Investments in Fixed Maturity Securities (HTM Allowance for Credit Loss) (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2020 USD ($)
Debt Securities, Held-to-maturity, Allowance for Credit Loss [Roll Forward]
Allowance for expected credit losses at January 1, 2020	$ 0
Cumulative effect adjustment resulting from changes in accounting principles	107
Provision for expected credit losses	38
Allowance for expected credit losses at March 31, 2020	107
Cumulative effect adjustment resulting from changes in accounting principles
Debt Securities, Held-to-maturity, Allowance for Credit Loss [Roll Forward]
Allowance for expected credit losses at January 1, 2020	69
Cumulative effect adjustment resulting from changes in accounting principles	$ 69