Investments - Special Deposits (Details) - Deposits with state insurance departments - USD ($) $ in Millions	Dec. 31, 2024	Dec. 31, 2023
Debt Securities, Available-for-sale [Line Items]
Fixed maturities	$ 12.2	$ 11.7
Delaware
Debt Securities, Available-for-sale [Line Items]
Fixed maturities	2.8	2.8
New York
Debt Securities, Available-for-sale [Line Items]
Fixed maturities	2.6	2.9
Washington
Debt Securities, Available-for-sale [Line Items]
Fixed maturities	1.2	1.2
Colorado
Debt Securities, Available-for-sale [Line Items]
Fixed maturities	1.1	1.1
Virginia
Debt Securities, Available-for-sale [Line Items]
Fixed maturities	0.9	0.8
New Mexico
Debt Securities, Available-for-sale [Line Items]
Fixed maturities	0.7	0.7
New Jersey
Debt Securities, Available-for-sale [Line Items]
Fixed maturities	0.6	0.6
North Carolina
Debt Securities, Available-for-sale [Line Items]
Fixed maturities	0.6	0.6
Nevada
Debt Securities, Available-for-sale [Line Items]
Fixed maturities	0.4	0.2
Ohio
Debt Securities, Available-for-sale [Line Items]
Fixed maturities	0.4	0.0
Arkansas
Debt Securities, Available-for-sale [Line Items]
Fixed maturities	0.3	0.1
Florida
Debt Securities, Available-for-sale [Line Items]
Fixed maturities	0.2	0.2
Massachusetts
Debt Securities, Available-for-sale [Line Items]
Fixed maturities	0.2	0.2
Kansas
Debt Securities, Available-for-sale [Line Items]
Fixed maturities	0.1	0.2
Kentucky
Debt Securities, Available-for-sale [Line Items]
Fixed maturities	$ 0.1	$ 0.1