Schedule of Reclassifications Out of Accumulated Other Comprehensive Income (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Reclassification Adjustment out of Accumulated Other Comprehensive Income
Net Investment Gain (Loss)	$ (4.4)	$ (0.1)	$ (22.3)	$ 85.4
Credit Losses on Fixed Matruity Securities	0.5	0.0	4.6	9.3
Benefits and Change in Reserves for Future Benefits	(1,579.3)	(1,753.9)	(5,181.3)	(5,659.2)
Net Investment Income	511.6	550.2	1,597.8	1,662.4
Other Expenses	(247.3)	(251.5)	(744.4)	(746.8)
Income Tax Expense (Benefit)	104.6	81.3	235.9	206.8
Net Income	(410.7)	(328.6)	(1,034.6)	(664.5)
Reclassification out of Accumulated Other Comprehensive Income (Loss) | Net Unrealized Gain (Loss) on Securities
Reclassification Adjustment out of Accumulated Other Comprehensive Income
Net Investment Gain (Loss)	(13.4)	(4.9)	(25.6)	62.8
Credit Losses on Fixed Matruity Securities	(0.5)	0.0	(4.6)	(9.3)
Benefits and Change in Reserves for Future Benefits	0.0	0.0	0.0	(133.1)
Income Before Income Tax	(13.9)	(4.9)	(30.2)	(79.6)
Income Tax Expense (Benefit)	(2.8)	(1.0)	(6.3)	(16.2)
Net Income	(11.1)	(3.9)	(23.9)	(63.4)
Reclassification out of Accumulated Other Comprehensive Income (Loss) | Net Gain on Hedges
Reclassification Adjustment out of Accumulated Other Comprehensive Income
Income Before Income Tax	12.6	15.1	39.5	49.5
Income Tax Expense (Benefit)	2.7	3.2	8.3	10.4
Net Income	9.9	11.9	31.2	39.1
Reclassification out of Accumulated Other Comprehensive Income (Loss) | Net Gain on Hedges | Interest Rate Swaps
Reclassification Adjustment out of Accumulated Other Comprehensive Income
Net Investment Gain (Loss)	0.0	0.2	0.0	2.0
Net Investment Income	14.1	14.5	40.5	46.2
Reclassification out of Accumulated Other Comprehensive Income (Loss) | Net Gain on Hedges | Foreign Exchange Contracts
Reclassification Adjustment out of Accumulated Other Comprehensive Income
Net Investment Gain (Loss)	0.0	0.1	0.0	0.1
Net Investment Income	(1.5)	0.3	(1.0)	1.2
Reclassification out of Accumulated Other Comprehensive Income (Loss) | Amortization of Net Actuarial Loss
Reclassification Adjustment out of Accumulated Other Comprehensive Income
Other Expenses	(4.0)	(5.5)	(11.8)	(16.9)
Reclassification out of Accumulated Other Comprehensive Income (Loss) | Prior Service Credit
Reclassification Adjustment out of Accumulated Other Comprehensive Income
Other Expenses	0.1	0.1	0.2	0.2
Reclassification out of Accumulated Other Comprehensive Income (Loss) | Unrecognized Pension and Postretirement Benefit Costs
Reclassification Adjustment out of Accumulated Other Comprehensive Income
Income Before Income Tax	(3.9)	(5.4)	(11.6)	(16.7)
Income Tax Expense (Benefit)	(0.8)	(1.1)	(2.4)	(3.5)
Net Income	$ 3.1	$ 4.3	$ 9.2	$ 13.2