Mortgage Loans on Real Estate (Allowance for Loan Losses Rollforward) (Details) - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2020	Mar. 31, 2019
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning allowance balance (1)		$ (9,179)
Ending allowance balance		(19,776)
Commercial Real Estate Portfolio Segment
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning allowance balance (1)		(9,179)
Ending allowance balance		(19,776)
Specific Allowance | Commercial Real Estate Portfolio Segment
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning allowance balance (1)	[1]	(229)	$ (229)
Charge-offs		0	0
Recoveries		0	0
Change in provision for credit losses		(2,197)	0
Ending allowance balance		(2,426)	(229)
General Allowance | Commercial Real Estate Portfolio Segment
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning allowance balance (1)	[1]	(17,550)	(8,010)
Charge-offs		0	0
Recoveries		0	0
Change in provision for credit losses		200	60
Ending allowance balance		$ (17,350)	$ (7,950)

[1] (1) Upon adoption of authoritative guidance effective January 1, 2020, we updated our accounting policies and methodology for calculating the general loan loss allowance, resulting in an adjustment to our commercial mortgage loan valuation allowance. See Note 1 for further details.