Basis of Presentation and Significant Accounting Policies - Guaranteed Minimum Death Benefit (Details) - Guarantee Minimum Death Benefit - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020
Net Amount at Risk by Product and Guarantee
GMDB reserve	$ 0.1	$ 0.1
Aggregate in-the-money death benefits under the GMDB provision	$ 22.3	$ 26.7
Variable annuity contract value distribution based on GMDB feature:
No guarantee	24.00%	26.00%
Return of premium guarantee	71.00%	69.00%
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%