SCHEDULE IV - MORTGAGE LOANS ON REAL ESTATE (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Mortgage Loans on Real Estate [Line Items]
Face Amount of Mortgages	$ 857,801,000
Carrying Amount of Mortgages	773,563,000	$ 710,858,000	$ 671,232,000	$ 639,343,000
Carrying Amount of Loans Subject to Delinquent Principal or Interest	$ 1,472,000
Michigan | Group 1
Mortgage Loans on Real Estate [Line Items]
Interest Rate	10.13%
Fixed/Variable	F(2)
Final Maturity Date	2029
Periodic Payment Terms	Interest plus approximately $139.0 of principal payable monthly with $356,985 due at maturity
Prior Liens	None
Face Amount of Mortgages	$ 415,000,000
Carrying Amount of Mortgages	380,799,000
Mortgage loans on real estate periodic payment, amount	139,000.0
Mortgage loans on real estate, periodic payment terms, balloon payment to be received	$ 356,985,000
Michigan | Group 2
Mortgage Loans on Real Estate [Line Items]
Interest Rate	9.73%
Fixed/Variable	F(2)
Final Maturity Date	2029
Periodic Payment Terms	Interest plus approximately $10.0 of principal payable monthly with $42,341 due at maturity
Prior Liens	None
Face Amount of Mortgages	$ 44,200,000
Carrying Amount of Mortgages	44,053,000
Mortgage loans on real estate periodic payment, amount	10,000.0
Mortgage loans on real estate, periodic payment terms, balloon payment to be received	$ 42,341,000
Michigan | Group 3
Mortgage Loans on Real Estate [Line Items]
Interest Rate	9.95%
Fixed/Variable	F(2)
Final Maturity Date	2029
Periodic Payment Terms	Interest plus approximately $3.0 of principal payable monthly with $10,466 due at maturity
Prior Liens	None
Face Amount of Mortgages	$ 11,000,000
Carrying Amount of Mortgages	10,932,000
Mortgage loans on real estate periodic payment, amount	3,000.0
Mortgage loans on real estate, periodic payment terms, balloon payment to be received	$ 10,466,000
Michigan | Group 4
Mortgage Loans on Real Estate [Line Items]
Interest Rate	9.98%
Fixed/Variable	F(2)
Final Maturity Date	2029
Periodic Payment Terms	Interest payable monthly until maturity
Prior Liens	None
Face Amount of Mortgages	$ 455,000
Carrying Amount of Mortgages	$ 455,000
Michigan | Group 5
Mortgage Loans on Real Estate [Line Items]
Interest Rate	9.02%
Fixed/Variable	F(2)
Final Maturity Date	2029
Periodic Payment Terms	Interest payable monthly until maturity
Prior Liens	None
Face Amount of Mortgages	$ 14,045,000
Carrying Amount of Mortgages	$ 14,045,000
Michigan | Group 6
Mortgage Loans on Real Estate [Line Items]
Interest Rate	11.31%
Fixed/Variable	F(2)
Final Maturity Date	2029
Periodic Payment Terms	Interest payable monthly until maturity
Prior Liens	None
Face Amount of Mortgages	$ 4,112,000
Carrying Amount of Mortgages	$ 4,112,000
Michigan | Group 7
Mortgage Loans on Real Estate [Line Items]
Interest Rate	11.60%
Fixed/Variable	F(2)
Final Maturity Date	2029
Periodic Payment Terms	Interest payable monthly until maturity
Prior Liens	None
Face Amount of Mortgages	$ 4,220,000
Carrying Amount of Mortgages	$ 4,220,000
Michigan | Group 8
Mortgage Loans on Real Estate [Line Items]
Interest Rate	11.04%
Fixed/Variable	F(2)
Final Maturity Date	2029
Periodic Payment Terms	Interest payable monthly until maturity
Prior Liens	None
Face Amount of Mortgages	$ 9,374,000
Carrying Amount of Mortgages	$ 9,374,000
Michigan | Group 9
Mortgage Loans on Real Estate [Line Items]
Interest Rate	10.23%
Fixed/Variable	F(2)
Final Maturity Date	2029
Periodic Payment Terms	Interest payable monthly until maturity
Prior Liens	None
Face Amount of Mortgages	$ 20,860,000
Carrying Amount of Mortgages	$ 20,860,000
Michigan | Group 10
Mortgage Loans on Real Estate [Line Items]
Interest Rate	9.73%
Fixed/Variable	F(2)
Final Maturity Date	2029
Periodic Payment Terms	Interest payable monthly until maturity
Prior Liens	None
Face Amount of Mortgages	$ 360,000
Carrying Amount of Mortgages	$ 360,000
Michigan | Group 11
Mortgage Loans on Real Estate [Line Items]
Interest Rate	9.50%
Fixed/Variable	F(2)
Final Maturity Date	2029
Periodic Payment Terms	Interest payable monthly until maturity
Prior Liens	None
Face Amount of Mortgages	$ 1,087,000
Carrying Amount of Mortgages	$ 1,087,000
Michigan | Group 12
Mortgage Loans on Real Estate [Line Items]
Interest Rate	9.95%
Fixed/Variable	F(2)
Final Maturity Date	2019
Periodic Payment Terms	Interest payable monthly until maturity
Prior Liens	None
Face Amount of Mortgages	$ 14,826,000
Carrying Amount of Mortgages	$ 14,826,000
Michigan | Group 13
Mortgage Loans on Real Estate [Line Items]
Interest Rate	9.95%
Fixed/Variable	F(2)
Final Maturity Date	2019
Periodic Payment Terms	Interest payable monthly until maturity
Prior Liens	None
Face Amount of Mortgages	$ 18,147,000
Carrying Amount of Mortgages	$ 18,147,000
Maryland | Group 1
Mortgage Loans on Real Estate [Line Items]
Interest Rate	13.75%
Fixed/Variable	F(2)
Final Maturity Date	2028
Periodic Payment Terms	Interest payable monthly until maturity
Prior Liens	None
Face Amount of Mortgages	$ 74,928,000
Carrying Amount of Mortgages	$ 35,964,000
Ohio | Group 1
Mortgage Loans on Real Estate [Line Items]
Interest Rate	10.39%
Fixed/Variable	F(2)
Final Maturity Date	2027
Periodic Payment Terms	Interest payable monthly until maturity
Prior Liens	None
Face Amount of Mortgages	$ 112,500,000
Carrying Amount of Mortgages	$ 112,500,000
Ohio | Group 2
Mortgage Loans on Real Estate [Line Items]
Interest Rate	8.50%
Fixed/Variable	F(2)
Final Maturity Date	2021
Periodic Payment Terms	Interest accrues until 12/1/2020 when interest becomes payable monthly until maturity
Prior Liens	None
Face Amount of Mortgages	$ 3,249,000
Carrying Amount of Mortgages	$ 3,249,000
Idaho | Group 1
Mortgage Loans on Real Estate [Line Items]
Interest Rate	10.00%
Fixed/Variable	F
Final Maturity Date	2021
Periodic Payment Terms	Interest payable monthly until maturity
Prior Liens	None
Face Amount of Mortgages	$ 19,000,000
Carrying Amount of Mortgages	$ 19,000,000
Texas | Group 1
Mortgage Loans on Real Estate [Line Items]
Interest Rate	8.00%
Fixed/Variable	F
Final Maturity Date	2025
Periodic Payment Terms	Interest plus approximately $109.0 of principal payable monthly with $60,272 due at maturity
Prior Liens	None
Face Amount of Mortgages	$ 72,960,000
Carrying Amount of Mortgages	68,389,000
Mortgage loans on real estate periodic payment, amount	109,000.0
Mortgage loans on real estate, periodic payment terms, balloon payment to be received	$ 60,272,000
Texas | Group 2
Mortgage Loans on Real Estate [Line Items]
Interest Rate	8.50%
Fixed/Variable	F
Final Maturity Date	2020
Periodic Payment Terms	Interest plus approximately $123.0 of principal payable monthly
Prior Liens	None
Face Amount of Mortgages	$ 1,481,000
Carrying Amount of Mortgages	1,481,000
Mortgage loans on real estate periodic payment, amount	$ 123,000.0
Massachusetts | Group 1
Mortgage Loans on Real Estate [Line Items]
Interest Rate	9.00%
Fixed/Variable	F
Final Maturity Date	2023
Periodic Payment Terms	Interest plus approximately $46.0 of principal payable monthly with $6,078 due at maturity
Prior Liens	None
Face Amount of Mortgages	$ 9,000,000
Carrying Amount of Mortgages	8,238,000
Mortgage loans on real estate periodic payment, amount	46,000.0
Mortgage loans on real estate, periodic payment terms, balloon payment to be received	$ 6,078,000
Tennessee | Group 1
Mortgage Loans on Real Estate [Line Items]
Interest Rate	8.35%
Fixed/Variable	F
Final Maturity Date	2015
Periodic Payment Terms	Past due
Prior Liens	None
Face Amount of Mortgages	$ 6,997,000
Carrying Amount of Mortgages	1,472,000
Carrying Amount of Loans Subject to Delinquent Principal or Interest	$ 1,472,000