Prior Period Consolidated Financial Statements - Consolidated Statement of Operations and Comprehensive Income (Loss)(Unaudited) (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Revenues
Net premiums and contract charges earned	$ 255.9	$ 255.8
Net investment income	100.4	97.9
Net investment losses	(3.9)	(15.5)
Other income	1.5	8.5
Total revenues	353.9	346.7
Benefits, losses and expenses
Benefits, claims and settlement expenses	183.2	175.2
Interest credited	48.7	39.7
Operating expenses	79.8	76.7
DAC amortization expense	23.7	22.0
Intangible asset amortization expense	3.7	4.2
Interest expense	6.7	3.9
Total benefits, losses and expenses	345.8	321.7
Income before income taxes	8.1	25.0
Income tax expense	1.5	4.7
Net income (loss)	$ 6.6	$ 20.3
Net income per share
Basic (in usd per share)	$ 0.16	$ 0.48
Diluted (in usd per share)	$ 0.16	$ 0.48
Weighted average number of shares and equivalent shares
Basic (in shares)	41.3	41.9
Diluted (in shares)	41.4	42.1
Other comprehensive income (loss), net of tax:
Change in net unrealized investment losses on fixed maturity securities	$ 93.2	$ (334.1)
Change in net reserve remeasurements attributable to discount rates	(41.2)	181.5
Change in net funded status of benefit plans	0.0	0.0
Other comprehensive income (loss)	52.0	(152.6)
Comprehensive income (loss)	$ 58.6	(132.3)
Previously Reported
Revenues
Net premiums and contract charges earned		255.9
Net investment income		97.9
Net investment losses		(15.5)
Other income		8.5
Total revenues		346.8
Benefits, losses and expenses
Benefits, claims and settlement expenses		177.0
Interest credited		40.8
Operating expenses		76.8
DAC amortization expense		26.4
Intangible asset amortization expense		4.2
Interest expense		3.9
Income before income taxes		17.7
Income tax expense		3.2
Net income (loss)		$ 14.5
Net income per share
Basic (in usd per share)		$ 0.35
Diluted (in usd per share)		$ 0.35
Weighted average number of shares and equivalent shares
Basic (in shares)		41.9
Diluted (in shares)		42.1
Other comprehensive income (loss), net of tax:
Change in net unrealized investment losses on fixed maturity securities		$ (270.7)
Change in net reserve remeasurements attributable to discount rates		0.0
Change in net funded status of benefit plans		0.0
Other comprehensive income (loss)		(270.7)
Comprehensive income (loss)		(256.2)
Effect of the Adoption of ASU 2018-12
Revenues
Net premiums and contract charges earned		(0.1)
Net investment income		0.0
Net investment losses		0.0
Other income		0.0
Total revenues		(0.1)
Benefits, losses and expenses
Benefits, claims and settlement expenses		(1.8)
Interest credited		(1.1)
Operating expenses		(0.1)
DAC amortization expense		(4.4)
Intangible asset amortization expense		0.0
Interest expense		0.0
Income before income taxes		7.3
Income tax expense		1.5
Net income (loss)		$ 5.8
Net income per share
Basic (in usd per share)		$ 0.13
Diluted (in usd per share)		$ 0.13
Weighted average number of shares and equivalent shares
Basic (in shares)		0.0
Diluted (in shares)		0.0
Other comprehensive income (loss), net of tax:
Change in net unrealized investment losses on fixed maturity securities		$ (63.4)
Change in net reserve remeasurements attributable to discount rates		181.5
Change in net funded status of benefit plans		0.0
Other comprehensive income (loss)		118.1
Comprehensive income (loss)		$ 123.9