Schedule IV - Mortgage Loans on Real Estate (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Mortgage Loans On Real Estate [Line Items]
Amount of Principal Unpaid at Close of Period	$ 30,855	$ 33,519	$ 32,366	$ 32,737
Borrower A [Member] | East Islip, NY [Member]
Mortgage Loans On Real Estate [Line Items]
Description	Seller financing
Interest Rate	9.00%
Final Maturity Date	2024-11
Periodic Payment Terms	P & I
Prior Liens	$ 0
Face Value at Inception	743
Amount of Principal Unpaid at Close of Period	$ 712
Borrower B [Member] | Middlesex, NJ [Member]
Mortgage Loans On Real Estate [Line Items]
Description	Seller financing
Interest Rate	9.00%
Final Maturity Date	2021-05
Periodic Payment Terms	P & I
Prior Liens	$ 0
Face Value at Inception	255
Amount of Principal Unpaid at Close of Period	$ 222
Borrower C [Member] | Valley Cottage, NY [Member]
Mortgage Loans On Real Estate [Line Items]
Description	Seller financing
Interest Rate	9.00%
Final Maturity Date	2020-10
Periodic Payment Terms	P & I
Prior Liens	$ 0
Face Value at Inception	431
Amount of Principal Unpaid at Close of Period	$ 368
Borrower D [Member] | Brooklyn, NY [Member]
Mortgage Loans On Real Estate [Line Items]
Description	Seller financing
Interest Rate	8.00%
Final Maturity Date	2020-06
Periodic Payment Terms	I
Prior Liens	$ 0
Face Value at Inception	2,000
Amount of Principal Unpaid at Close of Period	$ 2,000
Borrower E [Member] | Smithtown, NY [Member]
Mortgage Loans On Real Estate [Line Items]
Description	Seller financing
Interest Rate	9.00%
Final Maturity Date	2027-01
Periodic Payment Terms	P & I
Prior Liens	$ 0
Face Value at Inception	280
Amount of Principal Unpaid at Close of Period	$ 280
Borrower F [Member] | Nyack, NY [Member]
Mortgage Loans On Real Estate [Line Items]
Description	Seller financing
Interest Rate	9.00%
Final Maturity Date	2022-09
Periodic Payment Terms	P & I
Prior Liens	$ 0
Face Value at Inception	253
Amount of Principal Unpaid at Close of Period	$ 231
Borrower G [Member] | Baldwin, NY [Member]
Mortgage Loans On Real Estate [Line Items]
Description	Seller financing
Interest Rate	9.00%
Final Maturity Date	2020-09
Periodic Payment Terms	P & I
Prior Liens	$ 0
Face Value at Inception	300
Amount of Principal Unpaid at Close of Period	$ 260
Borrower H [Member] | Norwalk [Member]
Mortgage Loans On Real Estate [Line Items]
Description	Seller financing
Interest Rate	9.00%
Final Maturity Date	2022-04
Periodic Payment Terms	P & I
Prior Liens	$ 0
Face Value at Inception	319
Amount of Principal Unpaid at Close of Period	$ 286
Borrower I [Member] | Stafford Springs, CT [Member]
Mortgage Loans On Real Estate [Line Items]
Description	Seller financing
Interest Rate	9.00%
Final Maturity Date	2021-01
Periodic Payment Terms	P & I
Prior Liens	$ 0
Face Value at Inception	232
Amount of Principal Unpaid at Close of Period	$ 200
Borrower J [Member] | Waterbury, CT [Member]
Mortgage Loans On Real Estate [Line Items]
Description	Seller financing
Interest Rate	9.00%
Final Maturity Date	2021-02
Periodic Payment Terms	P & I
Prior Liens	$ 0
Face Value at Inception	171
Amount of Principal Unpaid at Close of Period	$ 148
Borrower K [Member] | Great Barrington, MA [Member]
Mortgage Loans On Real Estate [Line Items]
Description	Seller financing
Interest Rate	9.00%
Final Maturity Date	2021-04
Periodic Payment Terms	P & I
Prior Liens	$ 0
Face Value at Inception	58
Amount of Principal Unpaid at Close of Period	$ 50
Borrower L [Member] | Westfield, MA [Member]
Mortgage Loans On Real Estate [Line Items]
Description	Seller financing
Interest Rate	9.00%
Final Maturity Date	2021-11
Periodic Payment Terms	P & I
Prior Liens	$ 0
Face Value at Inception	303
Amount of Principal Unpaid at Close of Period	$ 268
Borrower M [Member] | Bristol, CT [Member]
Mortgage Loans On Real Estate [Line Items]
Description	Seller financing
Interest Rate	9.00%
Final Maturity Date	2026-05
Periodic Payment Terms	P & I
Prior Liens	$ 0
Face Value at Inception	76
Amount of Principal Unpaid at Close of Period	$ 75
Borrower N [Member] | Middletown, CT [Member]
Mortgage Loans On Real Estate [Line Items]
Description	Seller financing
Interest Rate	9.00%
Final Maturity Date	2026-05
Periodic Payment Terms	P & I
Prior Liens	$ 0
Face Value at Inception	308
Amount of Principal Unpaid at Close of Period	$ 305
Borrower O [Member] | Simsbury, CT [Member]
Mortgage Loans On Real Estate [Line Items]
Description	Seller financing
Interest Rate	9.00%
Final Maturity Date	2026-05
Periodic Payment Terms	P & I
Prior Liens	$ 0
Face Value at Inception	192
Amount of Principal Unpaid at Close of Period	$ 190
Borrower P [Member] | Milford, CT [Member]
Mortgage Loans On Real Estate [Line Items]
Description	Seller financing
Interest Rate	9.00%
Final Maturity Date	2025-03
Periodic Payment Terms	P & I
Prior Liens	$ 0
Face Value at Inception	398
Amount of Principal Unpaid at Close of Period	$ 384
Borrower Q [Member] | Fairfield, CT [Member]
Mortgage Loans On Real Estate [Line Items]
Description	Seller financing
Interest Rate	9.00%
Final Maturity Date	2025-03
Periodic Payment Terms	P & I
Prior Liens	$ 0
Face Value at Inception	390
Amount of Principal Unpaid at Close of Period	$ 377
Borrower R [Member] | Hartford, CT [Member]
Mortgage Loans On Real Estate [Line Items]
Description	Seller financing
Interest Rate	9.00%
Final Maturity Date	2024-03
Periodic Payment Terms	P & I
Prior Liens	$ 0
Face Value at Inception	70
Amount of Principal Unpaid at Close of Period	$ 66
Borrower S [Member] | Wilmington, DE [Member]
Mortgage Loans On Real Estate [Line Items]
Description	Seller financing
Interest Rate	9.00%
Final Maturity Date	2020-11
Periodic Payment Terms	P & I
Prior Liens	$ 0
Face Value at Inception	84
Amount of Principal Unpaid at Close of Period	$ 72
Borrower T [Member] | Fairhaven, MA [Member]
Mortgage Loans On Real Estate [Line Items]
Description	Seller financing
Interest Rate	9.00%
Final Maturity Date	2020-09
Periodic Payment Terms	P & I
Prior Liens	$ 0
Face Value at Inception	458
Amount of Principal Unpaid at Close of Period	$ 389
Borrower U [Member] | New Bedford, MA [Member]
Mortgage Loans On Real Estate [Line Items]
Description	Seller financing
Interest Rate	9.00%
Final Maturity Date	2021-10
Periodic Payment Terms	P & I
Prior Liens	$ 0
Face Value at Inception	363
Amount of Principal Unpaid at Close of Period	$ 320
Borrower V [Member] | Fitchburg, MA [Member]
Mortgage Loans On Real Estate [Line Items]
Description	Seller financing
Interest Rate	9.00%
Final Maturity Date	2021-10
Periodic Payment Terms	P & I
Prior Liens	$ 0
Face Value at Inception	187
Amount of Principal Unpaid at Close of Period	$ 165
Borrower W [Member] | Oxford, MA [Member]
Mortgage Loans On Real Estate [Line Items]
Description	Seller financing
Interest Rate	9.00%
Final Maturity Date	2023-03
Periodic Payment Terms	P & I
Prior Liens	$ 0
Face Value at Inception	86
Amount of Principal Unpaid at Close of Period	$ 79
Borrower X [Member] | Kernersville/Lexington, NC [Member]
Mortgage Loans On Real Estate [Line Items]
Description	Seller financing
Interest Rate	8.00%
Final Maturity Date	2026-07
Periodic Payment Terms	P & I
Prior Liens	$ 0
Face Value at Inception	568
Amount of Principal Unpaid at Close of Period	$ 53
Borrower Y [Member] | Pelham, NH [Member]
Mortgage Loans On Real Estate [Line Items]
Description	Seller financing
Interest Rate	9.00%
Final Maturity Date	2023-01
Periodic Payment Terms	P & I
Prior Liens	$ 0
Face Value at Inception	73
Amount of Principal Unpaid at Close of Period	$ 67
Borrower Z [Member] | Bayonne, NJ [Member]
Mortgage Loans On Real Estate [Line Items]
Description	Seller financing
Interest Rate	9.00%
Final Maturity Date	2020-03
Periodic Payment Terms	P & I
Prior Liens	$ 0
Face Value at Inception	308
Amount of Principal Unpaid at Close of Period	$ 256
Borrower AA [Member] | Belleville, NJ [Member]
Mortgage Loans On Real Estate [Line Items]
Description	Seller financing
Interest Rate	9.00%
Final Maturity Date	2021-03
Periodic Payment Terms	P & I
Prior Liens	$ 0
Face Value at Inception	315
Amount of Principal Unpaid at Close of Period	$ 273
Borrower AB [Member] | Ridgefield, NJ [Member]
Mortgage Loans On Real Estate [Line Items]
Description	Seller financing
Interest Rate	9.00%
Final Maturity Date	2021-04
Periodic Payment Terms	P & I
Prior Liens	$ 0
Face Value at Inception	172
Amount of Principal Unpaid at Close of Period	$ 149
Borrower AC [Member] | Irvington, NJ [Member]
Mortgage Loans On Real Estate [Line Items]
Description	Seller financing
Interest Rate	9.00%
Final Maturity Date	2022-07
Periodic Payment Terms	P & I
Prior Liens	$ 0
Face Value at Inception	300
Amount of Principal Unpaid at Close of Period	$ 188
Borrower AD [Member] | Jersey City, NJ [Member]
Mortgage Loans On Real Estate [Line Items]
Description	Seller financing
Interest Rate	9.50%
Final Maturity Date	2025-07
Periodic Payment Terms	P & I
Prior Liens	$ 0
Face Value at Inception	500
Amount of Principal Unpaid at Close of Period	$ 410
Borrower AE [Member] | Colonia, NJ [Member]
Mortgage Loans On Real Estate [Line Items]
Description	Seller financing
Interest Rate	9.00%
Final Maturity Date	2020-07
Periodic Payment Terms	P & I
Prior Liens	$ 0
Face Value at Inception	320
Amount of Principal Unpaid at Close of Period	$ 270
Borrower AF [Member] | Swedesboro, NJ [Member]
Mortgage Loans On Real Estate [Line Items]
Description	Seller financing
Interest Rate	9.00%
Final Maturity Date	2021-04
Periodic Payment Terms	P & I
Prior Liens	$ 0
Face Value at Inception	77
Amount of Principal Unpaid at Close of Period	$ 66
Borrower AG [Member] | Glendale, NY [Member]
Mortgage Loans On Real Estate [Line Items]
Description	Seller financing
Interest Rate	9.00%
Final Maturity Date	2025-07
Periodic Payment Terms	P & I
Prior Liens	$ 0
Face Value at Inception	525
Amount of Principal Unpaid at Close of Period	$ 444
Borrower AH [Member] | Seaford, NY [Member]
Mortgage Loans On Real Estate [Line Items]
Description	Seller financing
Interest Rate	9.00%
Final Maturity Date	2020-01
Periodic Payment Terms	P & I
Prior Liens	$ 0
Face Value at Inception	488
Amount of Principal Unpaid at Close of Period	$ 404
Borrower AI [Member] | Elmont, NY [Member]
Mortgage Loans On Real Estate [Line Items]
Description	Seller financing
Interest Rate	9.00%
Final Maturity Date	2021-10
Periodic Payment Terms	P & I
Prior Liens	$ 0
Face Value at Inception	450
Amount of Principal Unpaid at Close of Period	$ 353
Borrower AJ [Member] | Scarsdale, NY [Member]
Mortgage Loans On Real Estate [Line Items]
Description	Seller financing
Interest Rate	9.00%
Final Maturity Date	2025-11
Periodic Payment Terms	P & I
Prior Liens	$ 0
Face Value at Inception	337
Amount of Principal Unpaid at Close of Period	$ 290
Borrower AK [Member] | Pleasant Valley, NY [Member]
Mortgage Loans On Real Estate [Line Items]
Description	Seller financing
Interest Rate	9.00%
Final Maturity Date	2020-09
Periodic Payment Terms	P & I
Prior Liens	$ 0
Face Value at Inception	230
Amount of Principal Unpaid at Close of Period	$ 195
Borrower AL [Member] | Freeport, NY [Member]
Mortgage Loans On Real Estate [Line Items]
Description	Seller financing
Interest Rate	9.00%
Final Maturity Date	2020-05
Periodic Payment Terms	P & I
Prior Liens	$ 0
Face Value at Inception	206
Amount of Principal Unpaid at Close of Period	$ 173
Borrower AM [Member] | Colonie, NY [Member]
Mortgage Loans On Real Estate [Line Items]
Description	Seller financing
Interest Rate	9.00%
Final Maturity Date	2023-08
Periodic Payment Terms	P & I
Prior Liens	$ 0
Face Value at Inception	143
Amount of Principal Unpaid at Close of Period	$ 133
Borrower AN [Member] | Latham, NY [Member]
Mortgage Loans On Real Estate [Line Items]
Description	Seller financing
Interest Rate	9.00%
Final Maturity Date	2021-01
Periodic Payment Terms	P & I
Prior Liens	$ 0
Face Value at Inception	169
Amount of Principal Unpaid at Close of Period	$ 145
Borrower AO [Member] | Malta, NY [Member]
Mortgage Loans On Real Estate [Line Items]
Description	Seller financing
Interest Rate	9.00%
Final Maturity Date	2023-03
Periodic Payment Terms	P & I
Prior Liens	$ 0
Face Value at Inception	572
Amount of Principal Unpaid at Close of Period	$ 527
Borrower AP [Member] | Coxsackie, NY [Member]
Mortgage Loans On Real Estate [Line Items]
Description	Seller financing
Interest Rate	9.00%
Final Maturity Date	2021-07
Periodic Payment Terms	P & I
Prior Liens	$ 0
Face Value at Inception	153
Amount of Principal Unpaid at Close of Period	$ 134
Borrower AQ [Member] | Brewster, NY [Member]
Mortgage Loans On Real Estate [Line Items]
Description	Seller financing
Interest Rate	9.00%
Final Maturity Date	2022-10
Periodic Payment Terms	P & I
Prior Liens	$ 0
Face Value at Inception	554
Amount of Principal Unpaid at Close of Period	$ 501
Borrower AR [Member] | Lindenhurst, NY [Member]
Mortgage Loans On Real Estate [Line Items]
Description	Seller financing
Interest Rate	9.50%
Final Maturity Date	2026-06
Periodic Payment Terms	P & I
Prior Liens	$ 0
Face Value at Inception	350
Amount of Principal Unpaid at Close of Period	$ 347
Borrower AS [Member] | Kenmore, NY [Member]
Mortgage Loans On Real Estate [Line Items]
Description	Seller financing
Interest Rate	9.00%
Final Maturity Date	2020-12
Periodic Payment Terms	P & I
Prior Liens	$ 0
Face Value at Inception	74
Amount of Principal Unpaid at Close of Period	$ 64
Borrower AT [Member] | Rochester, NY [Member]
Mortgage Loans On Real Estate [Line Items]
Description	Seller financing
Interest Rate	9.00%
Final Maturity Date	2025-02
Periodic Payment Terms	P & I
Prior Liens	$ 0
Face Value at Inception	174
Amount of Principal Unpaid at Close of Period	$ 167
Borrower AU [Member] | Savona, NY [Member]
Mortgage Loans On Real Estate [Line Items]
Description	Seller financing
Interest Rate	9.00%
Final Maturity Date	2025-02
Periodic Payment Terms	P & I
Prior Liens	$ 0
Face Value at Inception	157
Amount of Principal Unpaid at Close of Period	$ 151
Borrower AV [Member] | Rochester, NY [Member]
Mortgage Loans On Real Estate [Line Items]
Description	Seller financing
Interest Rate	9.00%
Final Maturity Date	2025-10
Periodic Payment Terms	P & I
Prior Liens	$ 0
Face Value at Inception	230
Amount of Principal Unpaid at Close of Period	$ 225
Borrower AW [Member] | Greigsville, NY [Member]
Mortgage Loans On Real Estate [Line Items]
Description	Seller financing
Interest Rate	9.00%
Final Maturity Date	2025-11
Periodic Payment Terms	P & I
Prior Liens	$ 0
Face Value at Inception	200
Amount of Principal Unpaid at Close of Period	$ 196
Borrower AX [Member] | Horsham, PA [Member]
Mortgage Loans On Real Estate [Line Items]
Description	Seller financing
Interest Rate	10.00%
Final Maturity Date	2024-07
Periodic Payment Terms	P & I
Prior Liens	$ 0
Face Value at Inception	237
Amount of Principal Unpaid at Close of Period	$ 101
Borrower AY [Member] | Warwick, RI [Member]
Mortgage Loans On Real Estate [Line Items]
Description	Seller financing
Interest Rate	9.00%
Final Maturity Date	2022-08
Periodic Payment Terms	P & I
Prior Liens	$ 0
Face Value at Inception	333
Amount of Principal Unpaid at Close of Period	$ 304
Borrower AZ [Member] | Providence, RI [Member]
Mortgage Loans On Real Estate [Line Items]
Description	Seller financing
Interest Rate	9.00%
Final Maturity Date	2021-09
Periodic Payment Terms	P & I
Prior Liens	$ 0
Face Value at Inception	184
Amount of Principal Unpaid at Close of Period	$ 162
Borrower BA [Member] | Warwick, RI [Member]
Mortgage Loans On Real Estate [Line Items]
Description	Seller financing
Interest Rate	9.00%
Final Maturity Date	2021-10
Periodic Payment Terms	P & I
Prior Liens	$ 0
Face Value at Inception	357
Amount of Principal Unpaid at Close of Period	$ 315
Borrower BB [Member] | Cranston, RI [Member]
Mortgage Loans On Real Estate [Line Items]
Description	Seller financing
Interest Rate	9.00%
Final Maturity Date	2022-08
Periodic Payment Terms	P & I
Prior Liens	$ 0
Face Value at Inception	153
Amount of Principal Unpaid at Close of Period	$ 138
Borrower BC [Member] | E. Providence, RI [Member]
Mortgage Loans On Real Estate [Line Items]
Description	Seller financing
Interest Rate	9.00%
Final Maturity Date	2022-02
Periodic Payment Terms	P & I
Prior Liens	$ 0
Face Value at Inception	186
Amount of Principal Unpaid at Close of Period	$ 166
Borrower BD [Member] | York, PA [Member]
Mortgage Loans On Real Estate [Line Items]
Description	Seller financing
Interest Rate	9.00%
Final Maturity Date	2021-02
Periodic Payment Terms	P & I
Prior Liens	$ 0
Face Value at Inception	102
Amount of Principal Unpaid at Close of Period	$ 88
Borrower BE [Member] | Ephrata, PA [Member]
Mortgage Loans On Real Estate [Line Items]
Description	Seller financing
Interest Rate	9.00%
Final Maturity Date	2020-10
Periodic Payment Terms	P & I
Prior Liens	$ 0
Face Value at Inception	265
Amount of Principal Unpaid at Close of Period	$ 142
Borrower BF [Member] | McConnellsburg, PA [Member]
Mortgage Loans On Real Estate [Line Items]
Description	Seller financing
Interest Rate	9.00%
Final Maturity Date	2023-01
Periodic Payment Terms	P & I
Prior Liens	$ 0
Face Value at Inception	38
Amount of Principal Unpaid at Close of Period	35
Note Receivable On Mortgage Loans [Member]
Mortgage Loans On Real Estate [Line Items]
Prior Liens	0
Face Value at Inception	35,857
Amount of Principal Unpaid at Close of Period	$ 30,855
Note Receivable On Mortgage Loans [Member] | Various-NY [Member]
Mortgage Loans On Real Estate [Line Items]
Description	Purchase/leaseback
Interest Rate	9.50%
Final Maturity Date	2021-01
Periodic Payment Terms	I
Prior Liens	$ 0
Face Value at Inception	18,400
Amount of Principal Unpaid at Close of Period	$ 14,720
Note Receivable On Mortgage Loans [Member] | Various-CT [Member]
Mortgage Loans On Real Estate [Line Items]
Description	Promissory Note
Interest Rate	9.00%
Final Maturity Date	2028-12
Prior Liens	$ 0
Amount of Principal Unpaid at Close of Period	1,056
Mortgage Loans [Member]
Mortgage Loans On Real Estate [Line Items]
Prior Liens	0
Face Value at Inception	17,457
Amount of Principal Unpaid at Close of Period	$ 15,079