Mortgage Loans on Real Estate (Details)	12 Months Ended
	Dec. 31, 2017 USD ($)
Mortgage Loans on Real Estate
Prior Liens	$ 11,367,000
Face Amount of Mortgages	481,127,000
Carrying Amount of Mortgages	306,120,000
Principal Amount of Loans Subject to Delinquent Principal or Interest	$ 0
First mortgage loans | Triple Net [Member] | California 1
Mortgage Loans on Real Estate
Interest Rate	8.11%
Final Maturity Date	Dec. 15, 2020
Periodic Payment Amount	$ 2,011,590
Prior Liens	0
Face Amount of Mortgages	28,000,000
Carrying Amount of Mortgages	292,000
Principal Amount of Loans Subject to Delinquent Principal or Interest	$ 0
First mortgage loans | Triple Net [Member] | United Kingdom 1
Mortgage Loans on Real Estate
Interest Rate	7.25%
Final Maturity Date	Nov. 21, 2019
Periodic Payment Amount	$ 115,794,386
Prior Liens	0
Face Amount of Mortgages	18,805,000
Carrying Amount of Mortgages	18,805,000
Principal Amount of Loans Subject to Delinquent Principal or Interest	$ 0
First mortgage loans | Triple Net [Member] | United Kingdom 2
Mortgage Loans on Real Estate
Interest Rate	8.29%
Final Maturity Date	Jan. 16, 2018
Periodic Payment Amount	$ 9,521,615
Prior Liens	0
Face Amount of Mortgages	2,841,000
Carrying Amount of Mortgages	1,352,000
Principal Amount of Loans Subject to Delinquent Principal or Interest	$ 0
First mortgage loans | Triple Net [Member] | United Kingdom 3
Mortgage Loans on Real Estate
Interest Rate	8.00%
Final Maturity Date	Aug. 24, 2022
Periodic Payment Amount	$ 10,858,294
Prior Liens	0
Face Amount of Mortgages	11,712,000
Carrying Amount of Mortgages	1,645,000
Principal Amount of Loans Subject to Delinquent Principal or Interest	$ 0
First mortgage loans | Triple Net [Member] | United Kingdom 4
Mortgage Loans on Real Estate
Interest Rate	8.55%
Final Maturity Date	Jul. 01, 2019
Periodic Payment Amount	$ 83,119,990
Prior Liens	0
Face Amount of Mortgages	15,487,000
Carrying Amount of Mortgages	15,486,000
Principal Amount of Loans Subject to Delinquent Principal or Interest	$ 0
First mortgage loans | Triple Net [Member] | United Kingdom 5
Mortgage Loans on Real Estate
Interest Rate	7.00%
Final Maturity Date	Mar. 14, 2022
Periodic Payment Amount	$ 96,303,670
Prior Liens	0
Face Amount of Mortgages	28,374,000
Carrying Amount of Mortgages	16,139,000
Principal Amount of Loans Subject to Delinquent Principal or Interest	$ 0
First mortgage loans | Triple Net [Member] | United Kingdom 6
Mortgage Loans on Real Estate
Interest Rate	8.00%
Final Maturity Date	Jul. 06, 2019
Periodic Payment Amount	$ 137,884,551
Prior Liens	0
Face Amount of Mortgages	20,294,000
Carrying Amount of Mortgages	20,294,000
Principal Amount of Loans Subject to Delinquent Principal or Interest	$ 0
First mortgage loans | Triple Net [Member] | Oklahoma 1
Mortgage Loans on Real Estate
Interest Rate	9.02%
Final Maturity Date	Nov. 01, 2019
Periodic Payment Amount	$ 88,826,160
Prior Liens	0
Face Amount of Mortgages	11,610,000
Carrying Amount of Mortgages	11,595,000
Principal Amount of Loans Subject to Delinquent Principal or Interest	$ 0
First mortgage loans | Triple Net [Member] | Oregon 1
Mortgage Loans on Real Estate
Interest Rate	7.10%
Final Maturity Date	Dec. 31, 2017
Periodic Payment Amount	$ 1,356,780
Prior Liens	0
Face Amount of Mortgages	225,000
Carrying Amount of Mortgages	225,000
Principal Amount of Loans Subject to Delinquent Principal or Interest	$ 0
First mortgage loans | Triple Net [Member] | Pennsylvania 1
Mortgage Loans on Real Estate
Interest Rate	8.11%
Final Maturity Date	Mar. 01, 2022
Periodic Payment Amount	$ 36,683,720
Prior Liens	0
Face Amount of Mortgages	15,530,000
Carrying Amount of Mortgages	5,706,000
Principal Amount of Loans Subject to Delinquent Principal or Interest	$ 0
First mortgage loans | Triple Net [Member] | Florida 1
Mortgage Loans on Real Estate
Interest Rate	8.79%
Final Maturity Date	Jun. 23, 2021
Periodic Payment Amount	$ 94,519,150
Prior Liens	0
Face Amount of Mortgages	17,100,000
Carrying Amount of Mortgages	12,444,000
Principal Amount of Loans Subject to Delinquent Principal or Interest	$ 0
First mortgage loans | Triple Net [Member] | 7 properties in four states
Mortgage Loans on Real Estate
Interest Rate	10.00%
Final Maturity Date	Jan. 01, 2022
Periodic Payment Amount	$ 297,169,200
Prior Liens	0
Face Amount of Mortgages	65,796,000
Carrying Amount of Mortgages	25,832,000
Principal Amount of Loans Subject to Delinquent Principal or Interest	$ 0
First mortgage loans | Triple Net [Member] | 13 properties in Texas
Mortgage Loans on Real Estate
Interest Rate	10.00%
Final Maturity Date	Jan. 01, 2022
Periodic Payment Amount	$ 851,672,100
Prior Liens	0
Face Amount of Mortgages	103,620,000
Carrying Amount of Mortgages	82,041,000
Principal Amount of Loans Subject to Delinquent Principal or Interest	$ 0
First mortgage loans | Triple Net [Member] | 13 properties In six states
Mortgage Loans on Real Estate
Interest Rate	10.00%
Final Maturity Date	Jan. 01, 2022
Periodic Payment Amount	$ 1,139,453,100
Prior Liens	0
Face Amount of Mortgages	138,633,000
Carrying Amount of Mortgages	91,164,000
Principal Amount of Loans Subject to Delinquent Principal or Interest	$ 0
Second mortgage loans | Triple Net [Member] | Texas 3
Mortgage Loans on Real Estate
Interest Rate	12.17%
Final Maturity Date	May 01, 2019
Periodic Payment Amount	$ 32,033
Prior Liens	11,367,000
Face Amount of Mortgages	3,100,000
Carrying Amount of Mortgages	3,100,000
Principal Amount of Loans Subject to Delinquent Principal or Interest	$ 0