Income Taxes - Deferred Income Taxes and Other (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2022	Dec. 31, 2021
Deferred income tax assets:
Net operating loss carryforwards		$ 86.1	$ 68.2
Tax credit carryforwards		65.8
Net unrealized losses on available-for-sale securities		1,572.3
Employee benefits		305.3	377.9
Gross deferred income tax assets		2,029.5	446.1
Valuation allowance		(42.9)	(28.0)
Total deferred income tax assets		1,986.6	418.1
Deferred income tax liabilities:
Deferred income tax liabilities: Deferred acquisition costs		(794.7)	(582.3)
Investments, including derivative assets		(224.7)	(304.2)
Funds withheld embedded derivative		(767.1)
Net unrealized gains on available-for-sale securities			(1,118.1)
Deferred income tax liabilities: Real estate		(141.0)	(141.6)
Intangible assets		(386.9)	(408.0)
Insurance liabilities		(735.9)	(44.2)
Other deferred income tax liabilities		(27.6)	(54.9)
Total deferred income tax liabilities		(3,077.9)	(2,653.3)
Total net deferred income tax liabilities		(1,091.3)	(2,235.2)
Net deferred income taxes by jurisdiction
Net deferred income tax assets		115.5	85.0
Net deferred income tax liabilities		(1,206.8)	(2,320.2)
Total net deferred income tax liabilities		(1,091.3)	(2,235.2)
Deferred income tax disclosures
Adjustments to deferred tax assets and liabilities	$ 11.1
Accumulated but undistributed earnings from operations of foreign subsidiaries for which U.S. federal and state deferred income taxes have not been provided		1,157.2	912.8
Excess book carrying value over tax basis with respect to the original investment of foreign subsidiaries for which U.S. federal and state deferred income taxes have not been provided		106.2
Current income tax receivables associated with outstanding audit issues
Current income tax (receivables) payables associated with outstanding audit issues		5.6	(12.7)
U.S. Federal
Deferred income tax assets:
Tax credit carryforwards		131.9	0.0
Net deferred income taxes by jurisdiction
Net deferred income tax liabilities		(920.5)	(2,023.6)
State
Net deferred income taxes by jurisdiction
Net deferred income tax assets		83.1	61.2
Deferred income tax disclosures-operating loss carryforwards
Net operating loss carryforwards		250.0	267.3
Foreign
Net deferred income taxes by jurisdiction
Net deferred income tax assets		32.4	23.8
Net deferred income tax liabilities		(286.3)	(296.6)
Deferred income tax disclosures-operating loss carryforwards
Net operating loss carryforwards		229.5	164.1
Valuation allowances on income tax benefits primarily associated with foreign net operating loss carryforwards		$ 42.9	$ 28.0