Dividend Restrictions (Details) - USD ($)	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Nov. 30, 2024	May 31, 2024	Jan. 01, 2024
NEW HAMPSHIRE [Member]
Statutory Accounting Practices [Line Items]
Percentage of policyholder's surplus distributes as dividends and other distributions	10.00%
Dividends declared	$ 100,000,000.0	$ 100,000,000.0	$ 255,000,000.0
Dividends paid to parent	$ 100,000,000.0	100,000,000.0	255,000,000.0
NEW HAMPSHIRE [Member] | Scenario Forecast [Member]
Statutory Accounting Practices [Line Items]
Statutory amount available for dividend payments					$ 263,300,000
NEW HAMPSHIRE [Member] | Maximum [Member] | Scenario Forecast [Member]
Statutory Accounting Practices [Line Items]
Maximum dividends payable without prior approval of state regulators					$ 100,000,000
NEW HAMPSHIRE [Member] | Maximum [Member] | Subsequent Event [Member]
Statutory Accounting Practices [Line Items]
Maximum dividends payable without prior approval of state regulators						$ 163,300,000
MICHIGAN [Member]
Statutory Accounting Practices [Line Items]
Percentage of policyholder's surplus distributes as dividends and other distributions	10.00%
Dividends declared	$ 10,000,000	72,000,000	90,000,000
Dividends paid to parent	$ 10,000,000	$ 72,000,000	$ 90,000,000
MICHIGAN [Member] | Scenario Forecast [Member]
Statutory Accounting Practices [Line Items]
Statutory amount available for dividend payments				$ 59,900,000
MICHIGAN [Member] | Maximum [Member] | Scenario Forecast [Member]
Statutory Accounting Practices [Line Items]
Maximum dividends payable without prior approval of state regulators				$ 10,000,000
MICHIGAN [Member] | Maximum [Member] | Subsequent Event [Member]
Statutory Accounting Practices [Line Items]
Maximum dividends payable without prior approval of state regulators						$ 49,900,000