Schedule IV - Mortgage Loans on Real Estate (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Mortgage Loans on Real Estate
Prior Liens	$ 0
Face Amount of Mortgages	321,434
Carrying Amount of Mortgages	293,752	$ 145,686	$ 249,071	$ 306,120
Principal Amount of Loans Subject to Delinquent Principal or Interest	0
First Mortgage Loans
Mortgage Loans on Real Estate
Prior Liens	0
Face Amount of Mortgages	121,662
Carrying Amount of Mortgages	111,249
Principal Amount of Loans Subject to Delinquent Principal or Interest	$ 0
First Mortgage Loans | Triple-net | United Kingdom
Mortgage Loans on Real Estate
Interest Rate	7.25%
Monthly Payment Terms, Periodic Payment Amount	$ 143
Prior Liens	0
Face Amount of Mortgages	28,652
Carrying Amount of Mortgages	23,104
Principal Amount of Loans Subject to Delinquent Principal or Interest	$ 0
First Mortgage Loans | Triple-net | United Kingdom
Mortgage Loans on Real Estate
Interest Rate	8.53%
Monthly Payment Terms, Periodic Payment Amount	$ 144
Prior Liens	0
Face Amount of Mortgages	20,493
Carrying Amount of Mortgages	20,107
Principal Amount of Loans Subject to Delinquent Principal or Interest	$ 0
First Mortgage Loans | Triple-net | Pennsylvania
Mortgage Loans on Real Estate
Interest Rate	8.72%
Monthly Payment Terms, Periodic Payment Amount	$ 108
Prior Liens	0
Face Amount of Mortgages	15,530
Carrying Amount of Mortgages	14,795
Principal Amount of Loans Subject to Delinquent Principal or Interest	$ 0
First Mortgage Loans | Triple-net | North Carolina
Mortgage Loans on Real Estate
Interest Rate	7.83%
Monthly Payment Terms, Periodic Payment Amount	$ 92
Prior Liens	0
Face Amount of Mortgages	32,783
Carrying Amount of Mortgages	31,993
Principal Amount of Loans Subject to Delinquent Principal or Interest	$ 0
First Mortgage Loans | Triple-net | United Kingdom
Mortgage Loans on Real Estate
Interest Rate	8.50%
Monthly Payment Terms, Periodic Payment Amount	$ 95
Prior Liens	0
Face Amount of Mortgages	20,464
Carrying Amount of Mortgages	19,549
Principal Amount of Loans Subject to Delinquent Principal or Interest	$ 0
First Mortgage Loans | Outpatient Medical | Texas
Mortgage Loans on Real Estate
Interest Rate	7.86%
Monthly Payment Terms, Periodic Payment Amount	$ 24
Prior Liens	0
Face Amount of Mortgages	3,740
Carrying Amount of Mortgages	1,701
Principal Amount of Loans Subject to Delinquent Principal or Interest	$ 0
First Mortgage Loans | Outpatient Medical | United Kingdom
Mortgage Loans on Real Estate
Interest Rate	7.10%
Monthly Payment Terms, Periodic Payment Amount	$ 972
First Mortgage, Multiple Properties
Mortgage Loans on Real Estate
Prior Liens	0
Face Amount of Mortgages	181,022
Carrying Amount of Mortgages	173,361
Principal Amount of Loans Subject to Delinquent Principal or Interest	0
First Mortgage, Multiple Properties | Outpatient Medical | United Kingdom
Mortgage Loans on Real Estate
Prior Liens	0
Face Amount of Mortgages	181,022
Carrying Amount of Mortgages	173,361
Principal Amount of Loans Subject to Delinquent Principal or Interest	0
Second Mortgage
Mortgage Loans on Real Estate
Prior Liens	0
Face Amount of Mortgages	18,750
Carrying Amount of Mortgages	9,142
Principal Amount of Loans Subject to Delinquent Principal or Interest	$ 0
Second Mortgage | Triple-net | Florida
Mortgage Loans on Real Estate
Interest Rate	10.27%
Monthly Payment Terms, Periodic Payment Amount	$ 54
Prior Liens	0
Face Amount of Mortgages	6,250
Carrying Amount of Mortgages	6,098
Principal Amount of Loans Subject to Delinquent Principal or Interest	$ 0
Second Mortgage | Seniors Housing Operating | Florida
Mortgage Loans on Real Estate
Interest Rate	10.14%
Monthly Payment Terms, Periodic Payment Amount	$ 23
Prior Liens	0
Face Amount of Mortgages	12,500
Carrying Amount of Mortgages	3,044
Principal Amount of Loans Subject to Delinquent Principal or Interest	$ 0