Basis of Presentation and Significant Accounting Policies - Narrative (Details) $ / shares in Units, $ in Millions				1 Months Ended	12 Months Ended
	Oct. 01, 2022 USD ($)	Jan. 01, 2021 USD ($) cohort	Oct. 01, 2020 USD ($)	Oct. 31, 2021 USD ($)	Dec. 31, 2022 USD ($) $ / shares shares	Dec. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Amortization of acquisition costs for property and casualty contracts, first term					6 months
Amortization of acquisition costs for property and casualty contracts, second term					12 months
Amortization term for acquisition costs of annuity contracts					20 years
Amortization period of acquisition costs of interest sensitive life contracts					20 years
Amortization term for acquisition costs of indexed universal life contracts					30 years
Amortization of acquisition costs for individual life contracts, first term					10 years
Amortization of acquisition costs for individual life contracts, second term					15 years
Amortization of acquisition costs for individual life contracts, third term					20 years
Amortization of acquisition costs for individual life contracts, fourth term					30 years
Amortization of acquisition costs for supplemental and group benefits					6 years
Percentage of reversion to mean approach utilized to amortized policy acquisition costs					8.00%
Deferred policy acquisition costs, corridor around the mean					2.00%
Purchase price					$ 171.8
Amortization in 2023					14.8
Amortization in 2024					14.6
Amortization in 2025					14.4
Amortization in 2026					14.3
Amortization in 2027					14.2
Goodwill impairment	$ 2.0				$ 2.0	$ 0.0	$ 5.6
Reverse repurchase agreement, cash to value percentage					95.00%
Securities sold under agreements to repurchase					$ 70.2	$ 0.0
Purchase of FHLB activity-based common stock as percentage of borrowing, required					4.50%
Purchase of FHLB activity-based common stock as percentage of borrowing, percentage, authorized						25.00%
Principal repayment on FHLB funding agreements					$ 149.0	$ 362.0	0.0
FHLB advances					792.5
Share-based compensation expense					$ 6.9	6.6	4.8
Weighted average fair value of nonvested options outstanding (in usd per share) | $ / shares					$ 7.48
Unrecognized share-based compensation expense, nonvested options					$ 2.2
Antidilutive securities exclude from EPS computation (in shares) | shares					992,404
Minimum exercise price (in usd per share) | $ / shares					$ 38.99
Maximum exercise price (in usd per share) | $ / shares					$ 42.95
Retained earnings					$ (1,468.6)	(1,524.9)
Income before income taxes					(11.9)	174.9	159.6
Accumulated other comprehensive income					8.8	10.2
Impairment of infinite lived intangible assets					0.3
Other comprehensive income (loss)					(646.2)	(74.6)	135.5
Net income (loss)					(2.6)	142.8	133.3
Fair Value
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Securities sold under agreements to repurchase					73.9	0.0
Accounting Standards Update 2018-12 | Liability For Future Policy Benefits
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Accumulated other comprehensive income (AOCI)		$ (499.3)
Number of cohorts with net premium ratio capped | cohort		5
Net premium ratio cap, percent		100.00%
Retained earnings		$ 0.2
Accounting Standards Update 2018-12 | Deferred Policy Acquisition Costs
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Accumulated other comprehensive income (AOCI)		71.5
Accounting Standards Update 2018-12 | Market Risk Benefits
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Accumulated other comprehensive income (AOCI)		(1.3)
Retained earnings		$ 5.4
Retained Earnings
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Net income (loss)					(2.6)	142.8	133.3
Employee stock option
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Share-based compensation expense					1.2	1.2	1.1
Restricted stock units
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Unrecognized share-based compensation expense, equity instruments other than options					7.8
HMLIC and NTA
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Proceeds from FHLB funding agreements					159.0
Principal repayment on FHLB funding agreements					$ 149.0
Minimum
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Purchase of FHLB activity-based common stock as percentage of borrowing, required					2.00%
Minimum | Accounting Standards Update 2018-12
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Income before income taxes					$ 15.0	20.0
Minimum | Accounting Standards Update 2018-12 | Liability For Future Policy Benefits
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Net income (loss)					7.0	15.0
Minimum | Accounting Standards Update 2018-12 | Deferred Policy Acquisition Costs
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Net income (loss)					8.0	3.0
Minimum | Accounting Standards Update 2018-12 | Market Risk Benefits
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Other comprehensive income (loss)					(3.0)	(7.0)
Net income (loss)					0.0	2.0
Minimum | Accounting Standards Update 2018-12 | Measurement Input, Discount Rate
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Income before income taxes					7.0	15.0
Minimum | Accounting Standards Update 2018-12 | Deferred policy acquisition costs
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Income before income taxes					8.0	3.0
Minimum | Accounting Standards Update 2018-12 | Market risk benefits
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Income before income taxes					0.0	2.0
Maximum | Accounting Standards Update 2018-12
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Income before income taxes					31.0	35.0
Maximum | Accounting Standards Update 2018-12 | Liability For Future Policy Benefits
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Net income (loss)					17.0	25.0
Maximum | Accounting Standards Update 2018-12 | Deferred Policy Acquisition Costs
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Net income (loss)					10.0	4.0
Maximum | Accounting Standards Update 2018-12 | Market Risk Benefits
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Other comprehensive income (loss)					3.0	(1.0)
Net income (loss)					4.0	6.0
Maximum | Accounting Standards Update 2018-12 | Measurement Input, Discount Rate
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Income before income taxes					17.0	25.0
Maximum | Accounting Standards Update 2018-12 | Deferred policy acquisition costs
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Income before income taxes					10.0	4.0
Maximum | Accounting Standards Update 2018-12 | Market risk benefits
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Income before income taxes					$ 4.0	6.0
Real estate property | Minimum
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Property, plant and equipment, useful life					20 years
Real estate property | Maximum
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Property, plant and equipment, useful life					45 years
Lease hold improvements and other property and equipment | Minimum
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Property, plant and equipment, useful life					3 years
Lease hold improvements and other property and equipment | Maximum
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Property, plant and equipment, useful life					10 years
Benefit Consultants Group Inc.
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Impairment charges of intangible assets			$ 4.4
Goodwill impairment				$ 5.6
Value of business acquired
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Purchase price					$ 70.5
Amortization in 2023					5.8
Amortization in 2024					5.4
Amortization in 2025					5.1
Amortization in 2026					4.7
Amortization in 2027					4.4
Value of business acquired | Benefit Consultants Group Inc.
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Impairment of finite lived intangible assets			3.6
Value of distribution acquired | NTA
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Purchase price					38.9
Amortization in 2023					2.9
Amortization in 2024					2.9
Amortization in 2025					2.9
Amortization in 2026					2.9
Amortization in 2027					2.9
Value of distribution acquired | Benefit Consultants Group Inc.
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Purchase price					0.5
Value of agency relationships | NTA
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Amortization in 2023					1.6
Amortization in 2024					1.4
Amortization in 2025					1.2
Amortization in 2026					1.0
Amortization in 2027					0.9
Value of agency relationship					8.8
Value of customer relationships | Benefit Consultants Group Inc.
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Purchase price					53.2
Amortization in 2023					4.6
Amortization in 2024					4.9
Amortization in 2025					5.2
Amortization in 2026					5.6
Amortization in 2027					6.0
Impairment charges of intangible assets	2.5
Impairment of finite lived intangible assets					2.5
Interest sensitive life contracts
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Deferred policy acquisition costs, impact of unrealized investment gains (losses)					118.0	$ (71.9)	$ (90.5)
Trade names
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Impairment of infinite lived intangible assets					0.3
Trade names | Benefit Consultants Group Inc.
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Impairment charges of intangible assets	$ 0.3
Impairment of infinite lived intangible assets			$ 0.8		$ 0.3