Schedule III - Real Estate and Accumulated Depreciation and Amortization Part 15 (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
NEW YORK | Accumulated Depreciation And Amortization Description [Member] | Bellaire One [Member]
Schedule Of Investments In Real Estate [Line Items]
Initial Cost of Leasehold or Acquisition Investment to Company	330
Cost Capitalized Subsequent to Initial Investment	37
Land	215
Building and Improvements	152
Total Investment in Real Estate	367
Accumulated Depreciation and Amortization	$ 125
Date of Initial Leasehold or Acquisition Investment	1985
NEW YORK | Accumulated Depreciation And Amortization Description [Member] | 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
NEW YORK | Accumulated Depreciation And Amortization Description [Member] | 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	606
Land	502
Building and Improvements	756
Total Investment in Real Estate	1,258
Accumulated Depreciation and Amortization	$ 418
Date of Initial Leasehold or Acquisition Investment	1976
NEW YORK | Accumulated Depreciation And Amortization Description [Member] | Bronx One [Member]
Schedule Of Investments In Real Estate [Line Items]
Initial Cost of Leasehold or Acquisition Investment to Company	$ 104
Cost Capitalized Subsequent to Initial Investment	226
Land	90
Building and Improvements	240
Total Investment in Real Estate	330
Accumulated Depreciation and Amortization	$ 233
Date of Initial Leasehold or Acquisition Investment	1985
NEW YORK | Accumulated Depreciation And Amortization Description [Member] | 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
NEW YORK | Accumulated Depreciation And Amortization Description [Member] | Bronx Three [Member]
Schedule Of Investments In Real Estate [Line Items]
Initial Cost of Leasehold or Acquisition Investment to Company	$ 391
Cost Capitalized Subsequent to Initial Investment	53
Land	251
Building and Improvements	193
Total Investment in Real Estate	444
Accumulated Depreciation and Amortization	$ 160
Date of Initial Leasehold or Acquisition Investment	1985
NEW YORK | Accumulated Depreciation And Amortization Description [Member] | Bronx Four [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
NEW YORK | Accumulated Depreciation And Amortization Description [Member] | Bronx Five [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
NEW YORK | Accumulated Depreciation And Amortization Description [Member] | Bronx Six [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
NEW YORK | Accumulated Depreciation And Amortization Description [Member] | Bronx Seven [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	$ 119
Date of Initial Leasehold or Acquisition Investment	2013
NEW YORK | Accumulated Depreciation And Amortization Description [Member] | Bronx Eight [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	$ 124
Date of Initial Leasehold or Acquisition Investment	2013
NEW YORK | Accumulated Depreciation And Amortization Description [Member] | Bronx Nine [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	$ 138
Date of Initial Leasehold or Acquisition Investment	2013
NEW YORK | Accumulated Depreciation And Amortization Description [Member] | Bronxville One [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
NEW YORK | Accumulated Depreciation And Amortization Description [Member] | Brooklyn One [Member]
Schedule Of Investments In Real Estate [Line Items]
Cost Capitalized Subsequent to Initial Investment	$ 396
Building and Improvements	396
Total Investment in Real Estate	396
Accumulated Depreciation and Amortization	$ 195
Date of Initial Leasehold or Acquisition Investment	1970
NEW YORK | Accumulated Depreciation And Amortization Description [Member] | Brooklyn Two [Member]
Schedule Of Investments In Real Estate [Line Items]
Initial Cost of Leasehold or Acquisition Investment to Company	$ 100
Cost Capitalized Subsequent to Initial Investment	345
Land	67
Building and Improvements	378
Total Investment in Real Estate	445
Accumulated Depreciation and Amortization	$ 177
Date of Initial Leasehold or Acquisition Investment	1972
NEW YORK | Accumulated Depreciation And Amortization Description [Member] | Brooklyn Three [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	384
Land	31
Building and Improvements	428
Total Investment in Real Estate	459
Accumulated Depreciation and Amortization	$ 210
Date of Initial Leasehold or Acquisition Investment	1967
NEW YORK | Accumulated Depreciation And Amortization Description [Member] | Brooklyn Four [Member]
Schedule Of Investments In Real Estate [Line Items]
Initial Cost of Leasehold or Acquisition Investment to Company	$ 148
Cost Capitalized Subsequent to Initial Investment	394
Land	104
Building and Improvements	438
Total Investment in Real Estate	542
Accumulated Depreciation and Amortization	$ 238
Date of Initial Leasehold or Acquisition Investment	1972
NEW YORK | Accumulated Depreciation And Amortization Description [Member] | Brooklyn Five [Member]
Schedule Of Investments In Real Estate [Line Items]
Initial Cost of Leasehold or Acquisition Investment to Company	$ 237
Cost Capitalized Subsequent to Initial Investment	382
Land	154
Building and Improvements	465
Total Investment in Real Estate	619
Accumulated Depreciation and Amortization	$ 156
Date of Initial Leasehold or Acquisition Investment	1985
NEW YORK | Accumulated Depreciation And Amortization Description [Member] | Brooklyn Six [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	457
Land	176
Building and Improvements	563
Total Investment in Real Estate	739
Accumulated Depreciation and Amortization	$ 362
Date of Initial Leasehold or Acquisition Investment	1967
NEW YORK | Accumulated Depreciation And Amortization Description [Member] | Brooklyn Seven [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	334
Land	275
Building and Improvements	481
Total Investment in Real Estate	756
Accumulated Depreciation and Amortization	$ 249
Date of Initial Leasehold or Acquisition Investment	1985
NEW YORK | Accumulated Depreciation And Amortization Description [Member] | Brooklyn Eight [Member]
Schedule Of Investments In Real Estate [Line Items]
Initial Cost of Leasehold or Acquisition Investment to Company	$ 478
Cost Capitalized Subsequent to Initial Investment	318
Land	306
Building and Improvements	490
Total Investment in Real Estate	796
Accumulated Depreciation and Amortization	$ 254
Date of Initial Leasehold or Acquisition Investment	1985
NEW YORK | Accumulated Depreciation And Amortization Description [Member] | Brooklyn Nine [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	$ 273
Date of Initial Leasehold or Acquisition Investment	1985
NEW YORK | Accumulated Depreciation And Amortization Description [Member] | Buffalo One [Member]
Schedule Of Investments In Real Estate [Line Items]
Initial Cost of Leasehold or Acquisition Investment to Company	$ 312
Cost Capitalized Subsequent to Initial Investment	242
Land	151
Building and Improvements	403
Total Investment in Real Estate	554
Accumulated Depreciation and Amortization	$ 168
Date of Initial Leasehold or Acquisition Investment	2000
NEW YORK | Accumulated Depreciation And Amortization Description [Member] | Byron One [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	$ 130
Date of Initial Leasehold or Acquisition Investment	2006
NEW YORK | Accumulated Depreciation And Amortization Description [Member] | Chester One [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
NEW YORK | Accumulated Depreciation And Amortization Description [Member] | Churchville One [Member]
Schedule Of Investments In Real Estate [Line Items]
Initial Cost of Leasehold or Acquisition Investment to Company	$ 1,011
Land	601
Building and Improvements	410
Total Investment in Real Estate	1,011
Accumulated Depreciation and Amortization	$ 178
Date of Initial Leasehold or Acquisition Investment	2006
NEW YORK | Accumulated Depreciation And Amortization Description [Member] | Commack One [Member]
Schedule Of Investments In Real Estate [Line Items]
Initial Cost of Leasehold or Acquisition Investment to Company	$ 321
Cost Capitalized Subsequent to Initial Investment	26
Land	209
Building and Improvements	138
Total Investment in Real Estate	347
Accumulated Depreciation and Amortization	$ 110
Date of Initial Leasehold or Acquisition Investment	1985
NEW YORK | Accumulated Depreciation And Amortization Description [Member] | Corona One [Member]
Schedule Of Investments In Real Estate [Line Items]
Initial Cost of Leasehold or Acquisition Investment to Company	$ 114
Cost Capitalized Subsequent to Initial Investment	301
Land	113
Building and Improvements	302
Total Investment in Real Estate	415
Accumulated Depreciation and Amortization	$ 302
Date of Initial Leasehold or Acquisition Investment	1965
NEW YORK | Accumulated Depreciation And Amortization Description [Member] | Corona Two [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	$ 129
Date of Initial Leasehold or Acquisition Investment	2013
NEW YORK | Accumulated Depreciation And Amortization Description [Member] | Cortland Manor One [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
NEW YORK | Accumulated Depreciation And Amortization Description [Member] | 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	$ 213
Date of Initial Leasehold or Acquisition Investment	1985
NEW YORK | Accumulated Depreciation And Amortization Description [Member] | Dobbs FerryTwo [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
NEW YORK | Accumulated Depreciation And Amortization Description [Member] | 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	$ 214
Date of Initial Leasehold or Acquisition Investment	1985
NEW YORK | Accumulated Depreciation And Amortization Description [Member] | East Islip One [Member]
Schedule Of Investments In Real Estate [Line Items]
Initial Cost of Leasehold or Acquisition Investment to Company	$ 89
Cost Capitalized Subsequent to Initial Investment	549
Land	87
Building and Improvements	551
Total Investment in Real Estate	638
Accumulated Depreciation and Amortization	$ 259
Date of Initial Leasehold or Acquisition Investment	1972
NEW YORK | Accumulated Depreciation And Amortization Description [Member] | East Pembroke One [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	$ 108
Date of Initial Leasehold or Acquisition Investment	2006
NEW YORK | Accumulated Depreciation And Amortization Description [Member] | Eastchester One [Member]
Schedule Of Investments In Real Estate [Line Items]
Initial Cost of Leasehold or Acquisition Investment to Company	$ 1,724
Land	1,724
Total Investment in Real Estate	$ 1,724
Date of Initial Leasehold or Acquisition Investment	2011
NEW YORK | Accumulated Depreciation And Amortization Description [Member] | 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	$ 286
Date of Initial Leasehold or Acquisition Investment	1978
NEW YORK | Accumulated Depreciation And Amortization Description [Member] | Elmsford One [Member]
Schedule Of Investments In Real Estate [Line Items]
Cost Capitalized Subsequent to Initial Investment	$ 1,012
Land	581
Building and Improvements	431
Total Investment in Real Estate	1,012
Accumulated Depreciation and Amortization	$ 196
Date of Initial Leasehold or Acquisition Investment	1971
NEW YORK | Accumulated Depreciation And Amortization Description [Member] | 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
NEW YORK | Accumulated Depreciation And Amortization Description [Member] | 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
NEW YORK | Accumulated Depreciation And Amortization Description [Member] | Floral Park One [Member]
Schedule Of Investments In Real Estate [Line Items]
Initial Cost of Leasehold or Acquisition Investment to Company	$ 617
Cost Capitalized Subsequent to Initial Investment	175
Land	356
Building and Improvements	436
Total Investment in Real Estate	792
Accumulated Depreciation and Amortization	$ 219
Date of Initial Leasehold or Acquisition Investment	1998
NEW YORK | Accumulated Depreciation And Amortization Description [Member] | 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	$ 193
Date of Initial Leasehold or Acquisition Investment	1998
NEW YORK | Accumulated Depreciation And Amortization Description [Member] | Flushing Two [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	$ 110
Date of Initial Leasehold or Acquisition Investment	2013
NEW YORK | Accumulated Depreciation And Amortization Description [Member] | Flushing Three [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	$ 105
Date of Initial Leasehold or Acquisition Investment	2013
NEW YORK | Accumulated Depreciation And Amortization Description [Member] | Flushing Four [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	$ 131
Date of Initial Leasehold or Acquisition Investment	2013
NEW YORK | Accumulated Depreciation And Amortization Description [Member] | Forrest Hill 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
NEW YORK | Accumulated Depreciation And Amortization Description [Member] | 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	$ 146
Date of Initial Leasehold or Acquisition Investment	1978
NEW YORK | Accumulated Depreciation And Amortization Description [Member] | Friendship One [Member]
Schedule Of Investments In Real Estate [Line Items]
Initial Cost of Leasehold or Acquisition Investment to Company	$ 393
Land	43
Building and Improvements	350
Total Investment in Real Estate	393
Accumulated Depreciation and Amortization	$ 152
Date of Initial Leasehold or Acquisition Investment	2006