Schedule 2 - Parent Company Financial Statements - Statements of Income (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Condensed Income Statements, Captions [Line Items]
Net Investment Income	$ 427.3	$ 348.2	$ 364.3
Income (Loss) from Change in Fair Value of Equity and Convertible Securities	114.6	72.1	138.9
Net Realized Gains on Sales of Investments	64.8	38.1	41.9
Total Revenues	5,793.0	5,205.7	5,039.2
Interest Expense	43.6	36.0	42.5
Loss from Early Extinguishment of Debt	0.0	0.0	5.8
Pension Obligation Settlement Costs		64.1
Total Expenses	6,038.3	4,695.6	4,377.6
Income Tax Benefit (Expense)	124.8	(100.2)	(130.5)
Net Income (Loss)	(120.5)	409.9	531.1
Parent Company
Condensed Income Statements, Captions [Line Items]
Net Investment Income	3.4	1.4	2.1
Income (Loss) from Change in Fair Value of Equity and Convertible Securities	10.0	4.3	1.6
Net Realized Gains on Sales of Investments	10.6	0.1	0.3
Total Revenues	24.0	5.8	4.0
Interest Expense	32.0	24.2	28.5
Loss from Early Extinguishment of Debt	0.0	0.0	5.8
Pension Obligation Settlement Costs		64.1
Other Operating (Benefits) Expenses	5.9	(3.6)	4.0
Total Expenses	37.9	84.7	38.3
Loss before Income Taxes and Equity in Net Income of Subsidiaries	(13.9)	(78.9)	(34.3)
Income Tax Benefit (Expense)	(0.6)	13.4	9.4
Loss before Equity in Net Income (Loss) of Subsidiaries	(14.5)	(65.5)	(24.9)
Equity in Net Income (Loss) of Subsidiaries	(106.0)	475.4	556.0
Net Income (Loss)	$ (120.5)	$ 409.9	$ 531.1