Investments (Impaired Mortgage Loans) (Details) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019		Sep. 30, 2018	Dec. 31, 2018
Financing Receivable Impaired [Line Items]
Unpaid Principal Balance		$ 17,017		$ 17,017			$ 30,660
Recorded Investment		17,016		17,016			30,635
Related Allowance		0		0			0
Carrying Value		17,016		17,016			30,635
Average Investment	[1]	17,015	$ 30,641	20,436		$ 22,641
Interest Income		170	346	669		650
Impaired mortgage loans with valuation allowance recorded
Financing Receivable Impaired [Line Items]
Unpaid Principal Balance		0		0			0
Recorded Investment		0		0			0
Related Allowance		0		0			0
Carrying Value		0		0			0
Average Investment	[1]	0	0			0
Interest Income		0	0	0	[1]	0
Impaired mortgage loans with no valuation allowance recorded
Financing Receivable Impaired [Line Items]
Unpaid Principal Balance		17,017		17,017			30,660
Recorded Investment		17,016		17,016			30,635
Related Allowance		0		0			0
Carrying Value		17,016		17,016			$ 30,635
Average Investment	[1]	17,015	30,641	20,436		22,641
Interest Income		$ 170	$ 346	$ 669		$ 650

[1] Average recorded investment represents the average loan balances as of the beginning of period and all subsequent quarterly end of period balances.