Basis of Presentation and Significant Accounting Policies - Guaranteed Minimum Death Benefit (Details) - Guarantee Minimum Death Benefit - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Net Amount at Risk by Product and Guarantee [Line Items]
GMDB reserve	$ 77	$ 126
Aggregate in-the-money death benefits under the GMDB provision	$ 26,710	$ 29,367
Variable annuity contract value distribution based on GMDB feature:
No guarantee	26.00%	28.00%
Return of premium guarantee	69.00%	67.00%
Guarantee of premium roll-up at an annual rate of 3% or 5%	5.00%	5.00%
Total	100.00%	100.00%
Minimum
Variable annuity contract value distribution based on GMDB feature:
Guarantee of premium roll-up at an annual rate of 3% or 5%	3.00%
Maximum
Variable annuity contract value distribution based on GMDB feature:
Guarantee of premium roll-up at an annual rate of 3% or 5%	5.00%