Mortgage Loans on Real Estate (Allowance for Loan Losses Rollforward) (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2020
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning allowance balance	$ (20,089)	$ (9,179)
Charge-offs	0	1,485
Recoveries	0	712
Change in provision for credit losses	810	(3,697)
Ending allowance balance	(19,279)	(19,279)
Commercial
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning allowance balance	(18,439)	(9,179)
Charge-offs	0	1,485
Recoveries	0	712
Change in provision for credit losses	1,010	(1,847)
Ending allowance balance	(17,429)	(17,429)
Residential
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning allowance balance	(1,650)	0
Charge-offs	0	0
Recoveries	0	0
Change in provision for credit losses	(200)	(1,850)
Ending allowance balance	$ (1,850)	$ (1,850)