Total Investment in Real Estate	$ 1,345
Date of Initial Leasehold or Acquisition Investment	2011